WATER RESOURCES MANAGEMENT IN TANZANIA: IDENTIFYING RESEARCH GAPS AND NEEDS AND RECOMMENDATIONS FOR A RESEARCH AGENDA
iAGRI BACKGROUND PAPER on WATER RESOURCES MANAGEMENT
by 1
Mahoo, H., 2Simukanga, L. and 3Larry Brown
1
July 2012
1
Sokoine University of Agriculture, 2Ministry of Agriculture Food Security and Cooperatives, 3Ohio State University
List of Contents List of Contents ........................................................................................................................... i Abbreviations and Acronyms ...................................................................................................iii BACKGROUND AND SCOPE OF THE THEMATIC AREA ............................................... iv 1. LITERATURE REVIEW OF PUBLISHED RESEARCH ON WATER RESOURCES MANAGEMENT IN TANZANIA ........................................................................................ 1 1.1. Climate change impacts on water resources ............................................................ 1 1.2. Rainfed agriculture and Water resources management in Tanzania ........................ 3 1.2.1. Water management in rainfed agriculture systems ............................................ 3 1.2.2. Improving productivity of water under rainfed agriculture systems ................. 6 1.3. Water resources management in Irrigated agriculture systems ............................... 7 1.3.1. Background of Irrigation development in Tanzania .......................................... 7 1.3.2. Review of lessons learnt from past Projects/Programmes ................................. 9 1.4. Water resources management and Environmental flows ....................................... 11 1.4.1. Environmental flow concepts .......................................................................... 11 1.4.2. Environmental Flow Assessments studies in Tanzania ................................... 11 1.5. Water resources management: catchments studies ................................................ 13 1.5.1. Rationale for an Integrated Water Resources Management ............................ 13 1.5.2. Catchment studies in Tanzania ........................................................................ 14 1.5.3. Role of institutions in water resources management ....................................... 17 2. GLOBAL LITERATURE REVIEW ON WATER RESOURCES MANAGEMENT ....... 20 2.1. Climate change and water resources-global perspective ....................................... 20 2.1.1. Water scarcity .................................................................................................. 20 2.1.2. Water and Climate Change .............................................................................. 21 2.1.3. Climate impacts on water demand ................................................................... 23 2.1.3.1.
Irrigation .................................................................................................. 23
2.1.3.2.
Domestic use ............................................................................................ 23
2.2. Climate change and rainfed agriculture ................................................................. 24 2.3. Water resources studies at the global level ............................................................ 25 2.4. Effects of land use changes and climate on water discharge ................................. 26 3. KNOWLEDGE GAPS ON WATER RESOURCES MANAGEMENT IN TANZANIA .. 28 3.1. Climate and land use impacts on water resources ................................................. 28 3.2. Effects of catchment land use changes on hydro-climatic relationships ............... 28
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3.3. Water resources database for soils and water resources including surface water and ground water .......................................................................................... 28 3.4. Earth observation and water resources management ............................................. 29 3.5. Time scale on hydro-climate for water resources management............................. 29 3.6. Watershed Management......................................................................................... 29 3.7. Increase water productivity under rainfed and irrigated agriculture ...................... 30 3.8. Improved irrigation and drainage systems ............................................................. 30 4. PROPOSED RESEARCH AGENDA AND RESEARCHABLE ISSUES ......................... 32 4.1. The Priority Research Themes ............................................................................... 32 4.2. Theme 1: Agricultural Land and Water Management ........................................... 32 4.3. THEME 2: Develop adequate and sustainable management systems of natural resources for agriculture to maintain the quality of the environment. ....... 33 4.4. THEME 4: WATER RESOURCES AND CLIMATE CHANGE ........................ 34 4.5. THEME 4: IRRIGATED AGRICUTURE ............................................................ 34 References ................................................................................................................................ 36
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Abbreviations and Acronyms ASALs ASDP ASPS CAADP CAMP CPR DITS EAAFRO FAO FtF GCM GDP GHFSI iAGRI IPCC IWMI IWRM LAMP MAFSC MKUKUTA MSG NAFCO NAWAPO NIDSC NIMP PIDP PWAIS RBMSIIP RELMA RIPARWIN SACGOT SFRAs SII SMUWC SRI SUDECO TRMM UNFCCC URT WD&ID WEMA WUAs WWF-TCO
Arid and Semi-Arid Lands Agricultural Sector Development Programme Agricultural Sector Programme Support Comprehensive African Agricultural Development Programme Catchment Management and Poverty Common Pool Resources Directorate of Irrigation and Technical Services East African Agricultural and Forestry Research Organisation Food and Agriculture Organization of the United Nations Feed the Future General Circulation Model Gross Domestic Products US Government’s Hunger and Food Security Initiative Innovative Agricultural Research Initiative Intergovernmental Panel on Climate Change International Water Management Institute integrated water resources management Land Management Project Ministry of Agriculture Food Security and Cooperatives Mpango wa Kupunguza na Kuondoa Umaskini Tanzania MeteoSat Second Generation National Food Corporation National Water Policy National Irrigation Development sub-Component National Irrigation Master Plan Participatory Irrigation Development Programme Productivity of Water in Agriculture and Interacting Systems River Basin Management and Smallholder Irrigation Improvement Project Regional Land Management Raising Irrigation Productivity and Releasing Water for Intersectoral Needs Southern Agricultural Corridor Growth of Tanzania Stream Flow Reduction Activities Smallholder Irrigation Improvement Sustainable Management of the Usangu Wetland and its Catchment System of Rice Intensification Sugar Development Corporation Tropical Rainfall Measuring Mission United Nations Framework Convention on Climate Change United Republic of Tanzania Water Development and Irrigation Department Water Efficient Maize for Africa Water User Associations WWF Tanzania Country Office
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BACKGROUND AND SCOPE OF THE THEMATIC AREA The Tanzanian economy is highly dependent on water resources. About half of the GDP comes from the agriculture and livestock sectors which are highly dependent on water resources. However, the water resources are currently vulnerable to climate change and variability. In recent years, the major hydro-plants in the country underperformed due to low river flows. The power shortages caused significant economic losses in many sectors such as industry, agriculture, and mining, to mention only a few (Mwakalila, 2007). Water is, therefore, a key resource that requires good management. The social and economic circumstances prevailing today have made particular demands upon the country’s water resource base and the environment, and its sustainability is threatened by human induced activities. Over the past 20 years these demands have intensified with the increase in population and concurrent growth of economic activities requiring more water. These demands include hydropower generation, irrigated agriculture, livestock keeping, domestic, and wildlife (URT, 2002). Water scarcity is experienced in many places and sectors in Tanzania due to unreliable rainfall, multiplicity of competing uses, degradation of sources and catchments (MoWLD, 2002; URT, 2002; Munishi et al.., 2003; Kusiluka et al.., 2003). There are also increasing challenges of managing the multiple trans-regional watercourses and strengthening water resources management policy and legal and institutional frameworks. Inadequate regulations to monitor groundwater resources development has led to underutilization of the resources and in some places over exploitation and interference in the existing water sources. Fragmented planning, implemented following sector, regional or district interests, aggravates this situation even further (URT, 2002).
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Water resources management especially in agriculture is a critical factor in the reduction of poverty and hunger in Tanzania. The technologic capability for addressing water management problems is staggering. Various researches related to water resources management have been carried out in the country. At the same time, the exploitation of its potential is constrained by our inability to apply it within the realities of political and social systems. Scientific and technical understanding should be united with the goals of society. Optimal technical approaches may be socially unacceptable, and compromises often have to be struck. Water resources management research goals must be based on a blending of technical options with the public's view of what it deems to be an acceptable solution to the problem at hand. Technicians must take steps to ensure that the public view is understood and incorporated in their designs. While technology is only one of many factors affecting water resources decision-making, it is ubiquitous in that it permeates planning, policy-making, regulatory, design, and implementation processes. Tanzania for many years has been struggling to be food self suffiency. In order to achieve this, many programmes and strategies have been formulated and implemented. Among these include KILIMO KWANZA, ASDP, MKUKUTA, and very recently SACGOT to mention a few. In all these programmes and strategies, water and specifically agricultural water plays a central role. Some of the past research focused on breeding crops that can cope with droughts given the fact that two thirds of the country is semi-arid and crop production is mainly rainfed. With the emerging new challenges for example due to climate change, research will be required in order to have sustainable agricultural production for reduction of poverty and hunger in Tanzania. Water management affects related lands, and land use practices affect related waters. The linkages between land-water management practices underscore the need to coordinate water resources planning and management with land use planning and regulation. It is for this reason that this thematic area, ‘Water Resources Management’ will
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include researches that link both the water – land interface with a major focus on agricultural water management and the new challenges towards achievement of the Feed the Future (FtF) by increasing agricultural productivity which is guided by sound research results and guidelines. Therefore, the main objective of this paper is to review published literature on water resources management in Tanzania in order to highlight what is currently known and identify knowledge gaps and suggest areas that need further research. However the scope of the paper is limited to the following core areas: water resources as impacted by climate change; management of water resources in rainfed agriculture; management of water resources in irrigated agriculture and water management catchment studies.
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1.
LITERATURE REVIEW OF PUBLISHED RESEARCH ON WATER RESOURCES MANAGEMENT IN TANZANIA
1.1.
Climate change impacts on water resources
The effects of climate change and variability such as rising temperature and changes in rainfall are undeniably clear with impacts already affecting ecosystems, biodiversity and people. Africa is among the most vulnerable regions to the impacts of climate variability and change (Fischer et al.. 2005; IPCC 2001). The high vulnerability of Africa to the impacts of climate variability and change is also attributed to its low adaptive capacity (UNFCCC 2006). The projected climate change will have far-reaching, negative impacts on the availability of water resources, food and agricultural security, human health, tourism, coastal development and biodiversity. The impacts have potential to undermine and even, undo the progress made in improving the socio-economic well-being. Climate change is projected to have both positive and negative consequences for Tanzania’s water-resources, specifically for the three major river basins: Wami-Ruvu, Pangani, and Rufiji. (Initial National Communication, 2003; URT, 2003; OECD, 2003). The Wami-Ruvu basin is upstream of Tanzania’s major population center, Dar es Salaam. The Pangani basin supplies water to the Tanga, Kilimanjaro, and Arusha regions, supporting a number of economically important activities. The Rufiji basin is a large catchment in the south of the country. The basin, with the Great Ruaha River, is economically important to the nation because of the hydropower it generates at Mtera Kidatu Dam, tourism in the Ruaha National Park, and irrigated agriculture in the plains. According to the Initial National Communication (2003), the Wami-Ruvu basin is projected to experience a 10% decrease in runoff, while annual basin runoff in the Pangani basin is estimated to decrease by 6%. According to URT (2003), the Rufiji River, which houses Mtera and Kidatu hydropower stations, is expected to experience an increase in river flow by 5-11%. Floods on Rufiji and Pangani Rivers would cause damage to major hydropower stations and human settlements found along these river basins in the country. However, according to OECD (2003), all these estimates should be interpreted with some caution because they are based on scenarios from a single GCM. Nevertheless, decreases in runoff could potentially have serious effects on socio-economic activities in the regions of Dar es Salaam, Morogoro, Tanga, Coast, and Kilimanjaro. Dar es Salaam might be particularly vulnerable because it is the largest industrial, commercial, and administrative centre in Tanzania. Recently civil conflicts have been occurring between livestock keeper and farmers 1
over pasture and water in Morogoro, Mara and Kilimanjaro regions. Furthermore, these changing trends in water supply are likely to lead to power shortages. The cost of realising the UN Millennium Development Goals is likely to rise as poor access to water impacts adversely on livelihoods, health and productivity (CARE, 2006). In a study carried out by Valimba (2011) to assess the impacts of climate change and variability on the water resources in Tanzania, he reported that climate data is crucial for any study that is climate related including water resources management. However, he further reported that many basins and locations in Tanzania lack climate monitoring networks and this hampers long term analysis. Similar observations were made by Goman et al.. (2010) in the water catchments of the Uluguru Mountains. The study by Valimba (2011) also revealed that of the four major lakes of Tanzania i.e. Lakes Victoria, Tanganyika, Nyasa and Rukwa, their water levels had recently (1961/62-1964/65) risen to high levels but progressively declined thereafter. Through modelling using GCMs, the study by Valimba (2011), reported that the largest discharge decreases are predicted for all the Internal Drainage basins and Lake Victoria Basin while the lowest decreases are predicted for Kikuletwa, Ruhuhu and Rufiji (except the great Ruaha) River basins. Other studies undertaken to project the impacts of climate change on water resources in Tanzania include Mwandosya et al.. (1998), Hulme et al.., (2001) and de Wit and Stankiewicz, (2006). Most of these studies used GCMs in their analysis and concluded that some areas of the country, such as the Pangani basin area, may receive more rainfall under various climate change scenarios while the Central Regions, might receive less. In terms of temperature increases, the two studies reported a range of 1.5°C - 2°C for the first half of this century and around 2°C - 4°C for the second half. These findings are also within the range predicted for East Africa (IPCC, 2007). In terms of the impact of climate change on water flows in Tanzania, the results reported by these studies differ. Whereas Mwandosya et al.. (1998) predicts increased flows in the Rufiji basin and decreased flows in two other key basins (Wami-Ruvu and Pangani); the study by de Wit and Stankiewicz, (2006) projects a rise in flows in the internal drainage of the Central Regions to a total of136% and 125% in northwest Tanzania by the end of this century.
However, the study by Strzpeck and
McCluskey, (2006) reports that stream flows will be between 80-100% of 1961-1990 flows and only 80-90% of base period flows by 2100 nationwide. It is worth pointing out that, in assessing the predictions of these studies, it must be noted that other drivers of climate and water resources have roles. These include factors such as land use change, population growth and the rate of urbanization. These factors need to be considered and incorporated otherwise 2
planning of adaptation strategies will remain difficult.
1.2.
Rainfed agriculture and Water resources management in Tanzania
1.2.1.
Water management in rainfed agriculture systems
Many people in the world rely on rain-fed agriculture which is highly vulnerable to changes in climate variability, seasonal shifts, and precipitation patterns. Any amount of warming will result in increased water stress. In Tanzania, agriculture is the foundation of the Tanzanian economy since it accounts for about half of the national income, three quarters of merchandise exports and is source of food and provides employment opportunities to about 80 percent of Tanzanians. It has forward linkages to agro-processing, consumption and export sectors and provides raw materials to industries and a market for manufactured goods. In Tanzania, agriculture is dominated by smallholder farmers (peasants) cultivating an average farm sizes of between 0.9 - 3.0 hectares each. About 70 percent of Tanzania’s crop area is rainfed. Food crop production dominates the agriculture economy. The major constraint facing the agriculture sector is the falling labour and land productivity due to application of poor technology, dependence on unreliable and irregular weather conditions. Both crops and livestock are adversely affected by periodical droughts. The impacts of climate variability on agriculture sector in Tanzania include shifting in agroecological zones, prolonged dry episodes, unpredictability in rainfall, uncertainty in cropping patterns, increased weed competition with crops for (moisture, nutrients and light) and ecological changes for pests and diseases (Paavola, 2003, URT, 2007). Shortening and/or change of the growing season, a trend that has already been
observed in Tanzania is seen as a direct
consequence of the warming up and changes in rainfall. According to Funk, et al.., (2005), in Tanzania and East Africa at large, there has been a decrease in long-cycle crops and rainfall between March and May from 1996 to 2003. Even more worrisome, climate variability will require plants to adapt to the new situation, which keeps on changing (Paavola, 2003). The recent droughts and associated crop failures have led to severe hunger to many places in Tanzania that forced the government to organize food aid to the people. For example in Dodoma region there had been an 80% decrease in harvests as a direct result of poor or late arrival of rainfall. In 2005, the Vuli, short rains were very poor in many regions including areas where the rains are usually plenty, like Kilimanjaro region. The shortage of the mentioned rains again triggered food aids to the starving people especially in coastal and
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north-east regions (URT, 2007). The effects of the climate variability have contributed to shortage of food and increase in the rate of malnutrition to children in the country (URT, 2007). Studies already show dim figures for the continuing failure in agricultural productivity in Tanzania. Being a staple food for most Tanzanians, maize that is widely grown in Tanzania is projected to be affected the most by recent climate variability. Mwandosya, et al.., 1998 had projected that if the greenhouse gas CO2, will double and average temperature increase by between 20C to 40C, then maize harvest will decrease by up to 33%. The situation will even be bad in some regions like Dodoma and Tabora where up to 80% of this important source of carbohydrate will be lost (Paavola, 2003). Statistics show that maize is not the only crop that will be affected in the nation, according to URT, (2007), cotton yields could as well decrease by between 10%-20% with major economical implications. The alternative to effects of drought in Tanzania’s agriculture would be to strengthen irrigation projects; however irrigation in the country is also suffering from poor water supply. Water for irrigation is becoming very unreliable and thus places where their major economic activities depend on irrigated agriculture will have severe economic hardships on account of the continuing climate variability (URT, 2003). Even worse, in places where climate change is said to increase rainfall and thus flooding like coastal regions further effects on agriculture are eminent. Flooding are associated with nutrients leaching, water logging and sweeping away of crops and the top fertile soils. These effects have already been reported in many places in those regions (URT, 2003, 2007). In addition, infrastructures like roads are also swept away by floods which complicates the transportation of agricultural produce and farm inputs to market places and farming areas respectively, hence poverty intensification. Studies in rainfed agriculture addressing some water management issues include among those targeted to improve availability of water for plant growth in the semi-arid areas (SWMRG, 2001). According to SWMRG (2001), there are Districts in the country where the long-term average rainfall is more than 1000 mm per season, yet crop production is very low. The main reason is failure to manage the distribution of the rainwater, so as to ensure adequate availability of soil-moisture throughout the growing period. When it rains in the semi-arid areas, runoff occurs very rapidly and if not captured the water flows as a flood wave to sinks, 4
from where it is often not economical to recover it for beneficial use. Research has shown that only a small fraction of rainwater reaches and remains in the root zone, long enough to be useful to the crops. It is estimated that in many farming systems, more than 70% of the rain falling directly on a crop-field is lost as non-productive evaporation or flows into sinks before it can be used by plants. In extreme cases, only 4-9 % of rainwater is used for crop transpiration (Rockstrom et al.., 1998). Therefore, in rainfed agriculture, wastage of rainwater is a more common cause of low yields or complete crop failure than absolute shortage of cumulative seasonal rainfall.
Another study carried out by SWMRG (2005a) in the semi-arid areas of Tanzania aimed to develop and promote strategies that can improve the livelihoods of the poor living in semiarid areas. They reported that current institutional and regulatory mechanisms limited access to common pool resources (CPR) such as water and land by the poor. It was also observed by Hatibu et al.. (1999) that a gap exists between the emphasis given in national policies, strategies, and programmes and what is actually practised by farmers in semi-arid areas. There is, therefore, a real problem in Tanzania, whereby national level strategies and policies are not taken into account at local level. The study by SWMRG (2005a) identified the areas that required new or improved by-laws or regulations which included coordination between primary court and village government and harmonization of contradictory by-laws, regulations, traditions and customs. Analysis of transaction costs and benefits in CPR management indicated that individuals and communities incur transaction costs in both fiscal and time dimension. However, the poor and politically weak incurred more transaction costs than the rich. Based on the identified institutional weaknesses, tenure and management approaches that enhance equitable access to CPR were recommended. They include; formation of an autonomous committee for land management in villages with sub committees for residential land, agriculture land and grazing land, preparation of land use plans to demarcate grazing and agricultural land and water allocation should consider spatial and seasonal aspects (SWMRG, 2005a). Planning and managing rainwater harvesting systems in the semi-arid areas of Tanzania is sometimes difficult due to a number of reasons among which are lack of tools to assist planners and decision makers. This challenge was addressed through studies carried out by SWMRG (2005b) which resulted into the development of the PARCHED THIRST v2.4 model. SWMRG, (2005b) provided awareness on the potential of the software as well as providing advice and help to target users and collected feedback for future improvements and upgrading. The PARCHED THIRST v2.4
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has been used by various stakeholders as a planning and design tool in land and water resources management in particular the promotion and adoption of RWH systems, research and training.
However, there is still room for improvements to address large catchments/basins (SWMRG, 2005b). 1.2.2.
Improving productivity of water under rainfed agriculture systems
Given the persistently growing pressure on freshwater and soil resources, it follows that the challenge of feeding the ever increasing world population is, to a large extent, about improved water productivity within present land use. Producing more crops, livestock, fish and forest products per unit of agricultural water use holds a key to both food and environmental security. A variety of options exist for improving the productivity of water in agriculture through breeding, better management practices and supporting policies and institutions. Water productivity is a measure of the amount of water needed to generate an amount (or value) of produce. Because water productivity can be quantified it enables improvements to be charted, thereby encouraging faster progress. Therefore the main reason to improve agricultural water productivity (water productivity in crop, livestock and aquaculture production) is to meet rising demands for food from a growing, wealthier, and increasingly urbanized population, while there are pressures to reallocate water from agriculture to cities and to make more water available for environmental uses. An additional reason derives from the link between poverty reduction and economic growth. For the rural poor, more productive use of water can mean better nutrition for families, more income, and productive employment. In Tanzania, studies directly aimed at increasing water productivity under rainfed agriculture systems are scanty. However, total amount of benefits and the amount of water depleted are rarely known, monitored or measured. Often only the amount of the target crop is considered in as the only benefit obtained. Water recycling is always neglected. It is for this reason that productivity figures quoted in Tanzania are so low. For example, in Tanzania, productivity of water of 0.1- 0.14 kg/m3 for rice and 0.22-0.32 kg/m3 for other cereals have been recorded, which are even much lower when compared to the global water productivity situation. In the Usangu plains, productivity of water for rice is estimated to be in the range of 0.2 to 0.35 kg/m3 (SMUWC, 2001) at field scale, which is almost 50% higher to National figures obtained from the literature. The Land Management Project (LAMP) in Babati, Tanzania reported rainwater utilization efficiency increase in terms of maize yield, from 0.15 kg/m3 to 0.41 kg/m3 due to improved land management interventions (RELMA, 2000). 6
Results from the study carried out by Mahoo et al. (2007) in the Rufiji River basin to assess the productivity of water showed that the concept of productivity of water is not wellunderstood by many stakeholders and the practice of assessing productivity is insufficient. In most irrigation systems there are hardly any efforts to mainstream the assessment of productivity with respect to water, as yet. For example, irrigation schemes in Tanzania obtain water on the basis of permits - defining volume per unit of time but re-allocations of the same water and subsequent payments by individual users are determined by size of the land being irrigated. Furthermore, the amount of water given to individual farmers is not in terms of volume but through allocated hours of access to irrigation water and according to frequencies of irrigation decided by Water User Associations (WUAs). A more comprehensive analysis of water use and productivity in the Great Ruaha Basin was done by the RIPARWIN (Raising Irrigation Productivity and Releasing Water for Intersectoral Needs) project (Kadigi and Mdoe, 2004). This study on livelihoods and the economic benefits of water utilization showed the highest values of water for livestock, brick making and domestic uses, averaging at around a dollar per cubic meter (m3) of water consumed. Understanding such values of water is very important among stakeholders for efficient allocation of basin water resources. Some disagreements on actual water allocation will still remain due to the differences in values, goals, priorities and aspirations of people. However, the common understanding on values of water and productivity is a prerequisite in ensuring the equitable sharing of basin water resources. Unfortunately, there is evidence of the problem of a lack of common understanding and practice of the concepts of productivity of water among stakeholders in Tanzania. As a result it is a common practice to evaluate irrigation schemes in terms of yield, while it may have been more logical to measure performance per unit of water use (i.e., kg/l/s/ha).
1.3.
Water resources management in Irrigated agriculture systems
1.3.1.
Background of Irrigation development in Tanzania
Irrigation practice in Tanzania is said to have occurred several thousand years ago mostly at the foot of Rift Valley Escarpment in the northern part of the country. In more recent times, some indigenous irrigation systems that are still operational in the mountainous areas in the northeast of the country are known to date back more than 200 years. More traditional irrigation systems continued to emerge especially in areas where there were inadequate or 7
poorly timed rainfall and these are mostly found in Northern, central and southern highlands of the country. Most of these “traditional” irrigation schemes owned by smallholder farmers, use “run-ofriver” abstraction techniques. Rice and vegetables are the main crops produced in such schemes. On-farm water management is through traditional furrows or small basins. These are normally poorly drained and prone to salinasation. Smallholder farmers are unable to control abstractions of irrigation water from rivers and streams. Poorly designed traditional irrigation canals lose water. In such irrigation schemes, irrigation efficiency is quite low, estimated at 14-20%. Access to water is uneven within the schemes with uncertainty to farmers at the end of the canals. Crop production from these irrigation schemes is generally low, with typical average yield of paddy estimated at between 1.8 – 2.0 t/ha. The government increased its involvement in irrigated agriculture from 1970s, through its Water Development and Irrigation Department (WD&ID). Since then, the government has been striving to support the development of smallholder irrigation schemes to ensure food security and income generation at the household level. Development interventions which were undertaken include construction of dams in Dodoma, Tabora, Shinyanga, and Singida regions; intakes across rivers to abstract water for smallholder irrigation schemes and pumped water irrigation schemes along Lake Victoria. The government also has developed large, modern state farms which were operated by the National Food Corporation (NAFCO) and the Sugar Development Corporation (SUDECO), producing rice and sugar respectively. The total irrigated area under these farms is 25,000 hectares. There are also few private farms in the Moshi-Arusha area producing irrigated flowers and vegetables for international market. According to the National Irrigation Master Plan (NIMP-2000), Tanzania has a huge irrigation potential of 29.4 million hectares out of which, only 264,388 hectares are under irrigation. Recent interventions by the government through projects/programmes such as RBMSIIP, PIDP, ASPS have contributed significantly to the improvement of irrigation infrastructures in the traditional smallholder irrigation schemes and training of farmers in water management and crop production techniques. All these have resulted into increase in irrigation efficiency, crop yields and family incomes.
However, the remaining area which is potential for irrigation is still big, with some areas under unimproved smallholder traditional irrigation schemes associated with a number of 8
management problems. Hence a need for continued improvement of traditional irrigation schemes as well as development of new small, medium and large scale irrigation schemes using different irrigation methods. In general, irrigation research in Tanzania is still at its infancy stage. Recently, the Ministry of Agriculture and Food Security through the Directorate of Irrigation and Technical Services (DITS) held a workshop in Morogoro to chart out its irrigation agenda. They came out with the following research topics: i)
Assessment of drip irrigation systems for grape production, climate change adaptation and improved livelihoods in Tanzania;
ii)
Assessment of concrete pedal pump for micro irrigation systems for water and crop productivity, climate change adaptation in Tanzania
iii)
Institutional capacity building for irrigation and drainage research and development in East African countries;
iv)
Contribution of the private sector to irrigation and drainage development for food security in Tanzania;
v)
Economic analysis of different irrigation systems in Tanzania;
vi)
Effect of evaporation on water productivity in open canals irrigation systems in central province of Tanzania
1.3.2.
Review of lessons learnt from past Projects/Programmes
There are important lessons learnt from past projects and Programmes. Recent projects and/or Programmes to which reference is made include (i) River Basin Management and Smallholder Irrigation Improvement Project (RBMSIIP); (ii) Participatory Irrigation Development Programme (PIDP), Agricultural Sector Programme Support (ASPS) and other site specific interventions such as Mwega, Mwamapuli and Kitivo Irrigation schemes, Rehabilitation of Traditional Irrigation Canals in Kilimanjaro and Arusha regions (MAFS, 2006). Increase in Crop Production: In general terms, with improved irrigation systems, there is increase in crop production e.g. paddy production has increased from 1.8t/ha up to an average of 5.0t/ha in most of irrigation schemes, improved water management in traditional irrigation schemes has increased irrigation efficiencies from 15% to an average of 30%. Livelihoods of irrigators in improved irrigation schemes have changed positively enabling farmers to meet needs and wants. 9
Strengthening of Farmers Organisations: Formation and strengthening of farmers organisations has enabled the government to systematically hand over management responsibilities of irrigation schemes to the beneficiaries. Water Harvesting Techniques: Through the PIDP, it has been possible to develop 7,200ha in marginal areas using Water Harvesting Techniques. Capacity of Local Contractors: The capacity of local contractors is still very low for irrigation works. This is attributed to lack of experience in works execution, technical personnel and lack of equipment. There is a need for the sub-component to contribute in capacitating the private sector to be able to participate in these works through focused seminars at the onset of the sub-component. Participatory Approach: Despite the fact that participatory approach in developing irrigation schemes is expensive and time consuming, the end result of it is the sustainability of the irrigation scheme. Therefore due attention should be paid during planning of the subcomponent. Under the Smallholder Irrigation Improvement (SII) of the RBMSIIP, fifteen smallholder irrigation schemes with a total area of 5,059 hectares were improved, eight irrigation schemes in Pangani basin and seven in Rufiji basin. Improvement involved schemes infrastructure, training in farmers in crop production techniques, water management, scheme management, agribusiness, environmental management and formation of farmers’ organization as legal entities to oversee day to day activities of schemes etc. By the end of the project a total of 1,674 farmers were trained, out of which 1,052 were men and 622 women. On the other hand in terms of irrigation efficiency, the average baseline values of irrigation efficiency for the traditional irrigation schemes improved from to about 30%. This was derived from an average of 86% for conveyance efficiency, 76% for field canal efficiency and 47% for application efficiency (MAFSC, 2006). All these have a noticeable impact on the management of irrigation schemes, basin water availability, part of which serves to satisfy in-stream environmental flow requirements. Further increases in irrigation efficiency can be achieved if intensive on-scheme training of irrigators’ groups in water management and Operation and Maintenance (O&M) is maintained. Similarly crop yields were reported to have increased. Rice yields and total production almost doubled in both Pangani and Rufiji basins from 2.0 tons/ha and 1.8 tons/ha for Pangani and Rufiji basin respectively before the project to an average of 5.0 t/ha. The yields reported to be up to 8.0t/ha. Production of other crops such as onions, tomatoes, cabbages and other vegetables, generally grown during the dry season, also increased significantly. Beans yield increased from 0.4t/ha to 1.5 t/ha. 10
1.4.
Water resources management and Environmental flows
An environmental flow is a flow in a river or into a wetland or coastal zone (which may include groundwater) that maintains the ecosystem in a desired ecological condition, which maintain goods and services for people and supports biodiversity. This condition is decided by society and is a compromise between economic, social and ecological values of water for various uses. Environmental flow assessment thus provides a key element in integrated water resources management. The Government of Tanzania has developed a new Water Policy (NAWAPO, 2002) that gives priority for water to ecosystems once basic human needs are satisfied. Environmental flow assessment will be required for Tanzanian rivers to implement this policy. Tanzania has expertise in many relevant technical sectors including hydrology and biology and the management of water for irrigation and hydropower production, but lacks experience in inter-disciplinary hydro-ecological science that forms the basis of environmental flow assessments. 1.4.1.
Environmental flow concepts
There are two basic approaches to setting environmental flows; objective-based and scenariobased (Acreman and Dunbar, 2004). In objective-based environmental flows setting, the ecological and/or socio-economic objectives of the river are first established; then the river flow regime is defined that will meet these objectives.
In contrast to objective-based approach, with scenario-based environmental flow setting no objectives are pre-defined. Instead, the ecological and socio-economic implications for a river of different water management options (such as different allocations to direct use, such as irrigation or hydro-power production) are determined. This approach allows stakeholders to participate by assessing pros and cons of each option. 1.4.2.
Environmental Flow Assessments studies in Tanzania
Environmental Flow Assessments have been carried out in a number of basins in the Tanzania, such as Pangani, Wami-Ruvu, Rufiji (all in Tanzania) and Mara (Dickens, 2010). In the Pangani River Basin, Dickens (2010) reported that implementation of environmental flows was awaiting the conclusion of the project. Among the limitations and gaps which Dickens (2010) reported include: lack of information on ecological importance; 11
resources quality not described; insufficient local involvement; not all sections of the project were well focused on environmental flows and stakeholder involvement was inadequate. Similar results were reported by Gowing, (2004) in a comparative study carried out in the Mkoji sub-catchment in the Great Ruaha River. The results from the study by Gowing (2004) indicated that an integrated approach to land and water management that requires assessment of environmental services that are related to land use and stream flow was lacking in the Mkoji sub-catchment. In addition, the study revealed that there was limited knowledge on the baseline condition represented by ‘natural’ condition of the river basin and the concept of water for ‘human reserve’ should be extended beyond a narrow application to stream flow and/or groundwater.
In another study carried out by WWF Tanzania Country Office (WWF-TCO, 2010) on environmental flow assessment in the Great Ruaha River, they reported that one of the preferred options for the restoration of flows in the Great Ruaha River included institutional strengthening and support to ensure improved water resources management. The key recommendations from the study include the need for a socio-economic survey as well as an up-to-date study to disaggregate anthropogenic impact from climate change impact. Also the study emphasised the need to increase the number of rating measurements at gauging stations, spot measurements taken at catchment outlets, and incresed number of observation stations (discharge, rainfall, climate, groundwater) around the Eastern wetland and to carry out further field measurement studies to accurately estimate groundwater flows and evapotranspiration from the wetlands. Harmonisation of data sets, and further bathymetric surveys were also indicated as important. Further sampling of fish and invertebrates at a range of flows was recommended, together with monitoring of riparian vegetation. The need for more recent water quality data was also highlighted. The study by Kashaigili et al. (2006) on environmental flow modelling in the Usangu wetlands showed that between 1958 and 2004, inflows to the wetland declined by about 70 percent in the dry season months (July to November) as a consequence of increased human withdrawals, primarily for irrigation. This resulted in a decrease in the dry season area of the wetland of approximately 40 percent (i.e., from 160 km2 to 93 km2). In the last decade, outflows from the wetland have ceased for extended periods. An environmental flow model indicated that a minimum dry season outflow of approximately 0.6 m3 s-1 is essential to sustain the basic ecological condition of the river. To maintain this outflow from the wetland, a minimum average dry season inflow of approximately 7 m3 s-1 (i.e., approximately double 12
current dry season flows) is required. To achieve this, dry season flows in the perennial rivers discharging into the wetland would have to be apportioned so that 20 percent is used for anthropogenic purposes and the remaining 80 percent discharges into the wetland. There is significant potential for improving water use efficiency. However, to ensure minimum downstream flow requirements, consideration should also be given to active water management within the wetland itself. It is for this reason that sustainable water resources management in the Great Ruaha River Basin is of national importance in terms of utilisation of its water resources for significant crop production, maintaining a RAMSAR wetland site, meeting the ecological needs of the Ruaha National Park and the generation of hydro-electric power. However, one of the biggest challenges is how to balance and meet the different water needs of the different sectors without detrimental effects. The question of environmental flows is an issue that is not well understood and sometimes neglected. There is need to look into this and come up with criteria and guidelines to make sure that environmental flow is maintained in all the river basins in the country. 1.5.
Water resources management: catchments studies
1.5.1.
Rationale for an Integrated Water Resources Management
In view of the current challenges in water resources management in Tanzania, an integrated water resources management is needed to ensure that water does not become a constraint to national development. This calls for a new vision “A country where there is equitable and sustainable use and management of water resources for socio-economic development, and for maintenance of the environment" (URT, 2002). The existing approach to water resources development is sector oriented and does not fully recognize the multi-sectoral linkages in planning the use of water resources. Furthermore, it is based on a regional development and does not focus on institutional capacity to manage water resources. It is also oriented more towards the development of the water resources and not on the protection or management of the water resources, and is based on regulation as a primary instrument for implementing the water policy.An integrated approach addresses participatory, multi-sectoral, multidisciplinary river basin management, which, recognizes that water is a scarce resource and integrates the linkage between land use and water use and recognizes the important role water ecosystems play in the national economy. Evidence from studies carried out by Dungumaro (2006) indicate that for quite some time water resources management in the country has been carried out in isolation from other resources such as land, and the focus has been on a single purpose 13
of water use. Under the single purpose approach, Dungumaro (2006) reported widespread degradation of water resources and water scarcity in the study catchment. In order to achieve the benefits of IWRM, issues pertaining to population increase, environmental, socioeconomic and political factors (also referred to as ‘determinants’) must be addressed. The National Water Policy (URT, 2002) recognises that the river basin or sub-basin shall be the planning unit, and planning shall involve all stakeholders; will be inter-sectoral in character, and finally it shall consider requirements for bio-diversity and human health. This is often said than done. It is for this reason that a review of catchment studies is necessary because water resources in terms of quantity and quality have a strong bearing on how catchments are managed and/or utilised. 1.5.2.
Catchment studies in Tanzania
Catchment studies in Tanzania dates back in the 1960s under the East African Agricultural and Forestry Research (EAAFRO) though the focus was more on the effects of deforestation/afforestation on catchment discharge. For example, plantation forests and tea were found to have small effects on stream flow once plant canopy completely covered the ground and had established a deep rooted system (Dagg and Blackie, 1965; and Blackie 1972). In Mbeya, Tanzania where there is a six months dry period, long term average increases in stream flow of about 50% was recorded in a cleared forest compared with the control (forested) (Edwards and Blackie, 1975). Although the hydrological effects of complete clearing of forests are adequately established, few basic studies have been done to assess the effects of deforestation on the various components of the hydrologic cycle in Tanzania. Information relating the effects of deforestation on changes in the hydrologic cycle including water quality changes and crop evapo-transpiration is scanty. The hydrological effects of land use change have been a cause of controversy and debate for many years, especially the effects of deforestation and afforestation on the dry season flow. Lorup and Hansen (1997) carried out a study in three small headwater catchments in Iringa Region in the southwestern highlands of Tanzania. They compared one year's stream flow response from three catchments with similar physiographic and climatic characteristics. The results revealed that the annual runoff from a catchment with evergreen montane forest was 30 and 36% lower than from two cultivated catchments. The largest difference in runoff was found during the dry season where the total runoff was approximately twice as high from the cultivated catchments. Furthermore, the lowest annual flows from the forested catchment -
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recorded at the end of the dry season - were only about 30-45 % of the low flows from the two cultivated catchments. These results though preliminary, are similar to those reported in Mbeya by Edwards and Blackie (1981). Similar hydrological studies were carried out by the Forestry and Beekeeping Division, (2005) and they investigated the effects of forests cover changes on the quantity and quality of flows from rivers Sigi, Pangani, Wami, Ruvu, Kilombero, Ruaha and Kihansi in the Eastern Arc Mountain forests. In order to quantify the impacts of forest changes (deforestation and afforestation) on river flows, it is important to carry out modeling studies preferably for small forested catchments to understand the interactions between the forest cover, surface and subsurface water. In this case distributed models are appropriate. However, such models require extensive data sets that can only be assured once additional flow gauges, rainfall and climatic stations and observation wells are installed. Whilst observation wells, within the study catchments, will provide information regarding the subsurface conditions (e.g. groundwater fluctuations), river flow gauges will provide the resulting surface flow fluctuations while rainfall and climatic stations will provide information on the background climatic fluctuations. Monitoring of vegetation cover changes can therefore be linked to these hydro-geoclimatic fluctuations once suitable distributed models have been calibrated for selected forested catchments.
Other recent studies include those by Marloes (2009) and Kinoti et al. (2010) carried out in an un-gauged Makanya River catchment in the Pangani basin. The study by Marloes (2009) reported that the current hydrological and water resources situation in the catchment is a result of anthropogenic influences. There is increased water usage in the upper parts of the catchment especially through irrigated agriculture. Given the fact that there are no formal agreements in existence between the highland, midland and lowland water users, much of the water is used in the upstream part of the catchment. With the base flow no longer reaching Makanya village (i.e. the location of lowland farmers) the farmers were forced to change their irrigation practices from full to spate irrigation. Furthermore, changes in land use in the upstream parts have also impacted the hydrological processes, though due to the lack of historical data this was not quantified. The downstream farmers partly benefit as flash floods generated in the highlands reach Makanya, replenishing the unsaturated zone and local groundwater bodies and depositing fertile sediments. However, due to poor control, the flash floods cause damage to crops.
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The study by Kinoti et al. (2010) looked into the understanding the rainfall-runoff relations in the Makanya catchment using modeling approaches. The estimation of rainfall in this study was based on the blending of the geostationary MeteoSat Second Generation (MSG), infrared channel with the low-earth orbiting passive Tropical Rainfall Measuring Mission (TRMM), and microwave channel satellite data. Comparison of the results obtained from the blended TRMMMSG with the available ground gauge data for 2004 and 2005 periods, gave a good correlation of about 80%. In conclusion, the developed TRMMMSG blending procedure was found to be a reliable and robust way of obtaining spatial temporal rainfall distribution of a given area and particularly so for arid and semi-arid lands (ASALs) such as Makanya with sparse data acquisition networks. In a study carried out by Gomani et al.., (2010) in Ngerengere River catchment to establish a hydrological monitoring network, integrated participatory approaches were used. The results indicated that the integrated participatory approach helped considerably in setting up and maintaining the monitoring network. It benefitted from assimilating local and expert knowledge with respect to identifying appropriate sites for installation of instruments due to experiences from local people. Second, in contrast to the past whereby equipment that had been installed earlier had been vandalized, the new equipment that was installed did not suffer any vandalism. Third, support from local people and authorities minimized costs for installation and monitoring, and contributed to maintaining the monitoring network. The benefits of integrated participatory approach in catchment monitoring compared to conventional narrow scientific/technical approaches were shown by gaining rapid insight into the hydrology of the catchment, identifying best sites for the instruments; and voluntary participation of stakeholders in installation, monitoring and safeguarding the installations. Another key result from the study by Gomani et al.., (2010) is a Framework or model that can be used for establishing hydrological monitoring networks in catchments. The framework has sxs steps which include: (i) inception of idea; (ii) stakeholder identification; (iii) defining the scope of the network; (iv) installation, (v) monitoring, and (vi) feedback mechanism integrated within the participatory framework. However, the Framework requires further work to test its applicability in other catchments. A similar study was carried out by (Ludovic, 2012) in the Morogoro River and Ngerenger River sub-catchments. The study aimed to explore and model the influence of land use change and rainfall variability on water discharge in the two river sub-catchments. An empirical model was developed linking Land use change and water discharge. Although the methodological framework used to derive the model can be used in similar catchments, transferability to similar catchments in other basins 16
should be studied and explored. Understanding the areal changes, transformation, dynamics, and their associated trends will shed more light on the relationship of land use changes on water resources in river basins. Another demonstration of the role of integrated water resources management is the study by Ngana et al. (2003) carried out in the Lake Manyara drainage basin in northern Tanzania. The study aimed at developing an integrated water resources management plan for the sub-basin. The study reported a number of constraints which inhibited sustainable water resources management. These included low understanding of existing water policies, conflicting sectoral policies, and lack of coordination between sectors. Others include high human and livestock in-migration rates into the basin, and conflicts between sectors. There was also concern of high rates of soil erosion and sedimentation, lack of comprehensive data base on water resources and environmental flows. The study underscored the need of knowing and understanding the user dynamics and interaction within different institutions in any river basin As stated earlier in the section, catchment studies in Tanzania are few, the few that have been conducted have been driven by projects and once the projects come to an end the monitoring comes to an end. Given the current rate of land use changes that are taking place in the country and its effects on water resources, the study has shed some light on these effects on the water resources base. 1.5.3.
Role of institutions in water resources management
According to the National Water policy, (URT, 2002) the Institutional Framework of water resources management requires an effective institutional setup to perform core functions of (a) water resources exploration, (b) water resources assessment both in quantity and quality, monitoring and evaluation, (c) water allocation, (d) pollution control, and other cross-sectoral activities such as catchment management, basin planning and development. Strong institutional set-up will be responsible for enforcement of the water legislation. The management of water resources have five main levels; National level, Basin level, catchment level, District level, and Community or Water User Association level which will be the lowest level and will bring integrate users of the same source. Despite this set up, there are several challenges at each level. For example, it is stipulated that communities in general play a major role in the water sector because they are the primary users, guardians and managers of water sources. However, often times they are not consulted in key decision making
17
regarding the water resources. This argument is supported by results from a study carried out in the Mkoji sub catchment in the Rufiji Basin in Tanzania by Sokile et al., (2005). The study explored the interfaces and linkages between formal and informal institutional frameworks for water management in the Mkoji sub catchment. The study identified some positive linkages between formal and informal institutions; but there were also struggles and bickering between the two. In many river basins in Tanzania, both formal and informal institutions exist. However, how they function is not well understood and in several cases they are ignored by the formal institutions despite the fact that formal and informal institutions are closely linked and greatly depend on each other. As correctly put by the Sokile et al. (2005), there are no full-fledged mechanisms as yet to better align the formal and informal institutions. In some cases there is only superficial contact among similar institutions resulting into uncoordinated interventions, bypass and duplication of efforts, while in other cases there are troublesome overlaps resulting into power struggles and collisions in operation mechanisms. Water resources management requires that these two institutions co-exist and complement each other. Yet in another study carried out by Munishi et al. (2008) in the Uluguru Mountains to assess the socio-economic, cultural and livelihood factors that influence community participation in restoration and management of water resource, they reported that conflicts and competition for water during the dry season was a major factor hampering conservation efforts in the catchments. The paper raises the fundamental question of community’s participation in watershed management. In many cases, communities do not see the incentive for them to conserve the water resources in a watershed. The case is worsened by the fact that even new programmes and projects do not factor in incentive packages for community’s roles. As an example, water user permits requires the applicant/user to pay fees. However, the revenue is not ploughed back into the watershed so that community’s can see the results of the fees they paid. Another interesting case where there was some sort of institutional breakdown was reported by FAO, (2005). The study was carried out in the Mkoji River sub-catchment, in the Great Ruaha River basin and was looking at how different groups were affected by water resources management and allocation in the catchment. The results indicated that water management structures did not benefit the vulnerable groups such as the poor and the pastoralists. Even the water user associations were often dominated by middle and upper class landlords (FAO, 2005). In order to have a successful water resources management programme, there is need to have a good understanding of the local level dynamics, as well as the river basin and national 18
level policies and institutions that shape them. Therefore, an assessment of policies and institutions dynamics and the water resources management linkages at various spatial scales is necessary.
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2.
GLOBAL LITERATURE REVIEW ON WATER RESOURCES MANAGEMENT
2.1.
Climate change and water resources-global perspective
2.1.1. Water scarcity According to IPCC, 2007) the vast majority of the earth's water resources are salt water, with only 2.5% being fresh water. About 70% of the fresh water available on the planet is frozen in the icecaps of Antarctica and Greenland leaving the remaining 30% (equal to only 0.7% of total water resources worldwide) available for consumption. From this remaining 0.7%, roughly 87% is allocated to agricultural purposes (IPCC, 2007). These statistics are particularly illustrative of the drastic problem of water scarcity facing the world. Water scarcity is defined as per capita supplies less than 1700 m3/year (IPCC, 2007). According to the Comprehensive Assessment of Water Management in Agriculture, (CA, 2007) one in three people are already facing water shortages. Around 1.2 billion people, or almost one-fifth of the world's population, live in areas of physical scarcity, while another 1.6 billion people, or almost one quarter of the world's population, live in a developing country that lacks the necessary infrastructure to take water from rivers and aquifers (known as an economic water shortage). According to the IPCC (2007), there are four main factors aggravating water scarcity at the global level. These include: Population growth: in the last century, world population has tripled. It is expected to rise from the present 6.5 billion to 8.9 billion by 2050. Water use has been growing at more than twice the rate of population increase in the last century, and, although there is no global water scarcity as such, an increasing number of regions are chronically short of water. Increased urbanization: this will focus on the demand for water among a more concentrated population. Asian cities alone are expected to grow by 1 billion people in the next 20 years. High level of consumption: as the world becomes more developed, the amount of domestic water used by each person is expected to rise significantly. Climate change: this will shrink the resources of freshwater.
In some developing countries like Tanzania, water scarcity may be due to lack of capacity/infrastructure to transfer water from where it is abundant to those areas with shortage. According to IWMI, (2007), water scarcity, defined in terms of access to water, is a critical constraint to agriculture in many areas of the world. A fifth of the world’s people, more than 1.2 billion, live in areas of physical water scarcity, lacking enough water for everyone’s demands. About 1.6 billion people live in water-scarce basins, where human 20
capacity or financial resources are likely to be insufficient to develop adequate water resources. Behind today’s water scarcity lie factors likely to multiply and gain in complexity over the coming years. A growing population is a major factor, but the main reasons for water problems lie elsewhere - lack of commitment to water and poverty, inadequate and inadequately targeted investment, insufficient human capacity, ineffective institutions, and poor governance.
Therefore water scarcity can be viewed at two levels: i) Economic scarcity and ii) Physical scarcity (IWMI, 2007). Economic scarcity is caused by a lack of investment in water or a lack of human capacity to satisfy the demand for water. Much of the scarcity is due to how institutions function, favoring one group over another and not hearing the voices of various groups, especially women. Symptoms of economic water scarcity include scant infrastructure development, either small or large scale, so that people have trouble getting enough water for agriculture or drinking. And even where infrastructure exists, the distribution of water may be inequitable. Much of Sub-Saharan Africa is characterized by economic scarcity, so further water development could do much to reduce poverty. Physical scarcity, on the other hand, occurs when there is not enough water to meet al.l demands, including environmental flows. Arid regions are most often associated with physical water scarcity, but water scarcity also appears where water is apparently abundant, when water resources are overcommitted to various users due to overdevelopment of hydraulic infrastructure, most often for irrigation. In such cases there simply is not enough water to meet both human demands and environmental flow needs. Symptoms of physical water scarcity are severe environmental degradation, declining groundwater, and water allocations that favour some groups over others. 2.1.2.
Water and Climate Change
Water scarcity is expected to become an ever-increasing problem in the future, for various reasons. First, the distribution of precipitation in space and time is very uneven, leading to tremendous temporal variability in water resources worldwide (Oki et al., 2006). If all the freshwater on the planet were divided equally among the global population, there would be 5,000 to 6,000 m3 of water available for everyone, every year (Vorosmarty et al., 2000). Second, the rate of evaporation varies a great deal, depending on temperature and relative humidity, which impacts the amount of water available to replenish groundwater supplies. The combination of shorter duration but more intense rainfall (meaning more runoff and less
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infiltration) combined with increased evapotranspiration (the sum of evaporation and plant transpiration from the earth's land surface to atmosphere) and increased irrigation is expected to lead to groundwater depletion (Konikow and Kendy, 2005).
In many parts of the world, variability in climatic conditions is already resulting in major impacts. These impacts are wide ranging, and the link to water management problems is obvious and profound. Climate variability is already being observed to be increasing, although there are still large uncertainties about the link to climate change (IPCC, 2001). Floods, droughts and other extreme climate events, such as hurricanes, add to the major problems water managers face from population growth, urbanisation and land use changes. Every year they inflict severe damage on humans and the environment in many parts of the world, but particularly so in those so-called ‘hot spots’ where the frequency of occurrence is greater, the sensitivity higher, the devastation more severe or the communities more vulnerable. What we need to do, and can, is increase our capacity to cope with the extreme climate events, if we increase our knowledge to do so. Anticipated global warming is likely to exacerbate climate variability, and hence hydrological responses. Box 1 summarises some of the key issues in relation to climate change and water (IPCC, 2001).
Box 1 Key issues in relation to climate and water in Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2001)
“Climate change will lead to an intensification of the global hydrological cycle and can have major impacts on regional water resources, affecting both ground and surface water supply for domestic and industrial uses, irrigation, hydropower generation, navigation, in-stream ecosystems and water-based recreation. Changes in the total amount of precipitation and in its frequency and intensity directly affect the magnitude and timing of runoff and the intensity of floods and droughts; however, at present, specific regional effects are uncertain”. “The impacts of climate change will depend on the baseline condition of the water supply system and the ability of water resource managers to respond not only to climate change but also to population growth and changes in demands, technology, and economic, social and legislative conditions. In some cases - particularly in wealthier countries with integrated water-management systems - improved management may protect water users from climate change at minimal cost; in many others, however, there could be substantial economic, social and environmental costs, particularly in regions that already are water-limited and where there is considerable competition among users.”
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Both present variability and long-term climate change impacts are most severe in the developing world and particularly affect the poor, i.e. the segment of society least able to buffer itself against impacts. The vulnerabilities that climate variability and change create are, in consequence, a key issue in any poverty reduction programme. The impacts are widespread, but there are ‘hot spots’ where they are particularly severe: countries, regions and communities where the capacity to cope with, and adapt to, the hydrological effects of climate variability will influence their overall development prospects. In Kenya for example, Gichuki (2002) examined the Upper Ewaso Ng’iro North river basin located north-west of Mt. Kenya by analysing the river flows from 1960. The results showed a clear trend of decreasing dry season flows without a corresponding decline in rainfall. Similarly, an analysis of the surface and groundwater potential and domestic, livestock and irrigation water requirements to the year 2010 showed that the basin will experience serious water constraints. 2.1.3.
Climate impacts on water demand
2.1.3.1. Irrigation According to Kenneth (1997), irrigation, which is the most climate-sensitive use of water, accounts for 41 percent of all water withdrawn from ground and surface sources in the United States and 81 percent of consumptive use (that part of the water withdrawn that is evaporated, transpired, incorporated into crops, or otherwise removed from the immediate water supply). Expanding irrigation is helping feed the world's billions of people and may even mask global warming, but the future could bring problems. Some major groundwater aquifers, a source of irrigation water, will dry up in the future hitting people with the double blow of food shortages and higher temperatures. Irrigation has increased because it boosts crop yields, supporting many millions of small farmers. But concern is growing that groundwater supplies in places like India and China may not keep up. Near term and future climate predictions are essential for anticipating climate shocks and improving food security. It is important therefore to include irrigation in regional and global climate models so that projections of precipitation and temperature impacts can be made. 2.1.3.2. Domestic use Water for normal household purposes -- drinking, preparing food, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens -- accounts for 8 percent of withdrawals and 6 percent of consumptive use in the United States (Kenneth, 1997) . Water demands for gardening, lawn sprinkling, and showering are the most sensitive of these uses to 23
climate changes. Aggregate annual domestic water use is not very sensitive to changes in temperature and precipitation; estimates suggest that a 1 percent rise in temperature would increase use from 0.02 to 3.8 percent and a 1 percent decrease in precipitation would increase residential water use from 0.02 to 0.31 percent. Nevertheless, because they are likely to be greatest during the seasons and years when supplies are under the most stress, climateinduced increases in domestic demand can aggravate the problems of balancing supplies with demands during drought. A study of urban water use in four mountainous counties of Utah Kenneth (1997) illustrates how climate variables can increase domestic water demands when supplies are likely to be scarcest. This study found that potential evapotranspiration and rainfall best explain changes in residential water use attributable to the climate. Higher evapotranspiration attributable to a temperature rise of about 2.2 o C (4o F) increased residential water demand by an estimated 2.8 percent during the summer season and by as much as 8 percent during the month of June, when supplies in the region are likely to be in short supply. A temperature increase of 4.4 o C (8 o F) increased demand by 5 percent in the summer and as much as 16 percent in June. 2.2.
Climate change and rainfed agriculture
In Africa several studies have been conducted globally to assess the effects of climate change on agriculture. In a study by Jones and Philip (2003, they argue that the impacts of climate change on agriculture may add significantly to the development challenges of ensuring food security and reducing poverty. By using high-resolution methods to generate characteristic daily weather data for driving a detailed simulation model of maize crop in Africa and Latin America to 2055, the results indicated an overall reduction of only 10% in maize production to 2055, equivalent to losses of $2 billion per year. They conclude by saying that climate change urgently needs to be assessed at the level of the household, so that poor and vulnerable people dependent on agriculture can be appropriately targeted in research and development activities whose object is poverty alleviation. In the last 30 years the climate of the West African Sahel has shown various changes, especially in terms of rainfall, of which inter-annual variability is very high. This has had significant consequences for the poor resource farmers, whose incomes depend mainly on rainfed agriculture. The West African Sahel is already known as an area characterized by important interaction between climate variability and key socio-economic sectors such as agriculture and water resources. In a simulation study by Mohamed et al..,( 2002) in Niger,
24
they reported that by 2025, production of millet is estimated to be about 13% lower as a consequence of climate change. Subsequently, they proposed various potential strategies to compensate this loss including those to increase water use efficiency and to cultivate varieties that are adapted to such circumstances. In a similar study carried out in Niger by van Duivenbooden et al., (2002) they found out that in 2025, production of groundnut is estimated to be between 11 and 25% lower, while cowpea yield will fall maximally 30%.
In Asia, the impacts of climate change on potential rice production have been reviewed in the light of the adaptation to climatic variability and change. According to Murdiyarso (2000), studies carried out by using process-based crop simulation models showed that increasing temperature may decrease rice potential yield up to 7.4% per degree increment of temperature. When climate scenarios predicted by GCMs were applied, it was demonstrated that rice production in Asia may decline by 3.8% under the climates of the next century. In addition, changes in rainfall pattern and distribution were also found suggesting a possible shift of agricultural lands in the region. Furthermore, the study indicated that shifts in rice-growing areas are likely to be constrained by land-use changes occurring for other developmental reasons, which may force greater cultivation of marginal lands and further deforestation. This should be taken into account and lead to more integrated assessment, especially in other developing countries where land-use change is more a topdown policy rather than farmers' decision.
In China, the implications of climate change for agriculture and food are very important. The country depends on an agricultural system, which has evolved over thousands of years, to intensively exploit environmental conditions. Smit and Yunlong (1996) synthesized information from a variety of studies on Chinese agriculture and climate and reported that notwithstanding the yield-enhancing effects of warming and elevated carbon dioxide levels, expected moisture deficits and uncertain changes in the timing and frequency of critical conditions indicate that there are serious threats to the stability and adaptability of China's food production system. 2.3.
Water resources studies at the global level
Major rivers worldwide have experienced dramatic changes in flow, reducing their natural ability to adjust to and absorb disturbances. Given expected changes in global climate and
25
water needs, this may create serious problems, including loss of native biodiversity and risks to ecosystems and humans from increased flooding or water shortages. Palmer et al., (2008) projected river discharge under different climate and water withdrawal scenarios. The projections indicate that every populated basin in the world will experience changes in river discharge and many will experience water stress. They conclude by saying that proactive management efforts are required to minimize risks to ecosystems and people and may be less costly than reactive efforts taken only once problems have occurred. In a study to evaluate the relative impact of global warming and soil degradation due to desertification on future African water resources Feddema, (1999) simulated the potential impact of global warming and soil degradation on African water resources for the 2010-2039 time period. Results indicated that, on a continental scale, the impact of global warming will be significantly greater than the impact of soil degradation. However, when only considering the locations where desertification is an issue (wet and dry climate regions), the study reported that the potential effects of these two different human impacts on local water resources can be expected to be on the same order of magnitude. Drying associated with global warming is primarily the result of increased water demand (potential evapotranspiration) across the entire continent. 2.4.
Effects of land use changes and climate on water discharge
There are abundant studies showing that increase in forest cover can cause a decrease in water discharge due to increased evapo-transpiration (Hibbert, 1967; Bosch and Hewlett, 1982). However, studies in China by Zhang and Lu (2009) reported the contrary. They noted that although the forest area in the catchment had increased remarkably since the end of the 1980s, no decrease of water discharge was observed in the Luodingjiang River. On the other hand, changing trends in temperature and evaporation variables were significant at the 0.05 significance level suggesting their influence on the water discharge. It is well documented that the watershed hydrology is affected by vegetation types, soil properties, geology, terrain, climate, land use practices, and spatial patterns of interactions among these factors. There is also a consensus that all of these factors and interactions are influenced by human activities and climate change (Knox, (2006); Tomer and Schilling, (2009). Trends suggesting increases in precipitation and stream discharge have been documented in the Great Lakes Basin (Hodgkins et al., 2007) and Mississippi River Basin (Lins and Slack, 2005; Kalra et al., 2008) in the USA. Historical increases in base flow discharge have also
26
been documented in Iowa Rivers (Schilling and Libra, 2003). However, several analyses showed that increasing precipitation alone is insufficient to explain increasing discharge trends in agricultural watersheds of the Midwest (Schilling and Libra, 2003; Raymond et al., 2008). Raymond et al. (2008) suggested that land use change and management were more important than climate changes in explaining increasing water from the Mississippi River.
Therefore, water discharge is affected by agricultural land use change within agricultural systems and management. For instance perennial transformation into annual cropping systems causes water discharge increase. Usually, perennial crops have long roots that enable the plant to access water from the base flow reserve as compared to annual crops that are characterized by short roots. Transformation of perennial cropping system into annual crops results in limiting base flow accessibility and hence unable to extract water from the base flow reserve. In circumstances of intact base flow recharge, the base storage tends to increase. However, the increase may be revealed in the dry season low flows.
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3.
KNOWLEDGE GAPS ON WATER RESOURCES MANAGEMENT IN TANZANIA
3.1.
Climate and land use impacts on water resources
The review of literature has shown that water demand is forecasted to increase worldwide, including in those areas already experiencing high water-stress. The freshwater resources have been strongly impacted by climate change and land use change. Certain land use and land cover changes, some of which are occurring at an accelerating rate, have distinct negative impacts on water resources. The existing literature demonstrates that though progress has been made in identifying the likely consequences of various land use changes, an understanding of the areal changes, transformation, dynamics, and their associated trends are not well known in the River basins in Tanzania. Furthermore, the understanding of the effects of land use changes and associated trends for exploration of water resources changes is limited in Africa and Tanzania in particular. 3.2.
Effects of catchment land use changes on hydro-climatic relationships
The review showed that many studies have been carried out on the effects of land use change on water resources in water catchments. Land use changes altered the runoff, sediments and runoff relationships. Some of the methods used to study the effects of land use change have been discussed (Alansi et al., 2009). Moreover, the effects of land use change on sediments and runoff relationships have been undertaken under different conditions, for example arid and semi-arid conditions (Wei et al., 2007). Some studies addressed the effects of land use change on flows and sediment load in tropical areas (Ndomba et al., 2007; Ludovic, 2012). However, there are gaps in knowledge particularly in Tanzania on the effects of land use change on runoff, sediments and runoff relationships in many river basins in the country. 3.3.
Water resources database for soils and water resources including surface water and ground water
Many studies highlighted in the literature review are based on modelling which requires substantial amount of data. Both meteorological and hydrologic studies require long term data sets of more than 30 years. Currently existing data base on water resources and soils is either very coarse and lack the details required in planning and implementation of projects and programmes. As for ground water, the situation is worse; very few studies have been conducted. An understanding of historical variability of water resources in Tanzania is required and this should cover variability of surface water, ground water, rainfall, and water 28
quality parameters. In order to enhance this understanding, tools should be developed that will assist in modelling the surface-ground water interactions, surface water-climate linkages, ground water-climate linkages, and water quality-climate change linkages.
3.4.
Earth observation and water resources management
Though some research assignments have been undertaken in Tanzania, on spatial information systems related to water resources (for example Yanda and Munishi, 2007; Kongo et al., 2010; Obeko et al., 2010; Ludovic, 2012) still there is limited knowledge in the field of satellite data use for water resources management purposes in Africa and Tanzania in particular (van Lieshout, 2009). The capacity building strategies for earth observation and water resources in Tanzania can lead to better basin water resources information, historical trends leading to improved basin water resources planning and food security.
3.5.
Time scale on hydro-climate for water resources management
The review has shown that availability of water resources is greatly influenced by climate conditions that vary with decadal, seasonal and inter-annual time scales. Xu (2005) recommended the importance of studies based on monthly or seasonal hydrological data. Decadal variability analysis demonstrated the usefulness of information at decadal scale in assessing the dynamics of rainfall (Brunsell, 2010). The review has therefore shown that there is a gap in the understanding of rainfall and water discharge variability at decadal scale in Tanzania. There are limited examples of studies using synoptic and decadal time scale. 3.6.
Watershed Management
Watershed management and approaches such as integrated watershed management is required for better performance and increased food production. Already there are basins and sub-basins or catchments that are considered as ‘closed’ catchments. Examples include the Pangani River basin and some sub-catchments in the Rufiji River basin such as the Mkoji River sub-catchment. Water use competition and conflicts in these basins are high to the extent that new projects and programmes are difficult to implement. Institutions to govern these conflicts are weak and over-stretched. Studies are required to assess possibilities of water transfers and how best to manage the watersheds.
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3.7.
Increase water productivity under rainfed and irrigated agriculture
Irrigated agriculture especially where the crop is paddy is blamed for using too much water. Studies in water productivity especially those targeting the use of less water but ensuring high yields are required. In view of climate change and variability, technologies are required to counter the effects of climate change. Climate change projections in some river basins in Tanzania indicate less river flows. Studies are required that will provide solutions to ensure high productivity given future scenarios of climate change in the country. Similarly, studies on irrigation development and investments are required. Currently, there is little research in irrigation in the country, though efforts are underway. It is often claimed the irrigation efficiency in some irrigation schemes in the country are as low as 15-20%. Such figures are mere estimates and require research to give credible results. Knowing the efficiency is one thing, the issue is how we can improve the water productivity. Increasing water productivity will ensure not only high yields but also the possibility of inter-sectoral water transfers. This is important where water is already a major obstacle to food security.
3.8.
Improved irrigation and drainage systems
The irrigation potential of Tanzania is huge and it is claimed that irrigation if fully developed can take many Tanzanians out of poverty. While this is true in many countries, little has been achieved in Tanzania. One of the reasons is little or lack of agricultural research devoted to irrigated agriculture. Irrigated agriculture especially for paddy production uses a lot of water and it is not true that paddy rice has to be submerged for good yields. The System of Rice Intensification (SRI) for example advocates drying and wetting cycles and has resulted into yields of up to 10-15 tons/ha. The SRI technology needs to be studied and adopted in Tanzania. The fact that water is applied on drying and wetting basis, the system can save water up to 40 percent. There are other areas in irrigated agriculture that require critical analysis and provide answers that
30
will propel and promote higher water productivity in irrigated agriculture. These include among others
Assessment of drip irrigation systems for grape production, climate change adaptation and improved livelihoods
Assessment of concrete pedal pump for micro irrigation systems for water and crop productivity, climate change adaptation
Economic analysis of different irrigation systems
Effect of evaporation on water productivity in open canals irrigation systems
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4.
PROPOSED RESEARCH AGENDA AND RESEARCHABLE ISSUES
4.1.
The Priority Research Themes
The following major themes are being proposed i) Agricultural Land and Water Management; ii) Land Use Planning; iii) Development of the Farming Environment iv) Water resources and climate change
The themes are briefly described below and are highlighting the specific objectives and possible research topics. 4.2.
Theme 1: Agricultural Land and Water Management
Goal: Develop engineering knowledge on mechanisms involved in land and water systems and develop effective strategies for land and water utilization, management and conservation for sustainable agricultural production.
Objective 1: Evaluate and Develop Strategies for Managing Soil and Water for Sustainable Agriculture and Environment Conservation in High and Low Rainfall Areas.
Research topics:
Development of strategies for managing rainwater on agricultural land for plant growth and environmental conservation in semi-arid areas.
Development of land management practices that control rainfall run-off and minimize soil erosion in high rainfall highlands.
Objective 2: Develop strategies for effective organization, operation and maintenance to improve productivity and environmental sustainability of small-scale irrigation schemes.
Research Topics:
Evaluation and improvement of utilization efficiency of irrigation water;
Development of systems for tree crops irrigation;
Evaluation and improvement of environmental sensitivity and benefits of irrigation schemes. 32
Objective 3: Develop Techniques for effective and efficient rainwater utilization in order to increase Rice Yields under RWH rice systems.
Research will be required to address the following
Develop tools to assist planners in making sound decisions on how the water resources should be sustainably utilized
Assess policies and institutions dynamics and the water resources management linkages at various spatial scales.
4.3.
THEME 2: Develop adequate and sustainable management systems of natural resources for agriculture to maintain the quality of the environment.
Objective 1: Assess the suitability of natural resources, especially different types of land being mapped as land units, for selected and specified land use types. Land evaluation scenarios must be developed which indicate the natural properties, the potential constraints for land use types. In addition, it is prudent to look into the following research topics:
Development of GIS based databases on land and water resources
Establishment of an ecological and environmental monitoring system for land degradation and desertification processes.
Restoration and conservation of the degraded watersheds to improve household food security, poverty reduction for better livelihoods and sustainable environment.
Objective 2: Analyze the agro-ecological and socio-economic interactions of variables at farm level to give insight in possible and necessary improvements in existing ways of farming. Research will be required to analyze the farming environment and land use practices identify constraints on farm level performance and to derive recommendations with regard to the physical and institutional infrastructure. Objective 3: Develop experimental methods to test adapted technology at the farm level as a contribution to designing sustainable land use systems. 33
Research will be required to develop research methodologies to translate farm level constraints into testable technologies and to test these technologies under the conditions of an experimental station as well as on- farms.
Objective 4: Develop strategies for minimizing environmental degradation and pollution resulting from agricultural operations and processing.
There is little available information on environmental degradation and pollution in both rainfed and irrigated agriculture in Tanzania. This necessitates a fresh research thrust to enhance awareness/knowledge of environmental issues and hopefully lead to proper planning in environmental management. Research topics:
Assess environmental degradation resulting from inappropriate land use and management
Assess environmental degradation resulting from use of agricultural chemicals/fertilizers in agricultural production systems (rainfed/irrigated)
4.4.
Development of effective strategies for pollution control
THEME 4: WATER RESOURCES AND CLIMATE CHANGE
Under this theme, research will be required to address key climate - water interactions. Research topics can include the following:
Develop tools that will assist in modelling the surface-ground water interactions,
Develop tools that will assist in modelling the surface water-climate linkages, ground water-climate linkages, and
Develop tools that will assist in modelling the water quality-climate change linkages.
Assess the effects of climate change and variability on environmental flows, water balance and its effects on crop production
4.5.
THEME 4: IRRIGATED AGRICUTURE
Research will be required to address the following topics:
Assessment of drip irrigation systems for grape production, climate change adaptation 34
and improved livelihoods
Assessment of concrete pedal pump for micro irrigation systems for water and crop productivity, climate change adaptation
Develop Models that can assess the marginal values of water including scenarios as well as taking into account the risks of water transfer including virtual water
Assess effect of evaporation on water productivity in open canal irrigation systems
35
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