Strain, Water Demand, and Supply Directions in the most Stressed Water Systems of Eastern Africa
Maurice M. Ndege
Lecturer, Department of Civil Engineering, University of Nairobi, Nairobi, Kenya
This paper examines sources of strain and water demand and supply directions in the most stressed systems of eastern Africa. According to hydrologists, an annual renewable freshwater availability per person of less than 1 000 m³ constitutes water scarcity. This paper defines stressed system as a system where quantity and quality have been jeopardized because of overuse or exploitation.
The countries covered in this paper are Ethiopia, Kenya, Tanzania, and Uganda. Some attention will also focus on Somalia, Rwanda, and Burundi. Eastern Africa receives most rains from the monsoon system. The climate is equatorial, with great variation in the distribution of rains from the Indian Ocean front toward Central Africa and from the north to the south, as a result of different altitudes and latitudes.
Stressed water systems
The number of freshwater systems vary from one country to another in the region. In Burundi, fresh surface water is abundant, and springs are numerous. There are four hydrological regions: the Imbo Plains, the Zaire-Nile watershed, the high plateaus, and the Mosso Plains. The Imbo Plains include the hydrographic basin of the group of direct tributaries of Lake Tanganyika, including the Mushara, Rwaba, Murembwe, Dama, Ruzibazi, Mugere, Mutimbazi, and Ntahangwe rivers; and the Ruzizi Basin, which has 22 rivers, the main ones being the Luhwa, Myakagunda, Kaburantwa, Kagunuzi, and Mpanda.
All the rivers of Lake Tanganyika and the Ruvubu Basin rise in the Zaire-Nile watershed. The main watercourses of the high plateaus are the Ruvubu, Kanyaru, and Kagera. The Ruvyiranza is the southernmost course of the Nile. The Malagarazi flows into Lake Tanganyika after a long detour through Tanzania. In addition to Lake Tanzania, there are five smaller lakes: Cohoha, Rwera, Kanzigiri, Rwihinda, and Gacamirinda.
Ethiopia is well endowed with water resources. It has a number of Africa’s major rivers and extensive drainage networks, which cover much of the highlands and considerable portions of the lowlands. There are 14 river basins, from which a total of 105.1ñ x 109ñm³/year flows out of the country into transboundary water: 78.7ñ x 109ñm³ to Sudan (77.5%), 16.1ñ x 109ñm³ to Kenya (15.9%), 6.5ñ x 109ñm³ to Somalia (6.2%), and the remaining 0.2ñ x 109ñm³ to the Red Sea. Most of the lakes are in the southern region.
The availability and suitability of the groundwater in the hard-rock formations vary greatly from one location to another, depending on the possibility of recharge, the density of the fractures, the permeability of the rock, the presence of internal obstacles to the movement of groundwater, the concentration and nature of the chemicals in the water, the depth of the aquifers’ water table, and the physiography and difficulties encountered in drilling. The great depths and small yields of the boreholes are a hindrance to their wider use, other than for domestic purposes. Rational planning and exploitation of the resources are still limited because of inadequate reliable data and information about hydrogeological characteristics of various lithologic systems.
Kenya has five drainage basins: Lake Victoria, Rift Valley, Athi River, Tana River, and Ewaso Ng’iro. The country receives an average of 289.5ñ x 109ñm³ of rainwater annually, based on an estimated national annual mean precipitation of 510 mm. Most of this water escapes through evapotranspiration, and some infiltrates the ground. The rest is drained by rivers and streams into lakes and the Indian Ocean. Most streams are concentrated in the central highlands and western Kenya; in the rest of the country, dry valleys or seasonal rivers are common. Like Ethiopia, Kenya has an uneven distribution of water resources, which is well recorded. The Tana and Athi are the only two large rivers that transverse the dry areas in a southeastern direction, discharging into the Indian Ocean.
Groundwater resources are also unevenly distributed in quantity and quality. The drier areas have poor-quality water, with low borehole yields (less than 80 L/min), whereas the high-rainfall areas have many freshwater aquifers with high yields (about 117 L/min). In some areas, groundwater is not readily available; in others, potential aquifers lie at considerable depths and could be reached only through expensive drilling operations. In still other areas, available water is unsuitable for human consumption because of high salinity and high fluoride and other mineral-salt concentrations.
Rwanda has an abundance of surface water and springs. The main watercourses are the Kagera River and its tributary, the Nyabarongo. These are part of the upper Nile Basin and cover 40450 and 14600 km, respectively, with corresponding flows of 295 and 60-240 m³/s.
Somalia, with the longest coastline in Africa, has two large rivers, which rise in Ethiopia: the Juba and the Shebeli. The Juba River crosses the country for more than 875 km; at Bardera the annual flow is 100-120 m³/s, with a maximum of 1100 m³/s. The Shebeli is 750 km long and has a mean flow of 65 m³/s at Beled Wyne, near the Ethiopian frontier, and 500 m³/s at Afgoi-Andegle.
In Tanzania, the mean rainfall over most of the country varies from 250 to 1 000 mm. Higher rainfalls of 1 000-3 000 mm are recorded in northeastern Lake Victoria basin and in the southern highlands. Hydrologically, Tanzania is divided into five major drainage basins: the Indian Ocean basin, the internal drainage into Lake Eyasi, the Lake Natron-Buba depression complex, and the internal drainage complex.
The major river systems constitute the principal surface-water resources of the country, with mean annual runoff in millions of cubic metres. Half of the surface runoff flows into the Indian Ocean from the river systems of Pangani, Wami, Ruvu, Rufiji, Ruvuma, Mbwemkuru, and Matandu. The remainder drains northward, into Lake Victoria, westward, into Lake Tanganyika, and southward, into Lake Nyasa and the River Zambezi and then to the Indian Ocean. Some of the runoff also flows into drainage basins with no sea outlets. Groundwater is abundant in Tanzania and is a major source of water, particularly in the central regions of Shinyanga, Dodoma, Singida, and Arusha.
The chemical quality of water is generally good, except for pollution by municipal and industrial effluent of water sources in the Tanga, Kilimanjaro, and Arusha regions. Lake Victoria water is also polluted by untreated municipal sewage at a point close to the intake at the town of Mwanza. Salinity from brackish, saline connate waters or saline intrusion exacerbated by overpumping is found around Morogoro and in depressions near Lake Rukwa. High fluoride concentrations are found around the Arusha and Kilimanjaro regions. Boreholes are most common around the Dodoma, Singida, and Rukwa regions. The Ruvuma, Mbeya, and Kigoma regions have fewer than 100 of the country’s 4 500 boreholes. Most of the water supplies come from boreholes.
Uganda is the “water tower” of eastern and Central Africa. The country has many high plateaus 900-1 500 m above sea level, and 18% of its area is covered with freshwater-swamps and lakes. There are seven main basins:
• Lake Edward (1 935 km²) receives water from the Ntanga, Ishasha, and Nyamwere and other streams.
• Lake Victoria (58 161 km²) receives water from the Kagera and Ruwizi rivers.
• Lake Albert (16 699 km²) receives water from the Musizi, Nkusi, Wanbabye, Wake, and Weiga rivers.
• Victoria Nile (27 773 km²) receives water the Kafu and swampy areas.
• Lake Kyoga (57 004 km²) receives water from the Sezibwe, Victoria Nile, Okere, Okok, and Akweng. The water of this lake discharges into the Victoria Nile.
• Aswa is a tributary of the White Nile (26 558 km²).
• Albert Nile (19 773 km²) has tributaries from the West Nile hills.
Groundwater exploitation in the Karamajong region, an arid region, has yielded sufficient water to meet the needs of livestock and people. In areas around Lake Victoria, the groundwater has a salt content of 200-300 mg/L. Fecal pollution is a concern in Lake Kyoga and Karamajong, where groundwater aquifers rise almost to surface level during the rainy season.
Stressed systems occur in the northern districts, Jinja and Kampala regions, and around Lake Victoria. In Tanzania, the Rufiji, Pangani, Lake Victoria, Rukwa, and Ruvuma basins all are stressed. Kenya’s stressed systems include lakes Victoria, Nakuru, and Naivasha and rivers Nzoia, Nyando, Turkwell, Kerio, Athi, Voi, Tana, and Ewaso Ng’iro. All of Ethiopia’s rivers are under stress, except the Nile, which has not yet been used effectively for agriculture.
Sources of stress
A stressed water system is one that cannot adequately meet the demands of households, communities, and nations. The main factors that contribute to stress are population growth, irrigation, and livestock watering. Others include droughts and deforestation, poor land management, and pollution from human activities and industry. The most critical issue in the region is the deterioration of the water quality in lakes, rivers, springs, and groundwater, resulting in water resources becoming unfit for human consumption and other purposes.
The annual population-growth rate of most countries in the region is 2.5-3.1%. This high growth rate, combined with economic development, results in ever-increasing demands for a finite resource. Hence, water availability per capita is steadily decreasing. Human activities have impacts not only on the water quality but also on the general availability of water resources and the state of aquatic ecosystems in the region.
Increased population pressure in large parts of the region has led to deforestation and increased cultivation. This, in turn, is affecting the hydrology and water balance and may lead to increased flood and drought problems, as well as to land degradation, soil erosion, and siltation problems. Afforestation may, however, lead to increased evapotranspiration losses and hence reduced water availability for downstream users as in the Ruaha Basin in Tanzania.
Tanzanian agriculture is mostly rainfed, and irrigation is used for protection against drought and for stable crop production. In some areas, communities use irrigation for dry-season farming, mainly growing vegetables. The national irrigation potential is 1ñ x 106ñha, 60% of which is in the Rufiji Basin. Two thirds of this potential could be used for double cropping. Irrigation potential is estimated by the availability and easy exploitation of water. The Rufiji Basin comprises the three major basins, the Great Ruaha, the Kilombero, and the Luwegu. About 60% of irrigation potential in the Rufiji Basin is in the Kilombero and lower Rufiji; 40%, in the Great Ruaha. The Pangani Basin has the best developed irrigated agriculture.
The critical situation affecting the users is the competition for water between agriculture and hydropower production. Because agricultural activity takes place upstream from Pangani Dam, any increase in farming will affect the level of water in the dam. In the Great Ruaha, more irrigation upstream from Mtera Dam will cause shortages in the dam, especially during drought. Because of this, the Tanzania Electricity Supply Company (TANESCO) insists on the closure of all irrigation systems upstream from the dam. Increased irrigation in the two basins will therefore have an environmental impact on the basin. At the national level, the government is trying to improve the water management of the basins by instituting prohibitive measures for users and punitive measures for offenders. It is likely that TANESCO will have increasing difficulty, because farmers will continue to irrigate their fields. There is a need for users to sit and discuss ways to equitably share this limited resource.
In Uganda, about 206ñ x 106ñm³ of water is used annually for irrigation. More than 32510 ha is estimated to be under irrigation. Swamps provide the largest areas, with about 30000 ha of small-scale irrigation in the Tororo, Iganga, and Pallisa districts.
There has been an increasing interest in rice cultivation by farmers. In areas surrounding the Doho rice scheme, hundreds of small-scale farmers grow rice outside the regular scheme; each farmer has an approximate cultivated area of 0.5 ha.
In the Lake Victoria crescent area, many horticultural farmers plan to start small-scale irrigation. However, the generally undulating topography precludes the use of gravity irrigation in most areas. This necessitates the pumping of irrigation water from lakes and streams, and some farmers have already bought electrical pumps for this purpose.
The Olweny Swamp Rice Irrigation Project aims to develop 800 ha of the swamp in Lira District for smallholder rice farming. Six hundred smallholders are the beneficiaries, with individual holdings of 1 ha. Inputs, credit, extension, and other services are provided under the project.
In 1992, the failure of the usually reliable first annual rainfall undermined the food security of Uganda, causing crop failures and decreases in livestock production. Of the 38 districts of Uganda, 15 experienced a long dry spell; food-security problems reached crisis levels. The areas worst affected were Kasese, Kabale, Mbarara, Rakai, Bundibugyo, Masaka, Masindi, Mpigi, Mukono, Luwero, Moroto, Kumi, Soroti, Kotido, and Rukugiri.
In Kenya, irrigation is carried out at both the local and national levels. People are aware of the potential boost in harvest from irrigation. The present national policy relating to irrigation-water supply emphasizes taking low-cost approaches to implementation while increasing the acreage under irrigation.
The government has instituted the National Irrigation Board, and big irrigation schemes like the Mwea, Bura, and Ahero are partly government controlled. But unless legislation is enforced, communities upstream may use all the water, leaving little for downstream users. Another pressing issue of a regional nature is that extensive irrigation from rivers that flow into Lake Victoria may interfere with the ecosystem. The lake level will fall, and more pollutants will find their way into water. The Water Appointment Board, the body legally empowered to control and regulate the abstraction of water (surface water and groundwater) needs strengthening. Currently, the Water Act, first enacted in 1962 and revised in 1972, is awaiting another revision and approval by Parliament. In terms of protecting water resources from pollution the Act is weak. In a move to avert any environmental damage associated with flood irrigation projects, environmental-impact assessments are now preconditions for starting any irrigation projects in Kenya. In Ethiopia, Somalia, Rwanda, and Burundi, irrigation is not well developed.
Livestock makes significant water demands, especially in the semi-arid, pastoral areas, where surface-water sources are scarce and long dry seasons are experienced. The seminomadic pastoralists who inhabit these areas often encroach on natural reserves, such as Lake Mburo National Park in Uganda, in search of water and pasture. In the past, 425 medium-sized dams and valley tanks, as well as several small valley tanks, were provided. Most of these are silted because of lack of maintenance, poor animal-watering methods, and soil erosion that results from overstocking.
Domestic and industrial use
In Tanzania, most of the domestic and industrial water supplies are from surface water. Groundwater sources, though potable in most cases, are not used because abstraction requires sophisticated and sometimes expensive technology.
The installed capacity for rural water-supply schemes, as of June 1992, served about 47% of the population. However, the reliability of the data is questionable because more than 35% of the schemes were not in operation. Many of the pumping units were worn out and nonoperational and needed replacement. Urban water supply, by June 1992, served about 67% of the population. This figure didn’t take into account the quality of water supplied. Sometimes, because of the nonfunctioning of treatment plants and nonavailability of water-treatment chemicals, water is supplied either partially treated or untreated. The operational costs are normally higher than the revenue collected. This is because water tariffs do not meet running costs, and billing and revenue collection systems are insufficiently streamlined. In both the rural and the urban sectors, water demand far exceeds supply. Table 1 shows the low water-supply coverage.
Table 2 shows the distribution between investments in the rural and urban water supplies. The apparent bias in investment, toward the urban centres is attributed to differences in the levels of service, technology, and institutional requirements in the two areas. For example, although per capita investment in the rural areas may be as low as 6 United States dollars (USD) (spring protection), the corresponding figure in the urban centres often exceeds 120 USD.
In Uganda, water supply and sanitation in the urban areas are provided by the National Water and Sewerage Corporation (NWSC) and the Department of Water Development (DWD). NWSC is responsible for supplying water to about 1ñmillion people in Kampala, Entebbe, Jinja, Mbale, Tororo, Masaka, and Mbarara. The average coverage is 51% of the urban target population.
Existing water-supply systems are in a poor state of repair because of maintenance constraints, and most often the population has to rely on unsafe water sources. An umbrella program, the Rural Towns Water and Sanitation Programme, has been instituted to coordinate all the urban water projects under DWD. This reflects a major shift in government policy toward decentralization and represents a demand-driven participatory approach.
In 1992 DWD estimated the rural potable-water-supply coverage to be 26%. The level of investment required to raise the coverage to 100% is estimated to be 351 million USD. The major rural water-supply development programs are RUAWASA East Uganda Project (financed by Danish International Development Assistance), running up to 2000 and covering eight districts; and SWIP (financed by United Nations International Children’s Emergency Fund [UNICEF], Canadian International Development Agency, and Swedish International Development Agency), covering nine districts. Other programs include WATSON the National Water and Sanitation Programme (financed by UNICEF and various nongovernmental organizations [NGOs]), covering nine districts; and the West Nile Rural Water Supply Programme (financed by Italy and NGOs), covering two districts.
Ugandan industry is mainly engaged in processing raw materials from agriculture, livestock, and forestry. Major industrial activities include the production of textiles and garments, leather, sugar, foods, soft drinks, beer, and flour. These activities are concentrated in southern Uganda, particularly Kampala and Jinja, on the shores of Lake Victoria and the Victoria Nile. Uganda had a strong industrial base in the 1960s, but this was destroyed during the 1970s. To date, there are only about 5 000 factories, many of them operating below capacity. Industry contributes 5% of the gross domestic product, and industries are generally connected to the urban water-supply networks.
In Kenya, water for agricultural use will continue to command the highest demand. It is projected that the national water demand will progressively increase from 5.68ñ x 106ñm³/d in 1990 to 15.94ñ x 106ñm³/d by 2010. Of this, 73% will be for agriculture, 4% for livestock development, 22% for domestic use and industry, and 1% for inland fisheries and wildlife.
The government has recognized the need for environmental protection and promoted various measures to ensure sustainable agriculture. These include intercropping, under the agroforestry program, soil and water conservation measures, and proper use of agrochemicals to minimize adverse environmental effects. Other measures will include a shift from agrochemical dependence to organic farming, which has a lower environmental cost.
The water-supply needs of a rural person are estimated at 50 L/d; those of the urban dweller, 100 L/d. According to estimates, the total rural water-supply demand, based on the above figures, will be 749.3ñ x 106ñL/d by 2000; the total urban water-supply demand, 1.17ñ x 109ñL/d. The water demand for wildlife has been estimated at 21.0ñm³ of fresh water per day, on the basis of wildlife species and their distribution in the country. Water for fish-farming needs, based on a fish-production capacity of 2.5/ha, has been assessed at 0.96ñm³/s.
In Uganda, most hydropower generation takes place at Owen Falls Dam, at the Victoria Nile near Jinja. The present installed capacity is 180 MW. An extension program intended to bring about increases of 270 and 300 MW of generating capacity has been prepared. The identified hydropower potential on the Victoria Nile within the Ugandan territory is 2 700 MW, with the Murchison site having a potential for 600 MW and the Bujagali site having a potential for 250 MW.
At present, there is no artificial storage on the upper Nile, and river flows have been unchanged by the construction of the Owen Falls dam. The minihydropower stations have small storage reservoirs, and there is a slight tendency to equalize the natural river flows.
Hydropower generation can be expected to increase as a result of the transboundary distribution of electricity and the increase in rural electrification and industrial and in domestic demand. However, the impact on the water resource (Victoria Nile) will be negligible.
Most of Tanzania’s hydropower potential is in the Rufiji River system. Other rivers with hydropower potential are the Kagera, Ruhuhu, Wmai, and Rufirio. Most of the hydropower potential of the Pangani and Great Ruaha has been developed. Of the existing power-generating facilities, 86.5% are hydropower units. Of the total available hydropower-generation capacity, more than 99% is in the Great Ruaha and the Pangani.
In Kenya, about six hydropower projects are considered promising. These are proposed for commissioning toward 2010. There are also plans to develop hydropower on the Yala and Nzoia rivers.
Responses to water stress
Governments are recognizing that the problems of water stress are not confined solely within their national borders. Issues related to the management of international waters are being addressed at various forums, and various regional bodies have been formed for such purposes. One example is TECONILE, a body incorporating all the countries of the Nile Basin. TECONILE was formed for the sole purpose of proper management of the basin’s water resources. Treaties signed years ago are being revised and drafted to take into consideration the needs of all the upstream and downstream users.
ññññGovernments are also undertaking the following:
• forming high-level, cross-sectoral water-policy committees to formulate guidelines for task forces and to coordinate the legal framework for management of shared water resources;
• setting up modalities for tariff charges and prices;
• embarking on national environmental programs to preserve and conserve forests;
• promoting the operation of water projects by entrepreneurs in rural areas and by autonomous water entities in urban centres;
• preparing guidelines for estimating water-related opportunity and environmental costs; and
• preparing dynamic water action plans (covering water-resource assessment, required institutions, management instruments, etc.) based on water-resource policies.
Uganda, Tanzania, and Ethiopia are preparing water action plans, but Kenya has yet to develop one.
Communities are undertaking the following to address the problem of water stress:
adopting technologies and management approaches that increase the efficiency of water use, allocation, and distribution (such technologies and management practices make it easier to conserve water, to increase the efficiency of water use and conveyance, and to reuse wastewater);
• drilling boreholes, shallow wells, and pit and VIP latrines;
• discussing, planning and implementing development projects in their areas;
• promoting environmental protection practices, like planting trees and establishing nurseries;
• creating intersectoral project task forces;
• organizing education programs, targeted at the household level, on the benefits of potable water and on related costs, especially for operation and management; and
• setting prices and collecting fees to cover operation and management, either in kind or in cash.
Sources of stress should be looked at, not just from the hydrologic point of view, but also from the perspective of accessibility (distances users have to travel to collect water), socioeconomic development, poverty, pollution, human and livestock population increases, and increases in agricultural production (for instance, irrigation acreage).
Ethiopia, despite all its rainfall, has access to only 9% of its water resources for development because 91% flows into international waters. Each country should develop water policies, to be followed by water action plans. Uganda is a good example to be emulated.
Research opportunities and needs for different countries vary and may be linked to the levels of development and economic stability of each country. The following research initiatives are recommended.
1.ñ Launch a national exploratory program to map out areas suitable for future water development; identify the most suitable and economical methods for such development.
2.ñ Address pollution laws covering the contamination of surface waters and groundwaters by various activities and make the laws practicable and workable.
3.ñ Come up with pollution indicators that ordinary people can use at the community level.
1.ñ Adopt the technology needed for studying and recovering groundwater.
2.ñ Address the pollution from municipalities and agricultural sectors.
1.ñ Identify sustainable sources of water for human beings and livestock.
2.ñ Use technical staff from water-related government departments, instead of the private sector, to constrain water schemes. Look into the effects of this bias toward using the private sector on human-resource development at the national level.
3.ñ Look at pollution bylaws and improve them for efficient management of the water sector. In cases where no bylaws exist, develop some and enforce them.
Governments of all countries in the region
1.ñ Study hydrological regimes to understand why some rivers, like the Katonga and Kafu, in Uganda, are drying up.
2.ñ Develop technology for studying and recovering groundwater, including that in contaminated wells.
3.ñ Study the problems related to the operation and maintenance of water-supply schemes, with a view to making them sustainable and operational.
4.ñ Develop mechanisms, tools, and models for updating information in the water sector.
5.ñ Examine country-level institutions.
6.ñ Work out a cooperation framework for the management of common water resources.
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