«Water Allocation as a Planning Tool to Minimise Water Use Conflicts in the Upper Ewaso Ng’iro North Basin, Kenya Jeniffer Kinoti Mutiga · Shadrack ...»
Water Resour Manage (2010) 24:3939–3959
Water Allocation as a Planning Tool to Minimise
Water Use Conflicts in the Upper Ewaso
Ng’iro North Basin, Kenya
Jeniffer Kinoti Mutiga · Shadrack T. Mavengano ·
Su Zhongbo · Tsehaie Woldai · Robert Becht
Received: 23 September 2009 / Accepted: 29 March 2010 /
Published online: 28 May 2010
© Springer Science+Business Media B.V. 2010
Inadequate water resources management and a general decline in rainfall have aggravated water scarcity problems in the Upper Ewaso Ng’iro North Basin in Kenya. Furthermore, water use conflicts in the basin have escalated in recent decades due to increased competition for available water resources. Excessive abstraction of the declining river water mainly for irrigation in the Mount Kenya and Nyandarua foot zones often leads to reduced water flow during the dry seasons, greatly affecting downstream water users. Increased water use in the basin coupled with deterioration of the vegetative cover has resulted in reduced water flows in the Ewaso Ng’iro river and its major tributaries. In addition, lack of sufficient knowledge about available water resources and current lack of coordination in water resources management in the basin often result in water deficits which have hampered development in the downstream catchment. The goal of this study was to match the water requirements of various competing sectors in the basin with the available water resources in order to attain both economic and ecological sustainability. To achieve this, GIS techniques were used to quantify the spatial and temporal stream flow. The Water Evaluation and Planning (WEAP) model was applied to evaluate water resources development based on an equilibrium scenario of the current water demand. Water use was simulated for five different sectors (domestic, livestock, wildlife, irrigation and reserve). The analyses revealed that high water demand for irrigation was the main cause of excessive water abstraction particularly in the upstream catchments, giving rise to water shortages and consequently, water use conflicts downstream. The study, therefore, recommends that rainwater harvesting be promoted in the basin in order to improve water availability for productive use.
J. K. Mutiga (B · S. T. Mavengano · S. Zhongbo · T. Woldai · R. Becht ) Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, PO Box 6, 7500 AA, Enschede, The Netherlands e-mail: firstname.lastname@example.org 3940 J.K. Mutiga et al.
Keywords Water abstraction · Water evaluation and planning model · Water demand · Water allocation · Water use conflicts · Scenario development · Ewaso Ng’iro North 1 Introduction Many countries in the world are facing formidable fresh water management chal- lenges due to increased competition for the increasingly scarce natural resource.
Overexploitation of water resources continues to be the greatest constraint on sustainable agricultural development, an important factor to poverty alleviation.
Water has been recognized as an essential component of food security (UNWATER 2006), with the World Summit on Sustainable Development in 2002 drawing more attention to the importance of water resources management in meeting the Millennium Development Goals (MDGs; UN 2002).
Water resources sustainability means using the natural resource wisely and protecting the complex ecosystems with future generations in mind. But sustainability will not be achieved with current patterns of resource consumption and use (UN 2005). It is therefore of paramount importance to rational planning and decision making in equitable water management. This must be undertaken within the widely accepted integrated approach at all levels of the society.
Mountains often function as water towers of the earth and are rich in biological diversity, making them target areas for recreation. Approximately 12% of the world population depends directly on mountain resources (UNCED 1992). Mountain environments are essential for survival of global ecosystems, but their function as water towers is rapidly under threat as competition for natural resources increases.
They are susceptible to accelerated erosion, landslides and rapid loss of habitat and genetic diversity (Odermatt 2004). There is therefore a need to focus more on these regions to preserve their status as major water sources.
The high plateau of the Upper Ewaso Ng’ro North Basin in Kenya and the mountain foot zones referred to as the “White Highlands” during the colonial period consisted of ranches and large farms. After independence in 1964, the basin experienced changes in land use as land was subdivided into smaller plots for agropastoralists as people resettled from overpopulated foot zone areas. As a result, growth points such as towns and densely populated small scale farms as well as with large scale technical horticulture farms have been formed in the mountain foot zones while game parks and tourist resort centres occupy the dry lowlands of the basin. The population increased from 50,000 in 1960 to 500,000 in 2000 and has put demand for water resources under pressure (Kiteme and Gikonyo 2002). As more land is being converted to irrigated land to grow crops mainly for international markets, farmers now place their water intakes high up on the mountain in the tributaries of Ewaso Ng’iro river. At the same time, pastoralists and small scale farmers are establishing small scale irrigation schemes (Wiesmann et al. 2000). These developments affect communities, wildlife and the ecology downstream of the basin as water becomes scarcer. For instance, 98 abstraction points within a 30 km river reach, provide water to about 30,000 people. About 97% of this abstracted water is being used to irrigate only 9% of the total basin area (Aeschbacher et al. 2005), and thus greatly contributing to water shortages downstream and hence conflicts.
Water Allocation to Minimise Water Use Conflicts 3941 The Upper Ewaso Ngiro North Basin has a high economic status in the country due to its intensified agriculture, forestry and game reserves attracting tourists from all over the world. It offers a great deal of beautiful scenery. Therefore, careful management and negotiation of water resources is a priority in order to mitigate growing water crises and conflicts at local and national levels. While a lot of research has been done in the basin on water resources aspects, focus has been around the Mt.
Kenya area which is the main contributor of the Ewaso Ng’iro river (Aeschbacher et al. 2005; Ngigi et al. 2006; Notter et al. 2007) while no studies have been undertaken in the downstream catchments. Yet, in recent years (especially 1999 to 2002) the lower catchments have experienced water crises to an extent previously unknown (Aeschbacher et al. 2005).
Population growth and the intensification of irrigation on agricultural lands in the foot zones and along the rivers in the plateau have dramatically increased water demand over the past decade (Notter et al. 2007). As a result, water abstraction for irrigation, livestock and domestic use have severely stressed the water resources, particularly during dry seasons causing conflicts between upstream and downstream water users. There is therefore a need to understand the spatial and temporal water availability and to formulate a tool for planning and decision making in prioritisation of water allocation in the basin. However, given the complexity of the system and the interactions between water supply and demand, a large-scale water supply management tool would be useful for decision makers when formulating water management strategies for coping with future changes in water demands (Chung et al. 2008).
To contribute towards this goal, the current study adopted and applied Water Evaluation and Planning (WEAP) model as a decision support system (DSS) to assess water availability and investigate the impacts of different water allocation scenarios (water demand management strategies) aimed at meeting various sectorial water demands in the Upper Ewaso Ng’iro North basin in Kenya.
2 The Study Area
Kenya is divided into five major drainage basins namely, Lake Victoria, the Rift Valley, the Athi River, the Tana River and the Ewaso Ng’iro Basin. However, only two of these basins, (Lake Victoria and the Tana River) are said to have surplus water resources while the others often experience major water deficits (FAO 2003).
This study was conducted in the Upper Ewaso Ng’iro North Basin in Kenya.
2.1 Location of the Upper Ewaso Ng’iro North Basin
The Ewaso Ng’iro Basin is the largest of the five major drainage basins in Kenya covering an area of 210,226 km2. The Upper Ewaso Ng’iro North Basin lies in the upstream of the Ewaso Ng’iro North Basin between 0◦ 15 south and 1◦ 00 north, and 36◦ 30 east and 37◦ 45 east with an area of approximately 15,300 km2. The main Ewaso Ng’iro river originates in the Nyandarua mountains although most of its flow (50%) comes from the tributaries which drain the Mt. Kenya slopes (Jaetzold and Schidt 1983). Mt Kenya receives high rainfall giving rise to perennial rivers which, in the dry season, form the main source of freshwater in the semi-arid Laikipia plateau 3942 J.K. Mutiga et al.
northwest of the mountain, and the arid lowlands of the lower Ewaso Ngiro Basin.
However, groundwater resources remain largely untapped and thus Mt. Kenya is regarded as the water tower for the basin.
The basin drains from the Rift Valley escarpments to the west, the Nyandarua ranges to the south-west, Mount Kenya to the south, the Nyambene hills to the east, and the Mathews range to the north while the downstream outlet is at Archer’s Post (Fig. 2). 5CA8, 5D05 and 5E03 are flow monitoring stations in the Ewaso–Narok, Ewaso–Mt. Kenya and lowlands catchments respectively (Fig. 1).
The topography is dominated by Mt. Kenya and the Nyandarua ranges in the south and the Nyambene hills to the east of the basin (Fig. 2). Altitude ranges between 862 m above mean sea level (a.s.l) at Archer’s Post to 5,200 m at the Mt.
Kenya summit (Jaetzold and Schidt 1983). The mountain slopes consist of deeply incised V-shaped valleys where elevation varies from 2,500 m to 4,000 m a.s.l. The
gentle undulating Laikipia plateau at an elevation of 1,700 m to 1,800 m a.s.l occupies most of the central region of the basin (Fig. 2).
The large elevation differences in the basin give rise to various climatic zones, ranging from humid to arid. Annual rainfall pattern shows spatial and temporal variations from 300 mm in the north eastern areas of the basin to 1,500 mm/year in the Nyandarua ranges with a mean annual rainfall of about 700 mm/year in the basin (Berger 1989; Decurtins 1992; Liniger et al. 2005). There are three main rainfall seasons comprised of monsoon controlled long rains (March to May), followed by continental rains that are caused by humid airstreams from the west (July to August), and short rains (October to November) dominated by air masses due to the movement of the Inter-Tropical Convergence Zone (ITCZ). The continental rains are of great importance as they provide an extended growing period for crops and pasture development. The most distinct dry periods occur from December to February and in the month of September. The mean annual temperatures in the basin range from below 10◦ C at the top of Mt. Kenya to over 24◦ C at Archer’s Post, the outlet of the basin (Berger 1989).
Previous studies show that 70% to 90% of the downstream flow in the semi-arid environments of the basin comes from the mountains (Gichuki et al. 1998; Liniger et al. 2005; Notter et al. 2007) and more than 60% of the basin inhabitants irrigate their crops using water from the Ewaso Ng’iro river and its tributaries (Wiesmann et al. 2000). Other sources of water in the basin include groundwater (boreholes and shallow wells) and flood water usually stored in small dug water pans.
Fig. 2 Topographic variation in the upper Ewaso Ng’iro North basin, Kenya 3944 J.K. Mutiga et al.
Due to the arid nature of most parts of the basin, the atmospheric demand for water is very high with daily potential evaporation varying from 3 to 8 mm/day (Mutiga et al. 2010). Gichuki et al. (1998) observed that only 3% of the basin (mountain moorlands) receives a water surplus while 50% experiences water deficits of more than 1,000 mm/year. This is because potential evapotranspiration in the basin increases with decreasing altitude while precipitation decreases with decreasing altitude (Wiesmann et al. 2000; Mutiga et al. 2010) implying that water deficits increase with decreasing altitude away from the mountain. Moreover, if the amount of water abstracted for various uses is considered, the situation becomes worse thus water use conflicts become more critical downstream of the basin. Conflicts on the distribution of the available water resources are common here, mostly because of the spatial variation of the availability resulting from climatic conditions in addition to increased demand.
Large scale horticulture farms and an increasing number of small scale farms upstream of the basin all using water for irrigation contributes to further increase in water shortages particularly for the downstream users. Pastoralists, who occupy the lower parts of the basin, also use the river water for their domestic use and for watering their animals. About 60% to 95% of the available river water in the upper reaches of the basin is abstracted during the dry season with up to 90% of the total abstraction being illegal, resulting in decreased river flows in the lowlands (Kiteme and Gikonyo 2002; Notter et al. 2007). This has negatively affected downstream
populations as well as wildlife and the associated tourism activities leading to water use conflicts among different water resource users.
Population growth is estimated at 5% to 6% per annum (Kiteme and Gikonyo 2002), mostly as a result of immigration from the communal areas in search of jobs in the horticulture farms or from the neighbouring agricultural potential districts through land sub-divisions. In the upper Ewaso Ng’iro, the population averages 212 people per km2 in the highlands, 60 people per square kilometer in the midland and 24/km2 in the lowlands due to differences in land use (Ngigi 2006).