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.

ABSTRACT:Actual Evapotranspiration (ET a ) is one of the most useful indicators to explain whether the water is being used as "intended". ET a variations, both in space and time and from different land use types are seen to be highly indicative for the adequacy, reliability and equity in water use; the knowledge of these terms is essential for judicious water resources management. Unfortunately, ET a estimation under actual field conditions is still a big challenge to both scientists and water managers. The complexity associated with the estimation of ET a has lead to the development of various methodological approaches for estimating it over time.During the last two to three decades, significant progress has been made to estimate actual evapotranspiration using satellite remote sensing These methods provide a powerful means to compute ET a from pixel to the entire basin scale. In this study, Surface Energy Balance Algorithm for Land (SEBAL) was used to compute a complete radiation and energy balance along with the resistances for momentum, heat and water vapour transport for each pixel and then applied to assess the ET a at the basin scale and subsequently carryout a simple water balance for the basin. This was done for the Upper Ewaso Ng'iro North River Basin, in Kenya. Landcover/ landuse for 2000, 2003 and 2006 were assessed and compared with ET a for the same periods and a significant correlation was established. The ET a values obtained for the three time periods was used to analyse water use patterns across the basin thus giving insights on the underlying factors impacting on the water resources of the basin and hence facilitating the formulation of appropriate water resources management strategies for the basin.

Use and retention of river water in African highlands deprive communities in arid lowlands of their benefits. This paper reviews information on water use in the Ewaso Ng'iro catchment, Kenya, to evaluate the effects of upstream abstraction on the Lorian Swamp, a wetland used by pastoralists downstream. We first assess the abstractions and demands for water upstream and the river water supplies at the upper and the lower end of the Lorian Swamp. Further analysis of 12 years of monthly SPOT-VEGETATION satellite imagery reveals higher NDVI (Normalized Differential Vegetation Index) values in the swamp than nearby rainfed areas, with the difference in NDVI between the two positively related to river water discharged into the swamp. The paper next reviews the benefits derived from water entering the swamp and the vulnerability to abstractions for three categories of water: (i) the surface water used for drinking and sanitation; (ii) the surface water that supports forage production; and (iii) the water that recharges the Merti Aquifer. Our results suggest that benefits from surface water for domestic use and forage production are vulnerable to abstractions upstream whereas the benefits from the aquifer, with significant fossil water, are likely to be affected in the long run, but not the short term. OPEN ACCESSWater 2012, 4 1010

Changes in land cover and land use can lead to significant impacts to hydrology by affecting the amount of runoff, soil moisture and groundwater recharge over a range of temporal and spatial scales. However, hydrologic effects of these changes are still an unknown at watershed scale. Moreover, predicting the effects of land cover/use and climate change on hydrological cycle has remained a major challenge. This is because of the complexity and uncertainty of future climate changes making it difficult to predict the consequences. It is against this backdrop that, for sustainable water resources management, assessment of the impacts of land cover/use change on hydrological regime at all scales becomes critical. During this study, we applied the SWAT model to assess the impacts of area hydrology between baseline and alternative scenario (upscaling of rainwater harvesting technologies). Specifically, our overall objective was to quantitatively evaluate the effects of land use changes on watershed hydrology in the upper Ewaso Ng'iro North basin in Kenya. This was achieved by estimating hydrological responses under historical land use scenarios obtained from the multi-temporal satellite imageries of 1987, 1995 and 2003. The model performance was found to be relatively good (Nash and Sutcliffe efficient of 70%). Stream flow analysis was carried out for different parts of the basin to understand its hydrological responses, especially, the behavior of base flow. The results show a decrease in base flow during 1987–2003 period with decreasing forest, bush and grass covers, which can be attributed to poor natural vegetation emanating mainly from overgrazing and deforestation for agricultural activities. In conclusion, the study clearly shows that, assessment of hydrologic effects of land use changes is critical for a sustainable water resources planning and management of the basin

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