Abstract. Some of the most valued natural and cultural landscapes on Earth lie in river basins that are poorly gauged and have incomplete historical climate and runoff records. The Mara River Basin of East Africa is such a basin. It hosts the internationally renowned Mara-Serengeti landscape as well as a rich mixture of indigenous cultures. The Mara River is the sole source of surface water to the landscape during the dry season and periods of drought. During recent years, the flow of the Mara River has become increasingly erratic, especially in the upper reaches, and resource managers are hampered by a lack of understanding of the relative influence of different sources of flow alteration. Uncertainties about the impacts of future climate change compound the challenges. We applied the Soil Water Assessment Tool (SWAT) to investigate the response of the headwater hydrology of the Mara River to scenarios of continued land use change and projected climate change. Under the data-scarce conditions of the basin, model performance was improved using satellite-based estimated rainfall data, which may also improve the usefulness of runoff models in other parts of East Africa. The results of the analysis indicate that any further conversion of forests to agriculture and grassland in the basin headwaters is likely to reduce dry season flows and increase peak flows, leading to greater water scarcity at critical times of the year and exacerbating erosion on hillslopes. Most climate change projections for the region call for modest and seasonally variable increases in precipitation (5-10 %)Correspondence to: L. M. Mango (lm mango@yahoo.com) accompanied by increases in temperature (2.5-3.5 • C). Simulated runoff responses to climate change scenarios were non-linear and suggest the basin is highly vulnerable under low (−3 %) and high (+25 %) extremes of projected precipitation changes, but under median projections (+7 %) there is little impact on annual water yields or mean discharge. Modest increases in precipitation are partitioned largely to increased evapotranspiration. Overall, model results support the existing efforts of Mara water resource managers to protect headwater forests and indicate that additional emphasis should be placed on improving land management practices that enhance infiltration and aquifer recharge as part of a wider program of climate change adaptation.

Mara is a transboundary river located in Kenya and Tanzania and considered to be an important life line to the inhabitants of the Mara-Serengeti ecosystem. It is also a source of water for domestic water supply, irrigation, livestock and wildlife. The alarming increase of water demand as well as the decline in the river flow in recent years has been a major challenge for water resource managers and stakeholders. This has necessitated the knowledge of the available water resources in the basin at different times of the year. Historical rainfall, minimum and maximum stream flows were analyzed. Inter and intra-annual variability of trends in streamflow are discussed. Landsat imagery was utilized in order to analyze the land use land cover in the upper Mara River basin. The semi-distributed hydrological model, Soil and Water Assessment Tool (SWAT) was used to model the basin water balance and understand the hydrologic effect of the recent land use changes from forest-to-agriculture. The results of this study provided the potential hydrological impacts of three land use change scenarios in the upper Mara River basin. It also adds to the existing literature and knowledge base with a view of promoting better land use management practices in the basin

Mango, Liya M., "Modeling the Effect of Land Use and Climate Change Scenarios on the Water Flux of the Upper Mara River Flow, Kenya" (2010 This study found that land use change scenarios resulted in more erratic discharge while climate change scenarios had a more predictable impact on the discharge and water balance components. The model results showed the flow was more sensitive to the rainfall changes than land use changes but land use changes reduce dry season flows which is a major problem in the basin. Deforestation increased the peak flows which translated to increased sediment loading in the Mara River.vii and will still be above the 1,000 m 3 per capita mark for a country to be considered water scarce. Tanzania's water resources however, are unevenly distributed with rainfall being highly variable both spatially and temporally with some areas receiving around 1,600mmof rainfall annually, while the central drier areas receive lower amounts of around 600 mm annual rainfall. This variability in the supply causes localized and intermittent water shortages that impede and limit various economic activities. The perceived water shortages can be attributed to inadequacies in the national capacity to manage water resources and to inadequate water storage capacity in terms of adequate reservoirs and artificial storage facilities. Establishment of these facilities would be a significant step in harnessing the available water resources and achieving water security in the country as a whole (URT, 2007). In terms of natural storage however, Tanzania is not lacking and has plenty in the form of perennial rivers, lakes and groundwater however, these sources are mostly inaccessible to the greater population. The lack of storage and harvesting 3 infrastructure greatly reduces the potential for and access to the country's plentiful supply of water resources. The impact of the climate variability, specifically rainfall and air temperature is also very critical in land cover where it directly influences the plant phenological cycles and in hydrology where rainfall events and dry spells are almost directly reflected in the hydrograph of a watershed. Impacts of temporal variability of rainfall and air temperature on vegetation production in the Mara-Serengeti ecosystem are examined in a study by Ogutu et al., (2007). 8Most of these studies however, have focused on the whole basin in its entirety which may be inaccurately represented owing to the spatial extent, variability in; topography, land use/ land cover, soils and climate. The tributaries of the Mara River are critical headwaters that warrant focused attention and this study seeks to determine the impact of land use changes in the upper reaches of the Mara River basin on the flow of the MaraRiver and the impact of rainfall and air temperature variability. This study also seeks to assess the use of radar rainfall estimates as a viable option to compliment or substitute rain gage data which, in many cases may not be reliable due to various constraints. This will be a...

With the flow of the Mara River becoming increasingly erratic especially in the upper reaches, attention has been directed to land use change as the major cause of this problem. The semi-distributed hydrological model Soil and Water Assessment Tool (SWAT) and Landsat imagery were utilized in the upper Mara River Basin in order to 1) map existing field scale land use practices in order to determine their impact 2) determine the impacts of land use change on water flux; and 3) determine the impacts of rainfall (0%, ±10% and ±20%) and air temperature variations (0% and +5%) based on the Intergovernmental Panel on Climate Change projections on the water flux of the upper Mara River. <br><br> This study found that the different scenarios impacted on the water balance components differently. Land use changes resulted in a slightly more erratic discharge while rainfall and air temperature changes had a more predictable impact on the discharge and water balance components. These findings demonstrate that the model results show the flow was more sensitive to the rainfall changes than land use changes. It was also shown that land use changes can reduce dry season flow which is the most important problem in the basin. The model shows also deforestation in the Mau Forest increased the peak flows which can also lead to high sediment loading in the Mara River. The effect of the land use and climate change scenarios on the sediment and water quality of the river needs a thorough understanding of the sediment transport processes in addition to observed sediment and water quality data for validation of modeling results