Analyzing the extents of Basaka Lake expansion and soil and water quality status of Matahara irrigation scheme, Awash Basin (Ethiopia)

Basaka Lake, unlike most of the other terminal Lakes in Main Ethiopian Rift, is expanding at substantial rate. Its expansion is particular concern owing to its poor water quality. Different studies were conducted on Basaka Lake, but none of them addressed the complex Lake water balance components at different hydrologic periods and come up with decisive backgrounds for the cause and its potential damaging effect. The current study attempted to analyze the expansion of Basaka Lake since 1960s from Landsat images and other ancillary data and then assess the potential cause through conceptual water balance modeling. The work required combined use of remote sensing, GIS and hydrologic models. The decadal land use-land cover change (LUCC) was mapped and its effects on the hydrologic processes (runoff, soil loss and sedimentation) of the lake catchment were estimated. A conceptual Lake water balance model was systematically formulated, solved, calibrated and validated. Groundwater flux model was then developed as function of the other water balance components. Generally, a tremendous expansion of Basaka Lake, degradation of soil and water quality status at Matahara Sugar Estate (MSE), rapid LUCC and the resulting changes in the regimes of hydrologic processes in the Lake catchment are observed. These problems revealed the need for urgent mitigation measures. Therefore, sustainable Lake management measures that could minimize its potential environmental threats are suggested. Moreover, correcting measures that could reduce, if not prevented, the potential impacts of waterlogging and its allied problems at MSE are suggested. (author)