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SWAT based hydrological assessment and characterization of Lake Ziway sub-watersheds, Ethiopia

Desta, Hayal, Lemma, Brook
Journal of hydrology 2017 v.13 pp. 122-137
Soil and Water Assessment Tool model, agricultural development, aquifers, base flow, evapotranspiration, human population, humans, irrigation, lakes, livelihood, rivers, runoff, subwatersheds, vegetation types, water balance, Ethiopia
Lake Ziway watershed, Ethiopia.Lake Ziway and its watershed play a significant role in supporting the livelihoods of people in the region. However, the study region is currently under heavy human pressures mainly associated with the ever increasing of human population and the subsequent intensification of agricultural development activities. The present study therefore aims at quantifying and comparing water balance components, feeder rivers’ discharge and evapotranspiration (ET) in the study region using SWAT (Soil and Water Assessment Tool) model. Flow data from 1988 to 2000 and from 2001 to 2013 were used for model calibration and validation periods respectively.Results show that infiltration, surface runoff, base flow and aquifer recharge were large in Katar sub-watershed while ET and lateral flow were large in Meki sub-watershed. However, surface and base flows showed decreasing trends in both sub-watersheds, yet Katar sub-watershed showed major contribution of water to Lake Ziway. The model estimated Lake Ziway and its watershed mean annual ETs as 1920mm and 674mm respectively, but plantation showed more ET than other land cover types in the watershed. If the current trends in irrigation development continue in the region, it is suspected that Katar and Meki Rivers are likely to cease to exist after seven decades, and so is then Lake Ziway to dry out.