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

- Lake Ziway sub-watersheds have been assessed and characterized.
- The two sub-watersheds do not equally contribute water to Lake Ziway.
- The long-term mean annual runoff coefficient shows decreasing trends.
- 64-72% of the mean annual precipitation evaporates while 18-24% ends up in Lake Ziway.
- Evapotranspiration at Lake Ziway has been estimated.

Study regionLake Ziway watershed, Ethiopia.Study focusLake 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.New hydrological insights for the regionResults 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 1920 mm and 674 mm 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.