Estimating Surface Water Inflow into Lake Lego, a Closed Basin in Northeastern Ethiopia
Background: A surface water hydrologic characteristic of closed drainage basin of Lake Lego is not yet well-known amid constant reductions in depth and area over the last 72 years.
Objective: Predicting the amount of surface water inflow into the terminal Lake Lego and evaluating its impacts on Lake Morphometric parameters.
Materials and Methods: Weather (daily precipitation, minimum and maximum temperature), geospatial image (digital elevation model and land use and cover), physical and chemical soil characteristics and existing land management data were used. Soil and Water Assessment Tool and ArcGIS computer models were used for the analyses.
Results: The basin generated 304.3 mm of average annual surface runoff while the contribution of the baseflow was only 91.8 mm of water. In aggregate, the basin contributed an average surface water inflow of 21,984,159 m3 y–1 during the simulation period. The trend in precipitation was insignificant for the duration of analysis while the lake water volume has been reducing at the rate of 2,817,680 m3 y–1 for the same period. The declining lake water was affecting Lake Morphometric parameters. The depth, surface area, and volume of the lake were shrinking at the rate of 0.128 m y–1, 3.8 ha y–1 and 0.29% y–1, respectively. The water residence time of the lake was estimated as 45 years.
Conclusion: The results of the study revealed the contribution of surface water inflow into the lake and its impacts on depth, area and volume of the lake. The findings provide valuable information for policy development and decision making for implementation of integrated water resource management in the watershed and enhance streamflow into the lake.