Abstract
As opposed to most of the other closed basin type rift valley lakes in Ethiopia, Lake Basaka
is found to be expanding at an alarming rate. Different studies indicated that the expansion of the lake
is challenging the socio-economics and environment of the region significantly. This study result and
previous reports indicated that the lake’s expansion is mostly due to the increased groundwater (GW)
flux to the lake. GW flux accounts for about 56% of the total inflow in recent periods (post 2000) and
is found to be the dominant factor for the hydrodynamics and existence of the lake. The analysis of
the drainage network for the area indicates the existence of a huge recharge area on the western and
upstream side of the catchment. This catchment has no surface outlet; hence most of the incoming
surface runoff recharges the GW system. The recharge area is the main source of GW flux to the lake.
In addition to this, the likely sources/causes of GW flux to the lake could be: (i) an increase of GW
recharge following the establishment of irrigation schemes in the region; (ii) subsurface inflow from
far away due to rift system influence, and (iii) lake neotectonism. Overall, the lake’s expansion has
damaging effect to the region, owing to its poor water quality; hence the identification of the real
causes of GW flux and mitigation measures are very important for sustainable lake management.
Therefore a comprehensive and detailed investigation of the parameters related to GW flux and the
interaction of the lake with the GW system of the area is highly recommended.