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SWAT-based LULC impacts on groundwater recharge

A B

D C

Figure 1. Maps depicting the location of the study area: (A) Ethiopia; (B) Awash river basin; and (C) the
study site (Dire Dawa watershed). Maps aquired from https://www.ethiogis-mapserver.org/; https://search.
earthdata.nasa.gov/

September, reaching up to 450 mm. The dry season Adigrat sandstone, Hamaneli limestone, and Amba
spans from November to February, resulting in strong Aradam sandstone. These units, together with the
seasonal differences in water resources. The weather is Tertiary volcanic basalts from the Afar volcanic series
usually mild (9.8–20.9°C), and the two warmest months and the recent Quaternary alluvial deposits, form the
are February and March. Under this climate, the cyclic main hydrogeological framework. The Precambrian
changes in rainfall play a crucial role in shaping the basement rocks are highly weathered and fractured,
runoff and groundwater recharge patterns. During the creating secondary porosity; however, the porous
rainy season, the land experiences high runoff, resulting sandstones and limestones serve as the region’s primary
in water scarcity. The landscape is characterized by a aquifers. The volcanic basalts contribute to groundwater
diverse mix of plateaus, escarpments, and valleys, all of flow predominantly through fractures and weathered
which are shaped by volcanic activity. With elevations zones. The Quaternary alluvial sediments, particularly
ranging from 1,014 m to 2,408 m, the area encompasses in the lower-elevation areas within the Afar Depression,
steep mountains, flat plains, and fault-induced are significant groundwater reservoirs.
landforms, including half-grabens and horsts. These The groundwater flow in the area is strongly influenced
landforms directly impact how water moves through by major fault systems associated with the East African
the region. The steep slopes and rocky surfaces result Rift and the Afar Depression tectonics, creating zones
in high runoff and limited water retention, particularly of enhanced permeability and acting as preferential flow
during intense rainfall. pathways. The hydrogeology of the Dire Dawa watershed
is shaped by the complex interaction of geological
2.1.2. Geological and hydrogeological setting formations, tectonic activity, and the region’s varied
The geology of the Dire Dawa region is characterized topography. Groundwater occurs mainly in two primary
by ancient Precambrian basement rocks overlain systems: the rugged escarpment and the adjacent plains.
by Mesozoic sedimentary formations, including the The escarpment features a complex geology composed

Volume 22 Issue 6 (2025) 105 doi: 10.36922/AJWEP025180139