Comparative Evaluation Of Shallow Groundwater Dynamics Of Becho And Koka Plains Upper Awash Basin Central Ethiopia

The target area (Koka and Becho plains) are situated in the upper reach of the AwashrnRiver basin, geographically, Koka plain located between 38.750 – 39.120E and 8.380 –rn8.760N and Becho plain is located between 38.190 – 38.610E and 8.540 – 9000’N. Thernmain objective of this work is evaluating shallow ground water dynamics of Becho andrnKoka plains comparatively from water level fluctuation of monitoring wells and rechargernestimation of the two plains by Water balance method. The shallow groundwater flowrndirection is identified from water table contour map and cross sectional map of wellrnlithology in the target area. The water table contour map indicates that the groundwaterrnflow direction of Becho plain is toward the Awash River from the recharge area.rnHowever, in Koka plain the groundwater flows toward Koka reservoir by the effect ofrntopography and geological structures. The water balance method give recharge of thernBecho plain is 235.029mm/yr., this means 23.38% of annual precipitation was rechargedrnto groundwater and the recharge of Koka area is 22.2627mm/yrs., and i.e. only 2.65% ofrnthe annual precipitation is recharged to groundwater. The selected River gaging stationsrnfor baseflow separation are; Awash at Melka Kunture, Awash at Bello, Mojo at Mojornvillage and Mojo at Koka dam. Volume of baseflow, total volume and baseflow indexrnwere calculated from baseflow separation of the selected stations. The baseflow index ofrnAwash at Melka Kunture, Awash at Bello, Mojo at Mojo village and Mojo at Koka damrnare 0.65, 0.787, 0.18 and 0.343 respectively.rnThe index of base flow Calculated at Awash Bello and Awash at Melka Kunture wasrnmuch greater than the estimated BFI at Mojo village and Koka Dam; this implies that thernAwash river catchment has more stable flow regime and able to sustain river flow duringrnextensive dry period. Piezometers were used to monitor groundwater from Grofuturesrnproject. Based on their distance from the surface water and effect of irrigation, monitoringrnwells of the study area are grouped into four; (i) piezometers located far from a surfacernwatercourse and outside any irrigated area, (ii) piezometers close to a surfacernwatercourse but outside any irrigated area, (iii) piezometers located far from anyrnsurface watercourse but located in irrigated areas and finally, (iv) piezometers close torna surface watercourse and located in irrigated areas. The piezometer data indicatesrnthat the temperature of the shallow groundwater is more or less the same with that ofrnsurface temperature and has an inverse relationship with water level.

Get Full Work

Report copyright infringement or plagiarism