School of Earth Sciences, Bahir Dar University, Bahir Dar, Ethiopia; Laboratory for Applied Geology and Hydrogeology, Department of Geology, Ghent University, Gent, Belgium.
School of Earth Sciences, Bahir Dar University, Bahir Dar, Ethiopia; Laboratory for Applied Geology and Hydrogeology, Department of Geology, Ghent University, Gent, Belgium.
Sci Total Environ. 2020 Dec 15;748:142243. doi: 10.1016/j.scitotenv.2020.142243. Epub 2020 Sep 17.
Groundwater recharge estimation, aquifer response to meteorological variables, and evapotranspiration calculations have been performed on a semi-humid catchment, in northwestern Ethiopian plateau. The Soil Moisture Balance (SMB), WetSpass water balance model, Water Table Fluctuation (WTF), and Chloride Mass Balance (CMB) methods are applied to estimate the groundwater recharge. Accordingly, 431 mm, 462 mm, and 477 mm recharge amounts are estimated as mean annual value, respectively, using SMB, WetSpass, and CMB methods. Based on the WTF method, the annual recharge rates of the volcanic aquifers range from 157 mm to 760 mm. The SMB and WetSpass methods are less effective for the flat physiographic area, where the recharge rate is storage controlled rather than precipitation amount. The calculated high recharge for maintain-front aquifers using WTF is attributed to extra rising due to lateral groundwater flow, which restricts the reliability of the method for such aquifer geometries. High groundwater level rising rate (121 mm/day) has been observed for the steeply sloping, low rates (11 mm/day) for the flat floodplain, and intermediate rate (52 mm/day) for the gently sloping volcanic aquifers. Similarly, receding rates of 3.18 mm/day were found for the steeply sloping, 0.40 mm/day for the floodplain, and 1.14 mm/day for the gentle sloping aquifers. The recession, in all of the topographies, is happening with second-order polynomial decay function. A strong connection between the shallow and deep groundwater aquifers is noted. Storage change in the relatively deeper volcanic aquifers is due to vertical groundwater flow from the overlying alluvial aquifer. This indicates that the recharge mechanism is local, and may be the reason for the low aquifer productivity of the Dangila wellfield. Diurnal water table fluctuation is detrended from the receding trend of the dry period, and evapotranspiration from the groundwater is estimated at 28% of total ET.
已在埃塞俄比亚高原西北部的一个半湿润流域进行了地下水补给估算、含水层对气象变量的响应以及蒸散量计算。应用土壤水分平衡 (SMB)、WetSpass 水量平衡模型、地下水位波动 (WTF) 和氯化物质量平衡 (CMB) 方法估算地下水补给量。根据 WTF 方法，火山含水层的年补给率范围为 157-760mm。对于地形平坦的地区，SMB 和 WetSpass 方法的效果较差，因为该地区的补给率受储存控制，而不是降水总量。WTF 方法计算的前缘补给量较高，是由于侧向地下水流动引起的额外上升，这限制了该方法对这种含水层几何形状的可靠性。陡坡区地下水位上升速度较高（121mm/天），平原漫滩区较低（11mm/天），火山含水层较缓坡区居中（52mm/天）。同样，陡坡区的退水速度为 3.18mm/天，平原区为 0.40mm/天，缓坡区为 1.14mm/天。所有地形都呈二阶多项式衰减函数。浅部和深部地下水含水层之间存在很强的联系。相对较深的火山含水层中的储层变化是由于上覆冲积含水层的垂直地下水流动所致。这表明补给机制是局部的，这可能是 Dangila 井水场含水层生产力较低的原因。地下水位日波动是从干旱期的退潮趋势中减去的，从地下水中估算的蒸发量占总蒸发量的 28%。
