Numerical modeling of groundwater flow system in the Modjo River catchment, Central Ethiopia
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ORIGINAL ARTICLE
Numerical modeling of groundwater flow system in the Modjo River catchment, Central Ethiopia Ashebir Gebere1 · Nafyad Serre Kawo2 · Shankar Karuppannan3 · Aster Tesfaye Hordofa4 · Paolo Paron5 Received: 13 May 2020 / Accepted: 3 November 2020 © Springer Nature Switzerland AG 2020
Abstract In recent years, groundwater pumping has increased for domestic, industrial, and irrigation use in the Modjo River catchment. Understanding changes in groundwater levels is crucial for the sustainable use and management of aquifer. This study investigates the groundwater flow system and aquifer response to increased groundwater pumping and reduced recharge using the calibrated steady-state groundwater level and budget as a baseline. The groundwater flow corresponds to the direction of the Modjo River flow, following the topographic gradient. The simulated groundwater budget indicates that recharge from precipitation and surface water (crater lakes and river) are the main inflow to the aquifer, while the outflow from the aquifer is due to groundwater pumping, natural subsurface flow to downstream area, and base flow. Analysis of the different scenarios reveals that both an increase in well pumping and a decline in recharge resulted in a decrease of the base flow to Bishoftu crater lakes and Mojo River, and to the downstream subsurface flow. In conclusion, increasing human demand for groundwater and variability in recharge will affect groundwater contribution to surface water and ultimately will be a source of concern in the future for both environmental flows and groundwater management. Keywords Groundwater recharge · MODFLOW · Modjo River · Central Ethiopia
Introduction Groundwater has increasingly been used to meet water demand for agriculture and other domestic water supplies (Guppy et al. 2018). According to Siebert et al. (2010), about 70% of pumped groundwater is used for irrigation worldwide. In recent decades, groundwater pumping for irrigation has increased (Wada et al. 2012). Groundwater pumping * Nafyad Serre Kawo [email protected] 1
Ethiopian Construction Design and Supervision Works Corporation, Water and Energy Design Supervision Works Sector, Addis Ababa, Ethiopia
2
School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68583‑0996, USA
3
Department of Applied Geology, School of Applied Natural Science, Adama Science and Technology University, Adama, Ethiopia
4
Africa Centre of Excellence for Water Management, Addis Ababa University, Addis Ababa, Ethiopia
5
IHE Delft, Institute for Water Education, Westvest7 2611 AX, Delft, Netherlands
reduces groundwater storage and base flow to surface water (Gleeson and Richter 2017). Many researchers have used MODFLOW, a simulation program for groundwater flow, to investigate groundwater flow and dynamics in various parts of the world (Namaghi et al. 2015; Khadri and Pande 2016; Lachaal and Gana 2016; Bushira et al. 2017; Prasad and Rao 2018; Azerf and Bushira 2020), the impact of intensive groundwater withd
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