Jacobs Journal of Environmental Sciences

Estimation of Spatially Distributed Groundwater Recharge in Modjo River Catchment, Awash Basin, Central Ethiopia

*Negash Bedaso
Department Of Agricultural Sciences, Sinana Agricultural Research Center, Ethiopia

*Corresponding Author:
Negash Bedaso
Department Of Agricultural Sciences, Sinana Agricultural Research Center, Ethiopia
Email:baatii2004@gmail.com

Published on: 2019-07-05

Abstract

Sustainable groundwater management requires knowledge of recharge. Recharge is an important factor in evaluating groundwater resources but difficult to quantify. Hence estimation of groundwater recharge requires modeling of the interaction between all the important processes in the hydrological cycle. In this study the long term seasonal and annual groundwater recharge of Modjo river catchment (2,202 km2) was estimated and recharge map were developed through a grid based physically distributed model, WetSpass. Long term average hydro-meteorological data and spatial pattern of watershed physical grid maps were used as main inputs for the model. All input maps for the model were prepared using ArcGIS 10.2 spatial analysis tool. Soil, land use and runoff coefficient parameters in data base files, season independent gridded base map of topography, slope, and soil were used in the model; whereas precipitation, potential evapotranspiration, temperature, wind speed, groundwater depth and land use map were prepared and employed by the model, in ASCII grid format of 120m cell size with 647 numbers of row and 425 numbers of columns for both winter and summer seasons. From the result, it is found that the long-term temporal and spatial average annual rainfall of 933 mm was distributed as: surface runoff of 164 mm (17.6%), evapotranspiration of 686 mm (73.5%), and recharge of 83 mm (8.9%). Thus an average of 183Mm3 of groundwater will be recharged per year or 5,802 liter/second from the catchment area. Flood control dams (artificial recharge) practice was recommended in this study area to harvest the excess water (simulated annual surface runoff of 361Mm3) which is helpful in one way to reduce soil erosion and in the other way to enhance more recharge to groundwater.

Keywords

Groundwater, Flood control dams, Modjo river, Evapotranspiration, Reduce soil erosion

Introduction

Groundwater is a critical source of fresh water throughout the world. It has become an important and dependable source of water supplies in all climatic regions including both urban and rural areas of developed and developing countries. Comprehensive statistics on groundwater abstraction and use are not available, but it is estimated that more than 1.5 billion people worldwide rely on groundwater for potable water. Other than water stored in ice caps and glaciers, groundwater accounts for approximately 97% of fresh water on Earth. As the world population continues to grow, more people will come to rely on groundwater sources, particularly in arid and semiarid areas. Long-term availability of groundwater supplies for burgeoning populations can be ensured only if effective management schemes are developed and put into practice. Hence, knowledge of groundwater resource potential is important for its management and sustainable use, because the optimal exploitation of the groundwater requires previous knowledge on the aquifers potential.