GROUNDWATER FLOW MODELING AND ASSESSING THE IMPACT OF FERTILIZERS ON GROUNDWATER QUALITY: THE CASE OF HORMAT-GOLINA SUB-BASIN, AWASH BASIN, ETHIOPIA

Abstract

Groundwater is the source of water supply for different purposes including domestic, irrigation and depending on its capacity, it is suitable for industrial activities. Groundwater in many parts of the world is under risk because of increasing demands, mismanagement and contamination. All previous studies had not been explored the predicted groundwater flow dynamics in relation to climate change and anthropogenic stress, but this study has developed on the groundwater fluctuation with respect to human pressure and climate change. Visual mod flow flex 5.1 was used for simulating the groundwater flow in response to different stress periods. Groundwater flow and transport modeling in this Sub-basin have provided information about groundwater quantity as well as the quality aspect for decision makers about the groundwater accessibility. The initial head measured values in before and after irrigation season has varied to a maximum of 0.8 m. The groundwater head level in before and after irrigation season was varied from 9.3 m to 8.26 m in the Southern boundary and from 41.5 m to 38.83 m in Northwestern boundary of the Sub-basin respectively. While the predicted groundwater head and drawdown of increased pumping rate with decreased recharge rate scenario was magnify the bad effects in the Sub basin. The maximum depth of 0.27 m and 2.6 m drawdown was found in before and after irrigated season around the pumped wells respectively. The increased pumping rate with decreased recharge rate was replied to the groundwater head at the end of 2021has decreased by 2.81 min the Northwestern boundary of the Sub-basin as compared as using constant pumping rate with constant recharge rate. While decreased pumping rate with increased recharge rate was replied to the groundwater head at the end of 2021has increased by 2.23 m in the Northwestern boundary of the Sub-basin as compared as using constant pumping rate. The impacts of climate change and human pressure on groundwater have been the greatest threats in those supply wells. Decreased in pumping rate with increased recharge rate has accomplished to restore and protect the groundwater resources which is the best option for groundwater restoration and monitoring. Anthropogenic pressures including the application of fertilizers were a considerable cause of degraded groundwater quality in relation to Nitrate and Phosphate concentration with series of time. The groundwater quality has deteriorating with the applied Urea and DAP fertilizes in the selected wells of Hormat-Golina Sub-basin. Farmers have encouraged using practices that minimize the risk of groundwater pollution by carefully controlling and timing of the use of fertilizers to avoid over application.