Impacts of Climate Change on Groundwater Recharge & Discharge in Water Scarce Region: A Case Study of the Ubar/ Shisr Agricultural Region of Oman.

Abstract

<p> </p><p>*Correspondence: alaba@squ.edu.om</p><p><strong>Abstract: </strong>The primary objective of this study was to quantify the impacts of climate change on groundwater recharge using the 3D numerical-based HydroGeoSphere (HGS) model in the Ubar/ Shisr Agricultural region in South of Oman. This region has multi-million US dollar irrigated agriculture project purposely developed for the food security of the country. Excessive abstraction of groundwater for irrigation use (using the center pivot irrigation system) has contributed to the “drying-up” of several groundwater wells located in this area. Therefore, there is an urgent need to characterize the long-term sustainability of this agricultural project under a changing climate. HGS model was calibrated on both steady and transient states using selected monitoring wells located within the study area (approximately 980-km<sup>2</sup>). The coefficient of determination (R<sup>2</sup>) for the steady-state performance was 0.93 while the transient state performances correctly reproduced the seasonality for each monitoring well. A transient-based calibrated version of the HGS model, using 30-year historical observations (1980-2018) was termed “Reference” while model configurations were developed for the immediate climatic projection (period: 2020 – 2039) based on two Representative Concentration Pathways (RCP): - RPC4.5 and RCP8.5 extracted from the World Bank Knowledge portal. These two configured models (scenarios) were evaluated for monthly transient simulations (2020-2039). From the total hydraulic head (THH) fluctuations standpoint, there were reductions when compared with “Reference” for all the scenarios with up to 20% THH reductions for groundwater well levels under persistent seasonal agricultural activities. This study is very important in quantifying the trade-offs and synergies involved between sustainable water management and food security initiatives, especially for an arid climate.</p><p>Keywords: groundwater recharge; climate change, hydrogeologic modeling; Sultanate of Oman</p>