HGS RESEARCH HIGHLIGHT – Managing climate change impacts on the Western Mountain Aquifer: Implications for Mediterranean karst groundwater resources
Bresinsky, L., Kordilla, J., Hector, T., Engelhardt, I., Livshitz, Y., & Sauter, M. (2023). Managing climate change impacts on the Western Mountain Aquifer: Implications for Mediterranean karst groundwater resources. In Journal of Hydrology X (p. 100153). Elsevier BV. https://doi.org/10.1016/j.hydroa.2023.100153
“To assess the combined effects of climate change and groundwater demand scenarios on water resources, we employ a serial arrangement of two models, (1) a semi-distributed soil-epikarst water balance model (SEWB) and (2) a variably saturated dual-continuum groundwater flow model [HydroGeoSphere]”
Fig. 1. Location and extent of the Western Mountain Aquifer (WMA) and the adjacent Eastern Mountain Aquifer (EMA) catchment (Digital elevation data obtained from the data set SRTM 1 Arc-Second Global). The red line wells serve for the aquifer management, representing the northern, central and southern part of the aquifer (Amir and Livshitz, 2023).
A new study investigates the impact of climate change on water availability within a 9000 sqkm karstic aquifer in Israel and the West Bank, and couples HydroGeoSphere to a soil-epikarst water balance model. The HydroGeoSphere model in this study utilizes the dual-domain capabilities to investigate infiltration and precipitation partitioning based on regionally-downscaled climate projections including precipitation and potential evapotranspiration rates, to the year 2070. In addition to incorporating these regionally downscaled climate projections (IPCC RCP4.5 climate change scenario), the authors also incorporate three distinct groundwater demand scenarios into the forward looking forecasts of water availability.
“The results indicate that long-term average groundwater recharge volumes will decrease by circa 5-10% compared to the reduction in average precipitation by 30%. The mitigated impact on recharge is an effect of the pronounced heterogeneity of karst groundwater flow (i.e., preferential recharge along with karst dissolution features) and increased intensity of individual rainfall events[...]. However, despite the comparatively moderate decrease in recharge, the length and severity of consecutive drought years with low recharge values are likely to increase.”
This study builds on earlier HydroGeoSphere modelling efforts for the Western Mountain Aquifer, which you can read about here: https://www.aquanty.com/blog/hgs-research-highlight-variably-saturated-dual-permeability-flow-modeling-western-mountain-aquifer-israel
Fig. 9. The average annual recharge depth change until 2041-2070 compared to the reference period 1981-2010. Spatial reference is provided in Fig. 1.
Abstract:
Many studies highlight the decrease in precipitation due to climate change in the Mediterranean region, making it a prominent hotspot. This study examines the combined impacts of climate change and three groundwater demand scenarios on the water resources of the Western Mountain Aquifer (WMA) in Israel and the West Bank. While commonly used methods for quantifying groundwater recharge and water resources rely on regression models, it is important to acknowledge their limitations when assessing climate change impacts. Regression models and other data-driven approaches are effective within observed variability but may lack predictive power when extrapolated to conditions beyond historical fluctuations. A comprehensive assessment requires distributed process-based numerical models incorporating a broader range of relevant physical flow processes and, ideally, ensemble model projections. In this study, we simulate the dynamics of dual-domain infiltration and precipitation partitioning using a HydroGeoSphere (HGS) model for variably saturated water flow coupled to a soil-epikarst water balance model in the WMA. The model input includes downscaled high-resolution climate projections until 2070 based on the IPCC RCP4.5 scenario. The results reveal a 5% to 10% decrease in long-term average groundwater recharge compared to a 30% reduction in average precipitation. The heterogeneity of karstic flow and increased intensity of individual rainfall events contribute to this mitigated impact on groundwater recharge, underscoring the importance of spatiotemporally resolved climate models with daily precipitation data. However, despite the moderate decrease in recharge, the study highlights the increasing length and severity of consecutive drought years with low recharge values. It emphasizes the need to adjust current management practices to climate change, as freshwater demand is expected to rise during these periods. Additionally, the study examines the emergence of hydrogeological droughts and their propagation from the surface to the groundwater. The results suggest that the 48-month standardized precipitation index (SPI-48) is a suitable indicator for hydrogeological drought emergence due to reduced groundwater recharge.
Fig. 10. Impact of the IPCC RCP4.5 climate change scenario and the RNC, B, and RRI groundwater demand scenarios on (a) spring discharge at the Taninim spring and the hydraulic head in the (b) northern, (c) central, and (d) southern coastal plain. The RRI simulation was discontinued in 2042 due to dry pumping wells.