Projecting water availability within the Western Aquifer Basin: WEAP-MODFLOW Coupling (Briefing 2.6)

Abstract

Groundwater is one of the main sources of fresh water in the Middle East, with millions of cubic meters of water pumped from aquifers each year. The annual abstraction rates are increasing constantly in order to meet the rising demand, driven by an increasing population and climate change. As a result of these variables, over-pumping may occur, leading to unsustainable resource use. In order to inform management approaches, we quantified such effects for trans-boundary groundwater, namely the Western Aquifer Basin (WAB), using the Water Evaluation and Planning tool (WEAP) coupled to the groundwater model MODFLOW. The keyfindings were that the aquifer’s inflow is dominated by rainfall over the replenishment areas with an annual average of 373 MCM/yr during the period 1951-2007. The annual recharge is directly correlated with monthly rainfall, where the largest recharge occurred whenever the most annual rainfall is received between November and February. Under current climate conditions, two pumping scenarios could be considered: a) 85% of the aquifer yield (Constant pumping: 310 MCM/yr) and b) 85% of the (7-year) moving average of the estimated recharge (Avg. 328 MCM/yr). Under climate change and reduced recharge conditions, two actions could be taken: a) Immediate Action: reducing the average pumping rate to 221 MCM/yr and b) Stepwise Action: limiting the pumping rate to the 7-year moving average (average pumping rate: 254 MCM/yr).