Conjunctive use of groundwater and surface water resources with aquifer recharge by treated wastewater: evaluation of management scenarios in the Zarqa River Basin, Jordan

We study the effects of treated wastewater (TWW) discharge into the Zarqa River in Jordan and the underlying unconfined limestone Hummar Aquifer. The main objectives were to develop a conceptual model of the aquifer, to gain better understanding of water dynamics in the basin and to investigate different management scenarios of conjunctive use of groundwater and surface water. The model using MODFLOW 2005 code was developed over a selected part of the Zarqa River Valley of area 387 km², including the As Samra wastewater treatment plant (WWTP). The annual TWW discharge of 110 million m³ significantly augments the groundwater storage and allows for expansion of agricultural practices in the area, providing large reserve during dry spells. On average, the water table rises by 29 m following the inception of the WWTP. The results indicate that the aquifer will be able to accommodate extra discharge of TWW when the plant will operate at full capacity as planned and upon increase in the abstraction rate for irrigation by 30 %, based on farming land availability. This abstraction will result in an average water table drawdown of 0.3 m. Because around 20 % of the discharged TWW only reach the aquifer, we recommend direct use of river water, especially during drought periods to reduce the stress on the aquifer storage and its associated depletion. The simulated conjunctive use and MAR utilizing both TWW and the groundwater present a salient case study of intricate management of water resources in arid zone. Augmentation of groundwater resources by both banking of the TWW and management of water use will allow more agricultural activities that would result in a better income for farming communities and social stability in the MENA region, where water is a precious commodity.