Using electrical imaging for assessing suitability of reclaimed water recharge at Begur, Spain

Groundwater is increasingly being used for water supply; however, the present social demand is not only to detect new groundwater resources but also to protect them. Moreover, reclaimed water is also a valued non-conventional resource. Both statements are especially true in arid and semi-arid areas where water is scarce, but also in the Mediterranean countries because of the wide rainfall irregularity. When trying to perform an integrated management of water resources, groundwater volumes can be increased by reusing reclaimed water for recharge. Surface spreading is the simplest, oldest, and most widely applied method of artificial recharge. Wherever it goes, water remains in some part of the hydrologic cycle, but what is really desired when discharging or reusing wastewater is to prevent the effluent — or more correctly, the pollutants it contains — from causing water quality and public health concerns. When recharging with reclaimed effluents, to ensure an effective percolation through the soil and an adequate treatment of the effluent, the structure and properties of the vadose zone must be understood in detail. One of the easiest and cost-effective techniques for producing a large amount of information on aquifer geometry and subsoil properties is the electrical imaging technique. The underlying objective was to test the advantage of using this geophysical method for the continuous characterization of subsoil structure around the Begur treatment plant where treated wastewater is discharged and reused in a soil–plant–aquifer system. The good results of wastewater application in the area are also discussed.