Artificial recharge effects in water balance of a peri-urban semi-arid catchment: a case study in an Andean aquifer using WEAP-MODFLOW

Artificial recharge in urban and peri-urbans areas is not a typical practice, but the prolonged severe drought in central Chile has encouraged the study of this practice as an option for optimal and sustainable water management. The Andean piedmont of Santiago (Chile) has been urbanized that implies high water consumptions and increasing irrigation, which in turn acts as a new groundwater recharge. We simulated the period 1989-2015 using an integrated surface and subsurface model (WEAP-MODFLOW) to evaluate the impact of urbanization in groundwater recharge in a representative catchment in the area. An artificial recharge injection of 100 l/s (60,480 m3/day) was introduced in the model for a period of 26 weeks in a specific year (2009, between week 27 to 52, included). The recharge wells were implemented in key zones of the upper aquifer and monitoring wells were also implemented in different zones. The artificial recharge reproduced the hydraulic dome created by the infiltration flow, locally reaching a height of 6 m and beginning to dissipate approximately at 2.5 km (≤ 0.5 m) from the injection point. Moreover, we created a zone budget control section (2 km downstream) and we observed impacts on the water level in this sector, with a 1-year lag  year after starting artificial recharge. The maximum impact was observed after approximately 1.5 years. Not only the study watershed has a high natural storage capacity, which benefits natural water retention, but its average residence time (4 years) is quite. Thus, our results could encourage different public or private stakeholders in the watershed to implement low impact development practices that could infiltrate water to cope with water shortage periods.