Groundwater recharge using a subsurface irrigation system: A technical feasibility study

In view of humanity’s rising demand for water and rapidly depleting aquifers, managed aquifer recharge (MAR) is a proven approach to replenish groundwater resources. Different MAR techniques exist. Among them, surface spreading methods are widely used in Europe. In this method, surface water is spread over basins, furrows or trenches where water percolates through vadose zone to recharge the groundwater. This method is highly effective. However, it is associated with a number of challenges, e.g. high space requirements, installation along with removal expenses, high evaporation rate and, foremost, limited availability of the used land for other purposes during operation. A subsurface irrigation system can be an alternative solution to mitigate major limitations of surface spreading methods. However, its technical viability needs to be determined. In this research, infiltration characteristics of a subsurface irrigation system in the vadose zone was determined numerically, using Hydrus 2D/3D model for sandy soil. In addition, a test-size-scale one cubic meter soil tank experiment with a uranine tracer was set up to evaluate the model results. The wetting front velocity and pattern was traced using EC-5 soil moisture sensors and a fixedly positioned direct push optical image profile (OIP) probe. Experiments revealed that the subsurface irrigation system infiltrated 1.14 L/h/m in the considered sandy soil with a maximum percolation velocity of 9.84 cm/hr. The numerical and experimental outcomes are in good agreement and are now used to design a field application to practically assess the long-term performance of the subsurface irrigation system for managed aquifer recharge.