Where could surface water be used for Managed Aquifer Recharge (MAR) in the Besòs catchment, considering quantity and quality aspects? 

Abstract

In many parts of the world, including the Mediterranean region, climate projections indicate less average runoff available and more frequent extreme rainfall events. Several sub-catchments in the river basin district of “Cuencas Internas de Catalunya” already need to address an irregular availability of surface water and a high vulnerability to floods in a changing climate, as well as water quality issues in streams and aquifers. In this context, aquifers can play a key role as natural reservoirs to buffer the effects of climate change, although challenges exist to keep a balance between groundwater recharge (inflows) and discharge (outflows) while preserving water quality. With the Besòs catchment as a study area, monitoring data from 2007 to 2023 was gathered from the database of the Catalan Water Agency. Spatial distribution of surface water and groundwater hydrochemistry (CE, Cl, NO3-, PO43-, TOC, pH, T) were analyzed and contrasted for different river stretches, as well as time series of river flow and groundwater levels in alluvial aquifers. Potential interactions between rivers and underlying aquifers and differences in water quality were inferred through descriptive statistics and non-parametric tests for selected areas. Sites where Managed Aquifer Recharge (MAR) could be potentially implemented were identified, considering quantity and quality aspects at catchment scale as well as physical aquifer properties. These preliminary results will guide the development of numerical models where different schemes will be tested of MAR methods (e.g.: streambed channel modifications, bank filtration, water spreading, wells recharge) and recharge sources (e.g.: rivers and streams runoff, reclaimed water) for climate adaptation.