Analysis of the implementation of green-blue infrastructure for optimising recharge in coastal aquifers

Abstract

Coastal cities located on the sand-dune barrier of Buenos Aires Province have significantly grown over the last century, affecting the water balance due to rapid urbanisation and soil impermeabilization, which reduces aquifer recharge—the only source of fresh water in the region. This study aims to apply nature-based solutions through green-blue infrastructure (GBI) to optimise aquifer recharge in the Partido of Pinamar. Rain Gardens (RG) represent a promising nature-based GBI solution that enhance urban stormwater management and groundwater recharge. The research integrated geographic information systems, aerial photogrammetric surveys using unmanned aerial vehicles (UAVs), hydrological modeling, and field monitoring through levelogger installation with 5-min measurement intervals. Controlled infiltration tests were conducted using fire trucks, and hydrochemical analysis assessed water quality changes. Results demonstrated significant improvements in recharge efficiency, particularly for low-intensity precipitation events (<3.5 mm), where the ΔWT/P index increased from 5.56 to 36.27, representing a six-fold enhancement. The RG achieved a maximum infiltration capacity of 230 L/min with complete drainage within 2.6 h. Hydrochemical analysis showed complete removal (100 %) of urban pollutants including hydrocarbons, oils and fats, and methylene blue active substances, with a 7.3 % reduction in total dissolved solids. The Rain Garden achieved an annual effective recharge of 1242 m³, equivalent to daily water consumption of 4968 people. The study concludes that strategically implemented rain gardens can significantly enhance coastal aquifer recharge while providing effective stormwater treatment, representing a viable low-cost solution for developing coastal cities facing freshwater depletion.