Evaluation of microbiological and physicochemical contamination of groundwater in the coastal wet-land of Pantanos de Villa (Lima-Peru)

Background: Groundwater quality in tropical wetlands remains poorly studied. Los Pantanos de Villa, a key wetland located on Peru's desert coast, is recognized as a Protected Natural Area and a Ramsar site yet faces ongoing threats. This study aims to assess groundwater contamination in the wetland using microbi-ological (Escherichia coli, total and fecal coliforms) and physicochemical parameters, as well as water quality indices; (2) Methods: Annual sampling in 2023 was conducted at 12 locations (4 test pits and 8 piezometers), during the high recharge season (March) and low recharge season (September). Parameters were compared to national (Peru) and international (U.S.) standards. Two water quality indices—CCME and NSF—were applied; (3) Results: Microbiological contamination levels were dangerously high at all sampling sites. Physicochemical parameters exceeded permissible limits in at least one season. The CCME index classified 100% of samples as poor quality, and the NSF index classified 75% as poor and 25% as medium quality; (4) Conclusions: Groundwater in the Pantanos de Villa wetland exceeds national and international contamination thresholds. Microbiological pollution is particularly concerning. Water quality indices confirm a degraded state.