Geochemical, hydrochemical and remote sensing study of an Andean calcareous wetland in Huanta, Peru

Cardenas Morales B.K.; Forrest J.; Castro Aponte W.V.; Sanchez Cornejo H.E.; La Torre B.; Jhoncon Kooyip J.; Byrne P.; Nguyen T.T.; Barnes C.H.W.; De Los Santos Valladares L. · Journal of Hydrology: Regional Studies (2025) · DOI: 10.1016/j.ejrh.2025.102767

Resumen

Study region: The Huaper Wetland is located in the Huanta Province, Ayacucho Region, in the Central Peruvian Andes at 2353 m above sea level. This calcareous highland ecosystem has a key role for irrigation, biodiversity conservation, and local water supply. However, it is increasingly affected by unregulated tourism, agricultural runoff, and poor waste management. Study focus: This study presents the first integrated geochemical, hydrochemical, and remote sensing assessment of the Huaper Wetland. Water samples were collected during four campaigns across two hydrological years (March and November 2023–2024), representing both Austral summer and winter. Parameters analyzed included pH (6.92–7.22), electrical conductivity (0.87–0.94 dS/m), total dissolved solids, dissolved oxygen (min. 1.43 mg/L), and potentially toxic elements. Seventeen sediment samples were characterized using Energy Dispersive X-ray Spectroscopy (EDX) and X-ray Diffraction (XRD), confirming dominance of calcite (up to 43.8 %) and magnesium calcite (32.8 %), with traces of nitratine (NaNO₃) suggesting agricultural influence. Surface moisture dynamics were assessed using the Normalized Difference Water Index (NDWI) from Sentinel-2 imagery (2016–2023). New hydrological insights for the region: The results indicate initial signs of water quality deterioration, with nitrate levels in November 2023 (8.09 mg/L) exceeding national standards and a decline in the Water Quality Index from “Excellent” (94.92–100.00) in 2023 to “Good” (92.04) in 2024. NDWI analysis revealed a persistent decrease in surface moisture, with a minimum in 2017 (–0.4699; STD = 0.0716). Elevated sodium concentrations and low dissolved oxygen levels may destabilize redox conditions, potentially mobilizing arsenic and lead. These findings suggest a weakening of the wetland’s geochemical buffering capacity and highlight the urgency of implementing land-use regulation, salinity control, and cost-effective long-term monitoring in calcareous Andean wetlands.

Instituciones: Universidad Nacional Mayor de San Marcos; Universidad Nacional Agraria La Molina; Universidad Nacional Autónoma de Huanta; Universidad Nacional de Educación Enrique Guzmán y Valle