Water supply and water runoff quality in the sub deciduous forest of the Coast of Oaxaca, Mexico

Introduction: Land use change and waste discharge from coffee processing may be affecting quantity and quality of water supplying urban areas in the coastal region of Oaxaca.Objective: To determine the level of contamination of aquifers and estimate surface water runoff in micro-watersheds of Pluma Hidalgo and Santa María Huatulco in Oaxaca, Mexico.Materials and methods: Seven water supply points were analyzed during the rainy season of 2019. The following physicochemical parameters were determined: pH, total dissolved solids, electrical conductivity, hardness, total solids, chlorides, and chemical oxygen demand (COD). Surface runoff was estimated using the Raws and Prevert methods.Results and discussion. Water bodies are within the permissible limits for human use. The Chacalapilla spring was classified as moderately hard (85 mg CaCO3∙L-1), while the seven water bodies exceeded the permissible limit for COD (40 to 200 mg∙L-1); therefore, water is in a contaminated classification range and is not suitable for human consumption. Surface runoff values suggest a medium conservation condition of vegetation cover; areas with higher cover recorded lower runoff coefficients.Conclusions. The physicochemical parameters indicated that water from Pluma Hidalgo and Santa María Huatulco is suitable for human use, but not for drinking