Land use and water quality in a rural cloud forest region (Intag, Ecuador)

The Intag cloud forest region of northwestern Ecuador is characterized by exceptional biodiversity, large known and unknown deposits of copper and other valuable minerals, and a high level of environmental awareness and concern among the human population. Its 1000km of rivers and streams are essential for household use, crop irrigation, livestock production and sustaining unique ecosystems. However, no published data exist on water quality in the region. This study characterizes water quality in five river systems in Intag and relates it to land use (protected forest, agriculture/pasture, urban development or mining) upstream of the sampling point. Additionally, we sampled 15 community water supply systems. Parameters measured included turbidity, temperature, dissolved oxygen, pH, faecal indicator bacteria (FIB), nitrate, phosphate, ammonium, Ni, Mn, Cu, Zn, Cd, Pb, As, Cr, discharge and aquatic invertebrate diversity. Significant differences in pH, aquatic invertebrate diversity, and the concentrations of FIB, nutrients and dissolved metals were observed between land use groups. Forested streams consistently had the lowest pollutant concentrations, whereas those flowing past population centres or mining areas showed the greatest impairment. Elevated As concentrations were observed in association with abandoned mining boreholes, hot springs and wastewater discharges. FIB, nutrient and metal concentrations in water systems were similar to those in forested streams, indicating that these systems maintain water in an unpolluted condition. To preserve and enhance Intag's generally good water quality, we recommend installing wastewater treatment systems in larger towns and approaching all mining activity, including exploration, with extreme caution.