The origin and distribution of nitrate in groundwater from village wells in Kotagede, Yogyakarta, Indonesia

The causes and nature of nitrate pollution of wells in a village within Kotagede, a subdistrict of the city of Yogyakarta, Indonesia, were investigated in a detailed hydrological study. Nitrate concentrations in groundwater frequently exceeded the WHO recommended limit of 50 mg L^− 1. Groundwater nitrate concentrations were measured over a 19-month period in monitoring wells and in piezometers placed strategically in relation to sewage tanks within the village. Results indicate that the tanks are major sources of nitrate in the groundwater and that the input is markedly dependent on rainfall, resulting in a surge of nitrate into the groundwater at the beginning of each wet season. That the tanks are a major source was confirmed by measuring nitrate in soil cores obtained by augering close to selected tanks. Washrooms, where people wash themselves, are not significant sources of nitrate. Faecal coliform counts in groundwater from a random selection of wells are very high. The results have implications for the siting of wells and toilets within villages in Indonesia. Received, January 1999/Revised, August 1999/Accepted, August 1999