Nitrate in the Water-Supply Wells in the Mancha Oriental Hydrogeological System (SE Spain)

This study determines the spatial and temporal distribution of nitrate content within the water-supply wells in the Mancha Oriental System (MOS) for the period 1998–2003 and presents an example of the multiple nitrate pollution sources in the El Salobral–Los Llanos Domain (SLD, southwestern Albacete). The groundwater resources of the MOS are used to maintain approximately 800 km<Superscript>2</Superscript> of irrigated crops and are the sole water supply for a total population of 275,000 inhabitants. The average nitrate content varies from >0.5 mg l<Superscript> − 1</Superscript> (detection limit) to 125 mg l<Superscript> − 1</Superscript>. In some areas of the MOS statistical analyses show a growing tendency between 2001 and 2003. Nitrate content shows a heterogeneous spatial distribution but the highest levels can be associated with large areas of irrigated crops. However, there are also points in which nitrate has been detected in significant quantities which are not found to be spatially linked to this kind of crop. The presence of nitrate in these areas can be explained considering other sources of pollution, such us wastewater, or due to pollutant transport from contaminated areas through groundwater flow in a multiple-layered karstic aquifer. These results lead necessarily to reconsider the agricultural-derived nitrate as the sole source of pollution and to analyze the effectiveness of the current wastewater treatment practices from effluents in the MOS. Copyright Springer Science+Business Media B.V. 2009