The use of remote sensing and GIS in watershed level analyses of non-point source pollution problems

Basin characteristics such as land use/land cover, slope, and soil attributes affect water quality by regulating sediment and chemical concentration. Among these characteristics, land use/land cover can be manipulated to gain improvements in water quality. These land use/land cover types can serve as nutrient detention media or as nutrient transformers as dissolved or suspended nutrients move towards the stream. This study examines a methodology to determine nitrate pollution ‘contributing zones’ within a given basin based on basin characteristics. In this process, land use/land cover types were classified and basins and ‘contributing zones’ were delineated using geographic information system (GIS) and remote sensing (RS) analysis tools. A ‘land use/land cover-nutrient-linkage-model’ was developed which suggests that forests act as a sink, and as the proportion of forest inside a contributing zone increases (or agricultural land decreases), nitrate levels downstream will decrease. In the model, the residential/urban/built-up areas have been identified as strong contributors of nitrate. Other contributors were orchards; and row crops and other agricultural activities.