water Article Impact of Land Use Change on Non-Point Source Pollution in a Semi-Arid Catchment under Rapid Urbanisation in Bolivia Benjamin Gossweiler 1,2,* , Ingrid Wesström 2 , Ingmar Messing 2, Mauricio Villazón 3 and Abraham Joel 2 1 Center for Aerospace Surveys and Geographic Information Systems Applications for the Sustainable Development of Natural Resources, San Simon University, P.O. Box 5294, Cochabamba, Bolivia 2 Department of Soil and Environment, Swedish University of Agricultural Sciences, P.O. Box 7014, SE-750 07 Uppsala, Sweden;
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[email protected] (A.J.) 3 Laboratorio de Hidráulica, San Simon University, P.O. Box 1832, Cochabamba, Bolivia;
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[email protected]; Tel.: +46-76-710-73-42 Abstract: Changes in pollution pressure exerted on the Rocha River in Bolivia from diffuse sources were assessed using potential non-point pollution indexes (PNPI) for 1997 and 2017. PNPI is a simple, low-effort, time- and resource-saving method suitable for data-scarce regions, as it works at catchment level with commonly available geographical data. Land use type (obtained by Landsat imagery classification), runoff (determined by runoff coefficient characterisation) and distance to river network (calculated at perpendicular distance) were each transformed into corresponding indicators to determine their relative importance in generating pollution. Weighted sum, a multi-criteria analysis tool in the GIS environment, was used to combine indicators with weighting values. Different weighting values were assigned to each of the indicators resulting in a set of six equations.