Impact of Land Use Change on Non-Point Source Pollution in a Semi-Arid Catchment under Rapid Urbanisation in Bolivia

Changes in pollution pressure exerted on the Rocha River Bolivia from diffuse sources were assessed using potential non-point indexes (PNPI) for 1997 and 2017. PNPI is a simple, low-effort, time- resource-saving method suitable data-scarce regions, as it works at catchment level with commonly available geographical data. Land use type (obtained by Landsat imagery classification), runoff (determined coefficient characterisation) distance to river network (calculated perpendicular distance) each transformed into corresponding indicators determine their relative importance generating pollution. Weighted sum, multi-criteria analysis tool GIS environment, was used combine weighting values. Different values assigned of resulting set six equations. The results showed that higher corresponded human settlements high population density, shorter network, while lower semi-natural land type, longer distances river. positively correlated measured nitrate phosphate concentrations sub-catchment outlets. correlation statistical significant Maps produced identify priority source areas are more likely generate pollution, which important information future management.