A simple and rapid method to relate land cover and river flow rate to river nutrient concentration

The quantification of diffuse input loads of nutrients to rivers is a challenge due to limited observed data. This study aimed to develop a simple model that can relate in-stream nutrient concentrations due to diffuse sources with land cover categories within a catchment affecting a river reach. A previously developed point-diffuse model was used to distinguish the diffuse nutrient signature within South African Department of Water Affairs historical monitoring flow and water quality data for selected river gauges. The diffuse signature was related to land cover categories within respective catchments using Principal Component Analysis (PCA), and influential land cover categories were used to construct land cover models relating land cover categories with in-stream nutrient concentrations. Generally, the land cover categories affecting diffuse signatures of nutrients as indicated by PCA were expected. Using land cover information, the developed land cover models performed well in re-creating the diffuse in-stream nutrient signature as determined by the point-diffuse model.