| Summary: | In 2001, the water management responsibilities in the Kat River, Eastern Cape, South Africa were transferred from the Kat River Irrigation Board to the Kat River Valley Water Users Association (KRVWUA). The impact this institutional change may have on the quality of the Kat River water is not yet quantified, and is therefore unknown. This study therefore investigates the impact of the KRVWUA on the salinity and nutrient status of the Kat River in the first decade since its establishment. To realize this aim: i) the extent of land use and land cover (LULC) change between 2001 and 2011 was assessed, and ii) it was established whether there has been a statistically significant change in the salinity and nutrient status of the Kat River basin during the 2001-2010 decade compared to the 1991-2000 decade. The pixel-based supervised classification method was used with the minimum distance algorithm to classify land use from the 2001, 2007, and 2011 2.5m SPOT HRG satellite images. The extent of LULC changes was detected using the post-classification change detection technique. The images extracted from each satellite image were cross-tabulated with each other to establish the spatial distribution of the LULC classes using the cross-tabulation module in Idrisi Taiga. Results of this LULC study indicate that 30.5 percent of the study area was subjected to LULC change between 2001 and 2011. Also, a paired-samples t-test was conducted to compare the nutrients and salinity variables’ means of the two decades of a 20-year water quality dataset (1991 – 2000 and 2001 – 2010). Statistically significant differences (α = 0.05) were observed as follows: in the Kat Dam site, increases in calcium, potassium, ammonium, nitrate, and chloride; in the Balfour River site, decreases in calcium, chloride, electrical conductivity, sodium, sulphate, and pH. The following actions are therefore recommended in the upper catchment: that strong runoff controls be put in place, that animals be kept off the river, that environmentally friendly ...
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