Assessing the Effects of Land Use on Surface Water Quality in the Lower uMfolozi Floodplain System, South Africa

Abstract

This study investigated the impacts of cultivation on water and soil quality in the lower uMfolozi floodplain system in KwaZulu-Natal province, South Africa. We did this by assessing seasonal variations in purposefully selected water and soil properties in these two land-use systems. The observed values were statistically analysed by performing Student's paired t-tests to determine seasonal trends in these variables. Results revealed significant seasonal differences in chloride and sodium concentrations and electrical conductivity (EC) and the sodium adsorption ratio (SAR) with cultivated sites exhibiting higher values. Most of the analyzed chemical parameters were within acceptable limits specified by the South African agricultural-water-quality (SAWQ) water quality guidelines for irrigation except for sodium adsorption ratio (SAR), chloride, sodium and EC. EC, pH and nitrate content which were higher than the specified SAWQ limits in cultivated sites. Quantities of glyphosate, ametryn and imidacloprid could not be measured because they were below detectable limits. The study concludes that most water quality parameters met SAWQ's standards. These results argue for concerted efforts to systematically monitor water and soil quality characteristics in this environment to enhance sustainability by providing timely information for management purposes.

Keywords: chemical parameters; crop farming; seasonal variation; soil properties.

Figure 1

Study area: The uMfolozi floodplain in uMkhanyakude District Municipality. Red arrows show west to east water flow towards the Indian ocean.

Figure 2

Comparison of water quality constituents recorded in wetlands (uncultivated and cultivated) with South African water quality (SAWQ) target values in wet and dry seasons of 2017 and 2018, (a) EC, (b) Na, (c) SAR, (d) pH, (e) NO₂⁻, (f) NO₃⁻, (g) Cl⁻, (h) F, (i) B and (j) NH₄⁺.