Student: Dr SK Mantel
Supervisors: Prof DA Hughes, Dr WJ Muller
Degree: Postdoctorate

A vast amount of work has been done on the quality and quantity aspects of South African rivers as they relate to understanding the systems, setting guidelines for conservation, and water resource management. The aim of the present research is to quantify links between quantity (hydrology and hydraulics) and quality (water quality, species diversity) as they relate to river conservation and management in South Africa. The long term aim of the project is to incorporate these links into Reserve determination and implementation.

This project commenced in July 2006 and has utilized two national databases for analyses: River Health Programme (RHP) for physico-chemistry and biological data and the Hydrological Information System (HIS) for discharge data from stream flow gauges to establish any patterns that relate water quantity and quality data. Multivariate analyses were conducted to establish broad patterns across two South African regions - Western Cape (winter rainfall, temperate, southwestern coast) and Mpumalanga (summer rainfall, tropical, eastern coast). Impacts of large (related to dam's storage capacity) and small dams (in terms of number of small dams) were determined for each sampling location in the RHP database to assess their effects on water quantity and quality.

Multivariate analyses found that the changes in the invertebrate biological data and the stream's physico-chemistry were more strongly correlated with small dams relative to large dam impacts. Significance of changes in the measured variables was tested using t-tests after removing sites with upstream large dams from the database. High impact of small dams significantly reduced discharge statistics in foothill-cobble (in both the regions) and in foothill-gravel streams (in the Western Cape). Significant reductions in a river health index (Average Score per Taxon, ASPT) and in the invertebrate communities (in foothill-gravel streams in both the regions and in Mpumalanga foothill-cobble streams) along with significant changes in certain physico-chemistry variables (particularly total dissolved salts) were established. The results suggest that high number of small dams is impacting the quality and quantity of waters in South African rivers and that these impacts need to be incorporated into the ecological Reserve determinations. The results of this study are being formulated into a journal paper at present.

Last Modified: Fri, 14 Aug 2015 10:10:36 SAST