Theme

Global Change Research and Monitoring in the Maloti-Drakensberg Mountain System (South Africa-Lesotho)

Speaker

Chris Curtis –

Authors

Sue van Rensburg –

Aobakwe Lenkwe –

Abstract

The Cathedral Peak experimental catchments were initiated in the 1930s, primarily to investigate the effects of afforestation on catchment hydrology and, later, to investigate the additional effects of land management (grazing and burning regimes). Adjacent catchments with very similar physical attributes (vegetation, soils, geology, aspect) provided an ideal setup for comparing the effects of terrestrial management and processes on streamwater flows and chemistry. During the 1980s, both water quality and rainfall chemistry were monitored but these activities had largely ceased by the 1990s. The revival of aquatic and meteorological monitoring activities within the last decade at the Cathedral Peak experimental catchments by SAEON has presented opportunities not only for comparison of current and historical water quality across different land management strategies, but also for investigating the effects of climate change and acid deposition on biogeochemical cycles in Afromontane grassland catchments. The mountain streams draining these catchments in a strategic water source area provide critically important ecosystem services and harbour aquatic biodiversity in a designated National Freshwater Ecosystem Priority Area. We demonstrate that the history of catchment management in terms of fire regimes and catchment planting and deforestation have measurable impacts on water quality even after several decades. Small but significant differences in major ion chemistry, electrical conductivity and pH were found between the catchments which appear to be caused by differences in management history. Likewise, there have been some significant increases in major ions since the 1980s which differ between catchments and may also be linked to the longer-term impacts of catchment management. In addition, there are possible impacts of atmospheric deposition given the high wet deposition loads of fossil fuel and biomass burning derived compounds in this region.