An evaluation of the ecological impacts of sand mining on the Mokolo River in Lephalale, South Africa

Abstract

This study aimed to evaluate the ecological impacts of sand mining on the Mokolo River, in Lephalale. The study focused on the water quality, macroinvertebrates and physical disturbances as indicators in order to determine the ecological im-pacts of sand mining on the Mokolo River. The water quality variables, which this study entailed, were related to sand mining and other sources of pollution such as coal mining, power station industries, agriculture and wastewater treatment works on the Mokolo River. The water quality results for pH, electrical conductivity (EC), total alkalinity (CaCO3), sodium (Na), calcium (Ca), magnesium (Mg), potassium (K), chloride (Cl), fluoride (F), sulphate (SO4) and nitrate (NO3-N) were not over the limits, however turbidity, total coliforms and E. coli were over the limits as per the Target Water Quality Guideline (TWQG). The River Health Programme (RHP) was done at upstream, sand mining and downstream areas in the Mokolo River using the South African Scoring System Version 5 (SASS5). The ecological status at the upstream and downstream areas changed from class C (March 2018) to class B (November 2018), indicating that the ecological status improved in those areas of the Mokolo River. However, at the sand mining area the ecological status has not improved and it was seriously modified due to the physical disturbance as a result of sand mining. Ecological impacts, such as the removal of marginal and riparian vegetation, erosion, disturbed riverbed, undercutting and collapse of riverbanks, loss of adjacent land, river deepened, river widened, water pools, in stream sand stockpiles and river diversions, were determined at the sand mining area. No physical disturbances at the upstream and downstream areas were determined. The findings of this study indicate that the ecological impacts of change in water quality at the upstream and downstream areas was due to high turbidity, Total coli-forms and E. coli. The absence of sensitive macroinvertebrates and loss of ma-croinvertebrates and the physical disturbances within the Mokolo River was be-cause of sand mining. The study indicates that sand mining has negative impacts on the water quality, water quantity, macroinvertebrates and physical characteris-tics of the Mokolo River.