Impact of post-reclamation of soil by large-scale, small-scale and illegal mining on water balance components and sediment yield: Pra River Basin case study.

Abstract

Gold mining is extremely valuable for countries involved in it due to the potential for employment, income allocation and socio-economic development. As a result of the attraction of international investors by governments of countries rich in this natural resource and increasing gold prices, large-scale, small-scale and unlicensed and illegal (Galamsey) mining activities are expanding. This expansion can have significant effects on the environment, such as pollution and altering the hydrological regime, constituting a threat to the natural ecosystems and the health of the populace staying in gold mining zones. This research focuses on the evaluation of the effects of different types of soil reclamation measures used by large-scale, small-scale and galamsey miners on hydrological components and sediment yield in the Pra River Basin (PRB), Ghana, using the Soil and Water Analysis Tool (SWAT). Soil samples were collected from the reclaimed sites of the three mining types, analyzed and used as input into the SWAT model to assess their effect on the hydrological components and sediment yield. The results showed that apart from the first two soil layers of large scale, almost all the three mining types have a significant change in the reclaimed soil constituents of various layers of the soil. The trend and magnitude of post-reclamation impact on hydrological components from galamsey and small-scale mining are almost the same. With reference to the natural background, galamsey and small-scale activity, respectively, increased surface runoff by 51.5 % and 43.9 %, and reduced baseflow by 24.4 % and 22.9 %, while large-scale activity depicted the decrease in runoff and increase in baseflow. Sediment yield from all the three types of gold mining increased significantly. In the PRB, galamsey prominently produced much sediment (161.9 ton/year), followed by small-scale (151.1 ton/year) and large-scale (67.5 ton/year). This paper identified that the effects of land degradation linked to mining cannot be attributed only to galamsey but also to small-scale and large-scale mining. From the outcomes, special attention should be given to reclamation and water management activities that can solve emerging regulatory and environmental management problems that are being encountered by the mining sector.