Investigate the possible reduction of mine water ingress by introducing tree plantations: case study of Cooke 4 mine (South Africa)

Abstract

Continuous influxes of groundwater into underground mine workings require a significant financial investment related mainly to the high costs of pumping of large volumes of water ingress, consequently mines become unprofitable. An innovative alternative to pumping methods with the purpose to reduce water volumes, is the establishment of deep rooted, high water-use vegetation covers to act as “artificial pumps”. Hydraulic control is one of the leading applications of plant-based strategies for remediating and managing groundwater systems by introducing plantations in selected areas with high ingress potential. This study investigates the impact of plantation introduction on the reduction of effective groundwater recharge. A temperature-based field model was formulated to determine daily ET from measured and observed leaf and air temperature. Results were compared to the FAO (Food and Agricultural Organisation) Penman-Monteith reference crop ET (Evapotranspiration) model and the Shuttleworth-Wallace models in order to validate the predictions of the field model. The developed field model was then used to predict monthly ET values for the Cooke 4 study area (Gemsbokfontein West compartment) to determine the possible reduction of pumping volumes. The area chosen for the proposed plantation was selected based on groundwater levels and the agricultural potential. A water balance for the study area has been developed through the use of the SVF (Saturated Volume Fluctuation) method and inflows to the study area has been modelled as head dependent by using a conductance term