Using a multiple water balance approach to estimate recharge for the optimum mine, Mpumalanga
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Date
2018-02
Authors
Van Wyk, Morne
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
This dissertation focused on using multiple water balance recharge methods within
rehabilitated opencast mines at the Optimum Coal Mine, Mpumalanga,for the aim
that a combination of water balance methods will yield more conclusive recharge
from rainfall values within spoil material. It is known that different recharge methods
yield very different results concerning recharge. New recharge methods were
implemented based on the data received from the mine and compared to the
recharge method already developed and proven to work.
In the pursuit to solve the complicated issue of calculating recharge from rainfall, four
newly formulated methods were produced, called the Rainfall Infiltrated Volume,
Stage Curve Volume, Dry and Wet Calculations and Recharge from Stage Curve
Volume. These methods were compared to wellknown
recharge methods which
included the Saturated Volume Fluctuation, Cumulative Rainfall Departure and
Water Table Fluctuation methods over a fiveyear
period. These methods, combined,
narrowed the range between the minimum and maximum recharge values, usually
estimated for the study area, and in the process provided a better understanding of
the water management systems in this area.
Pit Volume Calculations yielded a 25% void space for spoils, which were used in the
recharge calculations. Each method yielded a minimum and maximum recharge
value from rainfall, but not all of them produced the results expected from the area.
The Zevenfontein opencast rehabilitated pit produced very accurate and believable
recharge from rainfall at 18–20% for the new recharge methods and 15–17% for the
known recharge methods. The Optimus opencast rehabilitated pit had numerous
problems, but in the end also produced believable results at 25–30% for the new
recharge methods and 15–20% for the known recharge methods.
Thus, it was concluded that a combination of recharge methods yielded more
conclusive recharge values.
Description
Keywords
Optimum, Coal, Recharge, Water balance methods, Pit calculations, Rainfall infiltrated volume, Stage curve volume, Dry calculations, Wet calculations, Saturated volume fluctuation, Cumulative rainfall departure, Water table fluctuation, Void space, Pumping cycles, Pumping rates, Water levels, Dissertation (M.Sc.Agric. (Institute for Groundwater Studies))--University of the Free State, 2018