When open cut mining operations cease, lakes often form in the remaining void. Managing these water resources is becoming an increasingly important issue in Australia.
Managing the environment once mining operations cease
The mining industry is under increasing pressure to manage the closure of operations and to minimise environmental impacts.
Pit lakes are a common feature in mine site closure projects yet very little was known about evaporation rates from such systems.
Evaporation is important as it controls lake evolution, dictates final lake level, controls hydro-chemical evolution and causes evapo-concentration. The evaporation environment is unique as the lake can be sheltered from wind and solar radiation inputs and water can have high salinity. These factors combine to make any pit lake evolution predictions highly uncertain.
Developing a new set of instrumentation for measuring evaporation
Using these measurements to build a pit lake evaporation model that can be run at any location using readily available weather station data. The model accounts for shading, salinity, sheltering and lake size.
Techniques now used in the field
BHP now has a pit lake evaporation model which they can apply to any of their existing or future mine voids. The model is already being used to assess pit lake evolution in the Newman area in Western Australia with a view to expand into coal operation in the near future.