Management of water balance in mining areas – WaterSmart: Final Report

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Title: Management of water balance in mining areas – WaterSmart: Final Report
Author: Krogerus, Kirsti; Pasanen, Antti
Belongs to series: Reports of the Finnish Environment Institute 39/2016
ISSN: 1796-1726
ISBN: 978-952-11-4648-0
Abstract: Although mining companies have long been conscious of water related risks, they still face environmental management challenges. Several recent environmental incidents in Finnish mines have raised questions regarding mine site environmental and water management practices. This has increased public awareness of mining threats to the environment and resulted in stricter permits and longer permitting procedures. Water balance modelling aids in predictive water management and reduces risks caused by an excess or shortage of water at a mining site. In this study the primary objective was to exploit online water quantity and water quality measurements to better serve water balance management. The second objective was to develop and test mathematical models to calculate the water balance in mining operations. The third objective was to determine how monitoring and modelling tools can be integrated into the management system and process control. According to the experience gained from monitoring water balances, the main recommendation is that the data should be stored in a database where it is easily available for water balance calculations. For real-time simulations, online measurements should be available from strategically defined positions in the mine site. Groundwater may also act as a source or sink with respect to mine site surface water, and therefore monitoring and investigations should be designed to account for the full water balance. In Finland it is possible to calculate water balance for planning or for operative purposes by using the Watershed Simulation and Forecasting System (WSFS) developed at the Finnish Environment Institute (SYKE). This system covers every sub-basin (10-50 km2) over the whole of Finland. WSFS automatically obtains the latest observations of temperature, precipitation, water level, discharge and other needed data provided by the Finnish Meteorological Institute (FMI), SYKE, as well as other sources. The system also uses these observations to follow-up on simulation and forecasting accuracy. The water balance model was further developed to simulate and forecast the water balance at the Yara Siilinjärvi mine site. The WSFS-model was also extended with one-way coupling to the groundwater flow model. The model is operated via a web-based user interface and can produce water-balance forecasts automatically, if necessary, several times a day. The water balance and water flow in the area are simulated using real-time weather observations. The model enables forecasting water levels and planning discharges and pumping at the mine site. Possible uses of the model include preparation for spring floods by emptying ponds for storage of water from snow melt, estimation of the effect of heavy rainfall and calculating the required outflow from the mine site reservoir. Thus, overflows and dam-breaks can be avoided and consequently prevent the leakage of contaminated water. Furthermore, as the model can be modified to simulate changes at the mine site, it can also be beneficial during the mine site-planning process. The water balance model is currently operational for Yara Siilinjärvi mine site and hydrological forecasts are produced on a daily basis. Water level, discharge and pumping data, essential for modelling the area, are provided by the mine operator and EHP-Tekniikka Ltd. The model uses meteorological observations and forecasts from FMI as inputs for the simulations and forecasts. In addition to the accurate weather forecasts, the real time observations are a key factor in the accuracy of the model forecasts. GoldSim is the most popular commercial simulation software solution chosen, not only by mines worldwide, but also in many other sectors. One of the main reasons for its extensive use is its versatility and the ability to expand the program as the needs of the mine require. As the mine project progresses, one of GoldSim’s strongest assets is risk analysis at different phases during both the planning and execution of mine operations. The use of the GoldSim platform was tested during the project and some new features were developed. The project has paid special attention to commercialization of the developed products and well thought out policies for possible joint bids.
Date: 2016
Subject (ysa): kaivokset

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