FORECASTING OF HYDROGRAPHS TO SIMULATE LONG TERM RECHARGE FROM RIVERS IN NUMERICAL MODELS OF MINING RESERVOIRS; APPLICATION TO A COAL MINE IN NW SPAIN

摘要

Although the natural permeability of rocks in the Asturian Central Coal Basin (NW Spain) is generally low, intensive mining activities over many decades has given rise to fracture flow paths that are far more permeable than those associated with the natural lithology. Abandoned and flooded mining works set up artificial pseudo-karst' aquifers, which can act as underground reservoirs, with many potential applications. In particular, a mining reservoir shaped by two connected mining shafts within the River Turon basin has been studied. A runoff model was used to produce accurate simulations of streamflow in three different gauging stations during a monitored period of 2years. The purpose was to use this model in the forecast situation, in order to predict long-term situations in a hydrogeological FEFLOW model. It was necessary to develop depletion curves for each gauging station based on the available daily effective rainfall and measured flow data, as well as the knowledge of the basin characteristics. The resulting simulated hydrographs were very similar to the measured hydrographs during the monitored period, so the adequate adjusting allows input of the flow for forecast purposes. The model produced forecast hydrographs that had a r=0.8 and difference in annual volume ranging from 1.6% to 5%. The defined model was applied to a rainfall data set of 30years, and the average recharge from the river to the mining reservoir could be adequately estimated. The method developed needs to be refined and tested on additional years, but the approach appears to be applicable to operational runoff forecasting for numerical models input data. Copyright (C) 2015 John Wiley & Sons, Ltd.