Simulated Hydraulic Heads Research Articles

Numerical Simulation of Potentiometric Surface Changes Caused by a Proposed Open‐Pit Anthracite Mine

ABSTRACTThe Trescott, Pinder, Larson (Trescott and others, 1976) finite‐difference flow model was modified and used to simulate potentiometric surface changes caused by the development of a proposed open‐pit anthracite mine. The modifications to the program code were made to account for site‐specific hydrogeologic conditions and to simulate the mining operation. In order to account for vertical changes in hydraulic conductivity caused by underground mine voids, the coefficient subroutine (COEF) was modified to permit the value of hydraulic conductivity to vary with depth. The lateral growth and deepening of the mine were simulated by changing the data input subroutine (DATAI) to allow the number, location, and hydraulic head of constant‐head nodes to vary with the time period. The mass balance subroutine (CHECKI) was modified to print out the flux into each constant‐head node at the end of each time period, thereby permitting calculation of changes in the rate of ground‐water flow into the mine.Site‐specific values of hydraulic conductivity, specific yield, aquifer recharge, streambed permeability, and hydraulic head initially were used in the modeling studies. Input parameter values were adjusted within the range of established field values during steady‐state model calibration. It was not possible to calibrate the transient model because the mining operation was in the planning stage and, therefore, no historical data existed. Nonetheless, transient simulations using the adjusted input parameter values and the simulated hydraulic head values were made to show that it is possible to model potentiometric surface changes caused by ground‐water flow into an open‐pit mine. These simulations predicted that, after eight years of mining, a cone of depression approximately 20,000‐feet long, 8000‐feet wide, and 1000‐feet deep would form around the proposed mine. The results of the transient simulations were used in a preliminary manner to assess the potential hydrogeologic impact of the proposed mining operation.

Simulation of Steady State Groundwater Flow in the Lower Pra Basin, Ghana

This study conceptualized the groundwater flow system; estimate the distribution of hydraulic conductivity and groundwater recharge in the lower Pra Basin in Ghana using the Groundwater Modeling System (GMS). It gives a detailed description of the site which consists of the Geographical, Hydrogeological and aquifer Characteristics of the region. The model was built by first developing a conceptual model which describes the hydrogeological framework, distribution of spatial and temporal boundary conditions, groundwater sources and sinks. This conceptual model was further converted to a numerical model for the flow simulation. Model calibration and sensitivity analysis were performed on the numerical model by comparing the observed hydraulic head with the simulated hydraulic head during calibration while model parameters were varied to obtain the most sensitive parameters in the model. The model performance was estimated to give RMSE = 3.32, R2 = 0.99 and ME = 0.07. This gives a high model performance for the study area.