Once the project’s stratigraphic model is completed, the groundwater flow model is configured to reflect the stratigraphic information. 

KOT Environmental Consulting Inc. (KOT-ECI) uses the USGS MODFLOW code.  This code is widely used and with which we have extensive experience.  This model has the capability of modeling all the geologic, hydraulic and hydrologic features that affect groundwater flow.  This includes different geologic formations, confined and unconfined aquifers, recharge, and stream, wetland and lake interactions.  MODFLOW models are based on a rectangular grid and a number of layers.  Current computer hardware allows a large number of cells to resolve features of interest both horizontally and vertically. 

KOT-ECI uses the hydrogeologic characteristics identified in the developed stratigraphic model as preliminary information in construction of a groundwater flow model.  This information is refined through the use site-specific measurements such as hydraulic conductivity and water level data.

Model Calibration

Following model development, it is calibrated by simulating a multiyear historical period and comparing predicted and measured groundwater levels.  The two major calibration parameters are hydraulic conductivities and recharge values.
 

• Hydraulic conductivities are adjusted by matching the drawdown due to large well withdrawals. 
• Recharge values are adjusted based on the groundwater volume and its distribution.  The overall volume should be matched adequately, following the water budget analysis.  However, the distribution of the recharge among the different aquifer boundaries may need adjusting.

The model is applied to simulate different scenarios:

• Effect of current pumping practices on the groundwater
• Predict longevity of the groundwater
• Determine the best areas for future groundwater extraction

The simulations that are conducted involve continued current withdrawals, predicted future withdrawals and different withdrawal locations.