An Animated Look at Groundwater Monitoring Data – Hydrographs in Map View

Water level hydrographs are used by hydrogeologist to help understand the behavior of an aquifer and the response to different stresses, however, the ability to separate out the spatial impacts from multiple stresses in the many hydrographs of a monitoring network can be very difficult. To overcome this problem, we have developed a method to animate multiple potentiometric surface maps created at short time intervals (days or weeks) from pressure transducer data. A MATLAB script is used to pick out data a given time interval, calculate means, and flag or fill in missing data. The water levels are then contoured using the finite-difference solver in MODFLOW. For the Mahomet and the Cambrian-Ordovician Sandstone Aquifers in Illinois, water levels from the observation wells were input as constant heads. Nodes for streams that are water table outcrops were also assigned constant head values. A uniform hydraulic conductivity was used for the entire aquifer, although the method is not sensitive to the specific value. No recharge or other flux boundary conditions were used. The thickness of the aquifer was used to capture the variation in transmissivity which can influence the results in areas where there are no data points. With this method the spatial changes in the potentiometric surface between measurements can be more clearly represented and the influence of different stresses more readily identified.