McGuire, V.L., Seanor, R.C., Asquith, W.H., Kress, W.H., Strauch, K.R., and Flynn, A.T., 2019, Data associated with potentiometric surface, Mississippi River Valley alluvial aquifer, spring 2016: U.S. Geological Survey data release, https://doi.org/10.5066/P9SV1HMQ.
The purpose of this study was to prepare and present a potentiometric-surface-contour map for the current extent of the MRVA aquifer using (1) groundwater-altitude data from wells measured in spring 2016, which is after water levels have generally recovered from pumping in the previous irrigation season and before pumping begins for the current irrigation season, and (2) the altitude in spring 2016 of the top of the water surface in rivers and streams, hereinafter referred to as surface-water altitude, from streamgages in the area. To best reflect hydrologic conditions in the MRVA aquifer, the groundwater altitudes used to create the 2016 potentiometric surface would be measured in a short-time frame of days or a week and there would be available data (for example from sets of short-screened wells installed near the top, in the middle, and near the bottom of the aquifer) to indicate vertical flow components. However, most wells screened in the MRVA aquifer were measured before the potentiometric surface map of the MRVA aquifer was planned and therefore the timing of each well’s measurement(s) was determined by the needs and schedules of the entities doing the measurements. Also, many of the measured wells have long screens, therefore their water-level measurements represent an average head in the aquifer for that location. For this study, recognizing the limitations of the available data, it was decided to assess all available groundwater-altitude data from wells measured from January to May 2016 for use in the potentiometric surface map for spring 2016. The resultant potentiometric surface would then represent the generalized central tendency for spring 2016, but it would not be useful for some purposes, such as for calibration of a groundwater flow model for early April 2016 or for some local scale assessments.