The U.S. Geological Survey (USGS) Lower Mississippi-Gulf Water Science Center, in cooperation with multiple State and Federal agencies, collects water-level data as part of a larger initiative to monitor and evaluate the status of groundwater resources in our five-state area. The potentiometric-surface shows the altitude at which the water levels would have risen in tightly-cased wells and represents synoptic conditions. The potentiometric-surface map shows a 2-dimensional representation of groundwater flow in an aquifer and provides a basis for comparison between current and historic groundwater flow conditions. The maps can be used to show both water-table conditions for unconfined aquifers and artesian conditions for confined [...]
Summary
The U.S. Geological Survey (USGS) Lower Mississippi-Gulf Water Science Center, in cooperation with multiple State and Federal agencies, collects water-level data as part of a larger initiative to monitor and evaluate the status of groundwater resources in our five-state area. The potentiometric-surface shows the altitude at which the water levels would have risen in tightly-cased wells and represents synoptic conditions. The potentiometric-surface map shows a 2-dimensional representation of groundwater flow in an aquifer and provides a basis for comparison between current and historic groundwater flow conditions. The maps can be used to show both water-table conditions for unconfined aquifers and artesian conditions for confined aquifers.
The datasets for the potentiometric-surface maps include, but are not limited to, well points, spring points, surface-water elevations and the contours drawn to represent the potentiometric surface. Groundwater elevations are determined from measured water levels and land surface elevation. The groundwater-level measurement data (well points) are collected and processed for quality control, reviewed and approved, and are available from the USGS National Water Information System (U.S. Geological Survey, 2018). Stream and spring altitudes (spring points) are calculated from available digital elevation model (DEM) data for consistency. Stream datasets are accessible from the National Hydrography Dataset (NHD) (U.S. Geological Survey, 2017). Contour datasets are created by contouring the data for groundwater-level altitudes, stream altitudes, and spring altitudes. These datasets are processed by a geospatial program that generates the contours and potentiometric surface. The contours, where needed, are manually adjusted based on any topographical influences, water-level altitudes, and professional knowledge to more accurately represent the potentiometric surface.
REFERENCES:
U.S. Geological Survey, 2017, USGS National Hydrography Dataset (NHD) Best Resolution 20170831 for State or Territory FileGDB 10.1 Model Version 2.2.1 - ScienceBase-Catalog, accessed at ScienceBase https://www.sciencebase.gov/catalog/item/581d79c4e4b0dee4cc8e7a41.
U.S. Geological Survey, 2018, USGS Water Data for the Nation, National Water Information System - Web Interface at http://dx.doi.org/10.5066/F7P55KJN.
