DISCLAIMER
This download facility provides digital copies of the GIS data that are used by the Water Withdrawal Assessment Tool (WWAT) to
estimate the likely impact of a proposed large-quantity water withdrawal on nearby streams. These data sets include (1) the Water
Management Area (WMA) boundaries, (2) the stream data and (3) the up-to-the-minute Water Accounting Database containing both the
initial and the current A,B,C,D cutoff values in gallons per minute. The accounting database keeps track of how much water is available
in each WMA, dynamically adjusting it as new withdrawals are registered, thus providing users with near-real-time water use information
as they plan new withdrawals. The amount of streamflow depletion caused by a groundwater withdrawal is affected by a number of factors,
including the distance from the stream, well depth, aquifer transmissivity, and the connection between the aquifer and stream.
The database contains the initial estimated Index Flow at the downstream end of each WMA; a safety factor which divided the estimated
Index Flow by two; and the amount of water available for withdrawal calculated according to stream classification.
The authoritative description of the WWAT and the data and processes within it are provided in Hamilton and Seelbach (2011). The WWAT
and its associated data only estimate the likely impact of a proposed water withdrawal on nearby streams. They do not indicate how much
groundwater may be available.
Watershed Boundaries