Source Water Assessment Program
Delineating Source Water Areas
Delineation of source water assessment areas for Wisconsin's groundwater systems differ widely from surface water systems.Groundwater System Source Water Assessment Areas
Source water assessment areas for public water supply systems using groundwater have been identified and delineated by methods that vary depending on system type and other factors.The following are source water area delineation methods used for the different types of groundwater public water systems:
Municipal Systems
Other-than-Municipal and Non-Transient Non-Community Systems
Transient non-community Systems
Special Situations & Considerations
Municipal wells:
Approved wellhead protection plan recharge area delineations or other advanced delineations were used if available. The SWAP effort included supporting regional hydrogeologic modeling studies to delineate source water areas for municipal systems in certain areas of the state. These "advanced delineations" were performed by hydrogeologists at the U.S. Geological Survey, Wisconsin Geological and Natural History Survey, and/or University of Wisconsin. Selection criteria for determining what areas of the state should be covered by the hydrogeological studies included community interest in follow-up source water protection efforts, inappropriateness of using CFRs in the hydrogeologic setting, likelihood of success of a modeling effort in the hydrogeologic setting, and population served. For all advanced delineations a 600-foot radius circle buffer was added to the delineation to insure that the source water areas are conservative. For systems without advanced delineations we have performed calculated fixed radius (CFR) delineations. These CFR delineations are calculated using: 1) five years of groundwater flow to the well, 2) the open interval length of the well, 3) aquifer material porosities weighted by percent length of open interval, and 4) the 1997 or 1996 annual pumping history. As a safety factor, a 1200-foot radius is used for all wells with a CFR of less than 1200 feet because 1200 feet is the maximum separation distance to any potential contaminant source found in the public water supply code (NR 811 Wis.Adm. Code).
Other-than-municipal community wells and
non-transient non-community wells:
CFRs were evaluated for these types of wells too, but it was determined that low pumping rates would result in all systems having less than 1200-foot radius delineations. Therefore 1200-foot fixed radius source water areas were used for all of these systems. A few of these systems located in karst hydrogeologic environments had more advanced delineations completed.
Transient non-community wells:
There are nearly 10,000 transient non-community wells in the state. The WDNR has proposed using a 200-foot fixed radius delineation for all of these wells based on the impracticality of developing more intensive delineations for these systems. A Minnesota study indicates that a 200-foot radius area is an adequate source water area for those systems in homogeneous, unconfined aquifers. These systems have very limited resources for protection programs and, like other-than-municipal and non-transient non-community wells, have no jurisdiction over land use outside of their property boundaries.
Special Situations & Considerations
Delineations for groundwater systems in certain problematic hydrogeological settings were addressed by a technical advisory committee. The committee recommended that mapping karst features in the vicinity of public wells would be useful for source water assessments. These features act as conduits from contamination sources at the surface to the wells. There was a consensus that this approach would be more effective than using a larger radius.
For confined settings, the committee saw much less potential for groundwater contamination from the surface around the well and greater difficulty in delineating recharge areas. However, there was a consensus that the threat of contaminants penetrating confining layers through conduits such as improperly filled and sealed wells justified doing advanced delineations with regional models.
Surface Water System Source Water Assessment Areas
The Surface Water Delineation Technical Advisory Committee determined how source water areas would be delineated for water systems using surface waters. The following strategies were developed for source water area delineations for these systems based on which surface water the system is located on.Lake Michigan and Lake Superior Systems
Based on the size of the water sources and intake distribution, each Lake Michigan and Lake Superior intake/intake cluster will be assigned an individual protection area that will include at least one locally discharging watershed.
Lake Winnebago Systems
Based on the well-mixed characteristics of the water sources, the entire Lake Winnebago and Rainbow Lake watersheds will be delineated and assigned to the associated intakes.
Map of Surface Water System Source Water Assessment Areas - Adobe Acrobat PDF Document.
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Last Revised: Tuesday July 17 2007
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