Aquifer versus wellhead protection

   

WELLHEAD VERSUS AQUIFER PROTECTION

Adapted from Witten and Horsley

A Guide to Wellhead Protection

APA Planning Advisory Service Report No. 457/458

FIGURE 1

WELLHEAD PROTECTION AREAS

The delineation of wellhead protection areas (WHPAs) is an important means for directly and immediately safeguarding the public water supply. As defined in the 1986 Safe Drinking Water Act Amendments, a WHPA is "the surface and subsurface area surrounding a water well or wellfield, supplying a public water system, through which contaminants are reasonably likely to move toward and reach such water well or wellfield." The pumping of wells within an aquifer results in artificially induced changes (such as drawdown and cones of depression) to the natural groundwater system. WHPAs are those land areas that contribute water (and potential contaminants) to the pumping wells. In this sense, these protection areas are subsets of the natural system (i.e., the aquifer).

Aquifer protection is an important means for safeguarding public water supplies over the long term. While many aquifers extend far beyond current wellfields, they store groundwater that might be needed in the future.

The protection of aquifers requires an understanding of the extent of both the aquifer and its overlying and upgradient lands from which its water is derived. The delineation of aquifer protection area boundaries is independent of the effects of pumping wells and is more directly related to the natural hydrologic flow patterns. Both surface and groundwater flow conditions must be factored into the delineation of aquifer protection areas.

A distinction can be made between aquifer and wellhead protection areas (WHPAs). Aquifer protection areas give consideration to the entire groundwater resource (both existing and potential water supply development areas). WHPAs are those areas, as subsets of the aquifer, through which contaminants are likely to flow and reach the pumping well or wellfield (see Figure 1)....it is important to distinguish....between wellhead protection and aquifer management. While aquifer protection may be more desirable, local goals, time, and monetary resources may dictate that initial efforts, at least, are focused on particular resources. Where aquifers are confined, the aquifer protection area may be limited to the outcrop of the aquifer unit and its immediate contributing area (see Figure 2). This area may be geographically isolated from the location of water supply wells within the aquifer.

FIGURE 2

How does this relate to the Laramie Regional Drinking Water Protection Program?

The challenge is unlikely to focus on whether the City of Laramie or Albany County has the right to establish the protection zone; rather, it will concentrate on how the protection zone was determined. Defending the use of an arbitrary formula (or technical approach) can be difficult. The choice of which technique to use depends in large measure on the anticipated breadth of protection tools to be employed. If the City and County hopes to pursue an aggressive management program, it should invest in a delineation approach that will sustain possible court and expert witness challenge and must ensure that the City/County recommendations are supported by hard science, not opinions. The proposed aquifer protection program tentatively adopted by the Environmental Advisory Committee is being designed with these challenges in mind. Come to the Environmental Advisory Committee meetings which are held on the second Wednesday of every month at 7 p.m. at the Fire Substation located at 23rd and Reynolds Street.

Any comments on this page may be addressed to the webmaster of this page, by e-mailing comments to roten at lariat.org (or by e-mailing tvedgar@uwyo.edu).

Return to The Aquifer Protection Home Page.