Whose Responsibility Is It To Prove A New Development Has An Adequate Water Supply?

By Marjo Curgus, Del Corazón Consulting and Waverly Klaw, Sonoran Institute

If you are an elected official, planning commissioner, or planning staff, inevitably you have had to answer the question “Where is the water going to come from?” during a public hearing for a development application. The Colorado Revised Statutes §29-20-301-306 squarely places the responsibility on local governments to determine whether a development application has successfully demonstrated that it can ensure an adequate water supply defined as “sufficient for build out of the proposed development in terms of quality, quantity, dependability, and availability to provide a supply of water for the type of development proposed, and may include reasonable conservation measures and water demand management measures to account for hydrologic variability.” If an applicant fails to demonstrate proof of a legal, adequate, and potable water supply then the local government is required to deny the application.

Working with communities across Colorado through our Growing Water Smart program, we have identified that many local governments are either unaware of this statutory responsibility or are struggling with a lack of information to make evidence-based determinations. We are supporting local governments to develop more robust review processes starting with busting the most common myths about water adequacy determinations.

Myth: A State Division of Water Resources (DWR) well permit is sufficient proof.

False. Counties too often defer to DWR using the approval of a well permit as determination of adequate water supply. A well permit is not a water right but rather the right to drill a well. DWR primarily reviews for injury to senior water rights, although they can offer local governments guidance on the adequacy of the hydrogeology if the application includes sufficient information. A clear indication that local governments are not requiring the right submission information is when the DWR letter includes a statement of “inadequate information to determine water adequacy.”

Myth: In over-appropriated basins an augmentation certificate is sufficient proof.

False. The purpose of augmentation is to ensure that an individual well does not negatively impact senior water rights. It does not always protect against localized groundwater decline.

Myth: The water supply report submitted by the applicant is sufficient proof.

Depends. For a development on wells, state statutes require an applicant to submit a water supply report prepared by a registered professional engineer or water supply expert that includes an estimate of total water demand for the development, a description of water source, and an estimate of water yield under different hydrological conditions. If the development regulations lack desired specificity of how these reports are to be prepared, then the quality of the reports will inevitably vary.

Myth: A water provider’s will serve letter is sufficient proof.

Depends. If the source of water is a water provider, state statutes require that the provider either has a current water supply plan on file with the local government or will submit a will serve letter demonstrating sufficient capacity to serve a development. Water providers, in their water supply plan or will serve letters, are expected to include a description of their water sources, estimates of water yield under different hydrological conditions, water demand measures they require for development, and a description of the water supply entity’s obligations. In reality, the letters rarely provide the detailed analysis of information beyond a simple statement of willingness to serve.

Myth: A citation of the state statute and definition of adequate water supply in our code is sufficient regulatory language.

False. While development standards usually include a requirement for adequate water supply, citing the state statute and definition, they often fail to be explicit in what criteria an applicant has to meet.
Rethinking Water Adequacy Requirements

Fortunately, state statute offers local governments great latitude to request “any other information required by local government.” The following methods are emerging as ways local governments can strengthen their regulations to better inform decisions for water adequacy:

  1. Require More Accurate Methodologies for Calculating A Development’s Water Demand
  2. Require Applicants to Reduce their Water Demand as Part of the Water Supply Plan
  3. Define Specific Requirements for Proof of Water Adequacy from Water Providers
  4. Use Zoning Based on Hydrogeology for Development on Wells with Specific Requirements for Each Zone

Putting revised requirements in place now ensures that a local government’s elected officials can make informed and accurate decisions to ensure their community has an adequate and sustainable water supply long into the future. The Sonoran Institute has developed a new report on best practices for local water adequacy regulation. Please contact to receive a copy of the report.
Growing Water Smart is a joint program of the Sonoran Institute and the Babbitt Center for Land and Water Policy, a Center of the Lincoln Institute of Land Policy. For more information, please see

Photo 1 by Jacek Dylag on Unsplash

Photo 2 by Poul Cariov on Unsplash


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