Part 1: Guidelines | IV. Drinking Water Assessment

Assessment Approaches/Methodologies​

​​To make the best possible plans for using water resources to serve a planning area, the comprehensive plan must identify the adequacy of existing water supplies, identify adequate sources and infrastructure for future needs and identify steps that need to be taken to protect existing and future water supply sources. These understandings must be made in the context of projected population growth and changing land use patterns. It is important to emphasize that this work can only be realistically and meaningfully accomplished within an interjurisdictional framework based on watershed rather than jurisdictional boundaries.

A number of approaches can be used to determine whether water resources and water supply infrastructure in the planning area have sufficient capacity to accommodate planned growth and development. These are described below.

1. Existing Supply Adequacy
Recent guidelines published by MDE, Water Supply Capacity Management Plans (WSCMP), provide a methodology for determining the net available capacity of existing water supplies (see pages 11-15 of the WSCMP). This available capacity, plus the estimated capacity from improving treatment of already existing sources or of obtaining water resources not yet permitted for withdrawal (to be determined using MDE-recommended methodologies), can then be used to develop an estimate of the approximate number or range of additional households and associated commercial, institutional and industrial water demand that can potentially be supported in a service area. If the capacity analysis shows a deficit, then the existing deficit must be addressed. This document is available at MDE’s website: If capacity management plans have not been completed for all community water supplies, the WRE should recommend the completion of these plans as an action item.

2. Water Quality Issues
Assess existing or potential water quality problems that may impact water supplies by reviewing source water assessment protection reports produced by MDE. Source water assessment protection reports identify vulnerabilities (e.g., susceptibility to pollution or naturally-occurring contaminants) specific to each public water system, including community and non-community water systems. Source water assessment reports, water quality assessments conducted by the U.S. Geological Survey or the Maryland Geological Survey and other available county or region-specific assessments can also provide information for assessing areas served by residential wells. Those making use of unconfined aquifers may need to be addressed. For example, water quality concerns related to naturally-occurring arsenic, radionuclides and radon have been identified in certain regions of the state and regions underlain by limestone aquifers are vulnerable to surface water contamination.  Comprehensive plans should be used to direct growth away from known contaminated and vulnerable areas and to identify regions that would be best suited for future community water service.

3. Untapped Water Supply Sources
Identify any existing untapped sources to meet projected need. This can include estimating ground water availability associated with lands owned or controlled by the county or municipality using MDE’s water balance methodology outlined in the appendix. MDE cautions that the water balance methodology may provide an estimate that exceeds the amount of water that is actually accessible, due to variable well yields in some regions. A jurisdiction may also have other untapped sources that should be identified and evaluated, such as unused or under-used surface water reservoirs and streams.

4. Alternatives and Costs Evaluation
Identify and evaluate various alternatives and costs for meeting projected needs, which can include purchasing water from other jurisdictions, acquiring additional property to supply ground water, investigating the possibility of building surface water reservoirs, identifying water reuse or conservation opportunities to reduce demand, purchasing water rights or prohibiting or postponing growth in specific geographic regions. In areas that have limited water resource information, the experience and knowledge acquired in similar situations must be used as the initial hypothesis for determining drinking water capacity. Under the best circumstances, water systems near the service area can provide significant data on potentially available water resources. For example, in the Piedmont region, a review of well yields for municipal water systems in similar geologic settings may provide the basis for estimating the amount of water that could potentially be obtained. Reviewing documentation related to the design and construction of existing or proposed surface water reservoirs may also provide a basis for estimating a potential
contribution as well as any challenges related to building a new surface water reservoir.

5. Water Quality Protection Strategies Development
Develop strategies to protect existing and future water supplies and/or address any existing or anticipated public health issues. Source Water Assessment Reports provide recommendations for each public water system, but countywide or regional solutions could also be considered. For example, interjurisdictional agreements for protecting regional reservoirs have been successful in reducing the risk to Baltimore area reservoirs. Where applicable, wellhead protection areas, reservoir watershed and other water supply areas should be protected from future development in the comprehensive plan.

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