Attribute Related Measures: Water Resource Adequacy

1. Water supply adequacy

Description: This measure assesses short-term and long-term water supply adequacy and explores related long-term supply considerations.

Example calculations and questions:

  • Short-term water supply adequacy: Period of time for which existing supply sourc­es are adequate. This can be measured as a ratio of projected short-term (e.g., 12-month rolling average) monthly supply to projected short-term monthly de­mand. Often an index or scale is used, for example, short-term supply relative to severe drought (assigned a “1”) to abundant supply conditions (assigned a “5”).
  • Long-term water supply adequacy: Projected future annual supply relative to pro­jected future annual demand for at least the next 50 years (some utilities project out as far as 70-80 years). Statistical forecasting and simulation modeling and forecasting techniques are typically used for such long-term projections. Analysis variables in addition to historical record (e.g., historical and year-to-date reservoir elevation data), forecasted precipitation, and flows can include:
    • Future normal, wet, dry, and very dry scenarios (including anticipated cli­mate change-related scenarios);
    • Anticipated population changes;
    • Future service areas;
    • Availability of new water supplies, including recycled water (plus availability of water rights for new supplies, where applicable); and
      Levels of uncertainty around the above.

2. Supply and demand management

Description: This metric explores whether the utility has a strategy for proactive supply and demand management in the short and long terms. Strategy needs will depend on community circumstances and priorities, anticipated population growth, future water supply in relation to anticipated demand, demand management and other conservation options, and other local considerations.

Example questions:

  • Has the utility developed a sourcewater protection plan (yes/no) and is the plan current (yes/no)?
  • Does the utility have a demand management/demand reduction plan (yes/no)? Does this plan track per capita water consumption and, where analytical tools are available to do so, accurately attribute per capita consumption reductions to demand reduction strategies (such as public education and rebates for water-efficient appliances) (yes/no)?
  • Do demand scenarios account for changes in rates (which can change for many reasons) and conservation-oriented, demand management pricing structures (yes/no)?
  • Does the utility have policies in place that address, prior to committing to new service areas, availability of adequate dry year supply (yes/no)? Alternatively, does the utility have a commitment to denying service commitments unless a reliable drought-year supply, with reasonable drought use restrictions, is available to meet the commitment (yes/no)?

More information on resources for this attribute-related measure can be found in the EUM Resource Toolbox.