Identifying and Adapting to Water Demand Uncertainties

Authors:

  • Jack Kiefer - Hazen and Sawyer

The three main drivers of uncertainty are climate, economics, and efficiency.

The participating utilities were asked "What types of management methods do you use to cope with uncertainty and mitigate potential consequences?"

Uncertainties about the future, as well as about the causes of historical and recent trends in water usage patterns, can affect (a) how long-term water demand forecasts are constructed and (b) why long-term water demand forecasts are seldom realized with very high degrees of accuracy. Inaccurate forecasts can lead to costs to water utilities, water rate-payers, and even to the environment. Over-building of supply and water treatment capacity can lead to stranded capital assets, higher water rates than might otherwise be necessary, and additional stress on watersheds. On the other hand, under-investment can result in imposition of water shortage restrictions, economic damages from water shortages, as well as harm to the credibility of water supply managers. These risks, the ways they are affected by planning uncertainties, and how water systems cope present a complex set of challenges, which are rooted in uncertainties about the demand for water.

This paper presents a summary of the principal causes of uncertainty in forecasts of water demand. Using data from multiple geographic areas and water utilities that have participated in projects as part of the Water Research Foundation’s Water Demand Focus Area, the paper illustrates examples of the prospective impacts of weather variability, climate change, economic cycles, and long-term changes in water efficiency on water demand. The discussion describes how these influences can be modeled and integrated into water demand forecasting. The paper shows ways in which these uncertainties can be portrayed and used to assess water supply planning risks and will demonstrate the fundamental importance of recognizing and addressing water demand uncertainties within an adaptive and anticipatory planning framework.

For more information, please contact the author at jkiefer@hazenandsawyer.com.

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