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Using WEAP as a decision support system for sustainable water supply planning

This case study uses the Water Evaluation and Planning (WEAP) Tool as a decision support system for sustainable water supply planning in the United States.
Multiple Authors
Downtown Austin, US buildings and river
Downtown Austin, US (credit: MJ Tangonan, Unsplash)

This case study is part of the SEI Urban Toolbox for Liveable Cities which has been developed by the SEI Initiative on City Health and Wellbeing. The Urban Toolbox is a collection of tools, developed within SEI or in coordination with SEI, aimed at supporting planning and decision-making for improving the health, well-being and resilience of city residents and urban systems more broadly.

This case study demonstrates how the Water Evaluation and Planning (WEAP) Tool can be used to support water resource planning.


The AwwaRF project’s research objective was “to develop a computerized decision support system (DSS) tool that will aid utility strategic planners to effectively evaluate options for managing and developing reliable, adequate, and sustainable supplies of water for their customers for the next 50 to 100 years.” Two elements of this research objective distinguish this effort from the water supply planning efforts that drinking water utilities have pursued for decades: the longer planning horizon and the focus on sustainability.

These elements bring a wide array of management objectives and opportunities into consideration, requiring a tool that extends beyond sequencing potential supply enhancements in response to unrelenting and unmanaged increases in demand. By its very nature, a long planning horizon offers the opportunity to consider a wide range of future water management alternative on both the supply development and demand management sides of ledger. The focus on sustainability suggests a commitment to balance the full spectrum of social, economic, financial, and environmental factors in defining an appropriate future course of action.

A computerized DSS allows for the evaluation of multiple future water management scenarios and lends itself to the integrated social, financial and economic analysis that is a requisite for sustainable, long-term water supply planning. Achievement of the stated research objective has lead to the availability of an AwwaRF sponsored computerized DSS, developed on the WEAP platform, which is available for distribution to AwwaRF subscribers.

*Thiscase study is an abridged version of the original text. Please access the original text for more detail, research purposes, full references, or to quote text. A summary of the report is outlined below.

*The original text is: Huber-Lee, Annette, Chris Swartz, Jack Sieber, James Goldstein, David Purkey, Charles Young Jr, Elizabeth Soderstrom, James Henderson, and Robert Raucher. 2006. Decision Support System for Sustainable Water Supply Planning. American Water Works Research Foundation.

Methods and Tools

Adopting the WEAP software, the research effort sought to refine and enhance the tool for the drinking water industry based on substantial interactions with three test utilities: Austin, Texas; Philadelphia, Pennsylvania; and Portland, Oregon. These utilities were selected because they represent different geographic regions of the country and face distinct sets of challenges in developing long-term sustainable water supply plans. The intent was that collaboration with these three very different utilities would offer insights into the variety of planning challenges faced by the drinking water industry in the United States.

The approach taken in implementing research collaboration with the test site utilities involved the implementation of several steps.

  1. Hold a planning meeting between the research team and planners at the three test site utilities to define and prioritize issues of interest.
  2. Undertake a collaborative effort by members of the research team and the utility staff to develop a first draft of a DSS for the utility.
  3. Define and implement enhancements to the WEAP framework needed to improve the draft utility DSS, including the integration of a financial module that was called for in the original call for research proposals.
  4. Implement scenarios of interest in the refined utility computerized DSS.
  5. Hold a meeting between the research team and planners at the three test site utilities to review the results of scenario modeling using the refined utility DSS.
  6. Report on findings and conclusions drawn from the test site utility applications of the computerized DSS.
  7. Synthesize the findings of the three test site utilities into general recommendations regarding the use of the WEAP-based computerized DSS by the drinking water industry.

In summary, the research approach involved specific and targeted collaboration with utilities in an effort to develop general insights about the role of computerized DSS in the development of long-term, sustainable water supply plans.

Outcomes and Impacts


As a result of collaboration with the test site utilities, the research team was able to demonstrate the utility of a computerized DSS in the development of long-term sustainable water supply plans. Issues that were encountered and addressed in an integrated fashion, included:

  • The timing of investments in future facility expansions;
  • Investments in demand management and water reuse and recycling;
  • The coordinated operation of multiple supply sources;
  • Changing environmental regulations;
  • Service area expansion and regional coordination; and
  • Water supply and waste water treatment management to improve the status of receiving water bodies.

While this is not an comprehensive list of planning issues facing utilities, they are very common and the research demonstrated that an integrated DSS framework allowed for analysis of future scenarios comprised of multiple elements. For example, at one test site utility it was possible to evaluate, with the DSS, a set of scenarios whereby different facility enhancement actions were sequenced differently in response to different assumptions about 1.) the coordinated operation of surface water and groundwater, 2.) the minimum flows required to comply with Endangered Species Act and 3.) the number of wholesale customers included in the utility service area. This sort of integrated analysis is very powerful and is made possible by an integrated DSS for water supply planning


The effort to develop a computerized DSS tool for the drinking water industry must confront the reality that individual utilities are very diverse in terms of their relevant planning challenges and in their current reliance on the use of computerized tools to support decision-making. This fact generates two distinct sets of recommendations, on for utilities that already utilizes decision support tools extensively and one for those utilities that have yet to invert in computerized simulation tools.

For utilities with established simulation tools the overarching recommendation is that these tools be benchmarked against an integrated system like the WEAP-based DSS. At one test site the utility already relied heavily on an existing simulation tool to support planning. This tool was designed largely to consider different supply options in the face of assumed levels of demand growth and hydrologic conditions. It works extremely well in that context and is suited to the type of facilities planning that typifies much utility planning. The critical question for a benchmarking exercise is how the tool responds to the fuller spectrum of planning considerations associated with long-term, sustainable water supply planning. In particular, can the tool be easily adapted to develop scenarios that capture different formulations of future social, economic, and environmental imperatives. For this test-site utility the existing tool was robust although somewhat difficult to modify. Nonetheless, the process of comparing models allows a utility to think strategically about the next generation of modeling tools needed to support increasingly complex water resource planning efforts.

For utilities where less of an investment has been made in developing water resource simulation tools to support decision-making, developing a test application can illuminate the types of integrated analysis that support sustainable water supply planning. One test site utility uses a set of analytic tools, several of them developed in a spreadsheet environment, to handle distinct elements of the planning process. The challenge for the planner is to integrate the output of these different tools into a narrative that supports decision-making. The critical question for a test application exercise is whether integrating these distinct tools in to a single analytical framework illuminates opportunities that would me more difficult to distinguish using separate tools.

In both cases, our collaboration with the test site utilities has been affirming. The WEAP-based DSS supported by AwwaRF specifically allows utility planners to think in an integrated fashion about the future. The research team feels that this conclusion is relevant to almost all utilities.

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