Long-term planning

Interstate Commission on the Potomac River Basin

Every five years since 1990, CO-OP has conducted a water demand and resource availability forecast for the Washington, D.C., metropolitan area. These studies assess whether or not the current water supply system will be able to meet the needs of the region 20 or more years in the future.

Recent Studies

Washington Metropolitan Area Water Supply Alternatives

Executive Summary │ Full Report

This study assesses a range of solutions to increase the capacity of the region’s water supply, which could fail to meet unrestricted demands by 2040. The Washington Metropolitan Area Water Supply Alternatives Study provides information on alternatives out to 2085 to help ensure strategic options are available over that planning horizon. Alternatives were evaluated by their abilities to maintain reliability in the face of growing metropolitan area water demand, decreasing river flows due to upstream use, and the potential impacts of climate change.

Evaluation of Travilah Quarry for Water Supply Storage

Summary Page │ Full Report – Phase 1 │ Full Report – Phase 2

A feasibility study of potential prerequisites for use of the Travilah Quarry as a raw water supply storage facility.

2015 Washington Metropolitan Area Water Supply Reliability Study: Demand and Resource Availability Forecast for the Year 2040 Cover Image: 2015 Washington Metropolitan Area Water Supply Study

Full Report │ Appendices │ Quick Fact Sheet

The 2015 iteration of the Washington Metropolitan Area Water Supply Study indicates that by 2035, the current water supply system could experience considerable stress during a severe drought, not accounting for the impacts of climate change. Managing water supply in that event would require mandatory water use restrictions. By 2040, in the event of a severe drought, there would be a chance that storage in Little Seneca Reservoir would be depleted and that flow in the Potomac River would drop below the minimum environmental flow level of 100 million gallons per day at Little Falls dam, though only by a small amount. When climate change is considered, a wide range of outcomes are predicted, from the depletion of most reservoirs in the system to there being no issues meeting unrestricted demand.

 

2010 Fact Sheet Part 1

2010 Washington Metropolitan Area Water Supply Reliability Study Part 1: Demand and Resource Availability Forecast for the Year 2040

Fact Sheet │ Full report

Part 1 of the 2010 study indicates that the current water supply system will likely be adequate in 2030, but might become strained by 2040. If in 2040 the region were to experience conditions similar to the worst drought on record (1930) mandatory water use restrictions would likely be required. (See figure 1 for a comparison of Washington metropolitan area average annual demand forecasts with current and past studies.)

 

2010 Washington Metropolitan Area Water Supply Reliability Study Part 2: Potential Impacts of Climate Change

Fact Sheet │ 2010 Fact Sheet Part 2Full report

Projected impacts of climate change on regional water supplies range from minor to major. In worst-case scenarios, with no changes to the current water supply system, a moderate drought in 2040 could cause:

  • Mandatory restrictions on water use,
  • Depleted reservoirs, and/or
  • Inability to maintain environmental flow-bys.

Past Studies

Water Supply Reliability Forecast for the Washington Metropolitan Area, Year 2025
Ani Kame’enui, Erik R. Hagen, and Julie E. Kiang, ICPRB-05-06, 2005

Year 2000 Twenty-Year Water Demand Forecast and Resource Availability Analysis for the Washington Metropolitan Area
Erik Hagen and Roland C. Steiner, ICPRB-00-6, 2000

1995 Water Demand Forecast and Resource Availability Analysis for the Washington Metropolitan Area
Mary G. Mullusky, Stuart S. Schwartz, and Roland C. Steiner, ICPRB-95-6, 1995

20-Year Water Demand Forecast and Resource Availability Analysis for the Washington Metropolitan
John Holmes and Roland C. Steiner, ICPRB-90-5, 1990