Water Supply Outlook and Status
Interstate Commission on the Potomac River Basin
What is the Outlook?
ICPRB’s Section for Cooperative Water Supply Operations on the Potomac (CO-OP) was established to serve as a cooperative technical center on water resources in the Potomac basin. CO-OP staff publish the Water Supply Outlook on a monthly basis between April and October of each year. It provides an update on the possibility of water supply releases from the area’s reservoirs based on long-term precipitation data, flows, and other information for the Potomac basin.
Download: Water Supply Outlook – November*
The Potomac’s Section for Cooperative Water Supply Operations (CO-OP) has been actively involved in its latest “Drought Monitoring” period since October 4. CO-OP commences drought monitoring when the flow at the U.S. Geological Survey (USGS) stream gauge in Point of Rocks, Maryland, falls below 2,000 cubic feet per second. During this phase, CO-OP issues daily email reports summarizing flow, weather, and demand conditions to stakeholders. These updates are accessible daily via the CO-OP Data Portal.
Due to the persistent dry conditions, the publication period for the Water Supply Outlook has been extended into November, even though the ICPRB’s Low-Flow Outlook model does not cover this month. Currently, the basin is experiencing a range of dry conditions, including 43.89% classified as abnormally dry (D0), 14.89% as moderate drought (D1), and 21.65% as severe drought (D2), as indicated by the U.S. Drought Monitor report for November 2.
With only 1.4 inches of precipitation in October, there is a 1.6-inch deficit from the typical average for the past month. Consequently, both streamflow and groundwater levels have decreased. These inadequate precipitation and depleted groundwater levels can lead to low flow conditions requiring releases from backup water supply reservoirs. For example, the graph below of Adjusted Daily Flow at Little Falls illustrates that this year’s river flow closely resembles fall flows observed in the pre-drought years of 1965, 1988, and 2001, leading up to historic CO-OP “Drought Operations” periods with significant reservoir releases. CO-OP begins drought operations when flow in the Potomac River at the U.S. Geological Survey gage at Little Falls dam drops below the total Washington metropolitan area supplier daily withdrawals plus the 100 million gallons per day flow-by, or when CO-OP flow forecasts indicate that there is a significant chance that releases from Jennings Randolph and/or Little Seneca reservoirs will be needed within the next nine days. However, it is important to emphasize that the Potomac River’s current flows sufficiently meet the total metropolitan area’s water demands without needing releases from upstream reservoirs. The region has well-established drought-contingency plans to ensure water supply reliability and prevent shortages.
- US Drought Monitor
- CO-OP Drought Monitoring Updates (link updated July 2022)
- Maryland Drought Status
- Virginia Drought Status
- West Virginia Drought Monitor
- Pennsylvania Drought Status
- Forecasted U.S. Conditions Summary
Recent precipitation and forecasts:
- CO-OP’s Potomac Basin Precipitation Map
- Precipitation maps from the MARFC
- Quantitative Precipitation Forecast, MARFC 3 days
- Quantitative Precipitation Forecast, NWS 1-5 days
Water Supply Outlook Archive:
*Due to the persistent dry conditions, the publication period for the Water Supply Outlook was extended.
Please contact us if you would like to be notified when new Water Supply Outlooks are posted.