Water Supply Outlook and Status

Interstate Commission on the Potomac River Basin

What is the Outlook?

A drinking water reservoir lake with a blue sky. Dam is seen in the background.

Little Seneca Reservoir

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 – December*

Unless conditions deteriorate, the monthly Water Supply Outlook will return to its normal schedule in 2024. The next report will be released in April, 2024.

Summary/Conclusions

The Potomac’s Section for Cooperative Water Supply Operations (CO-OP) suspended the “Daily Drought Monitoring” effort on November 22. This decision resulted from the flow at the U.S. Geological Survey’s gage at Point of Rocks, Maryland, rising above the daily monitoring threshold of 2000 cubic feet per second (cfs) after the basin received an average of about 1.4 inches of rain the day before. While recent rainfall has temporarily relieved dry conditions, it has not been enough to overcome the deficits observed in soil moisture, streamflow, and groundwater levels.

Due to the persistence of below-average precipitation, the publication period for the Water Supply Outlook has been extended into December, a month not covered by the ICPRB’s Low-Flow Outlook model. Currently, the basin is grappling with a range of dry conditions, with 33.29% classified as abnormally dry (D0), 28.40% as moderate drought (D1), and 30.12% as severe drought (D2), as indicated by the U.S. Drought Monitor report released on November 30.

In November, the basin received only 2.5 inches of precipitation on average, resulting in a 0.8-inch deficit compared to the typical monthly average. Over the past 12 months, the basin has accumulated a precipitation deficit of approximately 8 inches (approximately 20% of normal). This concerning trend is reflected in the graph of Adjusted Daily Flow at Little Falls, which is displayed in the section titled “Potomac River Flow” below. Prior to the recent rainfall, this year’s river flow closely resembled the autumn flows observed in the pre-drought years of 1965, 1988, and 2001, leading up to historic CO-OP “Drought Operations” periods that required significant reservoir releases. Without additional rainfall, the flow will likely return to pre-rainfall levels, requiring the “Daily Drought Monitoring” effort to resume.

However, it is important to emphasize that the Potomac River’s current flows 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.

Adjusted Daily Flow at Little Falls as of December 1, 2023

Drought Status:

Recent precipitation and forecasts:

Groundwater Conditions:

Water Supply Outlook Archive:

2023: April | May | June | July | August | September | October | November* | December*

2022: April | May | June | July | August | September | October

2021: April | May | June | July | August | September | October

2020: April | May | June | July | August | September | October

2019: April | May | June | July | August | September | October

2018: April | May | June | July | August | September | October

2017: April | May | June | July | August | September | October 

2016: April | May | June | July | August | September | October

2015: April | May | June | July | August | September | October

2014: October

*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.