Situational Awareness (Tuesday, 2024-06-25)
CO-OP is initiating daily drought monitoring and reporting today because Potomac River flow at the US Geological Survey’s gage at Point of Rocks, Maryland, has fallen below 2000 cubic feet per second (cfs), CO-OP's daily monitoring threshold. According to the Middle Atlantic River Forecast Center (MARFC) quantitative precipitation forecasts, 0.5 inches of rain are expected over the next 3 days. MARFC ensemble forecasts predict additional rain and rising river flows over the next 10 days.
We appreciate your continued successful submission of withdrawal, storage, and discharge data through regular emails! Please continue to keep up with those submissions on a daily basis and make sure the data is sent by 8:00 am for the duration of this drought monitoring period.
Should you have any questions or require further clarification, please do not hesitate to contact us at coop@icprb.org. Additionally, if your team has changed, kindly update us to ensure that our email list remains accurate and current.
Special conditions
The USGS’s MD-DE-DC Water Science Center collected field data at the Point of Rocks gage on June 24 to verify the stage/discharge relationship and adjusted flows downward to some extent.
A National Park Service contractor will be performing bathymetric surveys of the Potomac River at Potomac Dam No. 4 in Washington County, MD on Tuesday, June 25, and Wednesday, June 26 at Potomac Dam No. 5. During this time, the hydroelectric operator – Eagle Creek will be diverting water off of the run-of-river dam crest through the powerplant turbines.
Recent basin-wide average precipitation (above Little Falls):
(based on CO-OP's Low Flow Forecast System analysis of Middle Atlantic River Forecast Center (MARFC) gridded multisensor precipitation estimates)
Yesterday's area-weighted average basin precipitation: 0.1 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.15 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.17 (inches)
Daily flows:
Little Falls gage flow 2024-06-24: 1079 MGD (1670 cfs)
Little Falls gage flow 2024-06-25: 976 MGD (est., based on recently available real-time data) (1510 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2024-06-24: 1286 MGD (1990 cfs)
Point of Rocks flow 2024-06-25: 1293 MGD (est., based on recently available real-time data) (2000 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2024-06-24: 1079 MGD (1669 cfs)
Note: Estimated flow below Great Falls intake is flow at Little Falls plus Little Falls water supply withdrawal.
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2024-06-24):
Fairfax Water Corbalis withdrawal - Potomac: 139 MGD
WSSC Water Potomac withdrawal: 147 MGD
Washington Aqueduct withdrawal - Great Falls: 0 MGD
Washington Aqueduct withdrawal - Little Falls: 177 MGD
Loudoun Water withdrawal: 14 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 477 MGD
Total net Potomac withdrawal: 471 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1990 cfs
QPR, obs: 1990 cfs
QPR, WS: 0 cfs
Note to Loudoun Water: See NWS ensemble flow forecasts (HEFS, GEFS, NAEFS) for Point of Rocks flow for the next 7 days – https://www.weather.gov/erh/mmefs_marfc?id=PORM2&model=NAEFS. See US Army Corps of Engineers Potomac River Basin page for observed releases from Savage and Jennings Randolph reservoirs - https://www.nab-wc.usace.army.mil/nab/poto.html; See US Army Corps of Engineers North Branch Potomac River and Savage River page for scheduled releases - https://www.nab-wc.usace.army.mil/nab/northBranch.html.
Note: Potomac River flow at Point of Rocks has dropped below the low-flow threshold of 2,000 cfs. When this occurs, per the Water Supply Coordination Agreement of 1982, CO-OP begins daily monitoring and reporting of Potomac flows and withdrawals on behalf of the CO-OP suppliers, Fairfax Water, Washington Aqueduct, and WSSC Water. Suppliers can review data at CO-OP's Data Portal at www.icprbcoop.org. Reports formatted in approved templates should be submitted by email to coop@icprb.org by 8:00 am for automated processing. Published monitoring reports are at http://icprbcoop.org/products/monitoring-reports.