Situational Awareness (Wednesday, 2023-11-22)
CO-OP is suspending drought operations because flow at the US Geological Survey’s gage at Point of Rocks, Maryland, has risen above the daily monitoring threshold of 2000 cfs as the basin received an average of about 1.4 inches of rain yesterday. Middle Atlantic River Forecast Center predictions indicate that flows are expected to remain above the daily monitoring threshold for at least the next 10 days.
According to the Middle Atlantic River Forecast Center predictions, the next 24 hours may see 0.6 inches of rain. No additional rain is expected over the next week. We will resume monitoring should flows fall below the 2000 cfs threshold. Thank you for your continued support and cooperation.
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: 1.42 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 1.42 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 1.56 (inches)
Daily flows:
Little Falls gage flow 2023-11-21: 892 MGD (1380 cfs)
Little Falls gage flow 2023-11-22: 2546 MGD (est., based on recently available real-time data) (3940 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-11-21: 969 MGD (1500 cfs)
Point of Rocks flow 2023-11-22: 1609 MGD (est., based on recently available real-time data) (2490 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2023-11-21: 892 MGD (1380 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 (2023-11-21):
Fairfax Water Corbalis withdrawal - Potomac: 76 MGD
WSSC Water Potomac withdrawal: 127 MGD
Washington Aqueduct withdrawal - Great Falls: 118 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 8 MGD
Total Potomac withdrawal: 327 MGD
Total net Potomac withdrawal: 319 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1500 cfs
QPR, obs: 1500 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.