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, cumulative rainfall ranging from 1/10 to 3/4 inch is expected in the basin over the next 3 days. MARFC ensemble forecasts do predict additional rain and rising river flows over the next 10 days.
Note that the USGS’s MD-DE-DC Water Science Center collected field data at the Point of Rocks gage on June 8 to verify the stage/discharge relationship.
Thank you all for your ongoing 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 period of drought monitoring. If you have any questions, please contact us via coop@icprb.org.
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 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.03 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.04 (inches)
Daily flows:
Little Falls gage flow 2023-06-11: 1176 MGD (1820 cfs)
Little Falls gage flow 2023-06-12: 1125 MGD (est., based on recently available real-time data) (1740 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-06-11: 1312 MGD (2030 cfs)
Point of Rocks flow 2023-06-12: 1280 MGD (est., based on recently available real-time data) (1980 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-06-11):
Fairfax Water Corbalis withdrawal (Potomac): 123 MGD
WSSC Water Potomac withdrawal: 145 MGD
Washington Aqueduct withdrawal: 145 MGD
Loudoun Water withdrawal: 14 MGD
Loudoun Water Broad Run discharge: 4 MGD
Total Potomac withdrawal: 427 MGD
Total net Potomac withdrawal: 423 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 2030 cfs
QPR, obs: 2030 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 – see https://www.weather.gov/erh/mmefs_marfc?id=PORM2&model=NAEFS.
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.