Situational Awareness (Wednesday, 2023-10-18)
Potomac River flows at Point of Rocks are currently above 2000 cfs, the threshold for CO-OP daily drought monitoring, due to the past weekend’s rain. But flows are expected to begin falling again over the next couple of days. A small amount of rainfall, approximately 0.3 inches, is expected in the basin over the next week according to National Weather Service forecasts.
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: 0.01 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.17 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.77 (inches)
Daily flows:
Little Falls gage flow 2023-10-17: 924 MGD (1430 cfs)
Little Falls gage flow 2023-10-18: 1028 MGD (est., based on recently available real-time data) (1590 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-10-17: 1138 MGD (1760 cfs)
Point of Rocks flow 2023-10-18: 1396 MGD (est., based on recently available real-time data) (2160 cfs)
Yesterday's Patuxent, Occoquan, and Net Total System Withdrawal (2023-10-17):
FW Occoquan withdrawal: 70 MGD
WSSC Patuxent withdrawal: 62 MGD
Yesterday's total system withdrawal (2023-10-17): 432 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1760 cfs
QPR, obs: 1760 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.
Interstate Commission on the Potomac River Basin