No rain fell in the basin over the past 24 hours. Rainfall is expected over the next 3 days according to the Middle Atlantic River Forecast Center, ranging from 0.1 to 1 inch.
Hydropower operations continue to affect river flows. Large fluctuations in river flows are observed at the Shepherdstown and at the Point of Rocks gage and are expected to affect river flows at Great Falls and Little Falls.
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: 0.29 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.3 (inches)
Daily flows:
Little Falls gage flow 2023-08-26: 801 MGD (1240 cfs)
Little Falls gage flow 2023-08-27: 552 MGD (est., based on recently available real-time data) (854 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-08-26: 840 MGD (1300 cfs)
Point of Rocks flow 2023-08-27: 630 MGD (est., based on recently available real-time data) (974 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-08-26):
Fairfax Water Corbalis withdrawal (Potomac): 122 MGD
WSSC Water Potomac withdrawal: 140 MGD
Washington Aqueduct withdrawal: 147 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 5 MGD
Total Potomac withdrawal: 414 MGD
Total net Potomac withdrawal: 409 MGD
Yesterday's Patuxent, Occoquan, and Net Total System Withdrawal (2023-08-26):
FW Occoquan withdrawal: 72 MGD
WSSC Patuxent withdrawal: 42 MGD
Yesterday's total system withdrawal (2023-08-26): 523 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1300 cfs
QPR, obs: 1300 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.
Recommended operations for today (2023-08-27 A.M.):
Per operational preference.
Reservoirs - Usable storage (BG):
Facility, %Full, Current, Capacity*
WSSC’s Patuxent reservoirs, 54%, 5.5, 10.2
Fairfax Water’s Occoquan reservoir, 100%, 8.05, 8.05
Little Seneca Reservoir, 97%, 3.8 (estimated), 3.9
Jennings Randolph Total Reservoir, 81%, 23.8, 29.4
Jennings Randolph water supply**, 100%, 13.1, 13.1
Jennings Randolph water quality**, 66%, 10.7, 16.3
Savage Reservoir, 62%, 3.91, 6.3
*Storage and capacities for Occoquan, Patuxent and Little Seneca reservoirs are provided by Washington metropolitan area water utilities, and based on best available information. Storage and capacities for Jennings Randolph and Savage reservoirs are based on observed water levels and available US ACE water level/storage tables from 1998. ICPRB estimates that sedimentation has resulted in a loss of total available storage in Jennings Randolph Reservoir of 1.6 BG in recent years, and this loss is not reflected in the numbers above.
** ICPRB's initial estimate. Final accounting of Jennings Randolph water supply versus water quality storage will be provided at a later date by the US ACE.