Monitoring Reports

During periods of drought, the Cooperative Water Supply Operations on the Potomac (CO-OP) helps manage the Washington metropolitan area water supply system by coordinating withdrawals from the Potomac River and off-river reservoirs and recommending releases from upstream reservoirs when forecasted flow in the river is not sufficient to meet expected needs. These needs include water demands and an environmental flow-by of 100 million gallons per day (MGD) on the Potomac River at Little Falls dam near Washington, D.C.

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Daily Potomac flow and demand update (Friday 2019-10-18)

In the last 24 hours, trace amounts of precipitation fell in Washington County, Maryland. According to MARFC's precipitation departure calculations, last Wednesday's precipitation improved basin precipitation totals, which are now near normal for the month of October. Precipitation amounts between 0.5 and 0.75 are expected over the next 5 to 7 days.

Flow at the USGS gage at Point of Rocks is currently below 2000 cfs, the trigger for daily monitoring. Daily monitoring will be continued at this time. *

Recent basin-wide average precipitation (above Little Falls):

Daily Potomac flow and demand update (Thursday 2019-10-17)

According to the Middle Atlantic River Forecasting Center, between 0.25 and 1.5 inches of rain fell in the basin over the past 24 hours. This amounts to a basin-wide average precipitation of about 0.65 inches. Between 0.75 and 1.75 inches of rain is expected over the next 7 days.

​Daily Potomac flow and demand update (Wednesday 2019-10-16)

No significant amount of rain has fallen in the Potomac basin over the past 3 days. Around midnight last night, flow in the Potomac River at Point of Rocks temporarily dropped below CO-OP's threshold for drought monitoring of 2,000 cfs. We will reassess the need for daily monitoring after today's expected rainfall. According to Middle Atlantic River Forecast Center estimates, 1.25 to 2.5 inches is expected throughout the basin in the next 7 days. Slightly smaller amounts of 0.5 to 1.25 inches is expected in the next 5 days.

Daily Potomac flow and demand update (Tuesday 2019-10-15)

According to the Middle Atlantic River Forecasting Center, no rain fell in the basin over the past 24 hours. Between 0.25 and 1 inch of rain is expected over the next 3 days.

Although flows at the USGS gage at Point of Rocks are currently above 2000 cfs, the trigger for daily monitoring, daily monitoring will be continued at this time.

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)

Daily Potomac flow and demand update (Monday 2019-10-14)

No significant amount of rain has fallen in the Potomac basin over the past 3 days. According to Middle Atlantic River Forecast Center estimates, 1/4 to 3/4 inches is expected throughout the basin on Wednesday. Flow in the Potomac River at Point of Rocks is still elevated from last week's rainfall, and is above CO-OP's threshold for drought monitoring. We will reassess the need for daily monitoring after Wednesday's rainfall.

Recent basin-wide average precipitation (above Little Falls):

Daily Potomac flow and demand update (Sunday 2019-10-13)

Trace amounts of precipitation occurred around the outer perimeter of the basin, resulting in an average basin precipitation of 0.016 inches for yesterday. According to MARFC, the basin precipitation for the month of October is currently at 1 inch, which is about normal for this time of the month. Above the USGS gage at Point of Rocks, this precipitation has returned some of the precipitation totals to near normal or above normal for the month. However, below this USGS gage, greater than 75% below normal precipitation totals for the month remain throughout the basin.

Daily Potomac flow and demand update (Saturday 2019-10-12)

Dry conditions continue, and little rain is in the forecast over the next 7 days.

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 precip: 0 (inches)

Past 3-day cumulative area-weighted average basin precip: 0.04531 (inches)

Past 7-day cumulative area-weighted average basin precip: 1.08125 (inches)

Daily Flows:

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