Monitoring Reports

The basin received almost a ¼ inch of rain over the last 24 hours. Little rain is expected in the portion of the watershed above Little Falls over the next three days. According to Middle Atlantic River Forecast Center ensemble flow forecasts, flow at Point of Rocks is expected to remain above 1800 cfs over the weekend.

Though flow conditions are not yet of great concern, we intend to continue daily monitoring reports over the weekend, and would appreciate it if you can continue sending withdrawal and reservoir storage data.

The 3-day forecast (MARFC) estimates 0.01 to 0.1 inches of rainfall in most of the Potomac Basin. There is a chance that the North Branch may receive up to 0.5 an inch of rainfall. According to our recent basin-wide average precipitation, the basin received 0.03 inches of rain in the past 24 hours. The Little Falls gage is now reporting. The gage antenna had been blocked by a broken-down crane.

Potomac basin flows continue to slowly decline. The Middle Atlantic River Forecast Center predicts that from 0.10 to 0.75 inches of rain will fall over the basin over the next three days. The Potomac River gage at Little Falls is currently not reporting real-time flows and CO-OP is notifying USGS that this gage is down.

Today, CO-OP is initiating daily drought monitoring because Potomac River flow at the US Geological Survey’s gage at Point of Rocks, Maryland, has fallen below CO-OP's daily monitoring trigger of 2000 cfs. According to National Weather Service's (NWS) quantitative precipitation forecasts, a little over a 1/10 of an inch of rain is expected in the basin over the next 3 days.

This concludes the 2020 Washington Metropolitan Area (WMA) drought exercise. A report describing exercise assumptions, activities, and tools will be prepared and made available on ICPRB's website in the coming weeks.

Thank you for your help in maintaining the reliability of the regional water supply system! Special thanks to WSSC Water staff for providing a tour of the Little Seneca Dam and to the Black Hill Regional Park for posting signs prior to the release.

We hope that the webinar on Forecast Informed Reservoir Operations by Hazen and Sawyer was informative.

This is the third and last day of our 2020 Washington metropolitan area (WMA) annual drought exercise. Reported below are actual recent conditions and simulated drought operations.

Today we requested a simulated Little Seneca release of 22 MGD. This was based on the drought scenario and not yesterday’s actual release. We will provide analysis on the travel time of this test release in our report. You can follow the release at the USGS gage 01645000 SENECA CREEK AT DAWSONVILLE, MD here.

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RECENT CONDITIONS – ACTUAL

An actual Little Seneca test release was initiated this morning at 10:00 AM. The planned release rate was 400 MGD, but during ramping up the release, it was found that the maximum possible rate is 275 MGD. You can follow the release at the USGS 01645000 SENECA CREEK AT DAWSONVILLE, MD here: https://waterdata.usgs.gov/usa/nwis/uv?01645000.

Our afternoon report appears below. Note that an ACTUAL test release from Little Seneca Reservoir has been approved by the CO-OP General Managers and is planned to be initiated tomorrow morning at 10 AM at a rate of 400 million gallons per day (MGD) and continued for 12 hours. Due to this release, flow in Seneca Creek will be elevated between approximately 10 AM on November 17 and 6 AM on November 18.

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RECENT CONDITIONS – ACTUAL

Today is the first day of the 2020 Washington Metropolitan Area Drought Exercise, which will be conducted from Monday, November 16 through Wednesday, November 18.

From the suppliers we need

CONCLUSION OF THE DROUGHT EXERCISE - Afternoon simulated Potomac flow and demand update (Tuesday 10/11/2020) - DROUGHT EXERCISE

This afternoon email report concludes CO-OP's 2016 Washington Metropolitan Area Drought Exercise. We conduct these exercises every year to practice communications and operational procedures that would be used in case of actual low flow conditions in the Potomac River. Thank you all for helping us stay well prepared for drought!

ACTUAL - Basin and system conditions: