Boating, Swimming in the Potomac River: How Safe Is It? Judging by use, residents of the Potomac basin love their rivers and streams. As air and water temperatures rise in the summer, residents take to their favorite fishing, swimming and boating spots. Access areas and beaches along the river from its mouth to the North Branch Potomac draw crowds of people pursuing their favorite pastimes and a love of the river resource. |
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Water Supply Outlook & Status
What is the Outlook?The water supply outlooks are published by ICPRB's Cooperative Water Supply Operations Section (CO-OP) staff on a monthly basis between April and October. They are meant to provide an update on the possibility of water supply releases from the area's reservoirs based on long-term precipitation data, flows, and other information for the Potomac basin. Summary/conclusions:The probability of releases this summer and fall from the Washington metropolitan area’s back-up water supply reservoirs is above normal. Generally, the use of Jennings Randolph and Little Seneca reservoirs is triggered by low flows brought about by a combination of low summer rainfall, low precipitation in the prior 12 months, and low groundwater levels. Water resources in the Potomac Basin have been decreasing over the past few months. Groundwater levels remain normal but streamflow levels at Point of Rocks and Little Falls have been declining since the beginning of June. Potomac streamflow will continue to fall in the absence of significant, widespread rainfall. The U.S. Drought Monitor released on Thursday, July 1, indicates that most of the Potomac Basin is abnormally dry although portions of central and southern Maryland are experiencing moderate drought levels. With abnormally high temperatures and little chance for precipitation in the near term, the basin is becoming increasingly susceptible to drought conditions. But for now, from a water supply perspective, there is sufficient water in the Potomac River to meet Washington metropolitan area demands, and the upstream reservoirs are near-full to full. The overall decrease in rainfall, streamflows, and groundwater will be monitored in the coming weeks. In the event that conditions do not improve, daily monitoring by ICPRB CO-OP section and utilities may be needed in the near future.ICPRB outlook:There is a 20 to 27 percent conditional probability that Potomac flow will drop below 600- to 700-million gallons per day (MGD) at Little Falls through December 31 of this year; at these flow levels, water supply releases from Jennings Randolph and Little Seneca Reservoirs may occur. Releases occur when predicted flow is less than demand plus a required flow-by: demand ranges from 400 to 700 MGD during the summer months and the minimum flow-by at Little Falls is 100 MGD.The conditional probability is estimated by analyzing the historical stream flow records and giving consideration to recent stream flow values, precipitation totals for the prior 12 months, current groundwater levels, and the current Palmer Drought Index. Past years in which watershed conditions most closely resemble current conditions are weighted more heavily in the determination of conditional probability. The historical, or unconditional, probability is based on an analysis of the historical stream flow record without weighting for current conditions. The conditional probability of 20 to 27 percent compares to a historical probability of 10 to 16 percent and is considered the more reliable indicator. |
Graphical Updates of River Flow and Reservoir StorageRecent Potomac flow:2010 Flow at Little Falls Stage at Edwards Ferry Drought Status:National Weather Service Potomac Basin Monitor Recent precipitation and forecasts:Monthly Precipitation in the Potomac Basin Precipitation maps from the MARFC Quantitative Precipitation Forecast, MARFC 1-2 days Quantitative Precipitation Forecast, NWS 1-5 days Groundwater conditions:
Access more information on ICPRB CO-OP by returning to the Overview Page. |
Last Updated (Thursday, 08 July 2010 19:52)