May 23, 2007

Published in Wake Forest, NC

            In a year when there is already a 3-inch rainfall deficit locally, when the state Division of Water Resources says the area is abnormally dry and may place Wake County in the moderate drought category next week, and when the National Oceanic and Atmospheric Administration (NOAA) is predicting an active hurricane season, a lot of eyes will be turned to the skies and to the level of Falls Lake.

            Falls Lake – through the City of Raleigh, which provides water and sewer to Wake Forest and the towns of eastern Wake County – is the sole water source for close to 400,000 people.

            (There is an exception. Raleigh has continued to operate the G.G. Hill water treatment plant in Wake Forest on the Smith Creek Reservoir. George Rogers, the environmental coordinator for Raleigh Public Utilities, says the plant operates around the clock – “It makes prettier water that way” – and on average produces 1.8 million gallons a day. Town customers are currently using as little as 2.6 mgd and as much as 4 mgd, and the water to make up the difference is produced at the E.M. Johnson plant on Falls of the Neuse Road, reaching Wake Forest from pump stations on Capital Boulevard and Forestville Road and from a pump station in Rolesville.)

            Falls Lake is controlled by the U.S. Army Corps of Engineers, which bought the land, built the dam, and was authorized to operate the lake and dam for flood control, water supply, water quality downstream in the Neuse River and recreation. The lake was filled in the summer of 1984 and holds water that drains from three rivers and countless streams in a 770-acre basin.

            The lake is conceptually divided into three horizontal sections: the flood control pool at the top, the conservation pool in the middle, and the sedimentation pool at the bottom. 

            The flood control pool, the water retained in the lake to prevent downstream flooding as much as possible, is from 264.8 feet above mean sea level to 251.5 feet. The lake can hold up to 352,577 acre-feet of water (the amount of water to cover an acre at a depth of a foot) to prevent floods. We are probably not looking at this scenario this summer unless there is a widespread, drenching, sustained storm.

            We are also not concerned right now about the sedimentation pool, 36.5 feet at the bottom of the lake where sediment can build up.

            We are concerned with the normal conservation pool, which is from 251.5 feet above mean sea level down to 236.5 feet. This 15 feet of water is our concern because it holds both our drinking water and the water that helps keep the Neuse River flowing downstream all the way to the Pamlico Sound.

            After Raleigh’s Director of Public Utilities Dale Crisp sent out an e-mail last week to a very large list of people, explaining the new water restrictions, there were several return comments. Terry M. Brown, the water control manager for the Corps’ Wilmington District, replied to one with an explanation of the relationship between the City of Raleigh’s withdrawals and the downstream releases.

            “There is not a normal relationship between what the City of Raleigh withdraws from Falls Lake and what is released downstream from Falls Dam. This tends to be a large misconception with the public,” Brown wrote.

            “The City of Raleigh has purchased the rights to 45,000 acre-feet or 42.3 percent of the conservation pool storage within Falls Lake,” Brown wrote, “and 57.7 percent of the conservation pool or 61,322 acre-feet is used for water quality releases.

            “Water released from the dam is for water quality purposes only and is NOT normally related or linked to what the City of Raleigh takes out of Falls Lake.”

            Brown went on to say the Corps tracks the percent and the amount of storage for each of the two intermixed pools daily.

            As the conservation pool dwindles down from 251.5 feet, the amount of water available for our drinking water and for downstream water quality shrinks.

            During a drought, the Corps will tell the city daily how many days of water supply it has left using the withdrawal rates it provides. “That is basically the role that I have with the City.”

            Brown also had an interesting point. “If the City of Raleigh goes into conservation mode in a drought and less water is withdrawn from their intake, then logically, less water may be returned to the city for treatment and less treated water is released into the tributaries flowing into the Neuse River downstream of Falls Dam. This may mean that additional water quality releases may have to be released from Falls Dam to hit the fixed water quality flow downstream.

            “The level of Falls Lake may not be helped with less city withdrawals,” Brown ended.

            The state requires the Corps maintain a flow in the Neuse River of at least 254 cubic feet per second at Clayton from April through October and at least 184 cfs from November through March. The state also requires minimum releases at the dam of 100 cfs from April through October and, depending on the lake level, releases of between 55 to 65 cfs from November through March.

            “Any temporary lowering of flow targets has to be coordinated through many channels and ultimately I have to be given permission by higher authority within the Corps of Engineers to deviate from normal requirements,” Brown said.

            “You can be assured that we are doing our best to conserve and protect the level of Falls Lake every day, especially in dry times. We coordinate with the City of Raleigh and offices within the State of North Carolina as well as other stakeholders on a weekly basis; comparing notes, concerns, looking at extended weather forecasts, doing what-if analyses, projecting conditions weeks and sometimes months into the future to see what actions need to be done NOW to offset what COULD happen if no actions took place,” Brown concluded.

            Some of the other stakeholders in the use of Falls Lake besides Raleigh are the downstream cities and towns, Kinston, for instance, which use the Neuse River as their water supply, state agencies established to protect fish, marine life and wildlife, the Neuse River Foundation and its riverkeepers, fishermen in the Pamlico Sound and the hog farms which are in the Neuse basin.

            The water restrictions on the use of sprinklers begins July 2. For the complete details, see the article in the May 16 edition available in the archives.