LAKEWOOD - Although lake level protocol has been the same since approximately 1980, many people are curious why levels are set as they are.
Dave Gustafson, Jamestown Board of Public Utilities electric and gas resource manager, explained how lake levels are determined at the latest CLA annual meeting.
Gustafson was invited to the CLA's meeting as the program speaker. He explained what the BPU's involvement in controlling lake levels is, and explained basic theory behind the practices employed to regulate lake levels.
"We take our responsibility to try to follow the plan very seriously," said Gustafson. "But it's really a very simple plan. The target lake level for the summer is 1308.35 feet, so from May to October, the goal is to maintain that elevation."
Gustafson said that occasionally, maintaining the summer level of the lake can be difficult, depending on fluctuating rainfall. Because it is easier for lake levels to rise than it is for them to fall, it can make maintaining the proper lake level difficult.
"If there's a big rain storm ... the surface area of Chautauqua Lake is roughly 20 square miles, and the (watershed) is roughly 200 square miles, which means the drainage area is 10 times the size of the lake. One inch of water draining on that 200 square miles area, all funneling into the lake ... will cause the lake level to rise 10 times the amount that landed on the area around it. Very often the lake will rise a foot in a day, and it will take two weeks or so to drain that water off."
Gustafson explained that, although the Warner Dam, the device that is used to help regulate lake levels, can drain water at a faster level, the Chadakoin River can only accommodate so much.
"You really only need to look at the geography of the river going through Jamestown," said Gustafson. "It's a very narrow river, and there are so many tributaries going into the lake with only a single outlet. ... Warner Dam doesn't really control the maximum flow down the river; what controls the flow is the channel capacity itself."
Gustafson said that, after heavy rainfall earlier in June, the dam has recently been returned to minimum flow into the Chadakoin. Minimum flow will be maintained throughout the summer, unless there is heavy rainfall again, which occurred during the first week of July. As of Monday, the lake level was at 1,308.55, which means the dam will be reset to minimum flow. At the end of October, the dam will open back up to maximum flow, in an attempt to reach a winter level of 1,307 feet.
"(1,307 feet) is hard to do," said Gustafson. "As the water level goes down in the lake, the flow down the river channel decreases dramatically. If we were to open the gates right now, each gate can handle a maximum flow of 2,000 cubic feet per second, but the river can only handle 1,000-1,500 cubic feet per second. The reason there are three gates is simply a matter of safety: if one gate can't open, we have two more to try."
Gustafson explained that the goal of the lake level in the wintertime is simply to keep up with the flow of the springs into the lake. Even on the coldest winter days, the springs around the lake still flow about 300 cubic feet per second into the lake.
For up-to-date measurements of lake and Chadakoin River levels, visit waterwatch.usgs.gov/?m=real&r=ny.