Flash flooding impacts Seneca Lake
SENECA LAKE--Seneca Lake is experiencing the negative side-effects of June's flash flooding. Professor of Geolimnology and Hydrogeochemistry at Hobart and William Smith Colleges Dr. John Halfman said there are three significant issues with Seneca Lake following the flooding. Citing issues with turbidity (suspended sediment), phosphorus and high lake levels, Halfman described them as "three huge changes -- none for the better."
"The floods have made the lake more turbid throughout the spring," Halfman said. "For example, I couldn't see my toes in shin-deep water at my house last Sunday [July 12]."
Halfman mentioned he took several turbidity profiles from a central lake site. He stated turbidities are rarely above one Nephelometric Turbidity Unit (NTU) at the site. However this year, turbidity has exceeded one on at least five of Halfman's weekly lake monitorings, ranging from just above two NTUs to just above three NTUs between June 11 and July 9.
Halfman said the runoff has washed in more phosphorus along with the suspended sediment, which has stimulated more algal growth. This growth included both free floating algae along with algae attached to lake floor and things like boats, docks and moorings. Halfman stated the algae concentrations rarely exceed four milligrams per cubic meter (mg/m³) at the central lake site. However, the numbers exceeded this level, reaching as high as six mg/m³ July 2.
"I expect we'll have more algal blooms and perhaps extensive blue green algae blooms during the rest of the summer," Halfman said. "It will have an economic impact on the municipal water suppliers around the lake as they try to filter the water, and the water they supply may have a foul odor."
In addition to turbidity and phosphorus issues, Halfman noted the extra runoff generated higher than normal lake levels for this time of year. According to the New York State Canal Corporation, the Seneca Lake water elevation measured at Geneva exceeded the summer maximum target level of 446.3 feet during the flooding, and is currently near that level as of July 7. In the middle of June, the water level reached 446.8 feet, while also reaching 446.6 feet at the start of July.
Halfman mentioned this has probably caused issues with homes right on the lake shore, as some have foundations below this level.
"The lake is high because the canal cannot drain it fast enough, and in fact, canal authorities asked to stop the flow for a while due to flooding of homes in low lying areas in the Seneca River/Erie Canal," Halfman said. "None of this is good."
While Halfman said less rain would be beneficial, he added the turbidity and phosphorus issues can be remediated by decreasing erosion from agricultural land.
"Various Best Management Practices (BMPs) are critical here like minimal tillage, buffer strips, gully plugs and other processes," Halfman said. "It was unfortunate that the heaviest rains came when many of the fields were bare this spring (ready to plant or just planted), and nothing was on the fields to reduce erosion of the top soil. However it means a loss of arable land by the farmers, a cost they might not be able to bear."
Halfman noted the issues with the lake level are more problematic, as many competing groups look to control the flow down the outlet of the lake. He said hydroelectric dams downstream want constant flow, while Seneca Lake residents want rain inputs removed quickly, then have the lake stay at a constant level. Meanwhile, Halfman adds downstream residents and the various locks on the canal don't want to get flooded out.