Ithaca Journal

Conference examines phosphorus in Cayuga Lake

By Erica R. Hendry .Correspondent . October 25, 2009, 7:25 pm

The south end of Cayuga Lake has been considered "impaired" for the better part of the last 10 years.

In 2003, the New York State Department of Environmental Conservation listed the southern basin of the lake on a list, called the 303d list, of impaired water bodies because its levels of sediment and phosphorus - which attaches to soil and other runoff that empties into the lake. It made that list again in 2008.

On Saturday, the Cayuga Lake Watershed Network and the Cayuga Lake Intermunicipal Organization presented the results of data collection and modeling projects done since then in a conference called "Phosphorus Inputs into Cayuga Lake," a half-day event that brought together scientists and residents to raise awareness of what many called the biggest threat to area's waterways: phosphorus.

"It's a threat we've known about for quite some time," said John Mawdsley of Tompkins County, chair of the Cayuga Lake Watershed Network board. "Now that we have this monitoring and modeling, we can start running those options, and 'what-if' scenarios."

Phosphorus is particularly dangerous to the lake because high levels can create excessive algae and plant growth, which has already been noted as a problem in several parts of the lake. Excessive algae growth can also upset lake ecology because it reduces the amount of light penetration and oxygen levels, and sediment and algae also interferes with treatment of drinking
water supplies.

Phosphorus concentrations have declined overall because of wastewater treatment plant improvements, but the amount of phosphorus that enters the lake attached to sediments has yet to be addressed, speakers said.

Before 2004, when the watershed network and others began collecting new data about phosphorus, the only lake-wide estimate of contaminant loads of dissolved phosphorus (found in other materials like soil), total phosphorus and nitrogen was a one-year weekly or biweekly sampling program from 1970 to
1971, said Doug Haith, a professor of biological and environmental engineering at Cornell University.

Roxy Johnson from the City of Ithaca and Steve Penningroth from the Community Science Institute presented data from monitoring samples of lake water from various points around the lake and its outlets since 2004 and 2002, respectively, including Six Mile Creek, Salmon Creek, Seneca River, the Cayuga Inlet, Taughannock Creek, Fall Creek, Stewart Park and outside the Ithaca Youth Bureau. Johnson said the levels in the lake were at or below DEC's guideline for phosphorus, and most of them had increased throughout her data set. Pennigroth had similar results.

Both Haith and Todd Walter, another professor of biological and environmental engineering at Cornell, presented their data models, both of which aimed to identify where the phosphorus comes from and how it may be prevented.

Haith developed a watershed model called Generalized Watershed Loading Functions. He presented the data gathered from Fall Creek, one of the largest contributors to Cayuga Lake.

He found nearly half of the phosphorus in the lake came from agricultural runoff, which came from things like corn, hay and grains and manure, and about a quarter of phosphorus came from groundwater.

Haith also said it was unclear whether phosphorus levels had to do with negative developments in the lake, like Eurasian watermilfoil and zebra and quagga mussels.

"What do those have to do with phosphorus levels? I'm not sure," he said.

Walter presented a study that focused on management practices on several farms. He said the biggest source of phosphorus is the large puddles that form on farm land as a result of rain or snow runoff. This creates large pockets of phosphorus and allows it more mobility.

"We need to be able to predict where these wet areas are going to form in the landscape and when they're going to form."

To try to reduce some of the levels, Walters and his team helped area farmers implement new drainage systems that changed the direction of water flow, a new manure spreading schedule that kept manure away from the areas that generated the most runoff, installed fencing and buffers that kept cows
out of certain areas of the farm, which reduced the amount of manure that could get into the runoff, and made barnyard improvements, including diverting all the water around the barnyard, and putting a concrete pad around the outside. Walters said the biggest improvement was seen in soil
and manure, where phosphorus levels decreased drastically because of the changes.

"It's all about mobility, and keeping the phosphorus from moving," he said.

He said management practices like these are easier to implement in the farming community rather than the residential community, because they make up a smaller part of the area.

"It's easier to get a small group of people to do something than a large group of people," he said. "Residents are more worried about things like aesthetics, and marinating their property.

Haith said the data and models presented were progress, but that there is still a lot to know about what's causing problems in the lake.

"I'm a scientist, but I'm also a local resident ... I've used this lake a lot for many years," he said. I've got a vested interest in how this all works out. We certainly have some data on concentration, but we really don't know what's going on in the lake."