Summary: Lake Manager Meeting May 12, 2018
The long-term key to the clarity, recreational use, and ecological balance of Roaring Brook Lake is both in the water and on the land, Lake Manager Fred Lubnow told residents at a Town Hall meeting on May 12, 2018.
Fred, whose firm has helped manage numerous lakes in the Northeast, presented findings from several new studies of the lake, along with possible options for proceeding both in terms of lake water quality management and watershed management. He did not offer his final recommendations for how the Town of Putnam Valley, which hired him as lake manager, should proceed. But he gave some strong hints – long term health of the lake mostly depends on decreasing the infiltration of harmful nutrients—mostly nitrogen and phosphorus—from the surrounding area.
The top priority, he told the three dozen people gathered for the two-hour presentation at Putnam Valley Town Hall, is maintaining water quality in the lake. Water quality affects (1) aesthetics –the clarity and beauty of the lake, (2) ecological balance – the wildlife, fish, birds, frogs, turtles, and butterflies we enjoy, (3) recreational use – swimming, boating, and fishing, and (4) quality of life and property values around the lake. He was especially concerned about harmful algae blooms that closed beaches for 18 days last year, and about over-abundant lake weeds that affect swimming and boating.
Water quality suffers, Lubnow said, primarily because of nutrient pollutants – phosphorus and nitrogen – being added to the lake. In fresh water lakes in the Northeast, phosphorus is the rate limiting, and therefore most harmful, nutrient pollutant. “A little phosphorus generates a lot of algae,” he said. “We need to get the lake on a proper diet.”
Lubnow, illustrating his points with a slide show of graphs and charts said the three main sources of lake nutrient pollution were septic systems (29 percent), internal loading –nutrients released over time from the lake bed (23 percent) and watershed –nutrients coming into the lake with stormwater runoff and streambed erosion
He said rules requiring periodic pumpouts of septic systems are very helpful – something that Putnam Valley is now requiring every five years, thanks to a regulation initiated by Town Supervisor Sam Oliverio and passed by the Town Board. However, Lubnow said, homes on the lake or with older systems should probably pump out their septic systems every 2-3 years.
Lubnow also talked about grants available from the state to ease the cost for homeowners who want to update or replace their old systems, which he said is a good idea: the older the system, the more phosphates and other nutrients go into the lake. He said such updates can reduce the amount of nutrients going into the lake by 20-30 percent, or as much as 50 percent for older, failing systems, typically those over 50 years old.
He said other important steps lakeside homeowners can take on their property is planting trees anywhere on their property and dense shrubs or grasses at least 18 inches high right up against the waterfront. “Planting shoreline vegetation goes a long way for several reasons,” Lubnow said.
Tall waterside grasses keep geese off lawns. “Geese defecate about 28 times a day,” he said. “Basically geese are cows with feathers.” A buffer of deeply rooted bushes, trees, or tall grasses planted along the lake edge will absorb and filter water before it enters the lake.
Lubnow said it is possible that the introduction of the sterile carp into the lake – 500 small, young fish in October 2011 – may have made nutrients already in the lake in the form of weeds, more accessible by turning them into fish poop. But, he said, the carp, by eating so much aquatic foliage, may have improved recreation by decreasing weeds, even though there was no net change in the nutrients within the lake.
Lubnow also said a recent increase in non-nutrient watershed pollution could be from more road salt – something he has noticed in other lakes in New York.
He ticked off a number of things that could be done to reduce the most common bothersome lake weeds – bladderwort and milfoil – and the toxic algae, but did not enthusiastically endorse any of them: alum treatments, weevils, mechanical weed harvesting, herbicides, and systems that keep stirring the water to keep algae blooms from forming. Some he cited as being ineffective on Roaring Brook Lake, others as too expensive. Dredging, by removing nutrient-rich sediment from the lake, could be beneficial. However, dredging is expensive and it should not be done until after the nutrient loading of the lake from storm-water and septic systems is reduced, otherwise, the effect of the dredging will be quickly undone.
He said the water-level drawdowns in recent years may have been effective, provided the water was drawn down enough, and provided there was a hard freeze before snow to kill dormant weeds on the exposed lake bottom. Even in a cold winter, though, either an early snow or the normal water level (no drawdown) would insulate the roots and allow them to survive to sprout again in the spring. He said it appeared that this past winter had been a good one in this respect – the lake was drawn down five feet, and there was a prolonged cold spell in January before it snowed. However, he did not go so far as to predict that the weeds would not be as bad this year as last.
Lubnow drew murmurs of surprise and approval from the crowd when he presented the idea of 250-square-foot (roughly 12.5 feet by 20 feet) floating islands. Built on recycled plastic bases, these are densely planted artificial wetlands, anchored and floating in the shallow coves, where they would have the most impact in cleaning and clearing the water. He said his company could build those islands for about $11,000 each, but the community could defray much of the cost by using volunteer labor to plant and launch them.
Whatever the approach to remediation, Lubnow pointed out that the coves are more of a problem in our lake than the deep open water. The coves are shallower, get warmer, and have less mixing. Therefore, they tend to accumulate nutrients and are the most problematic with respect to algal blooms and weeds. He encouraged us to focus on the coves to identify problems in the lake and on the land around the lake, the watershed, to decrease the nutrient pollution that is the root cause of most of the lake’s problems.
Watch a video of the whole presentation by clicking here.