| Phosphorous and
Southern End of Cayuga Lake
Meeting organized by Community Science Institute and Cooperative
Extension – 27 Feb 08
Notes of key points
There were 5 speakers and a general discussion. The speakers were
– Bob Howarth of Cornell, John Halfman of Finger Lakes Institute,
Jose Lozarno of Ithaca Wastewater Treatment, Steve Penningroth of
CSI, and Dave Matthews from Upstate Freshwater Institute Dave Matthews
presented Lake Source Cooling data.
Most presented data on phosphorous, both dissolved and total, from
the southern end of the lake and tributaries. The data seemed to
largely agree. The dissolved phosphorous is easily taken up by algae.
The particulate phosphorous is bound to sediments, some tightly
and some loosely. There are processes of exchange from dissolved
to bound and back that are not well understood.
The main sources of phosphorous are as Doug Haith has described
– in order of magnitude, the tributaries, wastewater treatment
at Ithaca and Cayuga Heights and Lake Source Cooling. Since the
introduction of tertiary treatment at Ithaca Waste treatment the
loading has declined from this source (23lb/d to 10 lb/d) and this
can be seen in the concentrations in the lake (data from 50 odd
locations shown by Jose). Cayuga Heights is planning to introduce
tertiary treatment later this year. This will make the tributaries
an even larger % of the total.
DEC has classified the southern end of the lake as impaired because
of phosphorous (the limiting nutrient in the lake). They use 20ug/l
as an upper guide limit for total phosphorous in the lake. This
is now exceeded barely close to the outlet of Ithaca Waste treatment.
It can be exceeded significantly at times of high flows but at other
times the lake values are closer to 10-15. Data on loading from
tributaries in storm events is the big data gap.
Causes of the high total phosphorous loading from the southern
tributaries is not clear – some say it a legacy of agriculture
stored on the sediment (article by Dan Karig in Journal on 27 Feb
and referred to by Bob Howarth) and others say it is from runoff
from fertilized fields.
Comparisons with other Finger Lakes
Both Halfman and the speaker from Upstate Freshwater Inst gave data
on other lakes. Cayuga is significantly worse than Seneca (phosphorus
and chlorophyll (?) – he did not show his data on other water
quality parameters. I’ve been to some of his talks and I think
Cayuga and Seneca are close) and ranks 6-9th in best quality of
Finger Lakes. Halfman has noted large phosphorous readings near
bottom of deep water that is not found in other lakes – cause
unknown (Halfman hasn’t found it in other lakes, Howarth listed
several other lakes where it’s being observed – both
said cause is unknown). Dissolved phosphorous in deep water appears
to be increasing since 2003 in Cayuga but total seems constant –
reason unknown.
Skeneatles lake is exceptionally protected because it provides
drinking water to Syracuse and the city uses its larger resources
to tightly control potential sources of phosphorous, including frequent
inspections of septic systems and they have no waste water treatment
plants in the watershed. Skaneateles was already better than most
lakes – partly due to the kindness of a small watershed –
less opportunity for inputs.
Other Points of Note
However, all presenters agreed that the lake is generally in good
shape with some areas of improvement possible, notably at the southern
end of the lake. The total phosphorous data are similar in the deep
lake to values from 40-50 years ago.
Bob Howarth said that the proposed Ethanol plant at Seneca Depot
could pose a threat to the lake from new CAFO’s that are likely
to be linked to the plant. Apparently the corn is to come from the
mid-west but the waste from the plant can either be land filled
(too expensive) or turned to cattle feed. This will be sold but
only makes sense economically if consumed with in about 30 miles
– hence the probable rise of CAFOs. One participant asked
what about using trucks bringing corn to take this back?
Discussion
Disappointing discussion. Some appeared unconvinced by the presenters’
assessment of the lake quality and thought there were greater problems,
including smell problems. Various groups were blamed for these apparent
problems including agriculture, local politicians and poor road
drainage practices. Others stated that the causes of the elevated
phosphorous from the creeks is not clear and more work is needed
to establish them before making management decisions. All appeared
to agree that reductions in sediment loads would help.
Prepared by:
John Mawdsley and Roxy Johnson
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