The objective of this review is to identify information gaps in the watershed characterization of Cayuga Lake. The data requirements identified in this report can be used to plan and implement a monitoring program for Cayuga Lake.

This document was prepared based on Chapter 7 of the Cayuga Lake Intermunicipal Organization - Preliminary Watershed Characterization Report. It was written by Liz Moran, from EcoLogic, and it is currently under review by the Intermunicipal Organization Technical Committee. Public review of the preliminary report is scheduled for January-2000.

Cayuga Lake’s water quality is excellent. The lake supports its designated best use as a public drinking water supply and recreational resource; the fish community is diverse and productive. The lake has been well characterized and is the focus of several significant long-term monitoring initiatives. Tributary streams are, with some exceptions, characterized to a lesser extent. Available data indicate that most tributary streams exhibit moderate to high water quality and biological habitat. A few long-term monitoring programs are in place; most are directed at the southern tributaries.

Despite the finding that water quality in the watershed is high, this characterization effort has identified a number of specific areas of concern. These are specific locations in the lake or watershed with evidence of water quality degradation or use impairment. They also refer to water quality parameters suggesting potential degradation or use impairment throughout larger regions of the watershed.

Areas of concern include:

Agricultural chemicals such as nitrate-nitrogen and herbicides are detected in both tributary streams and the lake. While there are no exceedances of ambient water quality standards associated with human health or ecosystem protection, these data provide direct evidence of losses from agricultural lands and transport to the lake.

Sediment is a significant water quality, habitat, and use impairment issue, particularly in the southern tributaries and southern Cayuga Lake. Destruction and fill of wetland areas in southern Cayuga Lake in the early 1900s has exacerbated this problem by removing a natural filtration process. The primary source of sediment appears to be streambank erosion, not runoff from construction sites or cultivated fields.

Urban Stormwater Runoff. Heavy metals are detected in sediments of Fall Creek as it flows through the City of Ithaca. Near shore sediments of Cayuga Lake also exhibit elevated concentrations of some heavy metals. These data suggest the need for improved stormwater management. However, the risk is minimal that these heavy metals could enter into the food web of Cayuga Lake or be present in drinking water supplies. The chemical properties of the lake water (alkaline, well-buffered hard water) and sediments (high organic carbon and acid volatile sulfides) prevent these heavy metals from becoming biologically available.

Phosphorus. Cayuga Lake meets the NYSDEC phosphorus guidance value of 20 micrograms per liter, μ g/L, summer average upper waters, measured at a mid-lake station. However, near shore areas of the southern lake basin occasionally exhibit phosphorus concentrations above the guidance value. There is strong evidence that these elevated concentrations reflect sediment-borne phosphorus as well as phosphorus in the discharges of the two wastewater treatment plants. Phosphorus is the limiting nutrient for algal growth in Cayuga Lake. Ambient concentrations confirm that Cayuga Lake is mesotrophic, with moderate levels of primary productivity.

Exotic species . Because of its connections to the Great Lakes through the Seneca River, Cayuga Lake is vulnerable to invasion by nonindigenous species of plants and animals. There have been a number of exotic species invading Cayuga Lake over the years. Three recent invaders are a focus of special concern due to their potential to alter the food web. These organisms are the zebra and quagga mussel ( Dreissena polymorpha and Dreissena bugensis ) and a predatory cladoceran zooplankton ( Cercopagis pengoi).

Specific areas of concern for the tributary watersheds are summarized in Table 1. A similar table for the lake is presented as Table 2.

There are data gaps that limit our ability to draw conclusions regarding the status of the lake and its watershed. These data gaps exist for both the lake and the tributary watersheds.

Baseline characterization of water quality and loading

The 1970 – 1971 work of Likens represents the only synoptic survey of baseline water quality of all tributaries to Cayuga Lake. These chemical profiles provide important insights regarding quality of waters draining individual subwatersheds and total external loading to the Lake. There have been significant changes to loads of several subwatersheds over the last three decades; for example, salt loading to Gulf Creek has been greatly reduced, and the outfall of the Ithaca Area Wastewater Treatment Plant has been relocated from Cayuga Inlet. It is therefore recommended that a synoptic survey be conducted over at least one full year.

Monitored parameters should include: calcium, sodium, chloride, magnesium, potassium, sulfate and total alkalinity, total suspended solids, total P, total soluble P, soluble reactive P, and nitrate N. The sampling program should be conducted for at least one full year, with concentrated sampling during high flow events. Based on existing data, seasonal, event-driven, and land use activities in the subwatersheds all affect external loading.

The Nitrogen (nitrate) data sets of Bouldin, Likens and the NYSDEC Rotating Intensive Basin Survey, RIBS, program highlight the need for sampling to occur over an entire year in order to characterize ambient concentrations and estimate annual loads. There is a pronounced seasonal variation in concentration of nitrate; maximum concentrations occur in winter and minimum in summer.

Based on the Fall Creek data set, most of the annual loading of sediment and phosphorus to Cayuga Lake occurs during high flow events; both the RIBS and Bouldin data sets demonstrate strong correlations between TSS and flow and TP and flow. Including samples collected at high flows will greatly reduce the standard error of estimates of annual loading.

The July 1998 low level herbicide sampling of Yawger Creek, Salmon Creek and Paine Brook conducted by Eckhardt and colleagues of USGS illustrates the need to consider major land use activities in the watershed in designing a monitoring program.

Load estimates require accurate gauging in the watershed. Several gauging stations have been installed throughout the watershed and operated for various periods to meet specific program objectives. Only Cayuga Inlet, Fall Creek, Six Mile Creek, and Coy Glen Creek are currently gauged for flow. These stations monitor flow from approximately 204 square miles of the 744 square mile direct drainage. Reactivating the gauge at Salmon Creek would monitor an additional 81.7 square miles.

The work of Bouldin can be used to characterize background biogeochemical phosphorus concentrations and the incremental increase in concentration and load from agricultural areas. The Cayuga Lake watershed has diverse geological settings, and the results from Fall Creek may not be transferable to regions such as Yawger Creek, which drains an area of karstic limestone.

Watershed loading estimates

One desirable outcome of the watershed characterization process is an assessment of priorities for implementation. Limited resources will achieve the greatest environmental benefit if directed to areas of the watershed contributing disproportionate amounts of substances of concern. Data are not yet sufficient to define these resource-based priorities for the Cayuga Lake watershed. Additional soils and land use data, in digital form, are needed at a highly refined scale. For example, a similar effort in the Seneca lake watershed required definition of agricultural land use to the scale of crop rotation.

Atmospheric deposition

There are no recent data characterizing chemical quality of precipitation in the basin. This is important for load calculations as well as for general surveillance of acid precipitation.

Septic tank performance

Based on generalized geology and soils maps, there are large areas of the watershed with severe constraints to on-site wastewater disposal systems (septic tanks). There has been no watershed-wide effort to characterize the performance of these individual systems and how leachate from septic systems contributes to nitrate, phosphorus, and pathogen levels. The experience of Cayuga County, which has a comprehensive inspection program, could serve as a guide.

Species composition and abundance of the macroinvertebrate community is used as an indicator of water quality conditions. The biological community integrates the effects of different pollutant stressors and provides a holistic measure of their aggregate effect (EPA 1989). Benthic macroinvertebrates are good indicators of localized conditions. Because they have limited migration patterns or a sessile mode of life, they are well suited for assessing site-specific impacts of point and nonpoint discharges. Sampling is relatively easy and inexpensive.

The macroinvertebrate communities of several tributaries in the Cayuga Lake watershed have been assessed through various programs. Four sites were included in the 1995-1996 RIBS effort (Fall Creek, Salmon Creek at Ludlowville, Big Salmon Creek in Genoa and Little Salmon River in Little Hollow). Cascadilla Creek was sampled by Ichthyological Associates as part of Cornell’s Generic Environmental Impact Statement for development of the Orchards. Peckarsky and her students have been tracking changes in the macroinvertebrate community at a number of sites along Cayuga Inlet following a fuel oil spill.

There are other tributaries with water quality or land use data indicating that the biological communities could be stressed. We recommend that the macroinvertebrate communities of Taughannock Creek, Trumansburg Creek, Six Mile Creek, Yawger Creek (both branches) and Paines Brook be sampled. Sampling of the streams identified as impacted by agricultural chemicals would further the assessment of potential ecological impacts of trace concentrations of contaminants.

Streambank erosion is listed as a primary source of pollutants for four water segments on the Priority Waterbody List: southern Cayuga Lake, Sixmile Creek, Fall Creek and Cascadilla Creek. With the exception of Sixmile Creek, no watershed level assessment of causes/contributing factors, historical perspectives on the extent of streambank erosion, or potential mitigating measures has been made.

A systematic approach to estimating the extent of streambank erosion in the subwatersheds would help direct efforts on a “worst first” basis. This overall perspective is lacking. Standardized approaches such as an inventory of erosion and sedimentation sites and aerial photography at regular intervals would help address this gap. Aerial photos would document changes in the geometry (i.e. meanders) and locations of stream channels. Reference sites along the streams could be surveyed to use in periodic quantitative assessment of changes in streambed elevation and channel slope. Photographic records from reference locations could be used to document changes to streambanks. Geology and land use information is needed at a small scale along with detailed maps of riparian areas and floodplains.

Another effective approach is to complete an inventory of road side ditches and gullies to determine priority areas. This effort could be coordinated with county and town highway maintenance staff .

Effectiveness of mitigating measures (Best Management Practices) in reducing export of sediment and nutrients from subwatersheds

Before and after monitoring is lacking on tributaries where remedial measures such as streambank stabilization or stormwater controls has been implemented. Monitoring should occur over a range of hydrologic conditions, particularly high flow events.

Ecological and human health effects of trace concentrations of agricultural herbicides and other pesticides

Herbicides used in cultivation of corn have been detected at low concentrations in monitored tributaries and in the lake. Concentrations are at least one order of magnitude below the most stringent water quality criteria or standard. The analysis has been conducted on filtered samples, and the chemicals detected (atrazine, metolochlor and metabolites) have a high solubility in water. Additional assessment of human health and ecological impacts of these trace concentrations of chemicals is needed.

Based on land use and nitrate concentrations, Great Gully may also contain detectable concentrations of agricultural chemicals. This has not been assessed.

Watershed sources of heavy metals detected in Fall Creek sediments

The 1995 –1996 RIBS sampling program conducted by NYSDEC detected seven heavy metals above the assessment criteria, defined as the upper range of background levels but below thresholds that might cause adverse impacts. Near shore sediments in southern Cayuga Lake also contained levels of some heavy metals above thresholds of ecological concern. Based on land use patterns and data from other areas, urban stormwater is the likely source of these heavy metals in Fall Creek. Additional sampling of tributary sediment in subwatersheds and stream reaches with different mixes of land use might help identify factors contributing to the presence and concentration of heavy metals.

There are specific areas of research and monitoring where additional information would further characterize the lake’s water quality and ecological status. These are noted below.

Biological availability of sediment phosphorus.

The importance of sediment-borne phosphorus to Cayuga Lake’s trophic status is not well understood. This issue has implications for the relative value of investment in point and nonpoint source reduction.

Significance of low-level pesticides to human health and lake ecology

Using analytical methods with low detection limits, investigators from USGS and NYSDEC have documented trace concentrations of pesticides in Cayuga Lake and its tributary streams. The chemicals are present at levels far below ambient water quality standards or guidelines based on toxicology and risk assessment. It is important to continue to track these chemicals in all components of the ecosystem: water column, sediments, and throughout the food web.

Pathogens and indicator organisms

Measurements of pathogens and indicator organisms in Cayuga Lake are very limited. Storm event monitoring in the lake and streams could help define the importance of urban runoff as a source of pathogens. The importance of waterfowl as a source of microorganisms is not known.

The significance of exotic species

Because of its connections to the Great Lakes through the Seneca River, Cayuga Lake is vulnerable to invasion by nonindigenous species of plants and animals. The impacts on the food web and ecology of the Lake will be an important area of research.

TABLE 1

Summary of Areas of Concern, Tributary Subwatersheds

Cayuga Lake Watershed Characterization Report

Parameter	Location	Use Affected	Primary Cause	Potential for Improvement
Sediment	Fall Creek, Cayuga Inlet, Sixmile Creek, Yawger Creek, Cascadilla Creek	Fishing, fish propagation, water supply	Streambank erosion, agriculture, urban runoff	Moderate. Requires field investigations to identify causes and contributing factors. In some areas only viable solution may be riparian greenbelt to allow natural meanders. Requires watershed –wide commitment to land use and riparian zone management
Phosphorus	Salmon Creek	Water clarity, aesthetics	Agriculture	Moderate
Nitrate	Great Gully Paines Brook Salmon Creek Mack Br Williams Creek Indian Creek	Potential water supply	Agriculture	Unknown. Highly dependent on mix of agriculture and practices in watershed.
Petroleum products	Trumansburg Creek Cayuga Inlet	Benthos Fish propagation Fish tainting	Spills	Moderate – high (natural flushing and breakdown
Pesticides	Salmon Creek, Paine Brook, Yawger Creek (other locations not surveyed)	Presently, none detected over limits of concern. Could affect drinking water use.	Agriculture	Highly dependent on mix of agriculture and practices in watershed.
Heavy metals in sediment	Fall Creek (confirmed) Cayuga Inlet (likely based on land use)	Chronic toxicity to vulnerable biota Bioaccumulation	Urban runoff	High. Controls on point sources (including air emissions) more stringent. Sedimentation buries more contaminated sediments
Pathogens and Indicators	Unknown	Water consumption, contact recreation	Stormwater, on-site systems	Unknown, likely moderate

TABLE 2

Summary of Areas of Concern

Cayuga Watershed Characterization Report

Parameter	Location	Use Affected	Primary Cause	Potential for Improvement
Sediment	Mouths of tributaries, particularly southern lake	Aesthetics (water clarity and enhanced habitat for macrophytes) Drinking water	Streambank erosion, agriculture, Urban runoff	Difficult. Requires watershed –wide commitment to land use and riparian zone management
Exotic species	Lakewide	Ecological integrity, fishing, swimming, aesthetics	Entrance through Seneca River	Difficult to control. Requires technical and regulatory controls throughout Great Lakes, public education
Phosphorus	Lakewide, particularly in southern and northern basins	Water clarity, aesthetics	Southern: treated wastewater Northern: on-site systems	Reductions in point source loading are planned. Controls on nonpoint sources are more difficult
Pesticides	Lakewide	Presently, none detected over limits of concern. Could affect drinking water use and fish bioaccumulation.	Agriculture	Highly dependent on mix of agriculture and practices in watershed.
Metals in sediment	Spatial extent of problem is unknown. Near shore southern lake data show exceedances of some criteria.	Biological availability of metals appears to be low based on AVS. Minimal potential for release into water column, based on water chemistry and equilibrium partitioning models.	Historical industrial use, atmospheric deposition	High. Controls on point sources (including air emissions) more stringent. Sedimentation buries more contaminated sediments
Pathogens and indicators	Existence or spatial extent of problem is unknown.	Ingestion, primary water contact recreation	Unknown relative contribution of urban stormwater, waterfowl.	Depends on sources