Why Focus on Sediment?

An Overview of Watershed Priority Setting by the Technical Advisory Committee of the Intermunicipal Organization

Sediment-laden waters enter the lake from the Cayuga-Seneca Canal and surrounding lands in the northern watershed. Sediment is a priority concern at both ends of the lake.

In creating the Cayuga Lake Watershed Restoration and Protection Plan (RPP), municipal officials, residents, and other stakeholders described their vision for the future of Cayuga Lake and its watershed. The lake's use as a high quality water supply surfaced as the central aspect of that vision, followed by continued recreational use and aesthetic enjoyment. As part of this process, the Watershed Characterization Report identified pollutants that pose a threat to Cayuga Lake. Sediment was found to be of special concern because it is both a direct pollutant and a vehicle that carries other pollutants to Cayuga Lake and its tributaries.

We have all seen cloudy plumes in the lake following rainstorms and snowmelt. Studies indicate that sediment is the major factor affecting lake water clarity, particularly in southern Cayuga Lake. Sediment is also stressing many tributaries to Cayuga Lake, including, Cayuga Inlet, Fall Creek, Cascadilla Creek, Six Mile Creek, Bolter Brook and Yawger Creek, by degrading in-channel habitat for invertebrates and fish. These streams provide spawning habitat for many of the important recreational and commercial fish for which Cayuga Lake is renowned. Further, sediment clogging tributary mouths encourages excessive aquatic plant growth and inhibits recreational boating.

The Link Between Sediment and Phosphorus

Sediment particles transported from fields, parking lots and other areas carry with them many other contaminants, including phosphorus, pesticides, and heavy metals- all identified as concerns by the RPP- into the aquatic system. Phosphorus in Cayuga Lake is of particular concern because high levels lead to excessive algae and plant growth, which has been observed in some areas of the lake. Excessive algal growth reduces light penetration and available oxygen levels, upsetting lake ecology. Sediment and algal concentrations also interfere with effective treatment of drinking water supplies. While overall phosphorus concentrations have declined as a result of continuing wastewater treatment plant upgrades, the portion of phosphorus entering the lake system with sediments remains to be addressed.

Sediment originates via erosion from the landscape, or from the banks and beds of streams. In either case, erosion is strongly influenced by both natural and human factors. The southern portion of the watershed, for example, is vulnerable to erosion as a result of glacial soils and steep slopes. The processes that created the region's beautiful gorges and waterfalls continue to carve the landscape. Human activities, such as poorly planned construction, roadwork, and agriculture operations, expose erodible soils and further contribute to the volume of sediment delivered to local streams. Impervious surfaces, such as asphalt, also increase the potential for erosion by forcing more water into stream channels. Finally, loss of the extensive wetland areas in southern Cayuga Lake has removed a natural filtration process that captured sediment before it reached the lake.

Reducing Erosion and Sedimentation

Because sedimentation is by nature a "non-point source" phenomenon, control actions are required on multiple fronts. The RPP recommends voluntary, incentive-based programs and some changes in local laws to reduce sediment loads. It identifies priority areas for restoration of stream channels, vegetated stream corridors and wetlands. Additionally, new state regulations, commonly referred to as "Phase II Stormwater Rules", will require additional treatment, education and planning by many communities to further control sediment and associated pollutants. This combination of voluntary and regulatory controls will benefit the Cayuga Lake watershed, if properly balanced.

In the middle of the 1900s, national and state resources were dedicated to water quality improvements through control of point sources of pollution. However, evidence points to the increasing importance of non-point sources of water pollution, and the central role of sediment in delivering these contaminants to waterbodies. Controlling sediment poses a major challenge, which must be addressed if our vision for the future of Cayuga Lake is to be realized. Nonpoint sources of pollution are neither simple nor easily defined, and require active participation at all levels to protect the Cayuga Lake watershed for future generations. For these reasons, the IO has identified sediment as a top priority for restoring and protecting the Cayuga Lake Watershed.

Editor's Note: You can learn more about local projects being implemented in keeping with the RPP recommendations to reduce erosion and sedimentation in this and upcoming issues of the Network News!