CLEARWATERS: Managing water resources in Oneida Lake

The Oneida Lake Watershed and the surrounding Oswego River Basin contain diverse systems of streams, lakes, and canals (Figure 1). Water flows from the upland streams to lakes, then to low-gradient rivers, which are part of the New York State Barge Canal system, and ultimately to Lake Ontario (Figure 2). The natural and man-made components of this hydrologic system are known, but how the system functions and how the components interact are not completely understood.

Physiography

The Oswego River Basin has an area of 5,100 mi² and encompasses three physiographic provinces:

An east-west-trending belt of lowlands through which the Barge Canal flows—called the Clyde/Seneca River-Oneida Lake Troughs—is another physiographic feature that plays a vital role in the flow regime of the basin. The troughs are key to understanding the basin's flow system in its natural and human-altered state.

Troughs

The Clyde/Seneca River-Oneida Lake Troughs are a product of regional geology and glaciation. During and after the last Ice Age (ending about 14,000 years ago), glaciers eroded the soft shales that lie on either side of the less-erodible Lockport Dolomite and Onondaga Limestone Formations. This process created a series of bedrock ridges and troughs. The troughs later became filled with mixtures of clay, silt, sand, and gravel from the receding glaciers. The result is several east-west-trending flat low-lying areas containing many large areas of wetlands and lakes.

Boats on the NYS Barge Canal

Oneida Lake and the Cicero and Canastota wetlands lie in the eastern trough; the Seneca River and its associated wetlands are in the western trough. The New York State Barge Canal was constructed in these troughs because the gradient is exceptionally low. The Canal's surface elevation changes only 23 ft in 100 mi along the main stem between Locks 27 and 22. The river gradient before construction of the canal in the early 1800s averaged about 0.4 ft/mi. With the canal, the water-surface elevation changes in steps at each lock. The low gradient inhibits the rapid movement of large volumes of water and thereby poses a challenge to water-resources management.

Effect of the troughs on drainage

Surface water and ground water in the Oswego River Basin flow from the uplands to rivers and lakes, then through the troughs, which are traversed by the main stem of the New York State Barge Canal. In the Oneida Lake Watershed the uplands include the Appalachian Plateau to the south and the Tug Hill Plateau to the north which drain directly to the Oneida trough.

In the Finger Lakes region, water from the Appalachian Plateau drains to each Finger Lake, and these lakes empty northward into the Seneca River trough. The additive contribution of these lakes' outflows to their respective river system results in a bottleneck at Three Rivers Junction (the confluence of the Oneida and Seneca Rivers—creating the Oswego River). This junction receives water from 96% of the Oswego River Basin but is within the flattest (gradient about 0.4 ft/mi), and slowest-moving reach of the Oswego Basin (Figure 3).

Source: USGS, Managing the water resources of the Oswego River Basin in Central NY. Fact sheet FS 180-99. March 2000.

Fig 3. Lake and lock positions.. Click for larger image in new window.

At times, inflow to these rivers exceeds their channel capacity and causes flooding in the Oneida and Seneca Rivers and in the upstream lakes. The gradient in the Oswego River increases markedly to 4 ft/mi downstream of Fulton and allows the water to flow more rapidly toward Lake Ontario.

Flooding: not just a lake-level issue

The amount of water that enters any lake in the Oswego Basin from a rainstorm or snowmelt depends on local watershed conditions. For example, nearly all the water that falls on the Oneida Lake watershed (1382 mi²) when soils are saturated or frozen, flows into the lake (surface area nearly 80 mi²), and every 1 inch of runoff from the watershed can increase the lake level by 1.33 ft within several days. Once in the lake, this volume can take several weeks to drain to the Oneida River-Barge Canal because the river's low gradient allows the lake level to decline only 0.1 ft/day.

Inflow from the Seneca River—the other two-thirds of the Oswego River system—can further slow the draining of Oneida Lake. The natural drainage in the Oneida and other Finger Lake watersheds, with their cumulative and rapid inflows and slowly draining outflows, poses difficulties for water-level management. The New York State Barge Canal Corporation uses control points in the Oswego Basin to monitor and manage water levels. The management strategies of this system have been controversial for nearly a century because the users have differing water-level-management objectives. Reaching resolution is not simple nor is any decision likely to be favorable to all.

Shortcomings of weather forecasting

Today's skill or accuracy in forecasting the amount of precipitation that a given storm will produce is accurate to only about 2 days into the future. The accuracy beyond 2 days (extended forecasts) diminishes sharply. The prediction of precipitation is given only as a probability (as a percent), and the amount is not stated. Seasonal forecasts (3- to 4-months) are highly generalized and are given only in terms of wetter or drier and hotter or cooler than the long-term norm or average condition.

Having a lead time of only 2 days makes management of a region's water resources, especially those within a large complex system such as the Oswego River Basin, or the smaller Oneida Lake watershed, challenging.

Predictions of long-term weather and climate conditions, including the oft-heard but not-proven concepts of global warming and climatic variability, rely on long-term records of the earth's climate. Systematic records, however, only extend to 100 years ago or less. One means of extending the record farther back in time is through dendrochronology (the study of tree rings).

Studies in forests in the Northeastern U.S. indicate that precipitation and air temperature followed a generally calm cyclic pattern between 1890 and 1960, with relatively few departures from the norm, but since the 1960s the patterns have departed more frequently from this cycle in the form of droughts, floods, and periods of abnormally cold or warm temperatures. The mid-1960s were characterized by drought, yet the mid-1990s were extremely wet with heavy seasonal precipitation and rapid snowmelt.

The relatively erratic weather patterns since the 1960s may, in fact, be more typical for the Oswego River basin than the earlier decades of this century, because tree-ring data from the 1700s and 1800s indicate many departures from the norms of the 1890-1960 interval. One implication of this possibility is that watershed systems could be more difficult to manage in the future because the relatively short record of local rainfall and runoff conditions is not a reliable indicator of future weather nor of the resultant lake levels or river-flow conditions.

Water quality considerations

The quality of water entering and moving through any watershed can be adversely affected by human activities, and the resulting contamination can diminish the suitability of these water resources for certain uses. The phrase "we all live downstream" is a reminder that our actions can affect others.

Water quality in most of the Oswego River Basin is suitable for most uses after minimal treatment but cannot be expected to remain so indefinitely. For instance, the introduction of zebra mussels (a non-native species) to the Oswego River Basin rivers and lakes has led to an increase in the clarity of the water, but increased clarity does not necessarily imply diminished pollution. About 20 cities, towns, and villages use the lakes in the Finger Lakes region as drinking-water sources, and nearly the same number use the lakes for disposal of treated wastewater. Pesticides have been detected in all of the Finger Lakes and Oneida Lake, although at concentrations below current drinking-water standards.

Harvesting water chestnut, an exotic species, on Oneida Lake

How can the resource be improved?

Most water-resource problems of the Oswego River Basin (or any other watershed) tend to be seen as local water-level, property, water-quality, or other single-use issues. The first responsibility and challenge to water-resource managers and watershed users is to view all issues—be they water level, water-quantity, or water-quality—in the context of watershed- or basin-wide management. Although managing the water resources of the Oswego River Basin is a daunting task, some steps can be taken to improve these resources:

Understand the whole-watershed process: Everyone, from the upland farmer to the lake-side landowner, lives in a watershed. Thus, everyone's actions affect the quality and quantity of the water resource. The adverse effects of human activities can be minimized but only if the watershed management goals are clearly defined and met with resolve. Meteorological conditions of the natural system are in a state of perpetual change, and humans have only a limited ability to alter them. Although the effects of some extreme-weather conditions may be reduced, they cannot be eliminated.

Involve the public: The public needs to become educated in the whole-watershed concept, and the residents of the watershed need to become involved in planning, management, and goal-setting for their watershed as part of the Oswego Basin. Individuals must be encouraged to plan and manage their properties as part of a larger watershed system and to participate in basin-wide management planning and management meetings.

Ensure that local actions conform to basinwide water-management objectives: Basinwide water-management goals need to be defined before local objectives or solutions are established or implemented. Local problems need to be addressed within the context of total watershed management.

Develop goals that are consistent with the “real world”: Adoption of the proposed goals depends on whether they are realistic, and their success depends on whether they are consistent with the watershed's hydrologic characteristics, climate, meteorologic variability, and canal hydraulics.

Define the capabilities and limitations of watershed management: Study of watershed hydrology and canal hydraulics can be facilitated through computer models that can, when calibrated and verified with sufficient data, provide a basis for development and refinement of water-resource-management strategies and for defining the limitations of our ability to manipulate water resources.

Only when watershed residents, managers, and planners focus on the entire water-resource system can reasonable goals be defined and management and protection strategies be implemented to achieve these goals.

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William M. Kappel is a hydrogeologist with the U.S. Geological Survey. He is based in Ithaca where he has worked on New York's water-resource issues for the past 22 years.