Dam Effects Downstream
Dam management can affect the flow, temperature, and biology of downstream ecosystems. One type of management is winter water-level drawdowns. Drawdowns most often serve to control aquatic invasive species and protect infrastructure. When dam managers lower lake levels in the fall, downstream flows are much higher than normal. When managers refill lakes in the spring, the normal high flows are absent. Periods of low and no flow downstream can occur in the summer when the dam is not managed. Low flows increase water temperature, concentrate pollutants, and cause stress to aquatic organisms.
The goal of this project is to improve downstream flow and ecological condition while balancing in-lake needs. We aim to do this by changing dam management at high-priority sites.
What We're Doing
In the first phase of the project, we prioritized potential sites using GIS. We started with the 2921 dams mapped in the DER Restoration Potential Model. We narrowed to a subset of 104 dams that have a history of winter drawdowns. We then assessed sites for potential downstream ecological benefit. Sites with high-quality aquatic habitat, such as connectivity and coldwater fisheries, ranked higher. We eliminated sites with more degradation, like a lake with poor water quality. The remaining sites are better candidates for flow releases from managed dams.
For the second phase, we are doing site surveys to determine existing flow conditions. To do this, we deployed time-lapse cameras at several high-priority sites. This low-cost, low-tech method uses photos to assess and categorize flows. Based on conditions at these sites, we will assess next steps for modeling and changes to dam management.