3D GIS/GPS Water Quality Modeling Project
Connecticut River, Vermont and New Hampshire

The Louis Berger Group, Inc. conducted a water quality monitoring and modeling study of two reservoirs on the Connecticut River on the border of New Hampshire and Vermont at the Fifteen Mile Falls Hydroelectric Project. The study, commissioned by Pacific Gas and Electric Generating, used a multi-faceted approach to assessing water quality such as:

Berger developed these approaches to gain a better understanding of oxygen distribution in Moore and Comerford reservoirs during the warm summer months. Continuous monitoring was used in order to detect possible fluctuations in water quality just below each facility and from taps set into the penstock. Moore and Comerford developments typically go through two generation cycles a day, making this type of monitoring valuable to our overall water quality analysis.

Reservoir profiling was used to develop a model of DO distribution throughout the reservoirs, to detect possible stratification, and to assess the effect of project operations on water quality. Penstock aeration trials were conducted to determine if aeration could be used as a method to increase DO levels downstream of each development.

Exact positioning data were collected during each profile sample using a GPS unit; resulting water quality data was used to create a 3-D water quality model of each impoundment. The model could be changed so that specific cross sections, depths, DO levels and temperatures were visible from any angle. The model was critical in addressing water quality concerns relative to Vermont and New Hampshire water quality standards.

The final report incorporated the multiple sampling and analysis methods to create a comprehensive picture of reservoir water quality conditions. Ultimately, these data allowed Berger to identify possible water quality issues and propose operational measures that could potentially help maintain state water quality standards.