22-2 Quantifying Hydrologic Responses and Water Losses Caused by Hydropeaking Dam Management Practices.

Session: Advances in characterizing groundwater, surface water, and their interactions (Posters)

Presenting Author:

Authors:

Abstract:

Hydroelectric facilities’ operational strategies fail to consider surface water and groundwater interactions, leading to a multitude of unintended and understudied consequences. The Deerfield River, located in northwestern Massachusetts, USA has a long history of anthropogenic influence from its ten hydroelectric facilities. Previous work has demonstrated that, at the reach scale, there is up to a 10% loss of bank-stored water associated with anthropogenic stage changes caused by hydropeaking dam releases in the Deerfield River. Losses were attributed to transpiration of water not previously available to vegetation but made available by the aquifer’s hydrologic response to the river’s stage changes.

To better characterize the losses and mechanisms described in the existing literature, an extensive and multifaceted investigation was carried out. First, a three-dimensional model was developed using MODFLOW 6, specifically designed to highlight evapotranspiration (ET) fluctuations in relation to river stage change. This modelling effort was complemented by a time series analysis of hydrographs from ten locations along the river channel. Losses were quantified from event-scale to seasonal totals. Lastly, a field campaign was carried out at multiple sites along the river with varying topography and land cover. River stage and temperature and well level and temperature were collected at two-minute intervals at each site. Using these measurements, response magnitudes were assessed and analyzed for each dam release during the collection period.

The modelling showed a significant increase in ET with increased river stage, primarily in areas within one hundred meters of the channel. This is also supported by well data, which showed a sharp decrease in aquifer response with increasing distance from the river. Wide, low topographical areas of the valley are hotspots of increased ET, where the aquifer response may more readily increase groundwater levels into the rooting zone. Time series analysis from dam and gage discharge data showed that the river can lose water on the order of tens of thousands of cubic meters in a typical release. We also observed a seasonal fluctuation in the losses and gains in groundwater to the river, with the greatest water losses occurring in late summer. With this information, hydroelectric dam operational strategies can be updated to consider release induced losses. Modifying the timing, volume and waveform of each release could improve economic and ecological outcomes.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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