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Organization for
the Assabet River
Damonmill Square
Concord, MA 01742
Tel. (978-369-3956)
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[Tour of Groundwater | Water Use | Water Balance| Groundwater Model | Back to Main]

USGS and DEM using computer models to evaluate ground-water resources and management alternatives in the Assabet watershed

The Assabet River Consortium's water balanace provides a lot of useful information about the hydrologic health of water resources within the six Consortium communities. But it is a screening level analysis and does not include communities outside the Consortium. A more comprehensive and sophisticated analysis was required.

In response to requests from OAR and the EOEA SuAsCo Watershed Team (now defunct), the US Geological Survey (USGS) and the Department of Environmental Management (MA DEM) agreed to spend $425,000 over three years to evaluate ground-water management alternatives in the Assabet watershed. USGS staff in the Massachusetts-Rhode Island office are currently working on a MODFLOW groundwater model for the watershed to assess the impact of existing and proposed groundwater pumping scenarios on streamflows in the Assabet River and its tributaries.

Why is groundwater managmement so important to the Assabet River?

During the low flow period of July to September, groundwater or "base flow" seeps into the river and its tributaries from adjacent aquifers providing the relatively cool, clean water important to maintaining good habitat for fish and other aquatic creatures. In the tributaries baseflow is essential to keep the streams from drying up in the summer. In the mainstem Assabet it provides dilution for the nutrients and other pollutants in the wastewater effluent being discharged to the Assabet. In drier summers the proportion of effluent to baseflow in the mainstem Assabet gets very high. For example, during the July 1999 TMDL field survey, ENSR found that 80% of the flow in the Assabet at the USGS gage in Maynard could be accounted for by wastewater effluent.

Unfortunately, the Asabet has already lost much of its baseflow because of existing groundwater withdrawals, sewering, and extensive paved and otherwise impervious surfaces where water can't infiltrate back into the aquifers. For this reason, the impacts of new or increased groundwater withdrawals from the watershed must be carefully evaluated to ensure that they will not reduce groundwater or baseflow contributions to the river. Additional losses of these flows will exacerbate the river's existing eutrophication problem and undermine existing and future investments in nutrient control.


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