Between April and December 2000, the USGS injected and monitored a safe, fluorescent red dye in 13 New Hampshire rivers to measure the travel rate of a potential contaminant spill into the rivers. These studies were done, in cooperation with the NHDES, as part of the Drinking Water Source Assessment Program. The results of these studies will be used by local agencies to plan emergency responses to chemical spills into the rivers, including guiding decisions regarding closing and reopening of intakes to drinking-water systems.

Dye was injected, at low flow and mean flow, into the Ammonoosuc, Androscoggin, Connecticut, Contoocook, East Branch Pemigewasset, Exeter, Lamprey, Mascoma, Merrimack, Oyster, Piscassic, Salmon Falls, and Sugar Rivers. Rivers were then sampled to measure dye concentrations and the arrival times of the dye cloud. Relations were developed from this information that will allow emergency responders to estimate travel times and concentrations of contaminants at different flow rates and locations on these rivers.

In general, river velocities were slowest in the New Hampshire seacoast region, where topography is low and river slopes are mild such as on the Oyster River. Velocities were highest in steeper-sloped rivers, such as the Mascoma River, draining upland and mountainous areas.

--Thor Smith (603) 226-7814 or tesmith@usgs.gov

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