G.S. Hunt | USGS Science

USGS1983

Initial assessment of time of travel and mixing through Gulf Island Pond and the lower Androscoggin River, Maine

Flow-stratification patterns were observed in Gulf Island Pond during time-of-travel studies in May and August 1980. The stratification patterns in this 70 million cubic-meter impoundment were due to a temperature differences between inflowing water and reservoir water. Separation was observed at temperature differences of 0.5 degrees C in May 1980 and 1.0 degrees C in August 1980. The pathway taken by inflowing water through the reservoir was governed by the temperature-related density forces acting between the two water masses. Data collected during August 1980 to define differences in dye concentrations with depth at two fixed profile points in Gulf Island Pond showed average water velocity to be seven times faster near the bottom than near the surface. A concept of mass flow was used to analyze data collected at sites downstream from Gulf Island Dam where flow varied rapidly with time. This report presents the mathematical derivation of controid traveltime, skewness, and percentage recovery of dye mass as determined from mass versus time curves. (USGS)

Water-Resources Investigations Report↗

USGS1983

Time of travel and dispersion study in the Androscoggin River basin, Maine

In a series of dye tracer studies at discharge ranging from 45 to 212 cubic meters per second, time of travel and dispersion characteristics were determined at 12 sampling sites along 123 kilometers of the Androscoggin River (Rumford to Prejepscot Dam). Dye-cloud centroid traveltimes ranged from approximately 120 hours at high discharge to 410 hours at flows approaching 95 percentile duration. Longitudinal dispersion coeficients ranged from 21.3 to 76.7 square meters per second. In the 37.2 kilometer unsteady flow reach from Gulf Island Dam to Prejepscot Dam, the concept of mass flow versus time was applied to relate centroid traveltime to average discharge at five sites. This information was used to develop traveltime versus discharge relationships, traveltime versus distance relationships, and longitudinal dispersion coefficients. In Gulf Island Pond, a 70.4 million cubic meter impoundment, three complete dye clouds were traced. The range of observed centroid traveltime through the pound was 110 hours at a mean discharge of 84 cubic meters per second to 260 hours at 59 cubic meters per second. Traveltimes are dependent upon reservoir stratification and mixing as well as discharge. During 1981, inflowing dye-tagged water at 19.0 and 19.5 degrees Celsius was observed to seek its own temperature density level during movement along the thalweg. (USGS)

Water-Resources Investigations Report↗