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Accueil du site → Master → Etats Unis → 1993 → Groundwater elevations and temperature adjacent to a beaver pond in central Oregon

Oregon State University (1993)

Groundwater elevations and temperature adjacent to a beaver pond in central Oregon

Lowry, Michael M

Titre : Groundwater elevations and temperature adjacent to a beaver pond in central Oregon

Auteur : Lowry, Michael M

Université de soutenance : Oregon State University

Grade : Master of Science (M.S.) in Forest Engineering 1993

This study was designed and implemented to observe the spatial and temporal dynamics of groundwater levels and temperatures adjacent to a beaver pond in semi-arid central Oregon. The study site was located on the eastern boundary of Painted Hills National Monument along Bridge Creek, a tributary to the John Day River. Groundwater levels and groundwater temperature were monitored in 64 wells from July 3, 1991 to June 11, 1992. Groundwater elevations varied seasonally and were generally positively correlated with increased streamflow. In addition, beaver dam-building activity appeared to increase aquifer recharge near the beaver pond in comparison to downstream areas. The groundwater elevation of a well located near the pond rose 0.35 m between August and November 1991, while the Beaver pond stage increased by 0.22 m. Groundwater elevation at another well located downstream of the dam increased by only 0.17 in during this period with a corresponding increase in stream stage of 0.05 in. Groundwater levels throughout the study site averaged a 0.31 in gain from August to November 1991. All wells at the study site responded to changes in streamflow, and thus appear to be hydraulically connected to the stream. Hydraulic gradients adjacent to the pond were relatively low (i.e. 0.005 m/m). However, a zone about 50 m from the pond of relatively high hydraulic gradient (0.05 m/m) persisted over time, and groundwater flow directions in this area were both normal and parallel to the stream. Based on hydraulic gradients and observed groundwater elevations, the movement of water from the stream to subsurface recharge of riparian areas appeared to be greater near the pond than the streamside locations. Approximately 90 m³ of water could be drained from the aquifer if the dam were breached. Results of this study support the conclusion conmmonly expressed in the literature, but seldom quantified, that elevated water tables occur adjacent to beaver ponds. Groundwater temperatures for each successive month closely followed stream temperatures in wells next to the stream, indicating that stream temperatures readily influence groundwater temperatures adjacent to the stream. Wells located relatively far out on the floodplain (i.e. 50 meters) from the beaver pond had about a two month temperature response lag behind stream temperature. These results further indicate that stream temperature can influence groundwater temperature, and that groundwater recharge is highest near the pond.

Mots clés : Water table – Oregon, Eastern ; Groundwater temperature – Oregon, Eastern ; Beavers – Ecology – Oregon, Eastern ; Riparian ecology – Oregon, Eastern


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