Effect of Choptank Watershed Drainage Project on Stream Temperaturesby Thomas A. Iivari, USDA, Chester, United States,
Abstract: Between 1974 and 1982, the Soil Conservation Service, U.S.D.A conducted a stream study on the Choptank Watershed in Caroline County, Maryland to monitor the effects of channel construction and stream modification upon water temperature. The Choptank Watershed is a large drainage project implemented in Delaware and Maryland to alleviate flooding in agricultural areas and to improve soil drainage characteristics. Approximately 52 miles of surface drainage channel have been modified or installed in the Maryland portion of the watershed along with sediment control and other environmental mitigation measures, such as one sided and off sided construction techniques, in-channel sediment traps, daily seeding seeding of the banks, and berm construction. Significant changes in land use did not occur. Two adjoining subwatersheds were monitored daily before, during, and after channel construction in order to assess the effects of the drainage project on stream temperatures. A third adjoining watershed in which no channel modification occurred was also monitored daily and used as a control. Comparison of data shows that channels with no extensive removal of canopy did not experience any significant change in average monthly water temperatures. Constructed channels which had appreciable amounts of canopy removed, increased an average of 2-5°F during the early summer months. Spring, fall and winter stream temperature changes were not significantly effected. Stream temperatures in the modified channels ranged from 32° to 78°F throughout the year. Construction of in-channel sediment basins had negligible effect upon stream temperatures.
Subject Headings: Watersheds | Drainage | Temperature effects | Rivers and streams | Stream channels | Sediment | Construction management | North America | United States | Maryland | Delaware
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