Effects of Nonagricultural Human Activity on Sediment Quality--A Comparison of Trace Element Concentrations in Eight Small Reservoirs

Small reservoirs are valued by the general public both as a source of drinking water and for recreational activities. In addition to information on water quality and sedimentation, effective reservoir managment requires information on sediment quality. Sediment quality is an important environmental concern because sediment may act as a sink for some water-quality constituents and, under certain conditions, as a source of constituents to the overlying water column and biota. Once in the food chain, sediment-derived constituents may pose an even greater concern because of bioaccumulation. An analysis of reservoir bottom sediments can provide historical information on sediment deposition as well as the occurrence of sediment-bound constituents. Such information may be used to partly reconstruct historical sediment-quality and water-quality records and to determine a present-day baseline with which to evalute long-term changes in reservoir sediment and water quality that may be related to changes in human activity in the contributing basin. Moreover, such information may be used to assist in the development, implementation, evaluation, and revision of total maximum daily loads (TMDLs) for sediment and associated constituents that contribute to the water-quality impairment of reservoirs.

To investigate the effects of nonagricultural human activity on sediment quality, sediment cores were collected from eight small reservoirs in eastern Kansas with basins of diverse land-use combinations. The sediment samples were analyzed for trace elements. Most, if not all, trace elements may be toxic in animals and humans if the concentrations are sufficiently large. Specific study objectives were to: (1) determine the occurrence and trends of trace elements in the reservoir bottom sediments, (2) assess sediment quality with respect to available guidelines, and (3) interpret the effects of nonagricultural human activity (in the basin or the reservoir) on sediment quality within and among the eight reservoirs.

The eight small reservoirs selected for the study were Bronson City Lake, Centralia Lake, Crystal Lake, Gardner City Lake, Lake Afton, Mission Lake, Otis Creek Reservoir, and Pony Creek Lake. Each of these reservoirs is used as a public water supply and (or) for recreation. All but Otis Creek Reservoir were listed under Section 303(d) of the Federal Clean Water Act of 1972 for eutrophication. The 303(d) list is a priority list that identifies water bodies that do not meet water-quality standards on the basis of the use of the water bodies. For each impaired water body on the 303(d) list, a State is required by the Clean Water Act to develop a TMDL, which is an estimate of the maximum pollutant load (material transported during a specified time period) from point and nonpoint sources that a receiving water can accept without exceeding water-quality standards. Otis Creek Reservoir, which was not on the 303(d) list, was included in the study for the purpose of comparison.

Juracek, K.E., and Ziegler, A.C., 2006, Effects of nonagricultural human activity on sediment quality—a comparison of trace element concentrations in eight small reservoirs, in Proceedings of the Eighth Federal Interagency Sedimentation Conference, April 2-6, 2006, Reno, Nevada: Subcommittee on Sedimentation, CD-ROM, 8 p.