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|Title:||Water quality evaluation of proposed Trexler Lake, Jordan Creek, Pennsylvania|
|Authors:||Ford, Dennis E.|
Thornton, Kent W.
Lessem, Allan S.
|Publisher:||U.S. Army Engineer Waterways Experiment Station|
|Series/Report no.:||Technical Report (Wetlands Research Program (U.S.)) ; no. Technical Report Y-78-10|
|Abstract:||The water quality of proposed Trexler Lake, Pennsylvania , was evaluated with respect to its eutrophication potential and water quality criteria and standards appropriate for project purposes. Study approaches included review of existing water quality data taken on the four tributari es to the proposed project; review of existing data on surrounding impoundments; algal bioassay analyses on water samples taken in the proposed tributaries and in one surrounding lake; mathematical simulations; and nutrient loading analyses. Water quality data from Mill, Lyon, Switzer, and Jordan creeks indicated no major water quality problems. Nitrate concentrations were high but did not exceed standards for water supply. Fecal coliform counts exceeded 200 colonies/100 ml during periods of high runoff. Local problems on Mill Creek can be expected under low flow because of effluents from the Heidelberg Heights sewage treatment plant. The surrounding lakes can be classified as mesotrophic or mildly eutrophic, and none were able to meet the state standard of 5 mg/l for dissolved oxygen. Proposed Trexler Lake is expected to be similar in trophic status and in dissolved oxygen content. Algal bioassays were conducted on water samples taken in Mill, Lyon, Switzer, and Jordan Creeks and in Beltzville Lake. All samples were phosphorus limited, and all of the orthophosphate was available for algal growth. Mathematical simulations included both watershed and reservoir models. The Hydrocomp Simulation Program was used to predict inflows from each of the four tributaries. A reservoir ecological model was used to predict the trophic status of the impoundment and the effects of various reservoir regulation schemes on the water quality. Because insufficient water quality data existed on the project to quantify loadings accurately and on surrounding impoundments to calibrate the model, Monte Carlo simulations were used to specify water quality update data and coefficients. The mathematical simulations indicated that the downstream temperature objective could be met provided the selective withdrawal structure is redesigned to have six ports evenly distributed in two wet wells. Simulated algal concentrations were 5 to 11 mg/m³ chlorophyll a or similar to the concentrations found in surrounding lakes. The hypolimnion was predicted to be anoxic for about 1 month. No problems with fecal coliforms exceeding standards were predicted, but intermittent problems in the headwater regions are probable. Nutrient loading analyses were performed using the concepts of Vollenweider, Dillon and Rigler, and Larsen and Mercier. All three methods predicted proposed Trexler Lake to be eutrophic. Chlorophyll a concentrations estimated from the average in-lake phosphorus concentrations were equal to or slightly higher than the concentrations found in surrounding lakes . The proposed Trexler Lake is expected to be in the mesotrophic or early eutrophic stage and exhibit strong thermal stratification during the summer months with a 1-month period of hypolimnetic anoxia during the fall. The project purposes are not expected to be vitiated by water quality although the lake is expected to be anoxic for a short time during late summer. Appendix A describes the algal assay procedures. Appendix B discusses the Hydrocomp simulation of Jordan Creek drainage basin. Appendix C presents the initial conditions, coefficients, and updates for mathematical ecological simulations. Appendix D lists the coefficient references.|
|Gov't Doc #:||Technical Report Y-78-10|
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Technical Report|