Hydrologic and water-quality characterization and modeling of the Chenoweth Run basin, Jefferson County, Kentucky

Water-Resources Investigations Report 2000-4239

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Rainfall, streamflow, and water-quality data collected in the Chenoweth Run Basin during February 1996?January 1998, in combination with the available historical sampling data, were used to characterize hydrologic conditions and to develop and calibrate a Hydrological Simulation Program?Fortran (HSPF) model for continuous simulation of rainfall, streamflow, suspended-sediment, and total-orthophosphate (TPO4) transport relations. Study results provide an improved understanding of basin hydrology and a hydrologic-modeling framework with analytical tools for use in comprehensive waterresource planning and management. Chenoweth Run Basin, encompassing 16.5 mi2 in suburban eastern Jefferson County, Kentucky, contains expanding urban development, particularly in the upper third of the basin. Historical water-quality problems have interfered with designated aquatic-life and recreation uses in the stream main channel (approximately 9 mi in length) and have been attributed to organic enrichment, nutrients, metals, and pathogens in urban runoff and wastewater inflows. Hydrologic conditions in Jefferson County are highly varied. In the Chenoweth Run Basin, as in much of the eastern third of the county, relief is moderately sloping to steep. Also, internal drainage in pervious areas is impeded by the shallow, fine-textured subsoils that contain abundant silts and clays. Thus, much of the precipitation here tends to move rapidly as overland flow and (or) shallow subsurface flow (interflow) to the stream channels. Data were collected at two streamflowgaging stations, one rain gage, and four waterquality- sampling sites in the basin. Precipitation, streamflow, and, consequently, constituent loads were above normal during the data-collection period of this study. Nonpoint sources contributed the largest portion of the sediment loads. However, the three wastewatertreatment plants (WWTP?s) were the source of the majority of estimated total phosphorus (TP) and TPO4 transport downstream from the WWTP?s. HSPF, a hydrologic model capable of simulating mixed-land-use basins, includes land surface, subsurface, and instream waterquantity- and water-quality-modeling components. The HSPF model was used to represent several important hydrologic features of the Chenoweth Run Basin including (1) numerous small lakes and ponds, through which approximately 25 percent of the basin drains; (2) potential seasonal ground-waterseepage losses in stream channels; (3) contributions from WWTP effluents and bypass flows; and (4) the transport and transformations of sediments and nutrients. The HSPF model was calibrated and verified for flow simulation on the basis of measured total, annual, seasonal, monthly, daily, hourly, and 5-minute-interval storm discharge data. The occurrence of numerous storms during the study period permitted a splitsample procedure to be used for a model verification on the basis of storm volumes and peaks. Total simulated and observed discharge during the model calibration period differed by approximately -5.4 percent at the upper gaging station and 3.1 percent at the lower station. The model results for the total and annual water balances were classified as very good on the basis of the calibration criteria reported in other modeling studies. The model had correlation coefficients ranging from 0.89 to 0.98 for hourly to monthly mean flows, respectively. The coefficients of model-fit efficiency for daily and monthly discharge simulations were near the excellent range (exceeding 0.97). However, the model was calibrated for a comparatively short 24-month period during which flows were above normal. Increased model error might be expected during an extended period of nearnormal flows. The model was calibrated for simulation of sediment and TPO4 transport. The simulated mean-annual load (over 24 months) ranged from -33 to -28 percent of the estimated sediment load and within +/- 1 percent of the estimated TPO4 load at the two streamflow-gaging s

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USGS Numbered Series
Hydrologic and water-quality characterization and modeling of the Chenoweth Run basin, Jefferson County, Kentucky
Series title:
Water-Resources Investigations Report
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U.S. Dept. of the Interior, U.S. Geological Survey ;Branch of Information Services [distributor],
xi, 197 p. :ill., maps ;28 cm.