Techniques for estimating the quantity and quality of storm runoff from urban watersheds of Jefferson County, Kentucky

Abstract

This report presents techniques for estimation of storm-runoff volumes, and mean concentrations and loads of selected constituents in storm runoff from urban watersheds of Jefferson County, Ky. Estimation models were developed on the basis of runoff volumes, and concentrations and loads of selected constituents in runoff measured at 6 stormwater outfalls and 25 streams in Jefferson County. In addition, previously developed regional estimation models were evaluated to assess their suitability for use in the county. Adjustments to the previously developed models were determined from comparisons to data obtained in Jefferson County. The estimation techniques consist of sets of linear regression models for estimating mean concentrations and total loads of selected constituents in single storms, the quantity of the storm runoff, and annual and mean annual loads of selected constituents in storm runoff. Constituents modeled include dissolved oxygen, biochemical and chemical oxygen demand, dissolved and suspended solids, volatile residue, nitrogen, phosphorus and phosphate, calcium, magnesium, barium, copper, iron, lead, and zinc. Model estimations are a function of drainage area, percentage of imperviousness, climatological data, and land use. Purpose and Scope This report describes techniques for estimating the quantity and quality of storm runoff from urban watersheds of Jefferson County, Ky. Previously developed regional estimation models were evaluated to assess their suitability for use in the county. These models were adjusted, and additional new models were developed on the basis of storm data measured in Jefferson County. Regression models are presented for estimation of (1) selected constituent concentrations in storm runoff, (2) runoff volumes and selected constituent loads in runoff from single storms, and (3) annual total volumes of runoff and loads of selected constituents in runoff. The main constituents of interest for this study include chemical oxygen demand, biochemical oxygen demand, dissolved solids, suspended solids, total nitrogen, total Kjeldahl nitrogen, total phosphorus, dissolved phosphorus, total cadmium, total copper, total lead, and total zinc. Description of Study Area Jefferson County covers 386 mi 2 of the north-central part of Kentucky along the Ohio River (fig. 1) (Louisville Chamber of Commerce, 1992). Within its borders is Louisville, the largest city and the most densely populated area of the State. Approximately 69 storms, defined as 0.1 in. accumulation with at least 0.01 in. each hour, occur each year in Jefferson County (Steurer and Nold, 1986). EXPLANATION County boundary Drainage divide Basin area 0 2 4 6 8 10 MILES ' ' ' /""" r j \ | I 8503T30-.'/ f X-XJ