This paper presents a comparison of pollutant load estimations for runoff from two geographically distinct residential suburban neighborhoods in northern and southern California. The two neighborhoods represent a single urban land use type: low-density residential in small catchments (<0.3 km) under differing regional climates and irrigation practices. Pollutant loads of pesticides, nutrients, and drinking water constituents of concern are estimated for both storm and non-storm runoff. From continuous flow monitoring, it was found that a daily cycle of persistent runoff that peaks mid-morning occurs at both sites. These load estimations indicate that many residential neighborhoods in California produce significant non-storm pollutant loads year-round. Results suggest that non-storm flow accounted for 47-69% of total annual runoff and significantly contributed to annual loading rates of most nutrients and pesticides at both sites. At the Southern California site, annual non-storm loads are 1.2-10 times higher than storm loads of all conventional constituents and nutrients with one exception (total suspended solids). At the Northern California site, annual storm loads range from 51 to 76% of total loads for all conventional constituents and nutrients with one exception (total dissolved solids). Non-storm yields of pesticides at the Southern California site range from 1.3-65 times higher than those at the Northern California site. The disparity in estimated pollutant loads between the two sites indicates large potential variation from site-to-site within the state and suggests neighborhoods in drier and milder climates may produce significantly larger non-storm loads due to persistent dry season runoff and year-round pest control.
DisPatch, a graphically oriented interactive computer program, has been designed to model the far-field transport of wastewater discharge in the ocean environment Implemented on a microcomputer, DisPatch features high-resolution graphics, menus, and dialog boxes to facilitate user input of boundary conditions in such a way as to be accessible to a large audience of potential users. The DisPatch model is developed from the application of the advection-dispersion equation to a horizontally homogeneous, vertically averaged, turbulent velocity field representing the ocean environment in which a “patch” of discharged wastewater is presumed to travel. Designed to accept either average values or a stochastically generated set of values for initial dilution and trapping height, DisPatch displays the path of each discharge event onscreen as an animation of calculated patch position and dimension. Results are presented in the form of an elevation view of contaminant impact at a user-defined impact zone.
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