USGS Washington Water Science Center
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WA313 - Summary of Atmospheric Deposition Data Collected as Part of the U.S. Geological Survey National Urban Runoff Program - Completed FY1986
Problem - Atmospheric-deposition-quality data have been compiled and stored in a computer data base as part of this project. The data were collected at 10 cities throughout the conterminous United States and Alaska during the U.S. Geological Survey (USGS) urban-runoff studies. The data representation, in terms of areal coverage, of any one region is sparse and therefore may be limited if used to depict regional differences in the quality of deposition. An objective that is consistent with one of the objectives of the National Urban Runoff Program (NURP) is to compare constituent loads in atmospheric deposition to loads in runoff from urban catchments. Although these comparisons have been published by some of the individual studies, further analysis using the combined data will serve to verify, extend, and summarize previous findings.
Objectives - Compute wetfall yields at all sampling sites. Estimate the contribution of constituent loads in wetfall to observed loads in runoff from urban catchments. Estimates will be made for individual storms for all sampled storms. Attempt to determine functional relations between atmospheric-deposition loads and runoff loads for constituents of interest, and at least one, but maybe more, catchment characteristics of interest, such as the percentage of effective impervious area.
Approach - Wetfall yields will be computed by multiplying constituent concentrations in samples by rainfall depth and a conversion factor to obtain mass per unit area per day. The contribution of a wetfall load to an observed runoff load will be computed for individual storms. Maximum, minimum, and median contributions of wetfall loads to runoff loads will be reported by catchment for all constituents. If order-of-magnitude differences are found, an analysis of variance technique may be used to test for significance. Plots or descriptive statistics will be used to examine the relations between the contributions of wetfall loads to runoff loads and catchment characteristics.