Statistical Relationships of Storm Runoff Constituents with Storm Event Characteristics in Nine California Urban Watersheds

This research quantifies variation in chemical constituent concentration in urban stormwater runoff within urban watersheds. The research studies statistical relationships between storm event characteristics and event mean concentration of selected chemically-conservative constituents in runoff originating from those events. The analysis uses factors including storm precipitation, antecedent dry period, antecedent precipitation, and storm rainfall intensity, and establishes statistical correlations for chemical constituent data in runoff from selected urban watersheds in California. The correlations succeed in explaining a substantial part of the variation in event mean concentration, though some variation originates from other factors as yet unidentified. Results demonstrated a substantial difference in explanatory models among waterbodies and among constituents. The variation in concentration was better explained by storm variables for some watersheds, as expected, particularly smaller watersheds with more homogeneous land use. Antecedent conditions were more important for some watersheds and some constituents, and storm conditions more important for others.