Ecology–Soil Relations — Abstract of Paper


Turbidity and Total Suspended Solid Concentration Dynamics in Streamflow from California Oak Woodland Watersheds
David J. Lewis,¹ Kenneth W. Tate,² Randy A. Dahlgren,³ and Jacob Newell⁴


Resource agencies, private landowners, and citizen monitoring programs utilize turbidity (water clarity) measurements as a water quality indicator for total suspended solids (TSS – mass of solids per unit volume) and other constituents in streams and rivers. The dynamics and relationships between turbidity and TSS are functions of watershed specific factors and temporal trends within storms and across seasons. This paper describes these relationships using four years of water quality and stream discharge data from seven experimental watersheds in the northern Sierra foothills and north coast oak woodlands of California. Rating curves predicting TSS concentration as a function of turbidity were developed with simple linear regressions. Stream discharge rapidly rose and fell in response to winter storms once watershed soils were saturated. Turbidity and TSS concentrations paralleled this seasonal rise and fall in stream discharge. In addition, a hysteresis effect was observed for both TSS and turbidity during individual storms. Regression slopes for TSS versus turbidity were significantly different between watersheds of similar and differing soils, geology, and hydrology. These results indicate the need for intensive, storm-based sampling to adequately characterize TSS and turbidity in oak woodland watersheds. Water quality monitoring programs that account for the watershed specific nature of turbidity and TSS relationships and the influence that climate, soils, geology, and hydrology have on these relationships will better represent water quality and sediment transport in California oak woodland watersheds.