Statewide Perspective on Chemicals of Concern and Connections Between Stream Water Quality and Land Use

The California Surface Waters Ambient Monitoring Program (SWAMP) is tasked with assessing water quality in all of California’s surface waters. The program conducts monitoring directly and through collaborative partnerships, and provides numerous information products designed to support water resource management in California. The Stream Pollution Trends (SPoT) program is a statewide monitoring effort focused on the SWAMP priority of assessing the levels to which aquatic life beneficial uses are supported in California streams (SWAMP 2010). The program has three primary goals:

1. Determine long-term trends in stream contaminant concentrations and effects statewide.
2. Relate water quality indicators to land-use characteristics and management effort.
3. Establish a network of sites throughout the state to serve as a backbone for collaboration with local, regional, and federal monitoring.

The SPoT program is specifically designed to fill critical information needs for state, regional and local resource management programs, including Clean Water Act (CWA) §303d impaired waters listing, CWA §305b condition assessment, total maximum daily load (TMDL) assessment and allocation, non-point source program water quality assessment, stormwater and agricultural runoff management, pesticide registration and labeling, and local land use planning.

SPoT is a long-term trends monitoring program that will help managers understand how water quality conditions are changing over time in relation to land use change and resource management practice implementation. This report covers the rst annual survey, so trends assessment will not begin until the second and third year surveys are included in the next SPoT report (due in 2012). The focus of this report is on identifying chemicals of concern and the watershed land uses associated with their presence in California streams. The data collected can be used in a space-for-time-swap approach to estimate the effect that further land use change (such as increasing urbanization) would have on stream water quality in California.

The results indicate that, on a statewide basis, levels of most measured pollutants in stream sediment increased as urban land cover in their watersheds increased. Industrial compounds, some metals, and many pesticides were found at higher concentrations in urban watersheds than in agricultural or other watersheds statewide.

Pyrethroid pesticides were detected in stream sediments from more than half of the SPoT watersheds, and were measured at concentrations associated with toxicity in more than a quarter of the total samples. DDTs and PCBs, both banned for more than three decades, are still commonly detected in California streams, with DDTs frequently exceeding sediment quality guidelines. PBDEs and PAHs were common in urban areas, and mercury was above guideline values in a small number of samples from urban watersheds and watersheds where it is geologically abundant.