The Stream Pollution Trends Monitoring Program (SPoT) is one of several statewide programs under the California State Water Resources Control Board’s Surface Water Monitoring Program (SWAMP). The SPoT monitoring program conducts statewide surveys of California stream water quality, and has been generating sediment toxicity and contaminant data since 2008 from up to 100 diverse watersheds. Analysis has included toxicity testing with the amphipod Hyalella azteca and more recently, the midge Chironomus dilutus, as well as the measurement of metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, legacy pesticides, current use pesticides, and emerging contaminants such as fipronil and polybrominated diphenyl ethers (PBDEs) in watershed sediments. This extensive data set has been analyzed in the context of watershed land use to understand the nature of identified water pollution and its trends.
A complete set of reports, fact sheets and other documents covering the first ten years of monitoring can be found here, and the first five years of data are summarized in Siegler et al. (2015). Reports include complete methodology. Below are the latest highlights from the program and updates from the latest trends in toxicology and contaminant concentrations.
A complete set of reports, fact sheets and other documents covering the first ten years of monitoring can be found here, and the first five years of data are summarized in Siegler et al. (2015). Reports include complete methodology. Below are the latest highlights from the program and updates from the latest trends in toxicology and contaminant concentrations.
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SPoT sites are selected in large watersheds with heterogeneous land cover, and are located at or near the base of the watershed, defined as the confluence with either an ocean, lake, or another stream of equal or greater stream order; and located where site-specific conditions are appropriate for the indicators selected (e.g., depositional areas, sufficient flow, appropriate channel morphology, substrate).
Darker areas on the map indicate sub-watersheds. |
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Sediments collected from depositional areas at integrator sites provide a composite record of pollutants mobilized from throughout the watershed. While many hydrologic, engineering, and environmental variables affect the ability of this record to adequately characterize all pollutant-related activities, sediment samples collected from such areas are considered to be a relatively good and logistically feasible means of assessing large watersheds for long-term trends
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Toxicity tests with Hyalella azteca and Chironomus dilutus are conducted following U.S. EPA standard methods (U.S. EPA 2000). Hyalella azteca is an epibenthic amphipod that is native to California streams. Wild populations have been known to become resistant to anthropogenic chemicals such as pesticides (Weston et al. 2013), but laboratory cultured populations are sensitive indicators of contaminants. In 2015, SPoT added the midge Chironomus dilutus toxicity test at sites in watersheds with greater urban land use. This midge is also native to California streams and builds tubes from sediment particles. Use of both organisms in tandem provides additional information on sample toxicity
The SWAMP Assessment Framework provides guidance and context for developing question-driven monitoring to provide water quality information directly useful for resource management. The beneficial uses that are assessed pertain to aquatic life protections, and the water body types that are assessed are streams that range from ephemeral creeks to large rivers.
Level 1 Assessment Questions include: A) Are our aquatic ecosystems healthy? B) What stressors and processes affect our water quality?
Level 2 Assessment Questions include: A) Are beneficial uses impacted? B) Are conditions getting better or worse? C) What is the magnitude and extent of any problems? D) What’s causing the problem? E) Are solutions working?
Level 1 Assessment Questions include: A) Are our aquatic ecosystems healthy? B) What stressors and processes affect our water quality?
Level 2 Assessment Questions include: A) Are beneficial uses impacted? B) Are conditions getting better or worse? C) What is the magnitude and extent of any problems? D) What’s causing the problem? E) Are solutions working?
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As of 2020, there was no significant trend in the Hyalella survival endpoint. Although some contaminant concentrations have significant upward and downward trends at individual sites, sites that have been consistently toxic or highly toxic tend to remain so. Sites with toxic and highly toxic sites, as indicated by the X's, demonstrate that beneficial uses are being impacted. The lack of a significant toxicity trend at the statewide level makes it difficult to determine if conditions are getting better or worse.
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