3 special studies to be conducted during SMC 2021-2025 regional stream monitoring

The third cycle of the SMC’s Regional Watershed Monitoring Program, which runs from 2021 to 2025, will encompass not only a trends assessment to track stream condition over time, but also three special studies that will shed light on three key areas of management interest:

Higher-resolution insights for priority areas

  • Key management question: What are conditions at under-sampled areas of interest, such as restored sites, soft-bottom channels, small urban streams, and headwaters?

The SMC will target particular areas that tend to be under-sampled via the core monitoring program, which selects sites via a spatially representative, probabilistic sampling design. Among the priority areas are restored sites, soft-bottom channels, small urban streams and headwaters.

Not only will this study improve precision in estimates of the extent of healthy streams, but it will also help stormwater managers understand potential limits on biological conditions in different stream types.

Rapid causal assessment

  • Key management question: What are likely causes of poor conditions at selected low-scoring sites?

The SMC will work to determine specifically why some stream sites with degraded water quality score low using bioassessment-based stream scoring tools.

The causal assessment investigation will build off SCCWRP’s work to streamline the causal assessment process (Schiff et al. 2015, Gillette et al. 2020) using a rapid causal assessment screening followed by more detailed analyses of stressors of interest.

This iterative approach to causal assessment is intended to boost confidence without incurring new costs. Sites where water quality (rather than habitat degradation) is the likely cause of poor bioassessment scores were selected using the SMC’s Stream Quality Index (Beck et al. 2019).

Wet and dry mapping

  • Key management question: Where do streams support flows sufficient for assessing conditions with benthic macroinvertebrates?

The SMC will map wet and dry channels in the region to better understand which streams are ephemeral , intermittent, or perennial. Flow duration is important to understand, as managers use flow duration to determine which stream management tools and programs can be applied to which streams:

  • The California Stream Condition Index – which uses benthic macroinvertebrates to quantify the biological condition of streams – is calibrated for use in perennial streams only. SCCWRP is validating the tool for intermittent streams, while simultaneously developing a separate bioassessment tool for use in ephemeral streams.
  • The SMC’s core Regional Watershed Monitoring Program is centered around monitoring of perennial and intermittent streams – ephemeral streams are largely excluded from SMC monitoring efforts.
  • Existing and planned State and regional stream regulatory programs are centered around biological objectives for perennial and intermittent streams. Thus, ensuring that assessment tools can be used properly across the full gradient of flow duration is a management priority.