Assessment of Baseline Conditions in Liberty Cut

Science Center Objects

Monitoring habitat quality in the San Francisco Estuary (SFE) and Sacramento-San Joaquin Delta has been limited to mostly monthly discrete measurements of biologically relevant parameters (e.g. phytoplankton, dissolved organic matter (DOM), nutrients) that cannot fully characterize the physical and biogeochemical variability.

    Map of current and proposed USGS optical continuous monitoring sites in the Northern Delta

Location of current and proposed USGS optical continuous monitoring sites in the Northern Delta. Determination of exact location of the continuous monitoring station at Liberty Cut will be based on analysis of current flow data.

Monthly surveys often miss key events and are biased by the tidal stage under which sample collection occurred (Pellerin et al. 2012; Bergamaschi et al. 2012). Continuous measurements are needed to characterize complex, tidally dependent variance in food web dynamics that influences the river-estuarine ecosystem and its capacity for productivity. Establishing a continuous monitoring station to measure key habitat-quality characteristics and food-web effects is fundamental for establishing relationships to flow and for determining effects of wetland restoration efforts in the Yolo Bypass region of the Delta. Yolo Bypass, situated within the North Delta/Cache Slough/Liberty Island complex, provides natural habitat to fish and wildlife species in the Delta. Implementation of the 'Yolo Ranch restoration' within the Cache Slough complex, has the potential to change the magnitude of current processes in the region, because it will change the size of the tidal exchange, and thus, alter the timing and rates of nutrient utilization. Given the multiple timescales of the processes that shape the aquatic habitat, a long period of baseline measurements is needed against which to compare conditions following implementation of the wetland restoration project. Establishing a continuous monitoring station to quantify fluxes and characterize conditions in real time to measure key habitat-quality characteristics and food-web effects at Liberty Cut will form the basis of the comparison. This proposed work at Liberty Cut, in Liberty Island, will provide data that captures short-term and long-term variability in habitat quality, will help to identify hydrologic and biogeochemical conditions which drive the environmental health of the estuary, and will provide means to assess multiple interacting drivers of habitat quality and ecosystem change.

The proposed monitoring station at Liberty Cut will provide a necessary biogeographic link to existing continuous time-series stations we currently operate south of the proposed location in the lower Sacramento River Delta at Decker Island (USCG Channel Marker 17), Cache Slough (at Ryer Island), and the mouth of Liberty Island (moored buoy). Measurements will include acoustic velocity, DOM, nutrients, and particle sensors (e.g. turbidity and pigment), similar to stations we already have in operation under previously funded projects. Continuous measurements of nitrate, chlorophyll-a, phycocyanin, and DOM fluorescence will provide an essential database for interpreting environmental change against the background of climate and anthropogenic impacts on the Delta. Continuous measurements of water-quality parameters in the Delta have provided important information on the timing, drivers, and mechanisms influencing nutrient cycling, food web dynamics and contaminant transport (Spencer et al. 2007; Bergamaschi et al. 2011). Continuous measurements at Liberty Cut will expand our knowledge of important processes as well as provide a basis for fully understanding the benefits of wetland restoration (Downing et al. 2009; Pellerin et al. 2009; Bergamaschi et al. 2011). This project addresses the ecosystem and climate strategic directions in the USGS Science Plan, for example 'Understanding Ecosystems and Predicting Ecosystem Change' as well as 'Climate Variability and Change' (U.S. Geological Survey, 2007). This is accomplished by improving our understanding of how these variables are distributed around this region of the upper Delta and leads to a better understanding of habitat types and their distribution in the lower Delta. Understanding these variables over time also leads to a better understanding of the effects of freshwater flow and climate. Lastly, understanding baseline concentrations and flux monitoring will help resources managers to assess current conditions and evaluate conditions following implementation of wetland restorations in the lower Yolo Bypass area in Liberty Island.

Objectives

  • Install a continuous monitoring station at Liberty Cut to monitor concentrations and fluxes to help assess current conditions (baseline conditions) and to evaluate conditions following implementation of wetland restorations in the lower Yolo Bypass area.
  • Provide real-time discharge and concentration data from the new station at Liberty Cut in conjunction with real-time data from stations at Liberty Island, at Lower Cache Slough, and at the Lower Sacramento River, to help identify regional drivers of habitat quality. This information will be delivered to ecosystem mangers and scientists to improve understanding and management of the Bay-Delta system.
  • Analyze current and historic flow data to provide background information about flows over a variety of conditions.