Aquatic Ecosystem Assessment of the McCormack-Williamson Tract, Sacramento-San Joaquin Delta, CA, 2025

This dataset documents physical habitat, hydrodynamic, water-quality, structural cover, and aquatic community conditions within the McCormack–Williamson Tract (MWT), a tidally influenced floodplain wetland in the Sacramento-San Joaquin Delta near the confluence of the Mokelumne and Cosumnes rivers. Following levee breaches in 2017 and 2023, portions of MWT transitioned from agricultural land to connected tidal wetland, subtidal, and floodplain habitats. Data were collected between February and October 2025 to characterize spatial and temporal variability in hydraulic conditions, water quality, vegetation and structural cover, elevation surfaces, and aquatic communities under tidal stages including mean higher high water (MHHW), mean tide level (MTL), and mean lower low water (MLLW). Data include point time series from autonomous water-quality and water-level loggers; acoustic Doppler current profiler velocity measurements along transects; RTK-GPS topographic and bathymetric survey points; aerial lidar and drone-derived raster elevation surfaces; polygon cover maps derived from orthomosaic imagery; fish community observations derived from stereo video imagery; and zooplankton observations collected using a Deep-Focus Particle Imager. Continuous sensors recorded at 30-minute intervals. These datasets were processed to produce derived geospatial products including digital elevation models, water surface elevation time series, vegetation/structural cover polygons, fish and zooplankton community metrics, and modeled habitat suitability polygons based on defined hydraulic, cover, and water-quality criteria. The dataset provides spatially explicit environmental measurements, biological community observations, and modeled habitat suitability layers representing first-year post-breach conditions at MWT.