California’s State Water Resources Control Board (SWRCB) wishes to quantify how water and constituents introduced via the outflow from the Spring Creek Diversion Dam mix with water within Keswick Reservoir. Of primary interest is the degree of dilution that exists when this introduced flow reaches the main stem of Keswick Reservoir, and how this mixing is influenced by different operational parameters of the system. In addition to flows through the three relevant dams (Spring Creek Debris Dam, Keswick Dam, and Shasta Dam) that must be considered, there is additional flow entering the Spring Creek Arm of the Keswick Reservoir via two penstocks that carry water from Whiskeytown Lake to the Spring Creek Power Plant. In total there are thus four different flow rates to consider, all controlled by the U.S. Bureau of Reclamation to manage a combination of water supply, water quality and ecological interests. The problem was investigated by an approach that combines three-dimensional numerical modeling of hydrodynamics and an assumed conserved tracer with a small field measurement campaign to measure short-term mixing processes via monitoring of released dye for comparison to model results. The project involves the use of the public domain Delft3d hydrodynamic model, which includes conserved constituent transport. This data release contains data from: 1) a small-footprint bathymetric survey performed at the upstream end of the Spring Creek Arm on 12/3/21, and 2) Data from a Rhodamine dye mixing experiment conducted 4/4-4/8/22. This dataset includes: - discharge data to and from Keswick reservoir - some water level and water temperature data - a bathymetric survey dataset assembled from three different surveys, differing in scope, in 2010, 2016 and 2021. - data from 10 sondes deployed in Keswick Reservoir 4/4-4/8/22 to record Rhodamine dye concentration, water temperature, and specific conductivity, along with pressure head. - data from three GPS-equipped drifters that recorded surface flow pathlines for the first half-day of the April 2022 experiment. This data release includes all of the measurements required to run the hydrodynamic model to simulate the April 2022 field experiment.