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AcknowledgmentsThe cooperation of the National Park Service through the National Park Service-U.S. Geologi cal Survey WaterQuality Partnership program is gratefully acknowledged. This report presents a compilation of information supplied by several agencies and individuals. The authors would like to thank the U.S.
DatumVertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29).Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).Elevation, as used in this report, refers to distance above the vertical datum.
ix Supplemental InformationSpecific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C).
Concentrations
AbstractLake St. Croix is a naturally impounded, riverine lake that makes up the last 40 kilometers of the St. Croix River. Substantial land-use changes during the past 150 years, including increased agriculture and urban development, have reduced Lake St. Croix water-quality and increased nutrient loads delivered to Lake St. Croix. A recent (2012-13) total maximum daily load phosphorus-reduction plan set the goal to reduce total phosphorus loads to Lake St. Croix by 20 percent by 2020 and reduce Lake St. Croix algal bloom frequencies. The U.S. Geological Survey, in cooperation with the National Park Service, developed a two-dimensional, carbon-based, laterally averaged, hydrodynamic and water-quality model, CE-QUAL-W2, that addresses the interaction between nutrient cycling, primary production, and trophic dynamics to predict responses in the distribution of water temperature, oxygen, and chlorophyll a. Distribution is evaluated in the context of habitat for lake sturgeon, including a combination of temperature and dissolved oxygen conditions termed oxythermal habitat.The Lake St. Croix CE-QUAL-W2 model successfully reproduced temperature and dissolved oxygen in the lake longitudinally (from upstream to downstream), vertically, and temporally ove...