Using continuous measurements of turbidity to predict suspended-sediment concentrations, loads, and sources in Flat Creek through the town of Jackson, Wyoming, 2019−20 — A pilot study

First posted November 21, 2022 For additional information, contact: Director, Wyoming-Montana Water Science CenterU.S. Geological Survey3162 Bozeman AvenueHelena, MT 59601Contact Pubs Warehouse Flat Creek, a tributary to the Snake River in northwestern Wyoming, is an important source of irrigation water, fish and wildlife habitat, local recreation. Since 1996, section Creek within town Jackson has failed meet Wyoming Department Environmental Quality’s surface-water-quality standards for total suspended solids turbidity required by its State water-use classification. Quality water-quality prohibit increases greater than 10 nephelometric units (NTU) because human activities streambodies Wyoming. Sediment loading from urban stormwater runoff hypothesized previous publications be primary cause impairment, but relative fine sediment contributions various sources have not been quantified.In cooperation with Teton Conservation District, U.S. Survey began pilot study drainage basin investigate use continuous measurements predict suspended-sediment concentrations, loads, through Jackson, The predictions were based on collected every 15 minutes during parts water years 2019 2020. Analysis differences more 15,000 coincident between upstream downstream streamgages indicated that formazin (FNU) or composed about 1 percent accepted 2020 measurement periods. median difference measured records at was 0.20 FNU 0.0 FNU.Calculations mean loads indicate substantially below above town. Mean calculated streamgage 26 21 streamgage. occurring same time (coincident), entering 39 35 those exiting Creek. Incorporating statistical model uncertainty, predicted could potentially zero. annual period operations South Park Supply Ditch, which diverts into Gros Ventre River, constituted 91 90 load streamgage, 88 87 periods record 2020, respectively. However, absence simultaneous monitoring resulting outlet no robust method available quantify ditch.A moving average filter used identify isolate short-duration (minutes hours) spikes likely caused overland flow runoff. Suspended-sediment 8 (Flat Cache near Wyoming; 13018350), 6 4 Estimated events constitute 32 40 estimated respectively, indicating may contribute less percent, even as little 5 Estimation proportion site originate Ditch can only done assumptions potential equivalent associated