Water Center
Date of this Version
4-6-2018
Citation
United States Geological Survey, Data Series 1079
Document doi: 10.3133/ds1079
Data doi: 10.5066/F74M93RK
Data:
Abstract
Document abstract
The Ubited States Geological Survey (USGS), in cooperation with the United States Army Corps of Engineers, monitored a sediment release by Nebraska Public Power District from Spencer Dam located on the Niobrara River near Spencer, Nebraska, during the fall of 2014. The accumulated sediment behind Spencer Dam ordinarily is released semiannually; however, the spring 2014 release was postponed until the fall. Because of the postponement, the scheduled fall sediment release would consist of a larger volume of sediment. The larger than normal sediment release expected in fall 2014 provided an opportunity for the USGS and US Army Corps of Engineers to improve the understanding of sediment transport during reservoir sediment releases. A primary objective was to collect continuous suspended-sediment data during the first days of the sediment release to document rapid changes in sediment concentrations. For this purpose, the USGS installed a laser-diffraction particle-size analyzer at a site near the outflow of the dam to collect continuous suspended-sediment data. The laser-diffraction particle-size analyzer measured volumetric particle concentration and particle-size distribution from October 1 to 2 (pre-sediment release) and October 5 to 9 (during sediment release). Additionally, the USGS manually collected discrete suspended-sediment and bed-sediment samples before, during, and after the sediment release. Samples were collected at two sites upstream from Spencer Dam and at three bridges downstream from Spencer Dam. The resulting datasets and basic metadata associated with the datasets were published as a data release; this report provides additional documentation about the data collection methods and the quality of the data.
Data abstract
In the fall of 2014 (October-November) the USGS in cooperation with the US Army Corps of Engineers collected sediment samples (suspended and bed material) at several sites on the Niobrara River in Nebraska near the Spencer Dam prior to, during, and immediately after a sediment-flushing event. Suspended-sediment samples were analyzed for sediment concentration and percent finer than sand. Bed sediment samples were analyzed for particle-size distribution using standard classes by sieve analysis. In addition, a Sequoia LISST Streamside particle-size analyzer (PSA) was deployed during the first week of the flush; this unit collected suspended-sediment concentration and grain-size data. Sampled sites included the bridge on U.S. Hwy 281, county road 508 Ave bridge south of Lynch, Nebraska, and the county road bridge south of Verdel, Nebraska This part of the data release consists of discrete suspended-sediment and bed-sediment data tables, PSA data tables, and a data table of results from discrete samples collected manually at the intake to the PSA. An accompanying shapefile of sample locations may be found at https://www.sciencebase.gov/catalog/item/5a5e1596e4b06e28e9be47db.
Comments
United States government work