Hydrologic Connectivity and Residence Time Affect the Sediment Trapping Efficiency and Dissolved Oxygen Concentrations of the Atchafalaya River Basin
Abstract
Little is known about water movement, volume, or residence time (RT), and how those characteristics affect sediment trapping efficiency (TE) and dissolved oxygen concentrations (DO) in the United States' largest remaining bottomland hardwood swamp, the Atchafalaya River Basin. To better understand these dynamics, this study used bathymetry, lidar, and stage records to determine volumes in the Basin's hydrologically distinct water management units (WMUs). Discharge measurements determined flow distribution and RT. Residence time was compared with DO to identify conditions that coincided with DO increases or decreases. Suspended sediment concentrations (SSC) were used to determine TE relative to calculated and measured discharge and RT. Discharge through units (85–2,200 m3/s) and RT (0.37–231 d) depended on connectivity and river stage. At high stages, with water temperatures >20°C, DO in the largest WMU declined by −0.21 mg/l/day. DO trends indicated less well‐connected areas of the WMU contributed hypoxic waters as the flood wave lengthened and stages fell. In the two WMUs examined for TE, TE (−266% to 99% and up to 38 Gg/day) correlated with hydrologic connectivity, SSC, RT, water volume, and, in one WMU, discharge losses. Long RT and high TE indicated a high potential to process nutrients. These relationships varied among WMUs. Large volumes of sediment‐laden water moving over the floodplain combined with long RT, high TE, and hypoxia indicate that this ecosystem has continental‐scale importance in reducing nutrient loads to the northern Gulf of Mexico. Reports from other systems suggest similar processes may be operating on other large river floodplains globally.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 01, 2022
- Source ID
- 10.1029/2021wr030731
Entities
People
- Charles R. Demas
- Daniel Kroes
- Michael D. Kaller
- Raynie Harlan
- Richard H. Day
- Steven Roberts
- Tiffany E. Pasco
- William E. Kelso
Organizations
- Louisiana Department of Wildlife and Fisheries
- Louisiana State University
- National Institute of Food and Agriculture
- United States Army Corps of Engineers
- United States Department of Agriculture