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Webster BC, Waters MN, Golladay SW. Linking reservoir annual residence time to nitrogen deposition using paleolimnological techniques. WATER RESEARCH 2024; 265:122245. [PMID: 39173354 DOI: 10.1016/j.watres.2024.122245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 05/15/2024] [Accepted: 08/08/2024] [Indexed: 08/24/2024]
Abstract
In river networks, reservoirs are hotspots for nutrient transformations, providing multiple pathways for nitrogen processing. One of the less measured pathways is nitrogen deposition. Here, we investigated the decadal relationship between water residence time and nitrogen deposition using sediment cores from eight mainstem reservoirs within a river system containing two contrasting watersheds. One watershed was significantly urbanized with regulated flow and the other watershed was unregulated with extensive rural land use. We explored the relationship of sediment nitrogen concentrations across a range of residence times, land uses, and other parameters throughout this linked river-reservoir system. Results show that average annual residence time had the strongest relationship to nitrogen deposition when compared to reservoir volume, mean depth, surface area, outflow, and land use. Pigment analysis revealed that residence time influences nitrogen by allowing for longer periods of algal uptake, followed by deposition in particulate organic form. Supporting this mechanism, sedimentary C:N, with low values representing greater algal influence, expressed a strong and negative relationship with average annual residence time, as well as a positive relationship between residence time and photosynthetic pigments diagnostic of cyanobacteria, diatoms, and a combination of green algae+cyanobacteria. Furthermore, we investigated how drought conditions could alter residence times and intensify nitrogen cycling through primary productivity in reservoirs. Drought increased residence time by 45-60 %. This increase was estimated to raise sediment nitrogen concentrations by roughly 2.5-4 %.
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Affiliation(s)
- Benjamin C Webster
- Department of Crop, Soils & Environmental Science, Auburn University, Auburn, AL 36849, United States.
| | - Matthew N Waters
- Department of Crop, Soils & Environmental Science, Auburn University, Auburn, AL 36849, United States
| | - Stephen W Golladay
- Georgia Water Planning and Policy Center, Albany State University, Albany, GA 31701, United States
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Long Y, Yang T, Gao W, Liu Y, Xu C, Yang Y. Prevention and control of algae residue deposition in long-distance water conveyance project. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 344:123294. [PMID: 38182011 DOI: 10.1016/j.envpol.2024.123294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 12/29/2023] [Accepted: 01/03/2024] [Indexed: 01/07/2024]
Abstract
With the increase of operation cycle in long-distance water conveyance project, the problem of silt or algae residue deposition in river channels is becoming more and more prominent, especially in the vicinity of some uncommonly used bifurcation and outflow gates along the water conveyance project. When the deposition reaches certain thickness, it will not only affect the water quality of local water bodies, but also seriously affect the normal operation of these bifurcation and outflow gates. In order to alleviate this problem, the prevention and control of algae residue deposition in long-distance water conveyance project is mainly explored from two perspectives: (1) the scouring effect on the bottom of the side channel is compared by studying different diversion ratios of the side channel; (2) The arc guide wing wall is built near the junction of the main channel and side channel. The simulation is conducted at 6 different included angles including -10°, -5°, 0°, 5°, 10° and 15°, and for non-guide wing wall. The incoming flow is simulated at 280 m3/s of general flow and 320 m3/s of design flow. A total of 14 groups of experiments are carried out for numerical simulation. It can be concluded that, when the incoming flow is held constant, a higher diversion ratio results in a more effective scouring of the bottom sediment in the side channel; when the included angles of the guide wing wall are -10°, -5°, 0° and 5°, it has a significant effect on the prevention and control of algae deposition near the junction; when the included angles of the guide wing wall are 10° and 15°, it cannot play a role in prevention and control and also hinders the normal operation of the river channel.
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Affiliation(s)
- Yan Long
- School of Water Resources and Electric Power, Hebei University of Engineering, Handan, Hebei Province, 056038, China; Hebei Key Laboratory of Smart Water Conservancy, Hebei University of Engineering, Handan, Hebei Province, 056038, China
| | - Tongxin Yang
- School of Water Resources and Electric Power, Hebei University of Engineering, Handan, Hebei Province, 056038, China; Hebei Key Laboratory of Smart Water Conservancy, Hebei University of Engineering, Handan, Hebei Province, 056038, China
| | - Wei Gao
- School of Water Resources and Electric Power, Hebei University of Engineering, Handan, Hebei Province, 056038, China; Hebei Key Laboratory of Smart Water Conservancy, Hebei University of Engineering, Handan, Hebei Province, 056038, China
| | - Yuxin Liu
- School of Water Resources and Electric Power, Hebei University of Engineering, Handan, Hebei Province, 056038, China; Hebei Key Laboratory of Smart Water Conservancy, Hebei University of Engineering, Handan, Hebei Province, 056038, China
| | - Cheng Xu
- School of Water Resources and Electric Power, Hebei University of Engineering, Handan, Hebei Province, 056038, China; School of Civil and Hydraulic Engineering, Ningxia University, Yinchuan, Ningxia Province, 750021, China.
| | - Yilin Yang
- Tianjin Key Laboratory of Water Resources and Environment, Tianjin Normal University, Tianjin, 300387, China
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