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Title: Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects

Abstract

In this paper, we use a dynamic network flow model, coupled with a transient storage zone biogeochemical model, to simulate dissolved nutrient removal processes at the channel network scale. We have explored several scenarios in respect of the combination of rainfall variability, and the biological and geomorphic characteristics of the catchment, to understand the dominant controls on removal and delivery of dissolved nutrients (e.g., nitrate). These model-based theoretical analyses suggested that while nutrient removal efficiency is lower during flood events compared to during baseflow periods, flood events contribute significantly to bulk nutrient removal, whereas bulk removal during baseflow periods is less. This is due to the fact that nutrient supply is larger during flood events; this trend is even stronger in large rivers. However, the efficiency of removal during both periods decreases in larger rivers, however, due to (i) increasing flow velocities and thus decreasing residence time, and (ii) increasing flow depth, and thus decreasing nutrient uptake rates. Besides nutrient removal processes can be divided into two parts: in the main channel and in the hyporheic transient storage zone. When assessing their relative contributions the size of the transient storage zone is a dominant control, followed by uptake rates inmore » the main channel and in the transient storage zone. Increasing size of the transient storage zone with downstream distance affects the relative contributions to nutrient removal of the water column and the transient storage zone, which also impacts the way nutrient removal rates scale with increasing size of rivers. Intra-annual hydrologic variability has a significant impact on removal rates at all scales: the more variable the streamflow is, compared to mean discharge, the less nutrient is removed in the channel network. A scale-independent first order uptake coefficient, ke, estimated from model simulations, is highly dependent on the relative size of the transient storage zone and how it changes in the downstream direction, as well as the nature of hydrologic variability.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1047410
Report Number(s):
PNNL-SA-77838
Journal ID: ISSN 0043-1397; WRERAQ; TRN: US201216%%269
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Water Resources Research
Additional Journal Information:
Journal Volume: 48; Journal ID: ISSN 0043-1397
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; AVAILABILITY; CONTROL; DELIVERY; DEPTH; DISTANCE; DYNAMICS; EFFICIENCY; FLOODS; FLOW MODELS; NUTRIENTS; REMOVAL; RETENTION; RIVERS; SIMULATION; SIZE; STORAGE; TRANSIENTS; UPTAKE; USES; WATER; nutrient removal and delivery; channel networks; scaling; event dynamics; transient storage zone; modeling

Citation Formats

Ye, Sheng, Covino, Timothy P, Sivapalan, Murugesu, Basu, Nandita, Li, Hongyi, and Wang, Shaowen. Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects. United States: N. p., 2012. Web. doi:10.1029/2011WR010508.
Ye, Sheng, Covino, Timothy P, Sivapalan, Murugesu, Basu, Nandita, Li, Hongyi, & Wang, Shaowen. Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects. United States. doi:10.1029/2011WR010508.
Ye, Sheng, Covino, Timothy P, Sivapalan, Murugesu, Basu, Nandita, Li, Hongyi, and Wang, Shaowen. Sat . "Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects". United States. doi:10.1029/2011WR010508.
@article{osti_1047410,
title = {Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects},
author = {Ye, Sheng and Covino, Timothy P and Sivapalan, Murugesu and Basu, Nandita and Li, Hongyi and Wang, Shaowen},
abstractNote = {In this paper, we use a dynamic network flow model, coupled with a transient storage zone biogeochemical model, to simulate dissolved nutrient removal processes at the channel network scale. We have explored several scenarios in respect of the combination of rainfall variability, and the biological and geomorphic characteristics of the catchment, to understand the dominant controls on removal and delivery of dissolved nutrients (e.g., nitrate). These model-based theoretical analyses suggested that while nutrient removal efficiency is lower during flood events compared to during baseflow periods, flood events contribute significantly to bulk nutrient removal, whereas bulk removal during baseflow periods is less. This is due to the fact that nutrient supply is larger during flood events; this trend is even stronger in large rivers. However, the efficiency of removal during both periods decreases in larger rivers, however, due to (i) increasing flow velocities and thus decreasing residence time, and (ii) increasing flow depth, and thus decreasing nutrient uptake rates. Besides nutrient removal processes can be divided into two parts: in the main channel and in the hyporheic transient storage zone. When assessing their relative contributions the size of the transient storage zone is a dominant control, followed by uptake rates in the main channel and in the transient storage zone. Increasing size of the transient storage zone with downstream distance affects the relative contributions to nutrient removal of the water column and the transient storage zone, which also impacts the way nutrient removal rates scale with increasing size of rivers. Intra-annual hydrologic variability has a significant impact on removal rates at all scales: the more variable the streamflow is, compared to mean discharge, the less nutrient is removed in the channel network. A scale-independent first order uptake coefficient, ke, estimated from model simulations, is highly dependent on the relative size of the transient storage zone and how it changes in the downstream direction, as well as the nature of hydrologic variability.},
doi = {10.1029/2011WR010508},
journal = {Water Resources Research},
issn = {0043-1397},
number = ,
volume = 48,
place = {United States},
year = {2012},
month = {6}
}