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Title: Water and Nutrient Balances in a Large Tile-Drained Agricultural Catchment: A Distributed Modeling Study

This paper presents the development and implementation of a distributed model of coupled water nutrient processes, based on the representative elementary watershed (REW) approach, to the Upper Sangamon River Basin, a large, tile-drained agricultural basin located in central Illinois, mid-west of USA. Comparison of model predictions with the observed hydrological and biogeochemical data, as well as regional estimates from literature studies, shows that the model is capable of capturing the dynamics of water, sediment and nutrient cycles reasonably well. The model is then used as a tool to gain insights into the physical and chemical processes underlying the inter- and intra-annual variability of water and nutrient balances. Model predictions show that about 80% of annual runoff is contributed by tile drainage, while the remainder comes from surface runoff (mainly saturation excess flow) and subsurface runoff. It is also found that, at the annual scale nitrogen storage in the soil is depleted during wet years, and is supplemented during dry years. This carryover of nitrogen storage from dry year to wet year is mainly caused by the lateral loading of nitrate. Phosphorus storage, on the other hand, is not affected much by wet/dry conditions simply because the leaching of it ismore » very minor compared to the other mechanisms taking phosphorous out of the basin, such as crop harvest. The analysis then turned to the movement of nitrate with runoff. Model results suggested that nitrate loading from hillslope into the channel is preferentially carried by tile drainage. Once in the stream it is then subject to in-stream denitrification, the significant spatio-temporal variability of which can be related to the variation of the hydrologic and hydraulic conditions across the river network.« less
Authors:
; ; ;
Publication Date:
OSTI Identifier:
993658
Report Number(s):
PNNL-SA-76358
TRN: US201023%%545
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Hydrology and Earth System Sciences, 14(11):2259-2275; Journal Volume: 14; Journal Issue: 11
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; DENITRIFICATION; DRAINAGE; HYDRAULICS; IMPLEMENTATION; LEACHING; NITRATES; NITROGEN; NUTRIENTS; PHOSPHORUS; RIVERS; RUNOFF; SATURATION; SEDIMENTS; SIMULATION; SOILS; STORAGE; WATER; WATERSHEDS coupled modeling framework, tile drainage, process interaction