Modeling sediment loading and riverine water quality in intensively managed landscapes

Nutrient runoff from intensively managed agricultural landscapes owing to management practices (such as fertilizers, manures, and tillage) and augmented by tile drains and changes in climate have markedly altered stream water quality that has led to eutrophication and hypoxia in inland and coastal waters. Agricultural intensification has also accelerated soil erosion leading to reservoir sedimentation and loss of reservoir storage, ending with water stress for human livelihood. These severe water resources issues are likely to worsen with increasing hydroclimatic variability associated with climate change and human interventions. More frequent extreme events have the potential to deliver a larger proportion of the total annual nutrient and sediment loads in a shorter timeframe that can further degrade riverine water quality. Moreover, anticipated changes in seasonality with an increase in spring precipitation, especially in the Midwestern United States, could potentially decrease agricultural yields and increase nutrient loads, enhancing the possibility of a larger extent of hypoxia and dead zones. As a result, human adaptations—such as changing agricultural management operations/schedules and adding subsurface drainage infrastructures—to enhance agricultural production, could exacerbate or mitigate the water quality issues in the Midwest United States. The goal of this dissertation is to understand the water quality dynamics associated with riverine sediments, nitrate (NO3-N) and total phosphorus (TP) through hydrologic modelling of an intensively managed agricultural watershed located in the Midwestern United States. As the water quality dynamics are affected by several forms of human interventions such as presence of tile drains, point sources and reservoirs, we attempt to adequately represent these interventions through a semi-distributed hydrologic model known as Soil and Water Assessment tool (SWAT). Thus, the first part of the dissertation focuses on developing the SWAT model to satisfactorily simulate flow, sediment loads, NO3-N loads, TP loads and crop yields at multiple locations in a case study watershed—Upper Sangamon River Watershed (USRW) located in central Illinois. Moreover, several data challenges encountered during the model setup are discussed. After addressing these challenges, the model satisfactorily simulated flow, crop yield and nutrients and sediment loads in the USRW. The second part of the dissertation addresses the storage loss issue caused by sediment load to Lake Decatur, the source for water supply to City of Decatur. The efficacy of management practices such as cover crops, filter strips and rock riffles to reduce lake sedimentation are evaluated through SWAT scenario analysis. Moreover, costs of these practices are analyzed to assess their economic feasibility. Our analysis suggests that financial assistance such as Environmental Quality Incentive Programs administered by USDA can help to reduce the cost of these joint practices. The last part of the dissertation focuses on evaluating the water quality impacts of agricultural adaptations, such as adding tile drains and increasing fertilizer rates, to offset potential agricultural yield loss under near-future climate (2031-2059). SWAT is used to evaluate the water quality implications (i.e., NO3-N and TP yields) of such interventions with and without conservation measures to generate insights on the future riverine water quality of a Midwestern catchment. Simulation indicates increase in nitrate loads with given adaptations, while use of conservation measures such as cover crops and switchgrass may improve water quality without affecting the crop yield.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Niroula, Sundar

Contributors dc:contributor

• Cai, Ximing
• McIsaac, Gregory F.
• Sivapalan, Murugesu
• Bhattarai, Rabin

• Water Quality
• Intensively Managed Landscapes
• Agro-industrial Watershed
• Upper Sangamon
• Best Mangaement Practices
• Hydrologic Modeling
• Swat
• Climate Change

Statement dc:rights

• Copyright 2023 Sundar Niroula

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/122147

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F122147