Improved Assessment of Nitrogen and Phosphorus Fate and Transport for Irrigated

Agricultural Watersheds in Semi-Arid Regions(2013-2017)

Project Director: Mazdak ArabiCo-PD: Ryan T. Bailey

Co-PD: Tim Gates

PhD Student: Xiaolu WeiPhD Student: Seonggyu Park

Dept. of Civil and Environmental EngineeringColorado State University

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Project OverviewNitrogen and Phosphorus Transport in Semi-Arid Regions

1. Enhance the capacity of the SWAT model to simulate N and P transport in semi-arid irrigated agricultural watersheds

2. Improve understanding of the processes that govern N and P movement, transformation, and storage in irrigated agricultural watersheds

3. Assess viable remediation strategies for N and P contamination

4. Disseminate the new modeling tool to the research community

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

1. Improve SWAT Model

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Linking 3 Models:

SWAT

MODFLOW

RT3D

Land Surface ProcessesStream Processes

Groundwater FlowGW-SW Interactions

Chemical TransportMass Loading to SW

+

+

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

1. Improve SWAT Model

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Linking 3 Models: SWATMODFLOWRT3D

Water Table

Runoff

Volatilization canal

PumpingWell

Vadose ZonePercolation,

N, PConcentration

Overland flow

and transport

Lateral

FlowStream stage

Solute transport

Root Zone Processes

Groundwater discharge Groundwater flow

Uptake

ET

Confining Layer

Plant Growth

N, P mass loadingN, P reactive transport

Transport

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

1. Improve SWAT Model

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SWAT MODFLOW / RT3D

HRUs

Grid Cells Recharge / NO3, P

Channels Stream Stage

River Cells

GW Discharge

NO3, P conc.

NO3, P Loading

• HRU-Grid Linkage: GIS Pre-processing routines

• SWAT-MODFLOW-RT3D: single FORTRAN code

• Daily time step

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand ProcessesModel Applied to 3 Watersheds

Sprague River Oregon

4,100 km2

Arkansas River Colorado

500 km2 470 km2

Middle Bosque River Texas

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand Processes

MODFLOW Model (USGS)

Sprague Watershed

SWAT-MODFLOW-RT3D

- 1970-2004- Water table elevation- Stream discharge- NO3 concentration- In-stream NO3 loading

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand Processes

Annual Average Recharge

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand Processes

Average Groundwater NO3 Concentration

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand Processes

Groundwater Discharge to Streams

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand Processes

Average Annual NO3-N Loading to Streams

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand Processes

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand ProcessesArkansas River, Colorado

• Designate each cultivated field as an HRU

• Incorporate canal seepage

• Include N and P concentration in irrigation water

• Assess N and P storage in soil, groundwater, riparian areas

• Investigate influence of climate (e.g. drought)

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand ProcessesField Data Collection

• 22 Groundwater monitoring wells• 8 surface water sites

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand ProcessesField Data Collection

• 22 Groundwater monitoring wells• 8 surface water sites

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand ProcessesArkansas River, Colorado

What are the timing and amount of N and P loading at various locations along the main river and its tributaries?

What influence do spatially-variable aquifer properties and irrigation practices have on flow paths of N and P mass and subsequent timing of N and P loading to surface water bodies?

What is the overall influence of irrigation chemistry on N and P mass in groundwater and surface water?

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand ProcessesArkansas River, Colorado

Each field is an HRU

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand ProcessesArkansas River, Colorado

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

2. Understand Processes

MODFLOW-RT3D Model Results

Improve SWAT Model

Disseminate Tool

3. Assess Viable BMPsArkansas River, Colorado

BMPs to Analyze:• Fertilizer reduction (uniform and targeted)• Increased irrigation efficiency• Canal sealing• Rotational fallowing• Riparian enhancement

Assess BMPs

Understand Processes

(15-30%)(10-20%)

(0-20%)(15-25%)

(5-10%)

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

4. Disseminate Modeling Tool

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1.Conference Presentations

2.Workshops & Tutorials

3.Tools (User Interface)

4.Website

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

4. Disseminate Modeling Tool

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1. Conference Presentations2. Workshops & Tutorials3. Tools4. Website

• SWAT Conference (2015) Purdue• AGU Hydrology Days (2015, 2016) CSU• SWAT Conference (2016) Beijing• AWRA Conference (November 2017)

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

4. Disseminate Modeling Tool

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1. Conference Presentations2. Workshops & Tutorials3. Tools4. Website

• SWAT Conference (2015) Purdue• AGU Hydrology Days (2015, 2016) CSU• SWAT Conference (2016) Beijing• AWRA Conference (November 2017)

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

4. Disseminate Modeling Tool

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1. Conference Presentations2. Workshops & Tutorials3. Tools4. Website

SWATMOD-PrepGraphical User Interface

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

4. Disseminate Modeling Tool

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1. Conference Presentations2. Workshops & Tutorials3. Tools4. Website

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

4. Disseminate Modeling Tool

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1. Conference Presentations2. Workshops & Tutorials3. Tools4. Website

SWAT-MODFLOW Google Group127 Members (since 2015)

Assess BMPs

Improve SWAT Model

Understand Processes

Disseminate Tool

4. Disseminate Modeling Tool

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Current Collaborations with SWAT-MODFLOW-RT3D• Ogallala Aquifer Region (CSU, Texas Tech Univ., Univ. of Nebraska)

• South Platte River Basin (CSU)

• Little River Watershed, Georgia (CSU, USDA-ARS)

• Western Alberta, Canada (University of Alberta)

• Dee River Watershed, Wales, United Kingdom (Swansea University)

• Central Germany (University of Kassel)

• Tigris-Euphrates River Basin (Clemson University)

• Limpopo River Basin, Botswana (South Dakota State University)

• Australia (Flinders University)

• Buenos Aires, Argentina (Plains Hydrology Institute)

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Summary1. New Modeling Tool (SWAT-MODFLOW-RT3D) (Oct. 2015)

• GW level, GW flow, soil water, stream discharge

• Nutrient concentration in GW and stream water

• Nutrient mass loading between aquifer and streams

• Nutrient mass storage in soils and aquifer

2. Application of Model to 3 Watersheds (OR, CO, TX)

3. Next 2 years: more results for CO and TX watersheds

4. Model being used by research groups worldwide