Applying the SWAT model to a Managed Irrigated Watershed in a Semi-Arid Region:

Model Construction

Xiaolu WeiRyan T. Bailey

Ali TasdighiMazdak Arabi

Irrigated System – N and P Transport

Water Table

Irrigation WaterN, P

Improve SWAT performance in intensive, highly-managed irrigation systems

- Designating each cultivated field as a hydrologic response unit (HRU), so that irrigation can be applied according to water rights

- Relating the total applied irrigation water to the volume diverted from the river, also according to water rights

- Accounting for seepage from earthen irrigation canals to the underlying aquifer

- Including nitrate concentration in irrigation water as a source of nitrogen to the soil profile.

Motivation

Lower Arkansas River Valley- Study area: 500 km2

- Irrigation: Canals (earthen)- Irrigation: Groundwater Pumping- Canal seepage

Study Area (Irrigation Patterns)

Upstream study region

• Setup the SWAT model for the study area

• Modify each cultivated field to be a hydrologic response unit (HRU)

• Modify the .mgt files to provide seasonal planting, irrigation, harvest, and plowing to each of the field (HRU)

• Results

• Future work

Outline

Hydrography

Land Use

Soils

x y

Weather Stationsand Time Series

Processing and Display

HRU Definition

Watershed Delineation

WeatherStations

ArcGIS

SWAT Databases

ParameterizationRun SWAT

MODELEditing

.mgt files

Output maps

ArcSWAT

Input Data

DDS Calibration(Dynamically Dimensioned Search Algorithms)

GIS Environment

- Single land use type- Unique soil type- Single slope

For all cultivated Fields (3326)

HRU to Cultivated Fields

...

Original HRUs Cultivated Field HRUs

(56)

Single land use type:

HRU Definition- NASS data- Modified later in .mgt files

Unique soil type:

HRU Definition

- STASGO data

HRUs: - 5330 HRUs (5% land use threshold) - 4275 CF_HRUs- 3326 Cultivated Field

HRU Definition

Modify .mgt files

Modify .mgt files

Crop Type Planting Day

Harvest Day

TillageDay

Units - - -Alfalfa 30-Apr 30-Sep 20-OctBean 20-May 30-Sep 20-OctCorn 1-May 25-Oct 14-Nov

Melon 15-May 10-Aug 30-AugOnion 20-Mar 15-Sep 5-OctPasture 30-Aug 30-Sep 20-Oct

Pumpkin 1-Jun 30-Sep 20-OctSorghum 20-May 15-Oct 4-NovSpring Grain 1-Apr 15-Jul 4-Aug

Squash 20-May 25-Jul 14-AugSunflower 1-Jun 10-Oct 30-OctVegetable 25-Apr 30-Aug 19-Sep

Winter Wheat 30-Sep 5-Jul 25-Jul

- Planting/beginning of growing season, crop rotating [1]

- Irrigation operation [2]- Harvest operation [5]- Tillage operation [6]: Disk Plow

Planting Heat Unit: total heat units for plant maturity

𝐻𝐻𝐻𝐻 = �𝑇𝑇𝑎𝑎𝑎𝑎 − 𝑇𝑇𝑏𝑏𝑎𝑎𝑏𝑏𝑏𝑏 when �𝑇𝑇𝑎𝑎𝑎𝑎 > 𝑇𝑇𝑏𝑏𝑎𝑎𝑏𝑏𝑏𝑏

𝑃𝑃𝐻𝐻𝐻𝐻 = �𝑑𝑑=1

𝑚𝑚

𝐻𝐻𝐻𝐻

Modify .mgt files

- Planting/beginning of growing season [1]- Irrigation operation [2]- Harvest operation [5]- Tillage operation [6]

Date FieldID Area (m2) Rainfall (m) SurfWater (m) PumpWater (m)4/1/1999 1098 143235.473 0.013 0 0.0094/1/1999 2083 31223.626 0.013 0 0.0024/1/1999 3116 148320.272 0.013 0 0.0024/1/1999 3076 9341.440 0.013 0 0.0124/1/1999 3707 420183.008 0.013 0 0.0034/1/1999 3713 102005.479 0.013 0 0.1264/1/1999 3705 62775.957 0.013 0 0.0484/1/1999 3706 972101.375 0.013 0 0.0044/1/1999 3714 70875.227 0.013 0 0.0534/1/1999 1113 83599.240 0.013 0.063 04/1/1999 3456 58468.600 0.012 0.076 04/1/1999 3580 135559.928 0.011 0.079 04/1/1999 3670 81341.549 0.012 0.167 04/1/1999 1151 5900.879 0.012 0.073 04/1/1999 1150 81905.269 0.012 0.162 04/1/1999 1076 47180.328 0.013 0.423 04/1/1999 2178 165435.683 0.012 0.084 04/1/1999 3400 36664.159 0.012 0.035 0

MGT_OP: 2IRR_SC:

1 divert water from reach3 divert water from shallow aquifer

IRR_NO: reach/subbasinIRR_AMT: mm

Modify .mgt files

Modify .mgt files

Results

0.00E+00

2.00E+01

4.00E+01

6.00E+01

8.00E+01

1.00E+02

1.20E+02

1.40E+02

199901 199909 200005 200101 200109 200205 200301 200309 200405 200501 200509 200605 200701 200709

Flow

(m3 /

s)

Rocky Ford (Arkansas River) Simulated Flow

Observed Flow

Observed vs simulated streamflow

Results

Under-estimating

Over-estimating

- Canal Seepage

- Simulate N, P loadings in tributaries and Arkansas River

- Enhance simulation of sub-surface flow and reactive transport processes

dynamically dimensioned search algorithms

- dynamically dimensioned search algorithms

Future Work

Acknowledgements