Photo: Orchard Mesa Research Center 08/04/2015 PROJECT PARTNERS Dr. Perry Cabot │ Colorado State University Photo: Orchard Mesa Research Center 03/28/2016 Measuring Consumptive Use for Alfalfa and Grass Hayfields Using Reflectance-Based Methods at Ground Surface
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Photo: Orchard Mesa Research Center 08/04/2015
PROJECT PARTNERS
Dr. Perry Cabot │ Colorado State University
Photo: Orchard Mesa Research Center 03/28/2016
Measuring Consumptive Use for Alfalfa and Grass Hayfields Using Reflectance-Based Methods at Ground Surface
PROJECT PARTNERS
Measuring Consumptive Use for Alfalfa and Grass Hayfields Using Reflectance-Based Methods at Ground Surface
Dr. Perry Cabot │ Colorado State University
Photo: Orchard Mesa Research Center 08/06/2016Photo: Orchard Mesa Research Center 03/28/2016
Multi-Year / Multi-Site Study of Partial-Season Irrigation
Evapotranspiration Rates ?Conserved CU ?Forage Yields ?
Recovery after Stress Period ?
Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 3
Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 4
The 1929 cut‐off is June 25, 1929, the effective date of the Boulder Canyon Project Act, which became the basis for the apportionment of the lower mainstem in Arizona v. California. The 1922 cut‐off is November 24, 1922, the date that the 1922 Compact was signed.
Multi-Spectral Handheld Radiometer (MSR5) used to determine spectral signature of plants
MSR5 measures wavebands centered at blue (485 nm), green (560 nm), red (660 nm), near infrared (NIR, 830 nm), and short-wave infrared (SWIR, 1650 nm) similar to Landsat Thematic Mapper 5 satellite (ground-truth)
Vashisht (2016) Western Colorado Grass Kc = 1.195NDVI – 0.057
Alam et al. (2018) NSW, Australia Grass Kc = (1.84 ± 0.41) × NDVI2 ‐ (1.03 ± 0.48) × NDVI + (0.42 ± 0.14)Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 22
Developing a Spectral Signature Model
Reflectance‐based crop coefficient approachRequires multispectral bands, weather data
Crop ET is directly related to crop coefficients (Kc) and Vegetation Index (e.g., NDVI)
Kcr = a x NDVI +b
Radiometric Kc values have the advantages of capturing vegetation growth as affected by climate as well soil moisture stress
ETa = Kcr x ETrefWater Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 23
ET June 28, 2016 (mm)Field boundary
High : 10
Low : 0
±
Uncompahgre Valley Irrigated AcreageDelta alfalfa
Montrose grass hay
Radiometer Measurements as an additional ground truth
Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 24
Kruthaupt Ranch
ET June 5, 2016 (mm)Field boundary
High : 10
Low : 0
±
Upper Gunnison Irrigated Acreage
Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 25
LOMA, CODeveloping a Spectral Signature Model
Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 26
ETa is obtained using Soil Water Balance ETr is obtained using ASCE Standardized Equation Using these values together, we calculate a crop coefficient (Kca) defined as the ratio of ETa and ETr (Allen et al., 1998)
Kca = ETa/Etr
By comparing Kca at equivalent times as the VI, we can evaluate a relationship between Kca and the spectral signature of the field
LOMA, CODeveloping a Spectral Signature Model
Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 27
VIKCA = A × (VI) + B
A B R² RMSE MBE NSCESR 0.06 0.04 0.78 0.10 ‐0.001 0.78
LOMA, CONDVI Model for grass canopy (Gautam et al., 2018)
Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 28
y = 1.12x - 0.08R² = 0.87
0.00
0.20
0.40
0.60
0.80
1.00
0.00 0.20 0.40 0.60 0.80 1.00
Kca
NDVI
LOMA, CO Conclusion and General Procedure
Water Bank Workgroup│ November 2, 2018 │ Grand Junction, CO 29
Regular measurement of spectral signatures using a combination of handheld (MSR5) or satellite instrumentation (LANDSAT) spatio-temporal scales need to be considered!!
Daily recording of ETr using meterological data (CoAgMet) Use reflectance-based model to identify “canopy coefficient” Kca = 1.12 x NDVI – 0.08 (Gautam et al., 2018)
Calculate ETa (for specific field conditions on given days) ETa = 1.12 x ETr