ARI Project: 12-03-004 | Funding Round: Round 13 (2011-2012)  | Start Date: 07/01/2011  | Status: Completed

Spatial variability in evapotranspiration related to irrigation system distribution uniformity

ARI Member Campus: California Polytechnic State University, San Luis Obispo
Research Focus Area: Water and Irrigation Technology
Project Personnel: Director: Howes, Daniel, Irrigation Training and Research Center BioResource and Agricultural Engineering Department College of Agriculture, Food and Environmental Sciences Cal Poly State University
Co-Investigator: Styles, Stuart, Bioresource & Agricultural Engineering Department, College of Agriculture, Food, and Environmental Sciences, Cal Poly State University
Collaborator: Burt, Charles, Irrigation Training and Research Center, BRAE Dept., College of Agriculture, Food, and Environmental Sciences, Cal Poly State University
Cooperator: Gaudi, Franklin, Irrigation Training and Research Center, California Polytechnic State University
ARI Allocation: $40,000.00
Match Donors: $69,086.00 - County Sanitation Districts of Los Angeles County
Total Funding: $109,086.00

Project Objective: The following are the two main objectives and activities that will be used to identify the impact of irrigation system distribution uniformity on the spatial variability of evapotranspiration. 1. The first objective is to determine if it is plausible to evaluate LandSAT images using METRIC to evaluate evapotranspiration distribution due to distribution uniformity. 2. If the first objective is positive, the second main objective will be to evaluate the spatial distribution of evapotranspiration under water stress by comparing a predicted level of evapotranspiration non-uniformity with the measured evapotranspiration non-uniformity using METRIC processed images.

Project Abstract: A uniform, copious crop yield is the goal of any farmer. Crop yield is typically discussed on an average per acre basis. However there is spatial variability within a field where some areas have higher and lower yield than the average. The importance of maximizing crop yields throughout the field is becoming ever more important as the costs of inputs continue to escalate. The spatial non-uniformity of yield is due to many factors including spatial non-uniformity of applied irrigation water (termed irrigation distribution uniformity (DU)). There is a lack of information for farmers and irrigation designers on the impacts of yield non-uniformity caused specifically by irrigation distribution uniformity. For most crops there is a direct relationship between yield and evapotranspiration. Leveraging this relationship, this research aims to measure the spatial non-uniformity of evapotranspiration on a field level using LandSAT satellite images combined with surface energy balance model to compute evapotranspiration (METRIC). There are two goals of the research: 1. Measure the evapotranspiration non-uniformity caused by irrigation distribution uniformity only. This requires examining multiple large fields of the same crop type with water stress and without. 2. Compare this measured evapotranspiration non-uniformity with a predicted value that can be made independent of the LandSAT evaluation using detailed daily information gathered on site combined with actual measured irrigation system distribution uniformity. Once quantified, the level of importance of irrigation system distribution uniformity on evapotranspiration and thus yield nonuniformity can be evaluated. This will allow farmers and designers to make informed decisions on where investments (both initial and management) can be made to maximize crop yields due to irrigation distribution uniformity.

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