Study of Irrigation Scheduling Practices in the Pacific Northwest

1. Study of Irrigation Scheduling Practices in the Pacific Northwest Sponsored by:Bonneville Power Administration, Pacific Northwest Generating Co-Op., and Northwest Energy Efficiency Alliance April 5, 2005

2. Project Scope & Objectives Phase I: • Survey irrigation water management and scheduling practices in the region • Define scientific irrigation scheduling (SIS) and develop a baseline for its practice • Collect and analyze data on irrigation water use • Develop a plan for Phase II Phase II: • Measure water savings from the SIS • Develop a simplified methodology for calculating energy savings

3. Project Team Project Funding: • Bonneville Power Administration • Pacific Northwest Generating Authority • Northwest Energy Efficiency Alliance Utility Sponsors: • Franklin County PUD, Benton PUD # 1, Umatilla Electric Co-Op., Grant County PUD Technical Team: • Bonneville • Oregon State University Department of Bioengineering • IRZ Consulting • Ground Water Management Association • Franklin County Conservation District

4. Scope of the Study

5. Phase I Study Design • Working Hypotheses: • “All growers use a certain irrigation regime.” • “What distinguishes these regimes is the basis on which irrigation decisions are made and the intensity with which this information is applied.” • Corollary Assumptions: • “A good irrigation practice means knowing how much water to apply and when to do it.” • ” A well-managed irrigation regime can save water and, hence, pumping energy use.”

6. Phase I Scope & Methods Study Period: • Data Collection: January – March 2003 • Final Report: December 2003 Sample Size: • Surveyed 776 growers in three states (ID, OR, WA); 11 irrigation sub-regions; 13 PUDs (75%); 3 IOUs (25%) Data Elements: • Basic Farm Characteristics • Irrigation System • Irrigation Water Management Practices • Demographics

7. Scientific Irrigation Scheduling: Definition • Scientific irrigation scheduling generally refers to the practice of meeting crop moisture requirements by supplying the right amount of water at the right time based on measurement of actual soil moisture and evapotranspiration (ET). • Criteria for SIS: • Knowledge of crop ET • Appropriate measurement of soil moisture of crop water status • Measurement and monitoring of actual amounts of applied

8. Scientific Irrigation Scheduling: Criteria

9. Summary of Phase I Findings General Characteristics: • Alfalfa is the prominent crop (31% of irrigated acres), followed by wheat (17%), vegetables (10%), corn (15%), and potatoes (7%). • 94% of farms use pressurized pump systems. • Local utilities are the main source of power; 4% report using on-site generation. • On-line services, primarily AgriMet, are the most commonly used sources for ET and account for 45 percent of cases. • Sprinklers are the common irrigation system (82%); gravity systems (15%); micro-irrigation, sub-surface irrigation (3%). • Irrigation districts (44%), groundwater (29%), surface water (24%) are the main sources of irrigation water recaptured tail water, wastewater, and other sources account for the remaining 5%. Irrigation Scheduling Practices: • Nearly 80 percent of farms do not use irrigation water management and only 11% use irrigation practices that meet this study’s definition of SIS.

10. Summary of Phase I Results

11. Summary of Phase I Findings Scheduling Practices: • Nearly 80 percent of farms do not use irrigation water management and only 11% use irrigation practices that meet this study’s definition of SIS.

12. Phase II Scope & Methods Study Period: • Data Collection: 2004 Irrigation Season (March – October 2003) • Final Report: March 2005 Sample Size: • 44 fields (22 treatment and 22 control) farms in the Benton, Franklin, Morrow and Umatilla counties • 5 fields were dropped due to equipment failure/malfunction Data Elements: • General farm and field characteristics • Irrigation system specifications • 15-minute pump system status readings (using pressure gages and data loggers) • Soil water content (regular neutron probe readings) • Flow measurements (ultrasonic flow readings) • Evapotranspiration (AgriMet) • Precipitation (NOAA)

13. Phase II Study Design Study Group Treatment Control Actual Water Application Ideal

14. Calculation of Water Savings Water savings from SIS are derived by comparing the difference between Actual Water Use (AW), based on field measurements, and irrigation requirements, Ideal Water Use (IW), across the two groups, that is: Water Savings = (AWTreatment – IWTreatment) - (AWControl – IWControl)

15. Calculation of Ideal Water Requirements Where: • ΣGross IRS is the gross seasonal water requirement • ΣETc is the cumulative seasonal crop consumptive use of water • REff is the effective rainfall during that period • ΔSMS is the change in soil water storage during the season (the storage at end of season less the antecedent moisture) • Eappl is the application efficiency, the proportion of water delivered to the field that is effectively stored in the root zone for use by the crop

16. The Water Balance Model

17. Calculation of Energy Savings Where: • TDH = total dynamic head (pumping lift, pressure and head loss) • PPE = pumping plant efficiency • PCF = a factor to convert energy use from units of force x distance to kWh

18. Energy Savings Calculator

19. Summary of Phase II Findings Other Studies: • Review of 11 other studied of SIS show water savings in the range of 7% to 30%. • Variations in crop types, methodology, location, study design and sample sizes make comparison difficult. Alfalfa is the prominent crop (31% of irrigated acres), followed by wheat (17%), vegetables (10%), corn (15%), and potatoes (7%). Phase II Results: • Water savings are approximately 10% • Energy Savings are approximately 13.1% Caveats: • The results are on the conservative side given the location of the study. • Water management techniques used by the treatment group were more rigorous than normal SIS practices.