Study of Irrigation Scheduling Practices in the Pacific Northwest

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Study of Irrigation Scheduling Practices in the
Pacific Northwest
Sponsored byBonneville Power Administration, Pac
ific Northwest Generating Co-Op., and Northwest
Energy Efficiency Alliance
April 5, 2005
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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

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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

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Scope of the Study
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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.

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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

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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

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Scientific Irrigation Scheduling Criteria
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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 studys definition of
  SIS.

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Summary of Phase I Results
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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 studys definition of
  SIS.

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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)

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Phase II Study Design
Study Group
Control
Treatment
Actual
Water Application
Ideal
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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)
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Calculation of Ideal Water Requirements

• Where
• SGross IRS is the gross seasonal water
  requirement
• SETc is the cumulative seasonal crop consumptive
  use of water
• REff is the effective rainfall during that period
• ?SMS 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

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The Water Balance Model
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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

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Energy Savings Calculator
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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.