Irrigation Water Management

Irrigation Water Management

An essential ingredient of irrigation system –design –operation

VERY important

when applying

animal waste

John BuschIrrigation EngineerUSDA-NRCS3990 Midway LaneBaker City, OR 97814

541-523-7121 ext 111

john.busch@or.usda.gov

Basic IWM concepts

1. WHEN to irrigate ??

2. HOW MUCH water to apply ??

3. HOW MUCH is applied??

Irrigation Water Management

Improper IWM can cause INUNDATION!

How important ???

Irrigation Water Management

Improper IWM can leave one HIGh & DRY!

How important ???

Important Point…..

Errors in the timing and amount of irrigation applications can be

PROBLEMATIC

Potential problems can

increase when applying animal waste through an irrigation system

NRCS IWM Job Sheet

Available on the

Oregon NRCS

Engineering Web Site

IWM Plan Specifications

An IWM Plan shall be developed to assist the irrigator or decision-maker in the proper management and application of irrigation water. Factors to be included in the IWM Plan include the following:

• Statement of objective(s) for the IWM Plan• Description of the irrigation system and its

components including water supply, water conveyance and application systems, and any water measurement devices.

• Soils information including available water capacity, depth, and limiting conditions related to irrigation water management.

• Crop information including crops grown, irrigation water requirements, and physical characteristics including rooting depth.

• Description of irrigation scheduling and system management including methods for measuring and/or estimating crop water use and soil moisture levels.

• IWM record keeping requirements of appropriate detail for the IWM objectives. The detail of IWM may be specified as Detailed or By Irrigation Cycle with the associated level of record keeping as appropriate for the level of detail.

• IWM review requirements regarding the effectiveness of the IWM Plan and its implementation.

NRCS IWM Plan Specifications

• Statement of objective(s) for the IWM Plan

• Description of the irrigation system and its components

• Soils information including available water capacity, depth, and limiting conditions

• Crop information including crops grown, irrigation water requirements, and physical characteristics

NRCS IWM Plan Specifications

• Description of irrigation scheduling and system management

• IWM record keeping requirements of appropriate detail

• IWM review

IWM Objectives

Work with cooperator to

• Identify needs• Specify objectives to meet needs

Cooperator involvement is important !

buy-in from the beginning

Irrigation System

• Irrigation system characteristics

Includes Big Guns

Irrigation System• System type

• Operating characteristicsCoefficient of Uniformity (CU) data or distribution

uniformity (DU) shall be used in selecting sprinkler spacing, nozzle size, and operating pressure

For pivots: Min CU = 85%Fixed-Solid-set, Big Gun and Periodic Move

Sprinkler: Min CU = 75 % for deep-rooted crops (4 ft +)Min CU = 85 % for shallow-rooted crops

Irrigation System• Water Source(s)• Available flow rate and total amount• Water Quality

– Salts (Sodium)– Chemicals (Boron)

Soils Information

Including• Soil characteristics• Physical data – depth, limitations,

AWC• Soil chemistry – EC, SAR

Soils Information

Water balance in root zone

ET

Applied waterPrecipitation

Runoff

Capillary rise

Deep perc (leaching)

Root zone

-- Water storage

Infiltation

Soil-water basics

Gravitational Water

Unavailable Water

Available Water

Soil Particles

Saturated Saturated ConditionCondition

Field Field CapacityCapacity

Soil W ater Reservoir DefinitionsS

atu

rati

on

Fie

ld C

apa

city

Min

imu

m A

llo

wed So

il Wat

er M

anag

edby

Irrig

atio

n Sc

hedu

ling.

Per

ma

nen

t W

iltin

g P

oin

t

Wat

er A

vaila

ble

To P

lants

Unde

r Stre

ss

Soil W

ater

Una

vaila

ble

To P

lants

Ove

n D

ryManagement Allowed Deficit

MAD

AvailableWater

CapacityAWC

FieldCapacity

FC

Flocculation is important because water moves mostly in large pores between aggregates. Also, plant roots grow mainly between aggregates.

In all but the sandiest soils, dispersed clays plug soil pores and impede water infiltration and soil drainage.

Soils InformationDispersion and surface sealing from

sodium

Dispersion and surface sealing

Crop Information

• Crops grown• Irrigation water requirements• Rooting depth• Other physical characteristics

Scheduling & System Management

1. Check actual soil moisture levels2. Know the amount of irrigation

water applied3. Know irrigation guidelines for

crops grown4. Track crop water use –

evapotranspiration

Soil Water Reservoir

Measure applied water•Farm delivery

•Field application

Estimate CU•Monthly estimate from regional weather data

•Daily estimate from regional or on-site data

Measure soil water•Field probe + feel

•Instrumentation

Three elements for IWM

1.Estimate or measure soil moisture

2.Measure irrigation water applied

3.Estimate crop consumptive use

Need ALL 3 items

ESSENTIAL

• Knowledge of fields, crops, irrigation system

• Effective IWM requires judgment, observation, and local knowledge

• Use ALL available information proceed cautiously, test,

observe

Implementing IWM

NO one knows the farm as well as the manager !

Scheduling & System Management

1. Check actual soil moisture levels2. Know the amount of irrigation

water applied3. Know irrigation guidelines for

crops grown4. Track crop water use –

evapotranspiration

IWM Records

• Date and duration of each irrigation• Water applied in each irrigation• Dates and amounts of effective rainfall• Crop water use

– Daily evapotranspiration– Water use estimate between

irrigations• Soil moisture status

IWM Review

• Notes on how well IWM goals were met

• Description of crop response to IWM Plan

• Observations of soil erosion, etc.

• Notes on water/environmental quality issues (Relate to CNMP)

• Notes on irrigation system operations and maintenance

Thoughts,

Questions,

Comments??

NRCS IWM Plan Specifications

• Description of irrigation scheduling and system management

• IWM record keeping requirements of appropriate detail

• IWM review

• Knowledge of fields, crops, irrigation system

• Effective IWM requires judgment, observation, and local knowledge

• Use ALL available information proceed cautiously, test,

observe

Implementing IWM

NO one knows the farm as well as the manager !

Water balance in root zone

ET

Applied waterPrecipitation

Runoff

Capillary rise

Deep perc (leaching)

Root zone

-- Water storage

Infiltation

Water balance in root zone

ETApplied

water

Precipitation

Runoff

(erosion)

Capillary rise

Deep perc (leaching)

Root zone

-- Water storage

(Check uniformity)

Infiltation

System management

• Rainfall -- measure

• ET -- measure/estimate

• Soil water -- measure/estimate

• Application -- measure/estimate Infiltration -- measure/estimate

• Runoff -- measure/estimate

Conclusion

CANNOT depend onmeasuring/estimating

only ONE parameter

Soil Water Reservoir

Measure applied water•Farm delivery

•Field application

Estimate CU•Monthly estimate from regional weather data

•Daily estimate from regional or on-site data

Measure soil water•Field probe + feel

•Instrumentation

Irrigation System• System type

• Operating characteristicsCoefficient of Uniformity (CU) data or distribution

uniformity (DU) shall be used in selecting sprinkler spacing, nozzle size, and operating pressure

For pivots: Min CU = 85%Fixed-Solid-set, Big Gun and Periodic Move

Sprinkler: Min CU = 75 % for deep-rooted crops (4 ft +)Min CU = 85 % for shallow-rooted crops

Irrigation System• System type

• Operating characteristicsCoefficient of Uniformity (CU) data or distribution

uniformity (DU) shall be used in selecting sprinkler spacing, nozzle size, and operating pressure

For pivots: Min CU = 85%Fixed-Solid-set, Big Gun and Periodic Move

Sprinkler: Min CU = 75 % for deep-rooted crops (4 ft +)Min CU = 85 % for shallow-rooted crops