Grower Meeting Aug. 24, 20ll program was modified . lntroduction to - - PDF document

8/23/2OLL Old Allowed Water Table

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. Notthe correct definit¡on for lrrigation Efficiency

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Today

. Discuss some background on why the lE

program was modified

. lntroduction to the new lrrigation Allowance

Program

. Some issues that are being investigated . Future modifications likely with Grower lnput

lrrigation Efficiency

The technical definition of lEl is:

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xlq0o/o This equatim l¡m¡ts lE to less than or equal to 100%

• lrigatim wals b€neficially used cânnot be

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Fox Canyon Groundwater

Management Agency

Grower Meeting Aug. 24, 20ll lrrigation Training and Research Center

Cal¡fornia Polytechnic State Univeßity, San Luis Obispo (Cal poly)

• Dr. Stuart Styles, P.E. Director, ITRC
• Dr. Dan Howes, P.E. Senior Engineer, ITRC

zOtO- ITRC lnvestigated the lE

Program for FCGMA

. Task 2.1 - Analysis and annual plant

required watervalues for crops in the

FCGMA

. Task 2.2 - Evaluation of strengths and

weaknesses of the existing FCGMA lE program and specific suggestions for improvement xtwî-

Old FCGMA lE Program

. Strengths

• Attempts to account fur regional and year to year

diffurences in allowable water computations

• Simple methodology

. Weaknesses

• Too simple. Based on 3 crop categories while

there are dozens of difürent crop types grown in

FCGMA

• Historically weather data utilized has had quality

issues tnKr?r

8/23/207L

Genera I Recommendations

. Abandon FCGMA lE

• lmproper computation of lE and other issues

. Replace with new lrrigation Allowance

Program - More Accurate Assessment of ET

• lncreased number of crop categories (24+)
• Multiple cropping (double and triple cropping)
• Perennial crop age (canopy coverage) considered
• Utilize 3 ETo Zones

lrrigation Allowance lndex Formula . Simple Ratio

lrrigation Allowance lna.r = *ffi*ffik.

Volues less thon or equol to 1 ore ¡deøl

lrrigation Allowance I ncludes

. Evapotranspiration of lrrigation Water

. lncludes Santa Ana Winds

. lrrigation waterfor salinity management . Waterto overcome a reasonable irrigation

system distribution non-uniformity (DU = 0.8 is reasonable in FCGMA)

. lrrigation waterfor frost protection

InígotlonAlløuzce=

Crowing Per¡od 8T'. ((DU + Læol¡zed Deep Perc on Drip)x ( I - LR))

Salinity Management

. Research underway on strawberries and

already conducted on tomatoes show drip influences salinity management

. Utilized the most resent research to estimate

water needed for salinity management

. May need to be fine tuned as additional

information becomes available

Recommended FCGMA ETo Zones

. zone 1 (21)-

• xnard clMls and

FCGMA Etting Road Stat¡on

. Zone2 lZ2l-

Camar¡llo CIMIS and FccMA camarillo Airport Stat¡on

. Zone 3 (23) - Sånta

Paula clMls and FCGMA Moorpark Stat¡on

Use CIMISâ5 pr¡mâry and FCGMA stôt¡on as badup

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Salinity Management

. Assumed average basin wide EÇ = 1.8 ds/m . Value is high but common in some areas

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8123/20Lr DRAFT I rrigation Allowance

Year Type Selection

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lmproving Weather Station Site Conditions

. All weather stations should look similar to:

Santa Paula

clMls itt*':

Cama¡illo ctMts

Continue to Utilize Weather Stations

. 3 ETo Zones each with 2 weather stat¡ons. . CIMIS station is primary . FCGMA weather stat¡ons are backup . Collect ETo as a check . Collect precipitation data for year type

selection

. County precipitation gauges can be used as a

check as well.

Compar¡son of Allowed Water and lrr¡gation Allowance

New Allowance ProHram

. Single value for each ETo Zone dependent on

rainfall during the year - From CIMIS

. 3 year types - Wet, Dry and Typical

• Determined through examining modeled effective

precipitation vs, total precip¡tat¡on from 2000-

• 2009. General trends existed allowing grouping

¡ntothe 3 categories.

fêâr lroe Pr€dpltâtlon Tvolcel

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Allowance Values Compared to Several Strawberry Grower Applied Water Values

ETo bn. I

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8/23laOLL lmportant lmprovements w¡th Proposed lrrigation Allowance Program

. For some crops the New lrrigation

Allowance does not differ much from the original FCGMA values

. Key differences -

• Canopy coverage (orchard age and

thinning considerations)

• Differentiating single, double and triple

cropping

Canopy Coverage

• 20% Cover

*50o/o Cover 4

Difficulties . Vegetated vs, Total Farm Acreage . Canopy coverage/orchard age

• Requires grower estimates
• To confirm est¡mates it is recommended that

growers submit an aerial photo of årm from Google/Yahoo/Bing maps

• Aerial should be no more than 2-3 years old

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8/23/2OLL Difficulties (cont.)

. Nursery and Sod Farms

• lrrigation Allowance r,alues are br full canopy or

vegetative cover

• However, at any time only 50-90% (or less) of the

area may be cropped.

• Need growers to provide estimates ofthe average

vegetat¡ve area on an annual basis.

• May need further refìnement with addit¡onal

studies.

Greenhouses and Tunnels

. Used information from grower survey and

published data to estimate growing period

ETiw in greenhouses and tunnels

. Best available information:

• However, many different methods of greenhouse
• perat¡on.
• Should be refined w¡th more detailed e!êluation
• fgreenhouses in FcGMA (outside ofthe scope of

this evaluat¡on)

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8/23/z}tr

Example - 3 Strawberry Growers

. Crop - Strawberries . Zone- 1 . Rainhll year = typical

Exomple Colculotion - lrr¡gøt¡on Allwonce lndq =413 itt/29 6 in = 7 39

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Summary

. The proposed lrrigation Allowance Program provides

significant enhancements w¡th minimal increase in complexity

. Differentthan the original FCGMA Allowed Water which

had no fundamental basis other than ETo

. The l¡ritation Allowance values include ET of ¡rrigation

water, water for salinity management, and distribution un¡form¡ty

. The values are not "F|NAL", we will be examiningthem

forthe first year of the program and updating where

necessary.

jlfKãi Cu rrent DRAFT lrrigation Allowance

Tha n k You Qu estio n s? ?