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Determining Average Irrigation Need. Review Hearing Officer conclusions regarding supply needed to prevent material injury Selecting year to use as baseline supply Overview of adjustment technique to account for differing climatic conditions from baseline. IDWR – Spring 2009. - PowerPoint PPT Presentation
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Determining Average Irrigation Need
Review Hearing Officer conclusions regarding supply needed to prevent material injury
Selecting year to use as baseline supply
Overview of adjustment technique to account for differing climatic conditions from baseline
IDWR – Spring 2009
Hearing Officer Conclusion
The minimum full supply established in the May 2, 2005, Order is inadequate to predict the water needs of SWC on an annual basis. Recommended Order at 50 It is based on a decade old year that does not
reflect current efficiencies such as the increased use of sprinkler irrigation and computer monitoring or changes in the amount of land irrigated. Recommended Order at 49
...it is time for the Department to move to further analysis to meet the goal of the minimum full supply but with the benefit of the extended information and analysis offered by the parties and available to its own staff. Recommended Order at 51
• The parties have attempted to establish water budgets that reflect the needs of SWC members using sophisticated analytical techniques, but the parties' analyses are too far apart to reconcile.
Recommended Order at 49 • (…conclusions in SWC's expert testimony are closer to being
acceptable…) Recommended Order at 50 TWIN FALLS CANALS COMPANY
IGWA AND SWC ANALYSIS CONCLUSIONS
0
100,000
200,000
300,000
400,000
500,000
600,000
SWC IGWA
VO
LU
ME
(A
CR
E-F
EE
T)
SEEPAGE LOSS
ET
Hearing Officer Conclusion
Water Budget Schematic
ETCanal seepageCanal seepage
Deep PercolationDeep Percolation
Return Return flowsflows
Canal Head DiversionCanal Head Diversion
DeliveryDeliveryLossesLosses
Ignore for now other components: precipitation and soil moisture
Water budget summary as percent of average diversion for Twin Falls Canal:
SWCOTHER5%DELIVERY
LOSS53%
CROP WATER NEED42%
IGWA CROP WATER NEED30%DELIVERY
LOSS61%
OTHER9%
ETETCanal seepage
Deep Percolation
Return flows
Canal Head DiversionCanal Head Diversion
Known Values
Water Budget Schematic
Water budget approach using satellite imagery based ET can be used to establishes apparent project efficiencies:
Apparent project efficiency = 41%
Apparent project efficiency can be used in adjustment process of average annual irrigation need
OTHER7%DELIVERY
LOSS52%
CROP WATER NEED41%
Development of an average annual irrigation need:
“Predictions of need should be based on an average year of need, subject to adjustment up or down depending upon the particular water conditions for the irrigation season” Recommended Order at 49 Adjustment can be made using the measured in-
season ET from satellite imagery and project efficiency
Propose using 2006 irrigation diversions as the average annual irrigation need, or baseline demand: Adjust for above normal winter/spring rains in 2006 Normal Heise gage runoff and adequate storage
supply ET values generated with Landsat data available
Correct 2006 diversion for soil moisture excess using ETIdaho data (in progress)
HEISE GAGE APRIL THROUGH JULY RUNOFF
0
2,000
4,000
6,000
8,000
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
RU
NO
FF
(1
00
0 A
CR
E-F
EE
T) AVERAGE 1971-2000
Heise gage runoff volume
Regional weather data
WEATHER DATA - REGIONAL CROP EVAPOTRANSPIRATION GROWING AND DEGREE DAYS
20
22
24
26
28
30
32
34
36
38
40
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
YEAR
RE
GIO
NA
L P
OT
EN
TIA
L C
RO
P E
T
0
500
1000
1500
2000
2500
3000
GR
OW
ING
DE
GR
EE
DA
YS
REGIONAL POTNTL CROP ET GROWING DEGREE DAYS AVG ET AVG GDD
APRIL TO SEPTEMBER PRECIPITATION, TWIN FALLS WSO
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
YEAR
PR
EC
IPIT
AT
ION
(IN
CH
ES
)
AVERAGE
Twin Falls growing season precipitation
TOTAL IRRIGATION YEAR DIVERSION
0
200,000
400,000
600,000
800,000
1,000,000
1,200,000
1,400,000
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
YEAR
DIV
ER
SIO
N (
AC
RE
-FE
ET
)
AVERAGE TOTAL DIVERSION
TFCC
Twin Falls Canal Company annual diversions
97% of average
Summary of Baseline Demands for Surface Water Coalition members based on 2006 irrigation diversion with upward
correction for average soil moisture
NOTE: PRELIMINARY, UNCHECKED DATA
2006 TOTAL DIVERSION
(AF)
SOIL MOISTURE
CORRECTION TO AVERAGE
(AF)
2006 ADJUSTED DIVERSION (BASELINE DEMAND)
(AF)
MINIDOKA NS 352,300 16,000 368,300 MINIDOKA SS (BID) 247,800 10,000 257,800 A & B ID 57,500 3,000 60,500 MILNER ID 55,500 3,000 58,500 RES. DIST #2 404,200 13,000 417,200 NS TWIN FALLS 968,600 32,000 1,000,600 TWIN FALLS SS 995,800 41,000 1,036,800
TOTAL 3,199,700
Summary of Baseline Demands for Surface Water Coalition members, comparison to historic average
diversions (cont.)
NOTE: PRELIMINARY, UNCHECKED DATA
BASELINE DEMAND
(AF)
1990-2008 AVERAGE
(AF)
BASELINE DEMAND AS % OF
AVERAGE
MINIDOKA NS 368,300 358,800 103%MINIDOKA SS (BID) 257,800 246,900 104%A & B ID 60,500 56,100 108%MILNER ID 58,500 57,800 101%RES. DIST #2 417,200 428,500 97%NS TWIN FALLS 1,000,600 1,030,400 97%TWIN FALLS SS 1,036,800 1,072,700 97%
TOTAL 3,199,700 3,251,200 98%
Hearing Officer Recommendation:
The concept of a baseline is that it is adjustable as weather conditions or practices change, and that those adjustments will occur in an orderly, understood protocolRecommended Order at 51
IDWR Proposed Protocol: Each SWC canal begins season with reasonable
in-season demand equal to adjusted 2006 diversions, and called baseline demand (BD).
IDWR Proposed Protocol
Determine crop water needs (CWN) during season using Landsat generated ET: CWN = (ET – PEFF) * Area
where PEFF = effective precipitationArea = canal company total irrigated
area
Calculate revised reasonable in-season demand (RISD) as season progresses: RISD = CWN÷ Ep
where Ep = project efficiency
SUMMARY
Replace minimum full supply with the reasonable in-season demand, with baseline equal to 2006 SWC diversions, adjusted upward for beginning season soil moisture In-season adjustments made relative to 2006 crop water needs using Landsat generated ET and effective precipitationBaseline year for reasonable in-season demand will be amended in the future to reflect current average conditions