Court Opinion

ID: 3188203
Source: CourtListenerOpinion
Date Created: 2016-03-23 19:17:55.035902+00
Date Added: 2024-06-11T09:36:34.475129
License: Public Domain

IN THE SUPREME COURT OF THE STATE OF IDAHO

                               Docket Nos. 42775/42836

IN THE MATTER OF THE                         )
DISTRIBUTION OF WATER TO WATER               )
RIGHT NOS. 36-02551 & 36-07694               )
(RANGEN, INC.) IDWR DOCKET CM-DC-            )
2011-004.                                    )
                                             )
RANGEN, INC.,                                )
                                             )
        Petitioner-Respondent and Appellant, )
v.                                           )
                                             )
THE IDAHO DEPARTMENT OF WATER )
RESOURCES, GARY SPACKMAN, in his             )
official capacity as Director of the Idaho   )
Department of Water Resources, and           )
FREMONT-MADISON IRRIGATION                   )
DISTRICT,                                    )
                                             )
                                                     Boise, December 2015 Term
        Respondents-Respondents,             )
                                             )
                                                     2016 Opinion No. 33
and                                          )
                                             )
                                                     Filed: March 23, 2016
IDAHO GROUND WATER                           )
APPROPRIATORS, INC.,                         )
                                                     Stephen W. Kenyon, Clerk
                                             )
        Intervenor-Appellant and             )
        Respondent,                          )
                                             )
and                                          )
                                             )
CITY OF POCATELLO                            )
                                             )
        Respondent-Appellant and             )
        Respondent,                          )
                                             )
and                                          )
                                             )
A&B IRRIGATION DISTRICT, BURLEY              )
IRRIGATION DISTRICT, MILNER                  )
IRRIGATION DISTRICT, NORTH SIDE              )
CANAL COMPANY, TWIN FALLS CANAL )
COMPANY, AMERICAN FALLS                      )

                                           1
RESERVOIR DISTRICT #2, MINIDOKA                      )
IRRIGATION DISTRICT,                                 )
                                                     )
      Intervenors-Respondents.                       )
_______________________________________

       Consolidated appeals from the District Court of the Fifth Judicial District of the
       State of Idaho, Twin Falls County. Hon. Eric J. Wildman, District Judge.

       The decision of the district court is affirmed in part and reversed in part.

       Brody Law Office, PLLC, Rupert, Haemmerle Law Office, PLLC, Hailey, and
       May, Browning and May, PLLC, Boise, for respondent and appellant Rangen,
       Inc. Justin J. May argued.

       Racine Olson Nye Budge & Bailey, Chartered, Pocatello, for appellant and
       respondent Idaho Ground Water Appropriators, Inc. Thomas J. Budge argued.

       White & Jankowski LLP, Denver, and A. Dean Tranmer, City of Pocatello,
       Pocatello, for appellant and respondent City of Pocatello. Sarah Klahn argued.

       Honorable Lawrence G. Wasden, Idaho Attorney General, Boise, for respondents
       Idaho Department of Water Resources and Gary Spackman. Garrick L. Baxter
       argued.

       Rigby, Andrus & Rigby, Rexburg, for respondent Fremont-Madison Irrigation
       District. Jerry R. Rigby argued.

       Barker Rosholt & Simpson, LLP, Twin Falls, for respondents A&B Irrigation
       District, Burley Irrigation District, Milner Irrigation District, North Side Canal
       Company and Twin Falls Canal Company.

       Fletcher Law Office, Burley, for respondents American Falls Reservoir District
       #2 and Minidoka Irrigation District. W. Kent Fletcher argued.

                                      _____________________

J. JONES, Chief Justice
       The Idaho Ground Water Appropriators, Inc. (“IGWA”) and the City of Pocatello filed
separate appeals from a district court order, affirming in part and vacating in part an order issued
by the Director of the Idaho Department of Water Resources (“IDWR”) that curtailed junior
ground water pumping in the Eastern Snake Plains Aquifer (“ESPA”). On December 13, 2011,

                                                 2
Rangen, Inc. petitioned for a delivery call, alleging that junior ground water pumping in the
ESPA was materially injuring its water rights sourced from the Martin-Curren Tunnel. The
Director held an evidentiary hearing from May 1 to May 16, 2013. As relevant to these appeals,
the Director concluded that the Martin-Curren Tunnel was a surface water source and, therefore,
not subject to the Ground Water Act. Additionally, the Director found that ground water
pumping in the ESPA was materially injuring Rangen’s water rights and that a curtailment order
was appropriate. However, the Director concluded that the benefits of curtailment diminished
significantly if the order extended to pumping east of a volcanic rift zone in the ESPA known as
the Great Rift. The Director issued a curtailment order on January 24, 2014, mandating that
ground water users located west of the Great Rift, with water rights junior to Rangen’s, refrain
from diverting water from the ESPA.
       Rangen and IGWA petitioned for judicial review of the Director’s decision. The district
court upheld the Director’s decision in significant part but vacated the Director’s application of a
trim line at the Great Rift, concluding that the Director did not have a legal basis to apply a trim
line in this case. Rangen, IGWA, and Pocatello each timely appealed. Pocatello appeals the
district court’s order vacating the Director’s application of the Great Rift trim line, alleging that
the trim line should be upheld. IGWA appeals the district court’s affirmance of the Director’s
ruling that Rangen’s water source should be administered as surface water. Additionally, IGWA
alleges that the district court should have vacated the Director’s application of the Great Rift trim
line on the basis that the curtailment area was overly broad and ordered the Director to set a
smaller curtailment area. IGWA also argues that the Director erred by not providing a reasoned
statement to support the curtailment order.
                                     I.
                     FACTUAL AND PROCEDURAL BACKGROUND
  A. Rangen’s Water Rights and the Eastern Snake Plain Aquifer
       Rangen owns and operates a fish research and propagation facility at the head of
Billingsley Creek in the Thousand Springs area near Hagerman, Idaho. Rangen holds five water
rights for the Rangen facility that were decreed through the Snake River Basin Adjudication
(“SRBA”). Rangen’s petition for delivery call alleged injury only to water right nos. 36-02551
and 36-07694. Water right no. 36-02551 authorizes a diversion of 48.54 cfs for fish propagation
and has a priority date of July, 13, 1962. Water right no. 36-07694 authorizes a diversion of 26
cfs for fish propagation and has a priority date of April 12, 1977. The source element for water
                                                 3
rights nos. 36-02551 and 36-07694 is the Martin-Curren Tunnel, tributary Billingsley Creek. The
Martin-Curren Tunnel, also commonly referred to as the Curren Tunnel, is a large, excavated
conduit constructed high on the canyon rim that extends 300 feet into the canyon wall. Water
running through the Curren Tunnel is fed by the ESPA.
       The ESPA is the aquifer underlying the Eastern Snake Plain. The ESPA is about 170
miles long and 60 miles wide, and is defined as an area having a common ground water supply.
IDAPA 37.03.11.050. The ground water in the ESPA is hydraulically connected to the Snake
River and tributary springs, including the Thousand Springs area where the Curren Tunnel is
located. The ESPA is highly productive and is composed predominantly of fractured quaternary
basalt, which is generally characterized by high hydraulic conductivity. The amount of water that
discharges from the aquifer to hydraulically connected surface water sources is largely dependent
on ground water elevations and hydraulic conductance. From October 1980 through September
2008, average annual discharge from the ESPA exceeded average annual recharge by 270,000
acre feet, which resulted in declining aquifer water levels and declining discharge to the Snake
River and tributary springs. Rangen claims that the discharge from the Curren Tunnel has
declined significantly due to ground water pumping in the ESPA. Rangen brought this delivery
call seeking to have junior priority ground water pumping in the ESPA curtailed in order to
increase discharge to the Curren Tunnel.
  B. Development of ESPAM
       The Enhanced Snake Plain Aquifer Model (“ESPAM”) is a calibrated regional ground
water model representing the ESPA, meant to simulate the effects of ground water pumping from
the ESPA on the Snake River and tributary springs. ESPAM 1.0 was developed by IDWR and
the Eastern Snake Hydrologic Modeling Committee (“ESHMC”). Rangen had filed its first
petition for delivery call in September 2003. A curtailment order was issued in February 2004,
but it was withdrawn after ESPAM version 1.0 was released. Based on projections from ESPAM
1.0, former Director Karl Dreher found that Rangen’s delivery call was futile because
curtailment of junior ground water rights in the ESPA would not result in a meaningful increase
in the quantity of water discharging near the Rangen Facility. Following Rangen’s prior delivery
call, ESPAM 1.0 was superseded by ESPAM 1.1, which was used in the delivery call
proceedings instituted by Clear Springs Foods and Blue Lakes Trout Farm, Inc. to estimate the
effects of ground water pumping on springs in the Thousand Springs area.

                                               4
       ESPAM 1.0 and 1.1 were able to predict water flows only within a particular spring
reach, rather than a particular source. In delivery calls that used these versions of ESPAM, the
present and former Directors had set a “trim line” to limit the area of curtailment to areas in
which at least 10% of the water accrued from curtailment would accrue to the spring reach where
the caller’s point of diversion was located. Much of the water accumulated to the particular
spring reach would accrue at locations other than the caller’s point of diversion. For example, in
the Clear Springs Foods delivery call, the trim line limited curtailment to areas in which at least
10% of the water accrued from curtailment would accrue to the Buhl to Thousand Springs reach.
It was estimated that Clear Springs Foods would receive 6.9% percent of the benefit accruing to
that reach. Therefore, with the application of the trim line, Clear Springs Foods was predicted to
receive 0.69% of the water accrued as a result of the curtailment. Similarly, in the Blue Lakes
delivery call, the Director limited the curtailment order to areas where at least 10% of the water
accrued from curtailment would accrue to the Devil’s Washbowl to Buhl reach. It was predicted
that Blue Lakes Trout Farm would receive 20% of the benefit accruing to that reach. Therefore,
with the application of the trim line, Blue Lakes was predicted to receive 2% of the water
accrued as a result of the curtailment.
       In 2005, ESHMC and IDWR began developing ESPAM 2.0. This version was more
refined and was calibrated using monthly water levels and flow targets, including measured
spring discharges within fourteen specific model grid cells. The springs captured and used by
Rangen were measured throughout the model calibration period and the monthly spring
discharge in the model cell where spring flows are captured by Rangen was a target for model
calibration. This revision to ESPAM was in progress in 2011 when Rangen filed its instant
petition, and the parties agreed to wait until the model was updated before going to hearing.
       During the development of ESPAM 2.0 it was discovered that the values used to measure
the discharge for Thousand Springs for calibration of ESPAM 1.0 were inaccurate, and the
values were corrected in the calibration targets for ESPAM 2.0. These corrections resulted in a
significant increase in spring discharge targets in the Billingsley Creek Area, and, based on this
new information, Rangen challenged the previous determination of a futile call under ESPAM
1.0. The model was re-calibrated in November 2012, resulting in the release and adoption of
ESPAM 2.1, which was subsequently used in this proceeding to simulate the effects of ground
water pumping in the ESPA on flows available at the Rangen Facility.

                                                5
   C. Rangen’s Delivery Call
        On December 13, 2011, Rangen, Inc. filed a petition for delivery call alleging that junior
priority ground water pumping in the ESPA was materially injuring its water rights and
requested that the Director distribute water in the ESPA and curtail junior priority pumping.
IGWA intervened in the proceedings, while Pocatello and Fremont-Madison Irrigation District
were brought in as respondents. Additionally, A&B Irrigation District, American Falls Reservoir
District #2, Burley Irrigation District, Milner Irrigation District, Minidoka Irrigation District,
North Side Canal Company and Twin Falls Canal Company (collectively, the “Surface Water
Coalition”) intervened in the action to address the application of ESPAM 2.1 in the delivery call.
        Prior to the hearing on the delivery call, Rangen filed a motion for partial summary
judgment. As relevant to this appeal, Rangen asked the Director to rule that the source for its
water rights, the Martin-Curren Tunnel, should be administered as surface water not ground
water. The Director agreed with Rangen and ruled that the Curren Tunnel was a surface water
source and, therefore, was not subject to the provisions of the Ground Water Act. The Director
presided over the evidentiary hearing on Rangen’s delivery call, which was held from May 1
through May 16, 2013. The Director then issued an order on January 29, 2014, mandating
curtailment of ground water rights bearing priority dates later than July 13, 1962, with points of
diversion located both within the area of common ground water supply and west of the Great
Rift.
   D. The Curtailment Order
        The Director concluded that several factors contributed to the decline in water flow to the
Rangen facility, including ground water pumping in the ESPA, and that ground water pumping
in the ESPA was materially injuring Rangen’s senior water rights. In determining what effect
curtailment of ground water pumping would have on discharge to the Curren Tunnel, the
Director relied on ESPAM 2.1. The Director concluded that ESPAM 2.1 was the best available
scientific tool for predicting the effects of ground water pumping on discharge at the Rangen
spring cell. Unlike ESPAM 1.0 and 1.1, ESPAM 2.1 was able to predict the effect of ground
water pumping on springs located within a specific model cell rather than the larger spring reach.
The Director concluded that 63% of the water that accrued to the Rangen model cell accrued to
the Curren Tunnel.

                                                 6
        ESPAM 2.1 predicted that the curtailment of all junior ground water pumping in the
ESPA, within the area of common ground water supply, would accrue 16.9 cfs of reach gains to
the Rangen cell. The benefits of curtailment with respect to the number of acres curtailed
diminished significantly where the benefit to the Rangen cell approached 14.3 to 14.6 cfs. As the
Director found that 63% percent of the flow into the Rangen cell would accrue to the Curren
Tunnel, the Director found that the benefit of curtailment with respect to the number of acres
curtailed diminished significantly where the benefit to the Curren Tunnel approached 9.0 to 9.2
cfs. Relying on an analysis by IDWR staff, the Director found that this point of diminishing
benefits corresponded with the location of the Great Rift. The Great Rift is a volcanic rift zone
within the aquifer that extends north to south across the plain from the Craters of the Moon to
just west of American Falls Reservoir. The basalts in this area have low permeability and,
therefore, relatively low hydraulic conductivity which can impede the transmission of water
through the aquifer.
        The Director found that
                 Curtailment of junior ground water irrigation west of the Great Rift would
        curtail irrigation of approximately 157,000 acres, resulting in curtailment of
        irrigation of approximately 17,000 acres per cfs of predicted benefit to the Curren
        Tunnel. Curtailment of junior ground water irrigation east of the Great Rift would
        curtail irrigation of approximately 322,000 additional acres, resulting in
        curtailment of irrigation of approximately 204,000 acres per cfs of predicted
        benefit to the Curren Tunnel.
        The Director determined that, although there was no way to quantify the margin of error
associated with ESPAM 2.1, the model should not be abandoned. Rather, its use should be
tempered with the fact that it is a simulation or prediction of reality and uncertainty in the model
should be taken into consideration when setting a trim line. The Director found that the
uncertainty in the model was higher east of the Great Rift. Additionally, the Director found that
ESPAM 2.1 established that the benefits of curtailment diminished significantly east of the Great
Rift.
        The Director determined that it was within his discretion to apply a trim line and limit
curtailment to ground water pumping west of the Great Rift because a senior right holder’s
demand should be viewed in light of reasonableness and optimum development of water
resources in the public interest. Additionally, the Director determined that the uncertainty in
ESPAM 2.1 east of the Great Rift also provided a basis for implementing the trim line at that

                                                 7
location. Based on these conclusions, the Director implemented a trim line and limited the
curtailment order to junior ground water pumping west of the Great Rift. This limited
curtailment to an area where the Rangen model cell was predicted to receive at least 1% of the
benefits of curtailment and the Curren Tunnel was predicted to receive at least 0.63% of the
benefits.
  E. Proceedings on Judicial Review
       IGWA, Rangen, and Pocatello sought reconsideration of the Director’s order, including
the Director’s implementation of the Great Rift trim line. The Director issued an Order on
Reconsideration wherein he affirmed the application of the trim line. Rangen and IGWA filed
petitions for judicial review of the Director’s order. The district court granted motions to
intervene filed by Pocatello, Fremont-Madison Irrigation District, and the Surface Water
Coalition and the petitions were consolidated. The district court affirmed the Director’s order in
substantial part, but vacated the Director’s application of the Great Rift trim line and remanded
for further proceedings. The district court found that the Director did not have a basis to apply a
trim line and limit the area of curtailment. IGWA, Rangen, and Pocatello each timely appealed,
and the records for the appeals were consolidated. This opinion addresses the appeals of both
IGWA and Pocatello, as they both relate to the Director’s application of the Great Rift trim line.
                                             II.
                                      ISSUES ON APPEAL
  A. IGWA’s Issues on Appeal
            1. Whether the Director erred in concluding on summary judgment that the Martin-
               Curren Tunnel is a surface water source.
            2. Whether the Director’s implementation of the Great Rift trim line was an abuse of
               discretion because it results in an overly broad curtailment area.
                     a. Whether the Director failed to recognize the issue of whether to
                        implement a trim line as one of discretion.
                     b.Whether the Director’s application of the Great Rift trim line results in a
                       waste of water.
                     c. Whether the Director failed to account for model error when implementing
                        the trim line.
            3. Whether the Director failed to provide a reasoned statement to support the
               curtailment order.
  B. City of Pocatello’s Issue on Appeal
            1. Whether the district court erred in setting aside the Great Rift trim line.

                                                  8
                                         III.
                                   STANDARD OF REVIEW
       In an appeal from a district court where the court was acting in its appellate capacity
under the Idaho Administrative Procedure Act (“IDAPA”), “we review the decision of the
district court to determine whether it correctly decided the issues presented to it.” Clear Springs
Foods v. Spackman, 150 Idaho 790, 797, 252 P.3d 71, 78 (2011) [hereinafter “Clear Springs”].
However, we review the agency record independently of the district court’s decision. Spencer v.
Kootenai Cnty., 145 Idaho 448, 452, 180 P.3d 487, 491 (2008). A reviewing court “defers to the
agency’s findings of fact unless they are clearly erroneous,” and “the agency’s factual
determinations are binding on the reviewing court, even when there is conflicting evidence
before the agency, so long as the determinations are supported by substantial competent evidence
in the record.” A & B Irrigation Dist. v. Idaho Dep’t of Water Res., 153 Idaho 500, 505–06, 284
P.3d 225, 230–31 (2012). “This Court freely reviews questions of law.” Vickers v. Lowe, 150
Idaho 439, 442, 247 P.3d 666, 669 (2011).
       The district court must affirm the agency action unless it finds that the agency’s findings,
inferences, conclusions, or decisions are:
       (a) in violation of constitutional or statutory provisions;
       (b) in excess of the statutory authority of the agency;
       (c) made upon unlawful procedure;
       (d) not supported by substantial evidence on the record as a whole; or
       (e) arbitrary, capricious, or an abuse of discretion.
I.C. § 67-5279(3); Clear Springs, 150 Idaho at 796, 252 P.3d at 77. Even if one of these
conditions is met, an “agency action shall be affirmed unless substantial rights of the appellant
have been prejudiced.” I.C. § 67-5279(4).
       Discretionary decisions of an agency shall be affirmed if the agency (1) perceived the
issue in question as discretionary, (2) acted within the outer limits of its discretion and
consistently with the legal standards applicable to the available choices, and (3) reached its own
decision through an exercise of reason. Haw v. Idaho State Bd. of Med., 143 Idaho 51, 54, 137
P.3d 438, 441 (2006). “If the agency action is not affirmed, it shall be set aside, in whole or in
part, and remanded for further proceedings as necessary.” I.C. § 67-5279(3).
                                                IV.
                                             ANALYSIS

                                                9
  A. The district court did not err in affirming the Director’s conclusion that the Martin-
     Curren Tunnel was a surface water source.
       Prior to the evidentiary hearing, the Director granted in part Rangen’s Motion for Partial
Summary Judgment, concluding that the Curren Tunnel was a surface water source. The Director
found that water right nos. 36-2551 and 36-7694 were decreed in the SRBA to be from a surface
water source and that the SRBA court’s finding was conclusive in the delivery call proceeding.
The district court affirmed the Director’s conclusion on review. IGWA contends that the district
court erred in affirming the Director’s conclusion because the Curren Tunnel meets the definition
of a ground water source under the Ground Water Act and the partial decrees are not conclusive
as to whether the Curren Tunnel should be administered as surface or ground water.
       In Clear Springs, we held that the provisions of the Ground Water Act are not applicable
to holders of surface water rights because the Ground Water Act specifically applies only to
“appropriators of ground water.” 150 Idaho at 804, 252 P.3d at 85. However, we have not
previously addressed whether a partial decree issued in the SRBA is conclusive in a delivery call
as to whether the senior right holder’s source should be administered as surface or ground water.
       Chapter 14, title 42, Idaho Code modified the laws and procedures for adjudicating water
rights. I.C. § 42-1401. One of the purposes of this modification was “to establish, through an
adjudication a uniform description for surface water rights, ground water rights and water
rights.” I.C. § 42-1427(1)(a). The Legislature found that prior to the enactment of Chapter 14
“existing water rights [were] not uniformly described,” and “it is important that the elements of a
water right be standardized to allow for fair and efficient administration of the limited water
supply.” Id.
       Idaho Code sections 42-1409 and 42-1411 provide that a notice of claim to a water right
and the Director’s report on the water system must include the “source of water.” I.C. §§ 42-
1409(1)(b), -1411(2)(b). Although there is no requirement within the statute that the notice or
report specifically address whether the source is surface or ground water, IDWR’s Adjudication
Rule 60 does expressly address this issue.
               For surface water sources, the source of water shall be identified by the
       official name listed on the U.S. Geological Survey Quadrangle map. If no official
       name has been given, the name in local common usage should be listed. If there is
       no official or common name, the source should be described as “unnamed stream”
       or “spring.” The first named downstream water source to which the source is
       tributary shall also be listed. For ground water sources, the source shall be listed
       as “ground water.”
                                                10
IDAPA 37.03.01.060.02(c)(i).
       Here, the partial water decrees at issue identify the water source as Martin-Curren Tunnel
and the tributary as Billingsley Creek. The Director found that because the decrees followed the
naming conventions in Adjudication Rule 60 for surface water sources, a plain reading of the
decrees shows that the Martin-Curren Tunnel is unambiguously surface water. The district court
affirmed this conclusion, reasoning that if the source of Rangen’s senior rights was ground water,
the SRBA Court would have decreed the source as “ground water,” the same as every other
ground water right in the SRBA. The district court then concluded that if IGWA disagreed with
the Department’s recommendations, it should have timely file objections to the recommendations
in the SRBA rather than collaterally attacking the partial decrees in this delivery call proceeding.
       IGWA argues that the Director erred in relying on Adjudication Rule 60 because the rule
was merely meant to facilitate uniformity in naming water sources and the name of the senior’s
source is not conclusive of how water rights will be administered in response to a delivery call.
In support of this argument, IGWA relies on Am. Falls Reservoir Dist. No. 2 v. Idaho Dep’t of
Water Res., 143 Idaho 862, 154 P.3d 433 (2007) [hereinafter “AFRD2”]. There, the Court held
that the SRBA court’s issuance of partial decrees did not prevent the Director from considering
the material injury factors in the Conjunctive Management Rules during a delivery call because
the SRBA did not address these factors. Id. at 876, 154 P.3d at 447. The Court reasoned that
       the water rights adjudications neither address, nor answer, the questions presented
       in delivery calls; thus, responding to delivery calls, as conducted pursuant to the
       CM Rules, do [sic] not constitute a re-adjudication. For example, the SRBA court
       determines the water sources, quantity, priority date, point of diversion, place,
       period and purpose of use. I.C. §§ 42–1411(2)(a)–(j). However, reasonableness is
       not an element of a water right; thus, evaluation of whether a diversion is
       reasonable in the administration context should not be deemed a re-adjudication.
Id. at 876–77, 154 P.3d at 447–48 (case citation omitted). However, unlike the material injury
factors discussed in AFRD2, the issue of whether the Curren Tunnel is a ground water or surface
water source directly deals with the nature of Rangen’s water right, which was addressed in the
SRBA. Except for certain enumerated exceptions inapplicable here, “[t]he decree entered in a
general adjudication shall be conclusive as to the nature and extent of all water rights in the
adjudicated water system.” I.C. § 42-1420 (emphasis added). Where the partial decrees indicate
that Rangen’s rights are surface water rights, that finding is conclusive in Rangen’s delivery call.

                                                 11
         IGWA alternatively argues that the Director erred in relying on Adjudication Rule 60
because the Curren Tunnel fits within the definition of ground water under the Ground Water
Act and applying Rule 60 would conflict with the express terms of the Act. Under the Ground
Water Act, ground water is defined as “all water under the surface of the ground whatever may
be the geological structure in which it is standing or moving.” I.C. § 42-230(a). According to
IGWA, Adjudication Rule 60 cannot be construed in a manner that forces the Director to
fallaciously administer a ground water source as if it is surface water, contrary to the plain
language of the Act.
         IGWA couches its argument as a conflict between the application of Adjudication Rule
60 and the definition of ground water in Idaho Code section 42-230(a). However, Adjudication
Rule 60 does not address the definition of ground water or how the Director was to determine
whether a specific source is ground water or surface water. Adjudication Rule 60 provides the
naming conventions to be used once that determination is made. IDWR had authority to
promulgate the Adjudication Rules under Idaho Code sections 42-1414 and 42-1805(8). IDAPA
37.03.01.000. Adjudication Rule 60’s naming conventions provide a uniform system for the
identification of surface and ground water sources which corresponds with the Legislature’s
intent for initiating the SRBA.
         Conjunctive management of ground water and surface water rights is one of the
         main reasons for the commencement of the Snake River Basin Adjudication . . . .
         To conjunctively manage these water sources a good understanding of both the
         hydrological relationship and legal relationship between ground and surface water
         rights is necessary.
                  Although these issues may need to be resolved by general administrative
         provisions in the adjudication decrees, they generally relate to two classic
         elements of a water right—its source and priority. The SRBA should determine
         the ultimate source of the ground and surface water rights being adjudicated . . . .
         If the SRBA proceeds and these issues are not addressed, a major objective for the
         adjudication will not have been served. Conjunctive administration will be set
         back, and another generation of ground and surface water users will be uncertain
         regarding their relationship to each other.
A & B Irrigation Dist. v. Idaho Conservation League, 131 Idaho 411, 422, 958 P.2d 568, 579
(1997) (quoting INTERIM LEG. COMM. REP.        ON THE   SNAKE RIVER BASIN ADJUDICATION 36–37
(1994)). Adjudication Rule 60 provides a uniform standard for recording surface and ground
water rights, which is essential for conjunctive management of those rights in the Snake River
Basin.

                                                 12
       IGWA is essentially arguing that the Curren Tunnel was miscategorized as a surface
water source in the SRBA. However, Rangen’s delivery call is not the appropriate place to
challenge that determination. If IGWA wanted to challenge the partial decrees of Rangen’s water
rights it should have filed objections in the SRBA under Idaho Code section 42-1412. Allowing
IGWA to collaterally attack this determination would severely undermine the purpose of the
SRBA and create uncertainty in water rights adjudicated in that process. As this Court has
previously stated, “[f]inality in water rights is essential.” State v. Nelson, 131 Idaho 12, 16, 951
P.2d 943, 947 (1998). The partial decrees indicate that the Curren Tunnel is a surface water
source and the decrees are conclusive on that issue. Therefore, Rangen’s water rights are not
subject to the provisions of the Ground Water Act.
       We hold that the district court did not err in affirming the Director’s conclusion that the
Curren Tunnel was a surface water source and, therefore, not subject to the Ground Water Act.
  B. The District Court erred in vacating the Director’s application of the Great Rift trim
     line.
       At the district court, both Rangen and IGWA challenged the Director’s implementation
of the Great Rift trim line. IGWA argued that the curtailment area under the application of the
Great Rift trim line was overly broad because it resulted in a waste of water and did not
adequately account for model error. IGWA asked the district court to vacate the trim line and
order the Director to adopt a smaller curtailment area. Rangen argued that the trim line should be
vacated because the Director did not have discretion to apply a trim line at all in this case and the
curtailment order should include all junior ground water pumping in the ESPA within the area of
common ground water supply. The district court agreed with Rangen and vacated the trim line,
concluding that the Director did not have discretion to apply a trim line on policy grounds and
that applying the trim line based on model error impermissibly shifted the burden of proof on
material injury from the junior appropriators to Rangen. On appeal, Pocatello challenges the
district court’s order vacating the trim line, arguing that the application of the Great Rift trim line
was within the Director’s discretion. Rangen and the Surface Water Coalition contend that the
district court’s decision should be upheld. IGWA argues that the district court should have
ordered the Director to set a smaller curtailment area.
       Here, the first issue is whether the Director had discretion to implement a trim line in this
case. If the Director did have discretion, the next issue is whether the Director abused his
discretion by implementing a trim line at the Great Rift.
                                                  13
           1. The Director had discretion to implement a trim line based on the doctrine of
              beneficial use.
       Relying on the Court’s decision in AFRD2, the Director concluded that, given the nature
of the decisions which must be made in determining how to respond to a delivery call, the
Director must have discretion to impose a trim line if justified. See AFRD2, 143 Idaho at 880,
154 P.3d at 451. The Director then concluded that a trim line was justified in this case on two
bases: (1) to ensure maximum and beneficial use of the State’s water resources and (2) to
account for uncertainty in ESPAM 2.1. We find that the Director had discretion to implement the
trim line based on the policy of beneficial use. Therefore, we need not address whether the trim
line was also justified to account for model uncertainty and whether implementing a trim line on
that basis impermissibly shifted the burden of proof on material injury.
       The Director concluded that in determining whether to implement a trim line, he must
consider the diminishing benefits of curtailment beyond the Great Rift. The Director found that
low transmissivity at the Great Rift impedes the transmission of water through the aquifer.
Additionally, focusing on the results of ESPAM 2.1, the Director found that
       curtailment of junior ground water irrigation west of the Great Rift would curtail
       irrigation of approximately 157,000 acres, resulting in curtailment of irrigation of
       approximately 17,000 acres per cfs of predicted benefit to the Curren Tunnel.
       Curtailment of junior ground water irrigation east of the Great Rift would curtail
       irrigation of approximately 322,000 additional acres, resulting in curtailment of
       approximately 204,000 acres per cfs of predicted benefit to the Curren Tunnel.
       In concluding that he must consider the diminishing benefits of curtailment, the Director
relied on the policy considerations articulated in CMR 20.03, which provides that “[a]n
appropriator is not entitled to command the entirety of large volumes of water in a surface or
ground water source to support his appropriation contrary to the public policy of reasonable use
of water.” IDAPA 37.03.11.020.03. Additionally, the Director relied on the policy of promoting
the optimum development of the State’s water resources enunciated in Article XV, section 7 of
the Idaho Constitution and this Court’s decision in Clear Springs, where we stated that “[t]he
policy of the law of this State is to secure the maximum use and benefit, and least wasteful use,
of its water resources.” See Idaho Const. art. XV, § 7; Clear Springs, 150 Idaho at 808, 252 P.3d
at 89. Based on these considerations, the Director concluded that
       curtailment of ground water diversions on the east side of the Great Rift is not
       justified. To curtail junior ground water users east of the Great Rift would be
       counter to the optimum development of Idaho’s water resources in the public

                                                14
       interest and the policy of securing the maximum use and benefit, and least
       wasteful use, of the State’s water resources.
       IGWA, Rangen, and Pocatello each sought reconsideration on various aspects of the
Director’s final order. On reconsideration, the Director upheld the application of the Great Rift
trim line, reiterating the same policy considerations outlined above. Additionally, the Director
concluded that the use of the Great Rift to define a trim line is justified based on the evidence
presented in this proceeding and that the application of the trim line results in benefits to the
calling party that are consistent with those resulting from trim lines applied in previous
proceedings. The Director also concluded that in determining whether to implement a trim line
he had to consider to what extent the prior appropriation doctrine, as established under Idaho
law, allows a senior surface water user to call upon an aquifer to satisfy a senior water right. The
Director found that the Great Rift trim line struck an appropriate balance.
       On judicial review, the district court set aside the trim line, rejecting the Director’s
conclusions as to both the policy and model uncertainty grounds. The court observed that
although the disparity between curtailed acreage and realized water accruing to the Martin-
Curren Tunnel is large, the very nature of conjunctive management involves a large disparity
between the number of acres curtailed and the accrued benefit to a senior right. The district court
then found that under this Court’s holding in Clear Springs, the Director could not rely on CMR
20.03 or Article XV, section 7 of the Idaho Constitution to implement a trim line and administer
less than the full amount of water of which Rangen was entitled. The district court interpreted
Clear Springs as holding that Idaho law does not
       provide the Director the discretion to reduce the decreed quantity of a water right
       to which a senior appropriator is entitled based on the disparity between the
       impact to junior ground water pumpers resulting from curtailment and the
       quantity of water that would benefit the senior right, provided the water is put to
       beneficial use.
       On appeal, Pocatello argues that the Director had sufficient justification to implement the
trim line in order to promote principles of optimum use, consistent with Idaho law. It argues that
the disparity between the number of acres curtailed east of the Great Rift and the amount of
water received by Rangen was large where the curtailment of an additional 322,000 acres was
only predicted to accrue an additional 1.5 cfs of water to the Curren Tunnel. Pocatello also
argues that the Director must have some amount of discretion to administer water in conjunctive

                                                15
management situations and that setting aside the trim line in this case would essentially leave
him with none.
       The Director’s arguments on appeal mirror the reasoning in his agency orders. In
particular, the Director argues that
       in some circumstances, conjunctive management delivery calls can require idling
       hundreds of thousands of acres of productive agricultural land to deliver small
       increments of water to a senior water right holder. In such scenarios, the senior
       water right holder’s private interest in receiving additional water may directly
       conflict with the public’s interest in the optimum development of the State’s water
       resources. Certain “bedrock” principles of Idaho’s prior appropriation doctrine are
       launched into “tension.” Here, the bedrock principles that are in tension are a
       water right holder’s private proprietary interest in seeking curtailment of junior
       uses of water and the public’s interest in the optimum development of the State’s
       water resources. The Director has the statutory duty, authority, and discretion to
       resolve this tension.
               In this case, the Director resolved the tension through recognition of the
       Great Rift trim line . . . . [T]he Director concluded there is a point where Rangen’s
       delivery call would require curtailment of vastly more acreage to produce a very
       small increment of additional water, and that at this point, Rangen’s right to seek
       additional curtailment must give way to the public’s interest in optimum
       development of the State’s water resources. The Director also concluded that this
       point is the Great Rift.
       The Surface Water Coalition and Rangen argue chiefly that Idaho’s prior appropriation
doctrine precludes the Director from imposing a trim line that takes water that would otherwise
be put to beneficial use by a senior water right. They assert that the Director has no discretion to
impose a trim line in this case because doing so would violate the prior appropriation doctrine
and allow unmitigated injury to Rangen’s senior water right. They further argue that the prior
appropriation doctrine requires administration of all rights contributing to the material injury,
subject only to a showing by the juniors that the call would be futile or otherwise unfounded.
       The Court has previously held that hydrologically connected surface and ground waters
must be managed conjunctively. See Musser v. Higginson, 125 Idaho 392, 871 P.2d 809 (1994).
In 1994, IDWR promulgated the Conjunctive Management Rules (“CMRs”) [IDAPA
37.03.11.000 to 37.03.11.050] to provide the procedures for responding to delivery calls “made
by the holder of a senior-priority surface or ground water right against the holder of a junior
priority ground water right in an area having a common ground water supply.” IDAPA
37.03.11.001. The CMRs integrate “all elements of the prior appropriation doctrine as
established by Idaho law.” IDAPA 37.03.11.020.02 (CMR 20.02). The CMRs also integrate

                                                16
        administration and use of surface and ground water in a manner consistent with
        the traditional policy of reasonable use of both surface and ground water. The
        policy of reasonable use includes the concepts of priority in time and superiority
        in right being subject to conditions of reasonable use as the legislature may by law
        prescribe as provided in Article XV, Section 5, Idaho Constitution, optimum
        development of water resources in the public interest prescribed in Article XV,
        Section 7, Idaho Constitution, and full economic development as defined by Idaho
        law.
IDAPA 37.03.11.020.03 (CMR 20.03). Under these principles, “[a]n appropriator is not entitled
to command the entirety of large volumes of water in a surface or ground water source to support
his appropriation contrary to the public policy of reasonable use of water.” Id. CMR 40.03
provides that, in a delivery call, “the Director shall consider whether the petitioner making the
delivery call is suffering material injury to a senior-priority water right and is diverting and using
water efficiently and without waste, and in a manner consistent with the goal of reasonable use
of surface and ground waters as described in Rule 42.”1 IDAPA 37.03.11.040.03.
        “While the prior appropriation doctrine certainly gives pre-eminent rights to those who
put water to beneficial use first in time, this is not an absolute rule without exception . . . the
Idaho Constitution and statutes do not permit waste and require water to be put to beneficial use
or be lost.” AFRD2, 143 Idaho at 880, 154 P.3d at 451. In AFRD2, this Court concluded that the
Director must have some discretion to balance these countervailing considerations in a delivery
call.
        Somewhere between the absolute right to use a decreed water right and an
        obligation not to waste it and to protect the public’s interest in this valuable
        commodity, lies an area for the exercise of discretion by the Director. This is
        certainly not unfettered discretion, nor is it discretion to be exercised without any
        oversight. That oversight is provided by the courts, and upon a properly
        developed record, the Court can determine whether that exercise of discretion is
        being properly carried out.
Id.
        Idaho Code section 42-101 provides:
                Water being essential to the industrial prosperity of the state, and all
        agricultural development throughout the greater portion of the state depending
        upon its just apportionment to, and economical use by, those making a beneficial
        application of the same, its control shall be in the state, which, in providing for its
        use, shall equally guard all the various interests involved.

1
  CMR 42 sets forth several factors for the Director to consider when determining whether holders of water rights
are suffering injury and using water efficiently and without waste. See IDAPA 37.03.11.042.01(a)–(h).

                                                       17
As we recently stated in Clear Springs, the policy of securing the maximum use and benefit, and
least wasteful use of Idaho’s water resources, has long been the policy in Idaho.
               In Niday v. Barker, 16 Idaho 73, 79, 101 P. 254, 256 (1909), we stated,
       “The theory of the law is that the public waters of this state shall be subjected to
       the highest and greatest duty.” In Farmers’ Co-operative Ditch Co. v. Riverside
       Irrigation District, Ltd., 16 Idaho 525, 535, 102 P. 481, 483 (1909), we phrased it,
       “Economy must be required and demanded in the use and application of water.”
       In Poole v. Olaveson, 82 Idaho 496, 502, 356 P.2d 61, 65 (1960), we expressed
       the same concept by stating, “The policy of the law of this State is to secure the
       maximum use and benefit, and least wasteful use, of its water resources.”
Clear Springs, 150 Idaho at 808, 252 P.3d at 89. This policy limits the prior appropriation
doctrine by excluding from its purview water that is not being put to beneficial use. AFRD2, 143
Idaho at 876, 154 P.3d at 447. The policy of beneficial use serving as a limit on the prior
appropriation doctrine dovetails with the prescription in CMR 20.03 that “[a]n appropriator is not
entitled to command the entirety of large volumes of water in a surface or ground water source to
support his appropriation contrary to the public policy of reasonable use of water.” IDAPA
37.03.11.020.03.
       Although ground water in the ESPA is hydraulically connected to water in the spring
tributaries, the impact of ground water pumping in the ESPA on discharge in the springs is
attenuated. See Douglas L. Grant, The Complexities of Managing Hydrologically Connected
Surface Water and Groundwater Under the Appropriation Doctrine, 22 LAND & WATER L. REV.
63, 80–81 (1987). Necessarily, not all of the water collected due to the curtailment will accrue to
the senior water right holder; some will remain in the aquifer and some will flow to other
tributary springs. This complexity can make it very difficult to balance a senior right holder’s
interest in receiving additional water against the State’s interest in securing the maximum use
and benefit, and least wasteful use, of its water resources. In light of this challenging balancing
requirement, it is necessary that the Director have some discretion to determine in a delivery call
proceeding whether there is a point where curtailment is unjustified because vast amounts of land
would be curtailed to produce a very small amount of water to the caller. As discussed, Idaho
law contemplates a balance between the “bedrock principles” of priority of right and beneficial
use. In Matter of Distribution of Water to Various Water Rights Held By or For Benefit of A & B

                                                18
Irrigation Dist., 155 Idaho 640, 650, 315 P.3d 828, 838 (2013). The Director is authorized to
undertake this balancing act, subject, as he acknowledged here, to the limitations of Idaho law.2
         The district court erred by rejecting the Director’s reliance on CM Rule 20.03 and Idaho
Constitution Article XV, section 7 as a basis to implement a trim line. The Director did not treat
either source as directly granting him discretion to apply a trim line. Instead, the Director
recognized, correctly, that each source merely restated a broader understanding of Idaho law:
The prior appropriation doctrine sanctifies priority of right, but subject to limitations imposed by
beneficial use.3 The Director’s interpretation of the law was correct and it was error for the
district court to reject it.
         The district court held that the Director does not have discretion to reduce the decreed
quantity of water to which a senior appropriator is entitled based on the disparity between the
number of acres curtailed and the quantity of water that would benefit the senior. First, the trim
line here does not reduce the decreed quantities of Rangen’s water rights. Rangen remains
entitled to the full measure of its rights, subject to availability of water and beneficial use
limitations. Rather, the trim line represents the Director’s reasoned refusal to curtail irrigation to
hundreds of thousands of acres so that Rangen might get another 1.5 cfs of water. Second, it is
not the disparity per se between the impact to the juniors and the benefit to Rangen that justifies
the trim line. Indeed, as the district court accurately and aptly noted, the very nature of
conjunctive management involves a large disparity between the number of acres curtailed and
the accrued benefit to a senior surface right. Nonetheless, the Director may consider any such
disparity when seeking to balance priority of right with beneficial use requirements.
         Holding that the Director has discretion to impose a trim line by applying the policy of
beneficial use is consistent with Idaho law. In Schodde v. Twin Falls Land & Water Co., a senior
water right holder had erected water wheels to lift appropriated water out of a river so that he

2
  In determining whether to implement a trim line, the Director stated that he perceived the issue “as one of limited
discretion.” IGWA contends that the Director’s use of the word “limited” indicates that the Director improperly
limited his ability to evaluate whether Rangen’s means of appropriation is reasonable and to prevent hoarding of
water. However, as argued by IDWR, the Director’s recognition that his discretion is limited is in line with the
Court’s holding in AFRD2 that the Director’s discretion in this area is “not unfettered.” 143 Idaho at 880, 154 P.3d
at 451. The Director’s recognition that his discretion was limited does not mean that the director failed to recognize
the issue as one of discretion, only that the Director recognized that he needed to express legal and factual support
for his decision. This is not a situation where the Director failed to exercise any discretion.
3
  In Clear Springs, we held that “[t]here is no difference between securing the maximum use and benefit, and least
wasteful use, of this State’s water resources and the optimum development of water resources in the public interest.”
Clear Springs, 150 Idaho at 808, 252 P.3d at 89.

                                                         19
could divert it over his land. 224 U.S. 107, 114–115 (1912). A junior right holder had
subsequently constructed a dam downstream, which backed up the river and reduced the current
flow to the extent that the senior’s water wheels could not operate. Id. at 115–116. The senior
sued the junior in federal court, where the trial court dismissed the action and both the Ninth
Circuit and the U.S. Supreme Court affirmed the dismissal. Id. at 114. The Supreme Court noted
that
               [t]he trial court recognized fully the right of the plaintiff to the volume of
        water actually appropriated for a beneficial purpose. It nevertheless dismissed the
        complaint on the ground that there was no right under the Constitution and laws
        of the state of Idaho to appropriate the current of the river so as to render it
        impossible for others to apply the otherwise unappropriated waters of the river to
        beneficial uses. The Court . . . held that to uphold as an appropriation the use of
        the current of the river to the extent required to work the defendant’s wheels
        would amount to saying that a limited taking of water from the river by
        appropriation for a limited beneficial use justified the appropriation of all the
        water in the river as incident to the limited benefit resulting from the use of the
        water actually appropriated.4
Id. at 117. “The extent of beneficial use [is] an inherent and necessary limitation upon the right
to appropriate.” Id. at 120. The Court acknowledged “the disastrous results which would follow”
if the prior appropriation doctrine were not limited by beneficial use:
                If the plaintiff were permitted to own the current of the stream as
        appurtenant to his right of appropriation and diversion, he would be able to add
        indefinitely to the water right he would control and own. There might be a great
        surplus of water in the stream at and above plaintiff’s premises, and an urgent
        demand for a portion of this surplus for beneficial uses, but if an appropriator
        above should divert a sufficient quantity to lower the current under plaintiff’s
        water wheels so that they would not revolve, the plaintiff would have a cause of
        action to prevent such an appropriation. It is clear that in such a case the policy of
        the state to reserve the waters of the flowing streams for the benefit of the public
        would be defeated.
Id. It must be noted that Schodde dealt with the reasonableness of the senior appropriator’s
“means of diversion, not in his priority of water rights” (Clear Springs, 150 Idaho at 809, 252
4
  The Schodde quotes herein were originally stated by the trial court rather than the U.S. Supreme Court. However,
the Supreme Court stated
              [w]e have freely excerpted from the opinions of the courts below because, in our judgment,
         they so clearly portray the situation, and correctly apply the law to that situation as resulting from
         the Constitution and statutes of Idaho and the reiterated decisions of the court of last resort of that
         state . . . that we might place our decree of affirmance upon the reasons which controlled the
         courts below.
Schodde, 224 U.S. at 121–122.

                                                       20
P.3d at 90), but the principles stated in Schodde apply equally in this water management case
where the senior appropriator seeks to assert control over practically the entire aquifer, regardless
of the minimal benefit to the senior and the great detriment to the juniors.
       Another Idaho case is also instructive here. In Van Camp v. Emery, a senior appropriator
had allegedly erected a dam to flood irrigate his lands, thereby depriving a junior appropriator of
his water. 13 Idaho 202, 208, 89 P. 752, 754 (1907). The Court held:
       [i]n this arid country, where the largest duty and the greatest use must be had from
       every inch of water in the interest of agriculture and home building, it will not do
       to say that a stream may be dammed so as to cause subirrigation of a few acres at
       a loss of enough water to surface irrigate 10 times as much by proper application.
Id. Here, it will not do to say that access to an entire aquifer may be foreclosed so as to cause 1.5
cfs to accrue to a single tunnel at a loss of enough water to irrigate 322,000 acres.
       In this case, the Director acted within the scope of his limited discretionary authority—
“between the absolute right to use a decreed water right and an obligation not to waste it and to
protect the public’s interest in this valuable commodity” (AFRD2, 143 Idaho at 880, 154 P.3d at
451)—to impose the trim line at the Great Rift. We therefore hold that the district court erred in
concluding that the Director did not have discretion to implement a trim line based on policy
considerations and in vacating the trim line on that basis.
           2. The Director did not abuse his discretion by implementing a trim line at the
              Great Rift.
       IGWA argues that the Director abused his discretion by implementing the Great Rift trim
line because the implementation of the Great Rift trim line results in a waste of water and the
trim line fails to adequately account for model error.
               a. The application of the Great Rift trim line does not result in a waste of
                  water.
       IGWA contends that the Director abused his discretion by setting a trim line that allows
Rangen to “hoard” water in violation of the principle of beneficial use because Rangen is
commanding one hundred times more water than it will use. IGWA believes that the Director’s
beneficial use and reasonable appropriation analysis were insufficient because the Director did
not decide how much water Rangen can reasonably command without diverting it. Additionally,
IGWA contends that the Director arbitrarily implemented the Great Rift trim line because it is
inconsistent with the 10% trim line adopted in Clear Springs. Ultimately, IGWA wants the Court
to set a minimum bar on how much water use can be curtailed without the benefit accruing to the

                                                 21
senior water right holder and to find that a curtailment area where only 0.63% of the benefits
would accrue to the senior right holder is unreasonable.
          As discussed above, the Director specifically considered the beneficial use doctrine in
determining whether to implement a trim line at the Great Rift. The Director concluded that to
curtail the junior ground water users east of the Great Rift would be counter to the optimum
development of Idaho’s resources in the public interest and the policy of securing the maximum
use and benefit, and least wasteful use, of the State’s water resources. With the implementation
of the Great Rift trim line, curtailment was limited to an area where the Rangen cell was
predicted to receive at least 1% and the Martin-Curren Tunnel was predicted to receive 0.63% of
the benefits of the curtailment.
          The Director did not set a minimum bar as to how much water can reasonably be
curtailed in any delivery call but, rather, determined the point in this specific case where the
benefit that would accrue to Rangen was so small in comparison to the acreage that would have
to be curtailed so as to no longer justify curtailment. Concepts like beneficial use, waste,
reasonable means of diversion and full economic development require a highly fact driven
analysis. AFRD2, 143 Idaho at 869, 154 P.3d at 440. The circumstances that would justify a trim
line and the point at which to implement it necessarily depend on the specific circumstances in
each case. Setting a bright line rule dictating a minimum bar of what will be considered a
reasonable curtailment area in future delivery calls would, therefore, not be appropriate.
          Although Rangen would only receive 0.63% of the water accrued from the curtailment,
that does not necessarily mean that the curtailment results in waste. Necessarily, not all of the
water collected due to the curtailment will accrue to the senior water right holder, as some will
remain in the aquifer or flow to other tributary springs. As discussed above, this is why it is
necessary that the Director have some discretion to determine whether and at what point a
delivery call would require curtailment of an unreasonably vast amount of acreage to produce a
very small amount of water, and, therefore, not be justified. The Director’s determination that
this point was the Great Rift was reached through reason and supported by evidence on the
record.
          IDWR staff’s analysis of ESPAM 2.1 results showed that the benefit of curtailment with
respect to the number of acres curtailed diminished significantly where the benefit to the Martin-
Curren Tunnel approached approximately 9.0 to 9.2 cfs. IDWR staff found that this point of

                                                22
diminishing benefits corresponded with the location of the Great Rift, where low transmissivity
impedes the transmission of water through the aquifer. The Director concluded that curtailment
of junior ground water irrigation west of the Great Rift would result in curtailment of 17,000
acres per cfs predicted to benefit Rangen, while curtailment east of the Great Rift would result in
curtailment of 204,000 acres per cfs predicted to benefit Rangen. The evidence on the record
shows that there is a stark reduction in the benefit of the curtailment east of the Great Rift,
compared to west of the Great Rift. If ground water pumping east of the Great Rift were included
in the curtailment order, an additional 322,000 acres would be curtailed with only an additional
1.5 cfs predicted to accrue to the Curren Tunnel. Given the Director’s discretion and these
uncontested findings of fact, the Director’s application of the Great Rift trim line was proper. It
was not an abuse of discretion and it was supported by substantial evidence.
         IGWA further contends that the Director should have adopted a 10% trim line because a
10% trim line was adopted in the Clear Springs Foods and Blue Lake Trout Farm delivery calls.
There, the former Director found that the margin of error associated with ESPAM 1.1 was 10%
and he excluded areas within that margin of error from the curtailment order. Clear Springs, 150
Idaho at 812–13, 252 P.3d at 93–94. Here, the Director specifically rejected IGWA’s argument
that he should impose a 10% trim line. Unlike ESPAM 1.1, ESPAM 2.1 is able to predict the
impacts of curtailment on a single model cell rather than a multi-cell reach. As the Director
found,
         [b]ecause the 10% trim line applied in Clear Springs delivery call was based on
         model predictions of impacts to a multi-cell reach containing several springs,
         applying a 10% trim line based on model predictions of impacts to a single model
         cell . . . would result in a significantly different standard than was applied in the
         Clear Springs delivery call.
IDWR staff found that if a 10% trim line were applied in the present case, the benefit that would
accrue to the Rangen cell would be a negligible 0.01 cfs. Additionally, the trim line in Clear
Springs was based on the Director’s factual finding that the margin of error in ESPAM 1.1 was
10%. Clear Springs, 150 Idaho at 816, 252 P.3d at 97. Here, the Director was unable to quantify
the margin of error in ESPAM 2.1. It does not make sense to impose a 10% trim line in this case
because the margin of error in previous models was 10%. We find that a 10% trim line would not
be reasonable when applied to the facts of this case.
         Additionally, the Director specifically found that the benefit that would accrue to Rangen
with the imposition of the Great Rift trim line was in line with prior delivery calls. It was
                                                  23
predicted that Rangen would receive 0.63% of the water accrued as a result of the curtailment
order. The Director concluded that this was similar to the trim lines applied in the Clear Springs
and Blue Lakes delivery calls, where the calling parties were predicted to receive 0.69% and 2%
of the curtailed benefits, respectively. The Director’s implementation of the Great Rift trim line
was, therefore, not arbitrary.
       We hold that the Director had substantial evidence to support his decision to implement
the trim line at the Great Rift and that his decision to implement a trim line at that point does not
result in a waste of water.
               b. The Director did not fail to account for model error.
       IGWA contends that the Director abused his discretion by not considering localized
model error when implementing a trim line. Additionally, IGWA argues that the Director erred
in failing to account for the fact that ESPAM 2.1 overpredicts impacts to the Rangen cell. IGWA
contends that the Director should have set a margin of error based on the above issues with the
model and excluded all junior pumping within that margin of error from the curtailment order.
       The Director found that ESPAM 2.1 was the best available scientific tool for predicting
the effects of ground water pumping on discharge at the Rangen spring cell, although it was an
imperfect approximation of a complex physical system. All of the parties agree that ESPAM 2.1
was the best scientific tool available. The Director addressed IGWA’s arguments that the model
did not account for localized error and was biased toward overpredicting impacts in the
curtailment order. The Director found that IDWR staff disagreed that ESPAM 2.1 is biased
towards overpredicting impacts.
               [A]rguments that the model is biased to over-predict impacts are based
       largely on comparison of model results with well and spring discharge data
       collected only after the year 2000. Ignoring data collected before 2000
       compromises their interpretation . . . . Contrary to IGWA’s arguments, evaluation
       of ESPAM 2.1’s calibration results, which under-predict the difference between
       flows in the 1980s and the 2000s, suggests that the model would be more likely to
       under-predict the impacts of ground water pumping on springs flows in the
       Rangen cell.
       Here, the Director did not fail to address bias in the model, but specifically rejected
IGWA’s argument that such bias existed. It seems that IGWA is asking the Court to reweigh the
evidence of model bias and find that the Director lacked substantial evidence to support his
finding that the model was not biased toward overprediction of flow. Although IGWA presented
conflicting evidence, the findings of IDWR staff relied on by the Director provided substantial
                                                 24
evidence on the record to support the Director’s finding that the model was not biased toward
overpredicting water flow to the Rangen cell.
       Additionally, the Director relied on an IDWR staff memorandum in concluding that
although ESPAM 2.1 is a regional model, the discharge data for the Rangen cell reflects both
local and regional geological controls on hydrologic responses to ground water pumping and
other aquifer stresses. Also, based on findings from the IDWR staff, the Director concluded that
it was appropriate to use a regional rather than a local model because the effect of junior ground
water pumping in the ESPA on discharge in the spring reaches is a regional-scale question that
cannot be addressed with a small-scale, local model. The Director rejected the application of
alternative models suggested by IGWA’s expert that “accounted for localized error,” concluding
that the calibration methods in those models did not follow proper procedures. The Director
ultimately concluded that ESPAM 2.1 was the best available model because it incorporates much
more information about the aquifer than can be considered in other predictive methods available
to the Department, and it incorporates data that specifically reflect how spring discharge in the
Rangen cell has responded to regional aquifer stresses in the past. The IDWR staff memorandum
relied on by the Director provided substantial and competent evidence to support the Director’s
conclusion that ESPAM 2.1 was a more appropriate tool than the models that accounted for
localized error and that it did account for local geological controls on hydrologic responses.
       IGWA also argues that the Director erred in not setting a margin of error for ESPAM 2.1.
Although the Director found that the model had some uncertainty, he found that because of the
complexity of the model, the margin of error associated with the model predictions cannot be
quantified. Both the ESHMC and IDWR staff had found that a predictive uncertainty analysis to
determine a quantifiable margin of error could not be conducted in a reasonable timeframe.
There was also expert testimony on the record stating that it would not be feasible in terms of
resources or time to do the type of analysis necessary to come up with a reliable margin of error.
Based on the foregoing, the Director had substantial evidence to support his finding that the
uncertainty in ESPAM 2.1 could not be quantified, and he did not abuse his discretion by
refraining from setting a numeric margin of error.
       Accordingly, the Director did not abuse his discretion by failing to account for model
error when implementing the Great Rift trim line.

                                                25
  C. The District Court did not err in concluding that the Director provided a reasoned
     statement to support the curtailment order under Idaho Code section 67-5248(a).
       Idaho Code section 67-5248 provides that an agency order shall include “a reasoned
statement in support of the decision” and “shall be accompanied by a concise and explicit
statement of the underlying facts of record supporting the findings.” I.C. § 67-5248(a). The order
should “identify facts, as well as inferences drawn from the facts upon the application of its
expertise and judgment, which underlie its decision. Such an explanation is essential to
meaningful judicial review.” Woodfield v. Bd. of Prof’l Discipline of Idaho State Bd. of Med.,
127 Idaho 738, 747, 905 P.2d 1047, 1056 (Ct. App. 1995).
       IGWA alleges that the Director did not include a reasoned statement to support the
curtailment order because the Director failed to make a determination of how much water
Rangen can command without using. As discussed above, the Director did determine that
expanding the curtailment order to ground water pumping east of the Great Rift would be
unreasonable, and against the policy of maximum use and benefit of Idaho’s water resources.
The Director provided statements from the record to support his findings and identified which
findings supported his conclusions of law. This is sufficient to meet the requirements of Idaho
Code section 67-5248(a).
                                             V.
                                         CONCLUSION
       We affirm the decision of the district court, save and except for the district court’s
vacation of the Great Rift trim line, which we reverse. We decline to award costs on appeal.
       Justice BURDICK and Justice Pro Tem WALTERS CONCUR.

Justice EISMANN, concurring in the result with respect to Part B.
       I concur in the majority opinion, but concur in the result with respect to Part B.
       The majority states, “The Director then concluded that a trim line was justified in this
case on two bases: (1) to ensure maximum and beneficial use of the State’s water resources and
(2) to account for uncertainty in ESPAM 2.1.” The majority then states, “We find that the
Director had discretion to implement the trim line based on the policy of beneficial use.
Therefore, we need not address whether the trim line was also justified to account for model
uncertainty . . . .” Thus, the majority holds that the distribution of water when there is a shortage

                                                 26
can be based entirely upon the Director’s discretion “to ensure maximum and beneficial use of
the State’s water resources.”
       I do not read the Director’s order as being based upon alternative grounds. Rather, it is
clear that the director based his decision upon the inaccuracy of ESPAM 2.1 combined with the
large number of acres that would be dried up if the software’s prediction was incorrect. Before
addressing why I concur in the result, I will address why I do not concur in Part B.
       A. The majority abandons the constitutional requirement of prior appropriation.
       The majority opinion in Part B abandons the constitutional requirement of first in time,
first in right and states that the Director can apportion water in a manner “to ensure maximum
and beneficial use of the State’s water resources.” “Under the provisions of section 3, art. 15, of
the Constitution of this state, priority of appropriation gives the better right as between those
using water.” Brose v. Bd. of Dirs. of Nampa & Meridian Irr. Dist., 20 Idaho 281, 285, 118 P.
504, 505 (1911).    “This provision of the Constitution has been strictly adhered to in the many
decisions this court has rendered construing the same, and this court has universally recognized
the rule thus announced, that first in time of appropriation gives the first right to the use of
water.” Id.
       The relevant part of Article XV, section 3, states: “The right to divert and appropriate the
unappropriated waters of any natural stream to beneficial uses, shall never be denied, except that
the state may regulate and limit the use thereof for power purposes. Priority of appropriation
shall give the better right as between those using the water . . . .” As we stated in In re
Distribution of Water to Various Water Rights Held By or For Benefit of A & B Irrigation
District, 155 Idaho 640, 315 P.3d 828 (2013), we stated, “The prior appropriation doctrine is
comprised of two bedrock principles—that the first appropriator in time is the first in right and
that water must be placed to a beneficial use.” Id. at 650, 315 P.3d at 838.
       The water rights of Rangen, Inc. (“Rangen”), at issue are surface water rights, which
“shall never be denied” under the Constitution. “However, the Constitution makes no mention of
ground water rights.” Clear Springs Foods, Inc. v. Spackman, 150 Idaho 790, 801, 252 P.3d 71,
82 (2011). Thus, it is Rangen’s water rights that are protected by the Constitution, not the
competing water rights of ground water appropriators. There is no contention that Rangen is not
applying the water it diverts to a beneficial use.

                                                     27
       We have held that a water user can be required to change the water user’s manner of
diversion if it is unreasonable, Van Camp v. Emery, 13 Idaho 202, 89 P. 752 (1907), as did the
Supreme Court in Schodde v. Twin Falls Land & Water Co., 224 U.S. 107 (1912). There is no
contention that Rangen’s manner of diversion is unreasonable.
       The majority stretches these two cases to hold that the Director has authority to distribute
water not based upon priority, but based solely upon the Director’s understanding of “the
maximum and beneficial use of the State’s water resources.” The Director does not have the
discretion to ignore the Constitution, nor does the majority. Under the majority opinion, water
need no longer be distributed according to priority, which means that no one’s water rights are
secure. “Priority in time is an essential part of western water law and to diminish one’s priority
works an undeniable injury to that water right holder.” Jenkins v. State, Dep’t of Water Res., 103
Idaho 384, 388, 647 P.2d 1256, 1260 (1982).
       B. The majority changes the meaning of the words “beneficial use.”
       In order to eliminate the doctrine of prior appropriation, the majority changes the
meaning of the words “beneficial use” so that it becomes a discretionary determination by the
Director comparing the relative financial benefits of the senior appropriator using his decreed
water versus the loss sustained by the junior appropriators.          That is not the meaning of
“beneficial use” as that term is used with respect to water rights.
       We have previously explained that “beneficial use” does not mean the equitable
distribution of water. As we stated in Drake v. Earhart, 2 Idaho 750, 23 P. 541 (1890):
       [“]No distinction is made in those states and territories, by the custom of miners
       or settlers or by the courts, in the rights of the first appropriator from the use made
       of the water, if the use be a beneficial one.” In this case it is said: “The right of
       the first appropriator, exercised within reasonable limits, is respected;” that it “is
       not unrestricted. It must be exercised with reference to the general condition of
       the country, and the necessities of the people.” This language has been seized
       upon as justifying the equitable, if not equal, division of the water among all
       desiring or needing it, regardless of the claim of the prior appropriator. Such a
       construction is not justified, and would make the decision inconsistent with itself,
       as well as with the other decisions of the same court.
Id. at 756, 23 P. at 543 (emphasis added).
       It is clear that “beneficial use” refers to how the appropriator uses the water, not whether
other uses would be more beneficial. When the water is diverted from a watercourse, beneficial
use means how the appropriator uses it after diverting the water. Article XV, section 3, begins,

                                                 28
“The right to divert and appropriate the unappropriated waters of any natural stream to
beneficial uses, shall never be denied . . . .” The diversion came first and then the application of
the water to a beneficial use. As we explained in United States v. Pioneer Irrigation District,
144 Idaho 106, 110, 157 P.3d 600, 604 (2007):
               In Idaho it is “a well-settled rule of public policy that the right to the use
       of the public water of the state can only be claimed where it is applied to a
       beneficial use in the manner required by law.” Under the constitutional method of
       appropriation, appropriation is completed upon application of the water to the
       beneficial use for which the water is appropriated. When following the
       constitutional method, one “must depend upon actual appropriation, that is to say,
       actual diversion and application to beneficial use.” Under the statutory method
       of appropriation, the appropriation is not complete and a license will not issue
       until there is proof of application to beneficial use for the purpose for which it
       was originally intended. I.C. §§ 42–217, 42–219. Under either the constitutional
       or statutory method of appropriation, the appropriator must apply the water to a
       beneficial use in order to have a valid water right in Idaho.
144 Idaho at 110, 157 P.3d at 604 (emphases added).              To reiterate, “Under either the
constitutional or statutory method of appropriation, the appropriator must apply the water to a
beneficial use in order to have a valid water right in Idaho.” Id. (Emphasis added).
       We discussed what constituted “beneficial use” in Clear Springs Foods:
       The right to appropriate water is for “beneficial uses,” not merely for profitable
       businesses. Beneficial use is not defined in the Constitution, nor has it been
       comprehensively defined by statute or by this Court. However, a beneficial use is
       not limited to a use that generates a profit, or even income. For example, the
       Constitution lists using water for “domestic purposes” as a beneficial use. We
       have held that “firefighting” is a beneficial use of water. Likewise, the legislature
       has declared as beneficial uses “drinking water,” “the watering of domestic
       livestock,” using low temperature geothermal resources “primarily for heat
       value,” using instream water “for the protection of fish and wildlife habitat,
       aquatic life, recreation, aesthetic beauty, transportation and navigation values, and
       water quality,” and using water in lakes and water discharging from springs for
       “scenic beauty.”
Clear Springs Foods, 150 Idaho at 811, 252 P.3d at 92 (citations omitted).             All of these
beneficial uses were the manner in which the appropriator used the water appropriated. It was
not comparing the benefit to the senior appropriator and the harm to the junior appropriator from
applying the constitutional provision of priority of appropriation.
       The framers of our Constitution understood that the most beneficial use of water required
distributing water in accordance with the priority of water rights—first in time, first in right. As
this Court stated in Hard v. Boise City Irrigation & Land Co., 9 Idaho 589, 76 P. 331 (1904):
                                                 29
                It is certainly unnecessary for us to suggest that it was the evident intent of
        the framers of the Constitution to so husband the water of the state as to secure
        the most beneficial use thereof; that is, that it should always be so used as to
        benefit the greatest number of inhabitants of the state. They were careful to
        provide who should be entitled to the preference right to the use of the waters
        flowing in our natural streams.
                Nearly every session of our Legislature has attempted to improve upon its
        predecessor by so legislating as to improve the former use of water, and an
        inspection of the various acts plainly shows that the guiding star has always been
        to so legislate as to protect all users of water in the most useful, beneficial way—
        keeping in view the rule existing all over the arid region: “First in time first in
        right.”
Id. at 594, 76 P. at 332 (emphases added). The maximum beneficial use of water requires
certainty as to water rights, not, as the majority holds, the right of the Director to distribute water
according to his discretion. Indeed, the majority does not even give any guidelines as to how the
discretion it grants to the Director is to be exercised.
        There is no contention that Rangen is not applying the water it diverts to a beneficial use
and cannot apply water to the extent of its water right to a beneficial use. Thus, the doctrine of
beneficial use cannot be used to determine the amount of water it is entitled to receive. Whether
a particular appropriator is applying water to a beneficial use is based entirely upon what the
appropriator is doing with the water. What others may do with it has no bearing.
        Rangen’s right to obtain the amount of water that has been decreed cannot be based upon
comparing the harm to junior appropriators and the benefit to Rangen. As we held in Clear
Springs Foods, “A delivery call cannot be denied on the ground that curtailment of junior
appropriators would result in substantial economic harm.” 150 Idaho at 803, 252 P.3d at 84.
        Such a comparison in this case would stack the deck against Rangen. There is no
evidence that the water the junior appropriators would be unable to divert would be wasted. If
we were to institute the balancing test advocated by the majority, we must compare the juniors
against all of those holding senior water rights who are not obtaining all the water to which they
are entitled based upon the juniors’ diversions. Rangen sought to introduce that evidence in the
administrative proceeding, but the Director held it as irrelevant. If the Court is going to engage
in that balancing test under the rubric of “beneficial use,” then the balancing should include all of
the seniors who are not receiving their appropriated water.
        C. The conjunctive management rules cannot alter the Constitution.

                                                  30
       The majority relies upon conjunctive management rules to support its abandonment of the
prior appropriation doctrine. Administrative rules cannot modify the Constitution. The majority
relies upon Conjunctive Management Rule 20.03, which states, “An appropriator is not entitled
to command the entirety of large volumes of water in a surface or ground water source to support
his appropriation contrary to the public policy of reasonable use of water . . . .” That rule must
be construed in a manner that upholds its constitutionality. American Falls Reservoir Dist. No. 2
v. Idaho Dep’t of Water Res., 143 Idaho 862, 869, 154 P.3d 433, 440 (2007). As we stated in
Clear Springs, that can only apply to the means of diversion.
               Conjunctive Management Rule 20.03 states, “An appropriator is not
       entitled to command the entirety of large volumes of water in a surface or ground
       water source to support his appropriation contrary to the public policy of
       reasonable use of water . . . .” That is consistent with our holding in Van Camp.
       The senior appropriator in Van Camp was entitled to his water right; he simply
       had to change his unreasonable means of diversion. As we stated, “Whatever
       amount of water defendant shows himself entitled to for the irrigation of his
       meadows or other lands as a prior right over the plaintiff, the judgment should so
       decree, but beyond that he cannot go under any other pretext or claims for the
       natural condition of the stream.” Id.
Clear Springs Foods, 150 Idaho at 809, 252 P.3d at 90.
       As we also stated in Clear Springs Foods:
                       A delivery call cannot be denied on the ground that
               curtailment of junior appropriators would result in substantial
               economic harm. Such a holding would be contrary to the provision
               in Idaho Code § 42-233a (emphases added), stating:The director,
               upon determination that the ground water supply is insufficient to
               meet the demands of water rights within all or portions of a critical
               ground water area, shall order those water right holders on a time
               priority basis, within the area determined by the director, to cease or
               reduce withdrawal of water until such time as the director
               determines there is sufficient ground water.
       In this case, it would also be contrary to Article XV, § 3, of the Idaho
       Constitution, which states, “Priority of appropriation shall give the better right as
       between those using the water . . . .”
Id. at 803, 252 P.3d at 84.
       D. Following the Constitution is not wasting water.
       “We have long recognized that an appropriator may not waste water, but must permit
others to use the water when the appropriator is not applying it to a beneficial use.” Joyce
Livestock Co. v. United States, 144 Idaho 1, 15, 156 P.3d 502, 516 (2007). However, the policy

                                                31
against waste does not permit a junior appropriator to take water before it would reach the senior
appropriator.
        In Martiny v. Wells, 91 Idaho 215, 419 P.2d 470 (1966), we addressed the issue of
whether an upstream junior appropriator could deprive a senior appropriator of irrigation water
due to significant conveyance losses in spring water reaching the creek from which the senior
diverted water. The creek flowed through a swampy area that was fed by springs on both sides,
and the junior appropriator constructed a ditch between the creek and the springs on one side of
the creek to catch the water. Id. at 216, 419 P.2d at 471. The ditch was the junior’s only
diversion. Id. There was a dispute as to how much water from the springs would actually reach
the creek, and the district court found that “only a portion of the flow of the springs reaches
Spring Creek,” although it did not quantify what that portion was. Id. at 216-17, 419 P.2d at
471-72. However, the court did find that the “best use of the water flowing from the springs and
the swampy area around the [junior’s] ditch is the collection of said water in the [junior’s] ditch
for irrigation of the property served by said ditch.” Id. at 217, 419 P.2d at 472. We reversed the
district court, stating:
                Under the facts involved in this case, the court’s conclusion that the best
        use of the water was the use made of it by defendant, is immaterial and lends no
        support to the judgment. The policy of the law against the waste of irrigation
        water cannot be misconstrued or misapplied in such manner as to permit a junior
        appropriator to take away the water right of a prior appropriator. So long as the
        water from the springs and swamps, flowing in its natural channels, would reach
        Spring Creek in usable quantities, plaintiffs are entitled to enjoin defendant’s
        interference therewith. The fact that some of the water would be lost by
        evaporation or percolation would not afford this defendant any right to divert it.
Id. at 219, 419 P.2d at 474 (emphasis added). As we stated in Martiny, the junior
appropriator cannot take the water as long as the water would reach the senior
appropriator “in usable quanties.” Id.
        We reiterated that holding in Gilbert v. Smith, 97 Idaho 735, 552 P.2d 1220
(1976), wherein we stated:
               As a rule, the law of water rights in this state embodies a policy against the
        waste of irrigation water. Such policy is not to be construed, however, so as to
        permit an upstream junior appropriator to interfere with the water right of a
        downstream senior appropriator so long as the water flowing in its natural
        channels would reach the point of downstream diversion.

                                                 32
Id. at 739, 552 P.2d at 1224 (emphasis added). We added that a junior appropriator could take
the water only if “due to seepage, evaporation, channel absorption or other conditions beyond the
control of the appropriators the water in the stream will not reach the point of the prior
appropriator in sufficient quantity for him to apply it to beneficial use.” Id.
       There is no contention that Rangen is wasting the water it is diverting. The only issue is
whether water being taken by junior appropriators would reach Rangen’s point of diversion in
sufficient quantity for him to apply it to beneficial use.
       E. I concur in the result with respect to Part B of the majority opinion.
       As I stated above, it is clear that the Director based his decision upon the inaccuracy of
ESPAM 2.1 combined with the large number of acres that would be dried up if the software’s
prediction was incorrect.
       The Director found that ESPAM 2.1 is “an imperfect approximation of a complex
physical system,” but it was the best scientific tool currently available for predicting the effects
of groundwater pumping on the discharge at the Rangen model cell. That cell is not simply the
Curren Tunnel from which Rangen obtains water, but the Director found that 63% of the
curtailment benefits accruing to the model cell would accrue to the tunnel. In reaching his
decision, the Director took into consideration the inaccuracy of ESPAM 2.1 in predicting the
water that would flow to the Curren Tunnel if pumping east of the Great Rift were curtailed. The
Director stated:
       There is generally higher predictive uncertainty on the eastern side of the Great
       Rift, however impacts from several pumping locations evaluated on the eastern
       side of the Great Rift had negligible impacts on the spring cell evaluated in the
       Department’s predictive uncertainty analysis. Uncertainty in the model justifies
       use of a trim line.
       We held in Clear Springs Foods that the Director has the discretion to establish a trim
line based upon uncertainty in the computer model. We stated:
                The Director concluded that there was up to a 10% margin of error in the
       groundwater model due to the margin of error in the stream gauges, and he
       decided not to curtail appropriators who were within that margin of error when
       deciding whether they were causing material injury to the Spring Users’ water
       rights. The Director perceived the issue as discretionary, he acted within the outer
       limits of his discretion and consistently with the legal standards applicable to the
       available choices, and he reached his decision through an exercise of reason. The
       district court did not err in upholding the Director’s decision in this regard.
150 Idaho at 817, 252 P.3d at 98.

                                                  33
       In this case, the Director set the trim line at the Great Rift. Model uncertainty is the only
constitutional basis for doing so.

       Justice HORTON CONCURS.

                                                34