1.0 SUMMARY OF STUDY PURPOSE, MODEL SCOPE, AND RELATIONSHIP
TO OTHER STUDIES

This report documents a Hydrologic Model Analysis of the Provo River Basin conducted by the Central Utah Water Conservancy District (CUWCD). The study documented herein resulted in the development of a computer model called PROSIM (the Provo River Simulation Model) that simulates the Provo River system, including the Weber River, Utah Lake, and transbasin diversions into the Provo drainage.

The purpose of this document is to provide an understanding of the following:

1.0 The objectives and purpose for this study and the capabilities of PROSIM
2.0 The public involvement program and the analyses performed in the development of PROSIM
3.0 Model results from the analysis of historical conditions
4.0 Model results from the analysis of proposed demand conditions
5.0 Future plans for the use of PROSIM

Each of these topics is covered in the correspondingly numbered section of this report. Summaries of 1) transbasin diversion rights from the Weber River and 2) the "public involvement" in the preparation of this report are included in the appendices.

1.1 Authorization

The Central Utah Project (CUP) was originally authorized in 1956 as part of the Colorado River Project Storage Act. The entire project consists of five units in the Uinta Basin of the Colorado River and one unit that includes parts of the Colorado Basin and parts of the Great Basin. This last unit, the Bonneville Unit, includes the Provo River system.

The Central Utah Project Completion Act (CUPCA) is a part of PL102-575. CUPCA was signed into law by the President of the United States on October 30, 1992. CUPCA authorizes CUWCD to complete the remaining features of the Central Utah Project. The Completion Act is multi-faceted and includes requirements for CUWCD and/or the Utah Reclamation Mitigation and Conservation Commission (URMCC) to complete several separate features, including six studies of areas of the Provo River drainage and Utah Lake, collectively designated by CUWCD as Provo River/Utah Lake Special Studies.

The CUWCD provided funding for this Hydrologic Model Analysis project under authority of CUPCA, Section 202(a)(5)(A)(i), as part of the Provo River/Utah Lake Study of the Central Utah Project Special Studies Program. The authorizing legislation states,

...the District (is) to conduct with Public Involvement a hydrologic study that includes a hydrologic model analysis of the Provo River with all tributaries, water imports and exports and diversions, an analysis of expected flows and storage under varying water conditions, and a comparison of steady state conditions with proposed demands being placed on the river and affected resources, including historic diversions, decrees, and water rights....

1.2 Study Objectives and Purpose

As decreed by the authorizing legislation, the objectives of this Hydrologic Model Analysis of the Provo River Basin are to develop a comprehensive understanding of the hydrology, water rights, and operation of the Provo River system, and to translate that understanding into an effective planning tool that can be used to perform studies of the operation of the system. Specific objectives were developed for the hydrologic analysis, the water rights analysis, and the computer model itself.

The specific objectives of the hydrologic analyses include developing a consistent, complete database of the natural streamflow, historical diversions, and meteorology of the system. The water rights analysis objectives include identifying, describing, and assigning relative priorities for all water rights, applications, and institutional arrangements. The objectives for the PROSIM model itself include those listed below:
• The inclusion of all critical information gained from the hydrologic and water rights analyses.
• The ability to estimate how the waters of the Provo River are allocated to each major water right holder on the system over a lengthy study period, under a variety of operational conditions.
• The ability to estimate instream flow conditions throughout the system.
• The ability to estimate how much water the major reservoir projects may be able to store and release from storage.
• The ability to examine the effects of changes in operational assumptions upon any of the items listed above.

Because of the complex nature of the Provo River system and the increasing need to make decisions regarding the use of the valuable water resources of the system, it is important to understand the hydrology of the system and to be able to predict the impacts of possible future changes to the system. Changes in the operation or management of one part of the system can have significant impacts upon other areas. Without an overall systematic analysis procedure, it is impossible to predict the flows, water supplies, and storages on the system, or the impacts of potential changes.

The purpose of this study is to develop a more complete understanding of the present and future water resources of the Provo River. This purpose requires the creation of a comprehensive analytical tool. This tool, called an operational simulation model, will allow more effective planning and decision-making concerning proposed new facilities, operational procedures, and policies.

1.3 Scope of Study, Description of Study Area, and Model Capabilities

Within the authorizing legislation, the scope of this study was defined to include "all tributaries, water imports and exports, and diversions" in the Provo River Basin. Because the conditions within and outside of the Provo River Basin affect incoming transbasin diversions, it is necessary to include areas outside of the Provo River within the study area. Thus, the Duchesne River above the Duchesne Tunnel and the Weber River above Gateway were included in the modeled system. Also, because the storage in Utah Lake affects the ability to divert and store water on the Provo River, it is necessary to include Utah Lake in the study area. Transbasin diversions from Strawberry Reservoir to Utah Lake are an important component of the CUP water supply. However, conditions on the Strawberry River do not necessarily directly impact the magnitude of these diversions. Thus the Strawberry - Utah Lake transbasin diversions are part of the Provo River system, but the Strawberry River Basin itself is not included in the study area. The study area for the Hydrologic Model Analysis of the Provo River is described below and shown in Figure 1-1.

1.3.1 Description of the Study Area

The study area for the Hydrologic Model Analysis of the Provo River Basin includes the Provo River Basin, the Weber River Basin above Gateway, and diversions into the Provo from the Duchesne and Strawberry River basins. Most of the study area lies within or between the Wasatch and Uinta mountain ranges. The topography is generally characterized by mountainous terrain, with narrow river valleys. The three significant exceptions to this are flat irrigated agricultural areas of the Heber and Kamas valleys, and the gently sloping areas around Utah Lake. These areas consist of unconsolidated valley-fill and alluvial fan deposits ranging from less than 100 to more than 400 feet thick. The maximum elevations in the study area exceed 10,000 feet. The lowest elevation, where the Provo River enters Utah Lake, is about 4,500 feet.

Precipitation and temperature in the area vary with elevation. The average precipitation in the area ranges from about 12 inches annually near Utah Lake, to about 16 inches annually in the Heber Valley to more than 40 inches annually in the mountains. Most precipitation falls as snow, primarily from October through April. Monthly average maximum temperatures along the eastern shore of Utah Lake range from 37^o F in January to 93^o F in July; monthly average minimum temperature range from 19^o F in January to 60^o F in July. Monthly average maximum temperatures in Heber Valley range from 34^oF in January to 87^oF in July; monthly average minimum temperatures range from 8^oF in January to 48^oF in July. Temperature in the mountains varies widely as a function of both elevation and exposure. Summer maximum temperatures may reach the low-to mid-70's, while winter minimum temperatures ranging several degrees below 0^o F are common.

Streamflow in the study area is derived primarily from mountain snowmelt, although some streams originate in lower elevation springs and seeps along the edges and within the centers of the valleys. The timing and magnitude of flows on the Provo River are significantly altered from their natural pattern because of transbasin diversions into the Provo River from the Duchesne Tunnel and Weber-Provo Canal, irrigation diversions and return flows in the Heber Valley and Utah County, and municipal and industrial diversions out of the basin between Deer Creek Reservoir and the City of Provo. The aforementioned elements, plus the delivery of transbasin diversions from Strawberry Reservoir and the operation of Deer Creek and Jordanelle reservoirs, all significantly alter the flows into and out of Utah Lake, the downstream boundary of the study area.

The study area includes all or part of five major water supply projects constructed by United States Bureau of Reclamation (USBR) or by others. In order of completion these are: the Head of River Reservoirs (HOR) consisting of 15 small lakes at the headwaters of the Provo basin, operated by the Provo Reservoir Water Users Company and others; the Weber River Project (WRP), operated by the Weber River Water Users Association; the Provo River Project (PRP), operated by the Provo River Water Users Association (PRWUA); the Weber Basin Project, operated by the Weber Basin Water Conservancy District; and the Central Utah Project (CUP), operated by CUWCD. WRP includes Echo Reservoir and other facilities. PRP includes Deer Creek Reservoir and the Weber-Provo Diversion Canal. The Weber Basin Project includes Wanship and East Canyon Reservoirs and other facilities. CUP includes Jordanelle Reservoir, the rehabilitated Trial, Washington, and Lost lakes, and other facilities.

1.3.2 Description of the Model

The computer model developed within this study is a prioritized water balance allocation calculator. As shown on the conceptual diagram of Figure 1-2, PROSIM uses a database including information on hydrology, water rights, facilities, and water requirements. The model produces simulated output describing the flows, deliveries, consumptive use, and reservoir storages that would result given the data and assumptions used in simulating the scenario.

The model divides the Provo River system into stream reaches and model nodes shown on Figure 1-1. A more detailed process schematic is shown in Figure 1-3 to aid in describing the model operation. For simplicity, diversions, conveyance paths, reservoirs, and return flows are typically numbered to reference the reach and node where they are located.

For each timestep, PROSIM calculations start with the virgin or natural flow of the river at each node and each diversion point. Modeled processes are simulated in priority order, with the priority being assigned by the model user or based upon basin rank, interpretations of water rights laws, historical practice, or water user desires. As each prioritized process is simulated, three water balance accounts (physical, available, and bypass); are updated at each node in the system. Each of these accounts is added to or deducted from, based on the modeled processes (listed below in 1.3.3). The physical quantity of water represents the actual volume of "wet" water flowing past a given node. The available quantity of water represents the volume of natural water which has not been allocated to a specific user or instream requirement. The quantity of water being bypassed represents a volume of "wet" water that is required to go past the node because of its allocation to a downstream, higher priority use.

Reservoir account balances are similarly updated when the specific process being modeled involves a change in reservoir volume or ownership. Reservoirs are subdivided into one or more reservoir owners, which may be further subdivided into one or more reservoir users. This user and owner accounting allows water to be diverted to storage by a single owner under a single water right or rule. Subsequently the stored water is allocated into individual reservoir user’s accounts, from which the corresponding water users call water when needed. Alternatively, the reservoir could be set up in PROSIM to allow all water users to draw from a common owner pool. Depending upon the rules under which the reservoir operates, a user's storage balance is either carried over to the following year (as in the case of Deer Creek Reservoir) or reverted to the owner for reallocation among its users (as in the case of Jordanelle Reservoir).

Water user diversions and remaining demand are also updated at each timestep, when the process involves diversion of water to a user. A water user may have multiple direct flow water rights, multiple exchange agreements for water allocation, and rights to call on water stored in multiple reservoirs. Each water source or right is assigned a specific priority, and available water is drawn from the sources in order until the user’s entire demand is satisfied.

Model calculations proceed in priority order until each water right, hydrological process, institutional arrangement, operational rule, and user demand has been satisfied. The model timestep is then incremented, and the process begins again.

1.3.3 Modeled Processes

The PROSIM model is a flexible water accounting tool, capable of simulating the allocation of the available water supply of a river system according to user demands, water right priorities, and various sets of special operating rules associated with institutional arrangements. The primary function of the model is to estimate the volume of water that, under a given set of operational rules, can be allocated and diverted to each water user, stored in each reservoir, or retained in the river. PROSIM’s prioritized simulation capabilities include the following:

Water Rights
• Priority-order, direct-flow diversions from the main channel or tributaries
• Equalized allocation during times of shortage (meaning that, during times of shortage, all users owning rights at the same priority share equally, in proportion to their water right diversion rate)
• Diversions to and from reservoir storage
• Allocation of water for non-consumptive uses
• Reservoir releases for minimum instream flow requirements (IFRs)

Institutional Arrangements
• Replacement between upstream diversions and downstream reservoirs
• Upstream storage of water by replacement from downstream reservoirs
• Exchanges between reservoir users in the same or different reservoirs
• Recapture of reservoir releases used to satisfy IFRs
• Rediversion of reservoir releases or natural flows to meet non-consumptive uses
• Transbasin diversions by direct diversion, reservoir replacement, or exchange

The model also currently includes over 50 other detailed water distribution rules.

Hydrological Processes
• Diffuse (throughout reach) inflow and tributary (point) inflows
• Reservoir evaporation, precipitation, and seepage losses and gains
• Conveyance losses and non-agricultural (M&I) losses
• Evaporation/consumptive use calculations (two methods)
• Soil moisture accounting to calculate infiltration and groundwater return flows
• Surface and subsurface return flows with variable targets and delay patterns

Reservoir and Streamflow Operations
• Pre-assigned rule curves (or end-of-month target levels)
• Tracking of demands and diversions for each water user
• Accounting of river flows, diversions, gains, and available water in each reach
• Accounting of water stored in and released from each account in each reservoir
• Joint storage accounts in multiple reservoirs
• Reservoir storage holdover and carryover accounting

Other water rights, institutional arrangements, hydrological processes, and reservoir and streamflow operational rules can be added to the code as necessary to simulate new or proposed operating rules and conditions. Many of the hydrological processes can be adjusted based upon input from auxiliary runoff or groundwater simulation models. PROSIM can also be set-up to read inflow or demand data directly from the output of other models or to produce results that can be read directly by other models.

1.4 Relationship to Other Studies

As stated previously, the Hydrologic Model Analysis of the Provo River Basin was conducted as one part of the completion plan for the Bonneville Unit of the CUP, which was in turn a part of the CUPCA, included in PL102-575. Certain parts of the plan use results from the analysis documented herein, while others are being conducted independently. This Hydrologic Model Analysis relates to and may be used in the completion of the six Provo River/Utah Lake Special Studies. The six studies, and their relationship to the Hydrologic Model Analysis of the Provo River are described in Table 1-1.

This Hydrologic Model Analysis is similar in certain ways, though broader in scope, to previous studies of the Provo River conducted by USBR and USGS to estimate the water supplies associated with the Municipal and Industrial System of the Bonneville Unit. These previous studies include the "Deer Creek Operation Study" and the "Jordanelle Operations Study," included in the USBR's 1988 "Supplement to Definite Plan Report"; and the "Review of Water Demand and Water Utilization Studies," (USGS, 1991).

Table 1-1

Provo River/Utah Lake Special Studies and Relationship to

Hydrologic Model Analysis of the Provo River Basin

Name of Study	Purpose	Relationship to this Study
Wasatch County Water Efficiency Project (WCWEP)	Evaluate and implement irrigation efficiency improvements and acquire Strawberry Basin water rights which will increase instream flows	Uses PROSIM in evaluating environmental impacts on water and other resources
Utah Lake Salinity Control Studies (ULSCS)	Reduce impacts of CUP upon Utah Lake salinity levels	This Hydrologic Model Analysis uses certain Utah Lake data developed by ULSCS.
Strawberry-Provo Conveyance Studies (SPCS)	Evaluate feasibility of direct delivery of Colorado Basin water to the Provo River Basin; analyze hydrology of Provo River.	This Hydrologic Model Analysis was started within the SPCS, but then evolved into a separate study effort using a different period of record due to availability of data.
Increased Project Water Studies	Acquire water rights to augment instream flows on the Lower Provo River	These studies may use PROSIM in evaluating alternatives, environmental impacts and instream flow benefits
Provo River Excess Flow Study	Reduce or mitigate the impacts of Provo River high flows on fisheries and recreation	This study may use PROSIM in evaluating alternatives, impacts, and benefits
Provo River Diversion Dams	Evaluate measures to retain increased instream flows within the Provo River channel below Olmsted	This study may use PROSIM in evaluating alternatives, impacts, and benefits

2.0 CONDUCT OF THE STUDY, DEVELOPMENT OF THE MODEL, AND THE
PUBLIC INVOLVEMENT PROCESS

This Hydrologic Model Analysis of the Provo River Basin was initiated in January 1992, with the development of a conceptual model study. During this phase, a Technical Advisory Committee (TAC) was formed to provide public involvement and technical guidance. The TAC was involved during each of the remaining phases of the project, including analysis of Provo River hydrology and water rights, analysis of Weber River hydrology and water rights, and software development and calibration. Each of these phases is described in the following subsections.

2.1 Conceptual Model Development

The first step in conducting the Hydrologic Model Analysis of the Provo River Basin was the development of a conceptual format for the resultant computer model. This formulation step included the collection of basic data on the physical and institutional setting of the system, the formation of a public involvement program (described in section 2.2), and the development of objectives, limitations, and specifications for the computer software. The conceptual model development phase was concluded with the preparation of a revised draft Technical Memorandum #1 - Conceptual Model Development (CUWCD, 1992a).

2.1.1 Data Collection

The data collection effort was an important step in developing the conceptual model of the system. Relevant, historical data were obtained, reviewed, and processed into a digitized database. This included streamflows, meteorology, land use, irrigation and M&I diversions, reservoir storage(s), and water demands. Related previous studies were obtained and reviewed. Interviews were conducted with technical experts in the field of water rights and hydrologic modeling and with water resources managers from the area.

2.1.2 Development of Objectives, Limitations, and Specifications

As the result of the conceptual model development phase, the following objectives were delineated:
• To develop a better understanding of the Provo River system hydrology and water rights.
• To permit more efficient utilization of water among competing uses and users.
• To examine variables associated with importation of water from the Strawberry River into the Provo River drainage.
• To provide a tool for evaluating potential future changes to the operation and the facilities of the Provo River system.
• To evaluate the potential for changes in existing importation patterns and quantities from the Weber and Duchesne basins in the Provo River.
• To provide water budget information necessary for water quality modeling of Deer Creek and Jordanelle reservoirs.

The objectives delineated for the model itself included the capability to simulate the following:

Provo River physical parameters (flows, channel network, evaporation, etc.)
Deer Creek and Jordanelle reservoirs
Major Provo River and interbasin water rights
Minimum instream flow requirements
Institutional arrangements (exchanges, implementation of water rights, etc.)
Water demands and return flows for each major user
Transbasin diversions
Hydroelectric power generation

The modeled area was limited to the Provo drainage area above the Provo City gage. This was later modified to include Utah Lake and all of the Weber River above Gateway. The model was designed to operate on either a daily or a monthly timestep, with daily water rights distribution capabilities. Other model specifications included development in FORTRAN 77 with structured programming techniques and internal documentation, and operation on an IBM-PC compatible computer.

2.2 Technical Advisory Committee

Many elements of the objectives and capabilities described above were developed as a result of recommendations of the Technical Advisory Committee (TAC). Early in the model formulation process it was recognized that development of a useful, accepted model of the Provo River system would require the development not only of an accurate understanding of the system, but also a significant measure of consensus within the water resources community. In addition to generating consensus, the TAC also served the role of public involvement by providing a means of communicating with the individuals most knowledgeable about the issues of concern in the Provo River Basin. The TAC was involved throughout the Hydrologic Model Analysis of the Provo River Basin project. They met the project’s need for public involvement and provided valuable input, guidance, and expertise.

The Technical Advisory Committee included representatives of the following agencies and groups:

Utah Division of Water Resources
Utah Division of Water Rights
Provo River Water Users Association
Lower Provo Water Users
Wasatch County
Weber River Water Users Association
Weber Basin Water Conservancy District
Utah Outdoor Interests Coordinating Council
Stonefly Society
Salt Lake County Water Conservancy District
Provo City
Orem City
Central Utah Water Conservancy District
United States Bureau of Reclamation

Six TAC meetings were held to consider the following topics:

Meeting 1: The proposed Provo River Basin Hydrologic Model Analysis Project
Meeting 2: The conceptual model and draft Technical Memorandum #1
Meeting 3: The Provo hydrologic and water rights analyses; draft Technical Memoranda #2 and #3
Meeting 4: The Weber River modeling approach and draft Technical Memorandum #4
Meeting 5: The Weber River water rights analysis and draft Technical Memorandum #6
Meeting 6: The Weber River hydrologic analysis (draft Technical Memorandum #5) and PROSIM historical calibration

2.3 Provo River Hydrologic Analysis

The goal of the hydrologic analysis of the Provo River drainage was to develop a consistent, complete database of meteorology, water use, and stream flow throughout the Basin for use by the PROSIM model. This task included the collection and checking of data, and the extension and use of those data to represent conditions in the study area for the period 1950 through 1989.

2.3.1 Meteorological Analysis

PROSIM requires representative precipitation and temperature data for each agricultural water user. Precipitation and evaporation data are required for each modeled reservoir. A single set of precipitation and temperature data were developed from the Heber City gages for modeling consumptive use on irrigated land areas above Deer Creek Reservoir. For areas downstream of Deer Creek, the Utah Lake at Lehi precipitation record was used.

For reservoir accounting at Deer Creek and Jordanelle reservoirs, the Deer Creek precipitation record was used. Lake evaporation data were developed from the Morton equation for Utah Lake evaporation, with an 86 percent coefficient applied for Jordanelle and Deer Creek. The Utah Lake data are documented in the Draft Preliminary Planning Report - Utah Lake Salinity Control Studies (CUWCD, 1992b).

2.3.2 Water Use Data

River diversion and agricultural water use data were used in calculating natural flows, a critical component of the PROSIM hydrological database. The available historic data consisted of River Commissioner’s records for each of the major diversion points on the Provo River. Data for the years 1950 through 1989 were available from the Utah Department of Natural Resources. Data previous to 1950 are only available in unprocessed form in the River Commissioner’s annual reports.

Significant checking, processing, and adjustment were required to make the diversion records complete and consistent. This was largely because the accuracy of flow measuring devices is low, and because the data were not intended for use in a comprehensive hydrologic analysis of the system. However, these data were the best available information for estimating historic withdrawals from the river, and historic withdrawals were required to estimate the natural flow of the river. The recorded data were adjusted where obvious inconsistencies were noticed, or where incompatibilities existed with respect to the other water balance elements. However, the errors in the diversion estimates are expected to be significant at times, and it is understood that the magnitude of these errors may prevent accurate estimation of return flow timing and volume.

2.3.3 Streamflow Data

Historical streamflow data were required for each model node in the basin, and for each significant tributary. However, measured streamflow data were only available at selected points on the river, and in most cases, only for portions of the study period. Streamflow correlations and water balance calculations were used extensively to estimate missing streamflows and to develop flows at ungaged locations. Prior to correlating with historic streamflow data, measured flows were naturalized by adding back in the historical diversions and removing the effects of transbasin inflows and reservoir storages and releases. The following methods were used, depending upon the information available:

1. If available gaged data included man-made alterations, natural flow was computed by removing those man-made influences.

2. If the historical, natural gaged record was incomplete, the data were extended by correlating with natural flow data in a long-record basin.

3. If the available altered record was incomplete, natural flows were computed from the available record, then correlated and extended.

4. If gaged data were not available, streamflows were estimated by correlating flow with physiographic characteristics, or by calculating a water balance using upstream and downstream gage records.

Twenty-nine separate sets of natural flow data were developed for mainstream and tributary gage sites within the Provo River Basin using the above methods. Flow data for four additional gage sites were developed from other data sources and studies.

Water balances were subsequently computed at each node to verify the accuracy of the extended and calculated flow data. The water balance adjustments were minor, and showed that the developed streamflows agreed with the recorded streamflow data within the accuracy of the gages and diversion measurements themselves.

Following the development of all of the hydrologic data, the data were loaded into the PROSIM model, and PROSIM was used to simulate the historical flow that would have resulted, had conditions been exactly as predicted by the data. A comparison of these simulated historical flows with recorded flows allows the accuracy of the data to be estimated. These PROSIM results were then used to adjust selected data sets to more accurately simulate historical conditions.

In the adjustment process, measured flows were assumed to be accurate, while return flow delay patterns, local inflows between gage locations, and diversion data were modified sequentially until the simulated flows matched the measured flows.

After adjustment, PROSIM’s hydrologic database was able to accurately replicate historically recorded Provo River streamflows. The combination of water balance factors - inflows, diversions, and return flows - are only as accurate as the streamgage measurements themselves. The balanced hydrologic database should give useful, predictive results. Additional documentation of the hydrologic analysis is presented in draft Technical Memorandum #2 - Hydrologic Analysis (CUWCD, 1993a).

2.4 Provo River Water Rights Analysis

The purpose of the water rights analysis of the Provo River drainage was to develop a complete, prioritized database of the significant water rights and institutional arrangements that affect the allocation of water throughout the Basin. A second purpose was to translate this database into a form usable by the PROSIM model. The analysis process included collecting available information on specific water rights and institutional arrangements, discussing these rights and arrangements with individuals knowledgeable and concerned about Provo River water rights, and analyzing and simplifying this information into formats that would be usable by the model code.

2.4.1 Collection of Water Rights Data

Water rights data were collected from the Utah State water rights database; the Provo, Weber, and Duchesne river commissioners; the USBR; the Provo River Decree; and major water users. The State database is a computerized index of all water rights in the State. Searches were conducted of this database by source (Provo River), name of owners, and location. The result of these searches was combined into a master water rights file for further analysis.

Meetings were conducted with the Weber River Commissioner and the Provo River Commissioner and Deputy Commissioner. Telephone conversations were conducted with the Duchesne River Commissioner. Schedules and tables of deliveries and water rights were reviewed, and information about the operation of the rivers was obtained.

A listing of water rights held in the name of the USBR was obtained from USBR staff. Additionally, the following information from the Draft Supplement to the Bonneville Unit Definite Plan Report (USBR, 1988) was reviewed and discussed.
• Weber River Divertible Flow Study
• Provo River Project Operations Study
• Jordanelle Reservoir Operation Study
• Upper Provo River Lakes Stabilization Study

The Provo River Decree (also known as the Morse Decree (1921)) was reviewed and digitized to allow computer searches by name, flow, or location. A number of major rights did not include diversion points or location of use. By comparing the State database, the Decree, and the lists obtained from the Deputy River Commissioner, all significant rights were identified by location and flow.

Meetings were held with representatives of the following major water users:
• Orem City
• Provo City
• Provo Reservoir Water Users Company
• Salt Lake County Water Conservancy District
• Metropolitan Water District of Salt Lake City
• Provo River Water Users Association
• Central Utah Water Conservancy District
• United States Bureau of Reclamation

These users provided information about water ownership, as well as projections of future water usage.

2.4.2 Analysis of Water Rights

The accumulated water rights information was analyzed to determine which significant rights would be modeled individually by PROSIM and to identify other valid rights that could be lumped together in the model. Significant rights included all those belonging to canal companies and public entities. An attempt was made to account for or lump together all rights specifically identified in the Provo River Decree, regardless of the size of flow. The collection phase identified 875 water rights in the system. These were aggregated into 119 modeled rights, by combining smaller rights diverting at a single location or canal. This combination of water rights mirrors the way water is actually allocated by the Provo River Commissioner.

To facilitate the analysis of water rights, and the review of the water rights information by water users, water rights abstracts were developed for the following six major water users on the Provo River: USBR, Provo City, Provo Reservoir Water Users Company, Wasatch Division canal companies, Provo Division, and Orem City. Abstracts prepared for these users were important in identifying the completeness of the data and comparing water right numbers with Provo River Decree classes and paragraphs. USBR's abstract was important because USBR holds the water rights for the Weber River Project, the Provo River Project, and the Central Utah Project.

Each water right was assigned a relative ranking associated with its priority for diversion. A low rank corresponds to high or early priority, while a high rank corresponds to low or late priority. PROSIM allocates water to lower numbered rankings prior to allocating water to higher numbered rankings. In times of water shortage, equivalent rankings share in the allocation of available water in proportion to the relative diversion rate of their right. The rankings were developed in accordance with paragraph 121 of the Decree.

2.4.3 Analysis of Institutional Arrangements

Institutional arrangements are contracts, operating agreements, and delivery or allocation practices that may not strictly be water rights, but do have direct impacts upon water rights and how they are administered. Institutional arrangements describe the rules and agreements used to operate the Provo River system or a component of the system, and, in certain respects, are more important than the water rights themselves. Accurate modeling of institutional arrangements permits the model to simulate how the system truly operates. Modifying how these arrangements are modeled helps to demonstrate the importance of each arrangement, and the critical nature of its interpretation or application in the prototype. Twelve of the most significant issues, specifically defined by institutional arrangements are listed below.

• Provo River Class Rights
• Utah Lake Distribution Plan
• Deer Creek Reservoir/Jordanelle Reservoir Operating Agreement
• Diversion of System Storage
• Conversion of System Storage to Priority Storage
• Instream Flow Requirements
• River Losses
• Olmsted Facility Priority of Use
• Deer Creek Reservoir Accounting
• Jordanelle Reservoir Accounting
• Utah Lake Accounting
• Utah Lake Water Rights

Some of these arrangements are quite involved. The Utah Lake Distribution Plan, for example, affects each of the others and controls how most of the water on the River is stored, owned, and used. The Deer Creek/Jordanelle Operating Agreement controls the storage, the allocation of storage, and exchanges of water between the two reservoirs. Although this agreement was finalized in late 1994, after most of the programming was completed, the provisions of the agreement, to the extent they are applicable to a monthly timestep, have been included in the model. Each of the arrangements was carefully analyzed prior to inclusion in PROSIM. A complete description of these arrangements, and of the overall Provo River water rights analysis, is presented in draft Technical Memorandum #3 Water Rights Analysis (CUWCD, 1993b).

2.5 Weber River Analysis

The purpose of the analysis of the Weber River drainage was to develop an understanding of how the hydrology and water rights of the Weber River affect the operation of the Provo River. Transbasin diversions from the Weber River provide a significant portion of the water supply of the Provo River Water Users Association (PRWUA) and the Provo Reservoir Water Users Company (PRWUC). Because of the effect of these users’ operations on other Provo River water users, detailed analysis and modeling of the Weber River water rights that affect the Weber-Provo Diversion Canal was necessary. Hydrologic analysis of the Weber River was necessary because Weber River hydrology affects the availability of water to PRWUC and PRWUA (CUWCD, 1993c).

2.5.1 Weber River Hydrologic Analysis

The methods applied in the analysis of Weber River water rights and hydrology were very similar to those used on the Provo River, with one significant exception. Because the objective of the Weber River portion of the study was limited to the accurate modeling of transbasin diversions to the Provo River, only those portions of the Weber River that impact transbasin diversions were analyzed. Therefore, diversions and water rights of users lower in priority than PRWUA and PRWUC were not analyzed, and the Weber River study area was limited to lands upstream of Gateway. Water rights below Gateway with higher priority than PRWUC and PRWUA were accounted for as a lumped high priority right.

With this in mind, the hydrologic analysis included the collection, review, and analysis of available facility, meteorological, streamflow, reservoir storage, and diversion data for the Weber River above Gateway. Consistent, reliable records were developed of each of the types of data required to run PROSIM. As for the Provo hydrologic analysis, natural or virgin inflows were developed by backing-out the effects of diversions and reservoir storage. Complete record flows were then developed by correlation with the flows recorded at the Weber River near Oakley gage. Final local inflow and tributary flow data were produced using water balance calculations and historical flow measurements to adjust the inflows. A more complete description of the Weber River hydrologic analysis conducted to develop PROSIM is presented in draft Technical Memorandum #5 - Weber River Hydrologic Analysis (CUWCD, 1993d).

2.5.2 Weber River Water Rights Analysis

The collection and analysis of Weber River water rights data proceeded in much the same fashion as the Provo River water rights analysis, with the exception that rights lower in priority than those associated with Provo River transbasin rights were not analyzed. Weber River water rights and institutional arrangements with a priority date prior to 1939 were included. This cut-off date was selected to simplify the analysis, and because rights and arrangements after 1939 should not affect diversions through the Weber-Provo Canal. The Weber-Provo diversion rights A9568, A9580, A12141, and A9569 are exercised as direct flow rights and through exchanges with Echo Reservoir. Contracts associated with these diversion rights include the 1926 contract between USBR and the Weber River Water Users Association, and the 1938 Power Contract.

Information was collected from four different sources. The Weber River Decree (Civil 7487, dated 1937) and its associated Findings of Fact, Conclusions of Law were reviewed. Portions of the tabulated surface rights upstream of Gateway were digitized for search. The Utah State Division of Water Rights database was searched by user name and by diversion location. Meetings were held with Weber River water users, and Weber River Commissioner’s Reports were reviewed.

Weber River water rights were analyzed to determine the rights that would be modeled individually, and the rights that could be lumped or included in the natural flow hydrology of the basin. The Weber River Decree and the River Commissioner’s Reports were used to determine which rights to model. A total of 678 water rights were identified as being without diversion data in the Commissioner’s Reports. These rights, which represent 27,600 acres, were included in the natural hydrology of the basin. Pre-1939 decreed rights downstream of Gateway were identified and modeled as a lumped demand on the model at the Gateway node. More than 850 identified rights with priorities junior to the Weber-Provo diversion rights were not modeled.

The water rights and arrangements that allow diversions from the Weber River to the Provo River were analyzed extensively. The applications and associated changes, agreements, and previous interpretations were obtained and examined. Representatives of the parties to the agreements, and the staff of the State Division of Water Rights were questioned concerning their interpretations of the water rights, and the actual practices followed in implementing them. A brief summary of how PROSIM implements the primary Weber-Provo transbasin diversion rights is presented in a table in Appendix A. A more complete discussion of these and other Weber River water rights, and of how these are simulated by PROSIM is contained in draft Technical Memorandum #6 - Weber River Water Rights Analysis (CUWCD, 1993e).

2.6 Model Coding, Documentation and Calibration

The source code for PROSIM was developed based upon guidance received from the Technical Advisory Committee and the Conceptual Model Study, and the information gained from the hydrologic and water rights analyses of the Provo and Weber rivers. This section describes the development and documentation of the source code and the calibration of the model using historical data.

2.6.1 Model Coding

The source code itself is written in structured FORTRAN. The more than 14,000 lines of code are organized into 175 subroutines, which are grouped into 23 files. The subsidiary program that generates virgin flows for input into PROSIM consists of 39 additional subroutines, grouped into 11 files. The groupings are by function and are intended to facilitate modifying and debugging the code. The basic operation of the source code is displayed in Figure 2-1.

A separate graphical user interface (GUI) was developed for PROSIM. The graphical interface permits the user to edit input data, review output results, produce tabular summaries, graphically review results, and perform simulation runs. The graphical interface is written in Visual Basic for operation within the Microsoft Windows environment. A sample screen from the graphical interface is shown in Figure 2-2.

2.6.2 Model Documentation

A draft PROSIM User’s Manual was prepared (CUWCD, 1993g) to assist CUWCD staff in:

1. Running the executable version of the model by specifying the required input and output files and their formats,

2. Better understanding and using the model results by outlining PROSIM capabilities, limitations, and the design of the output files,

3. Making minor changes in the model input files to simulate different "what if" scenarios.

The manual includes a description of how to set up the model to operate on a new computer system, and how to create a new or revised simulation scenario. The manual also describes model input files and output tables. The source code structure is outlined and presented in a series of flowcharts.

The User’s Manual documents the variable names and common error messages. The document also includes a quick guide to running the model, with a description of hardware and software requirements, installation procedures, and model terminology. Operation of the graphical interface is explained as well.

2.6.3 Model Calibration

PROSIM was calibrated by simulating historical conditions on the Provo River system. The objective of the calibration was to make minor adjustments to the input data as necessary, and to verify the accuracy of the model for use in simulating future conditions on the river. The calibration process involved the following steps:
• Select separate calibration and verification periods for the model.
• Develop model input data.
• Perform initial simulations for the calibration period and compare with historical data.
• Adjust model input data for the entire period of hydrological record.
• Repeat until good agreement is achieved between model output and actual observed conditions during the calibration period.
• Run calibrated model for the verification period and compare with actual conditions to evaluate the calibration accuracy.

Separate calibration (1960 to 1970) and verification (1971-1984) periods were selected to calibrate the model and to demonstrate the accuracy of the model calibration. These periods were selected because reasonably accurate diversion and reservoir storage data were available, and because they did not include any major operational or facility changes. The results of the calibration process were related to the accuracy of simulated flows, reservoir contents, and river diversions. Each of these is discussed below.

Simulated Provo River flows were compared with historically recorded flows at the streamgages at Woodland, at Hailstone, above Deer Creek, below Deer Creek, and at Provo City. All simulated average annual flows were within one or two percent of the recorded values. Individual annual flows were within four percent at Woodland, Hailstone, and above Deer Creek. Annual flows were within five to seven percent below Deer Creek. Simulated annual flows at Provo City were within ten percent in 22 of the 25 years evaluated. Simulated monthly average flows were within one to four percent of historical values at all gages except Provo City, where three out of twelve months had variations of up to 30 percent.

Simulated reservoir contents results compared favorably with historical results until the mid-1980’s, when unmodeled reservoir operational changes occurred, including the Deer Creek/Strawberry Exchange, operations to mitigate high flows, and agricultural water conversions. During the 1960 to 1984 period the PROSIM Deer Creek Reservoir results were within 10 percent of the historical values, 83 percent of the time. At Utah Lake, simulated results were within 10 percent in 96 percent of all months modeled.

PROSIM-simulated river diversions closely match the historical diversions. On the Provo River above Deer Creek Reservoir, simulated diversions are within one percent of historical values. On the lower river, PROSIM results are within five percent of the historic values more than 93 percent of the time.

The conclusions of the calibration and verification process are that simulated results are in close agreement with recorded values. The PROSIM model and its hydrology and operations logic are judged to be adequately calibrated and ready for use in simulating future Provo River operational scenarios. Additional detail concerning the calibration process is presented in the draft Technical Memorandum - Preliminary Simulation Results, Historical Calibration Scenario (CUWCD, 1994a). The simulated historical results are documented in the following section.

3.0 ANALYSIS OF FLOWS, STORAGES, AND WATER SUPPLIES UNDER HISTORIC CONDITIONS

This section presents a brief summary of the results of the historical modeling scenario simulated with PROSIM. A more complete presentation of these results is included in the draft Technical Memorandum - Preliminary Simulation Results, Historical Calibration Scenario (CUWCD, 1994a). The data and assumptions used in modeling the historical condition, and selected streamflow, reservoir content, and river diversion results are presented below.

3.1 Description of Historical Modeling Data and Assumptions

The hydrological, river demands, and meteorological data used in the historical scenario were developed as part of the Provo River and Weber River hydrologic analyses, documented in CUWCD 1993a and CUWCD 1993d. Diversion/demands data reported by the River Commissioner’s reports were subdivided in some cases, where only lumped user results were available. Historical diversions were assumed to equal historical demands. Demands that were not satisfied by direct flow rights were satisfied by reservoir calls, if the user had reservoir storage available.

Water rights and operational rules data and assumptions were developed as part of the Provo and Weber river water rights analysis, as documented in draft Technical Memorandum #3 and draft Technical Memorandum #6, CUWCD 1993b and CUWCD 1993e. Water rights for most Provo River direct flow water users were increased significantly during the calibration process, to eliminate simulation discrepancies where water users apparently diverted more water than their entitlements.

Reservoir operational rules (especially those pertaining to Deer Creek Reservoir) were modeled as accurately as possible given the complex and varying criteria used during the 30-year simulation period. Deer Creek Reservoir (PRWUA) ownership accounts and calls, and holdover and carryover rules were simulated. Historical data were used in simulating Weber-Provo, Duchesne, and Strawberry transbasin diversions. A maximum monthly limit was developed from historical data and used to control the storage of Provo River water in Deer Creek Reservoir. Excess Weber-Provo diversions, above those needed to fill Deer Creek Reservoir, were diverted to Utah Lake for exchange back to Deer Creek in subsequent years. The following historical PRWUA operations were not specifically simulated: extra allotment releases, power generation releases.

3.2 Streamflow Results

PROSIM produced simulated historical monthly streamflow results at each model node for the period 1960 through 1989. PROSIM-produced historical flows are compared graphically with recorded flows in Figures 3-1 through 3-3. Simulated results agreed well with recorded flows at all streamgages.

3.3 Reservoir Contents Results

PROSIM simulated historical monthly reservoir volume results at the Head of River Reservoirs, Deer Creek Reservoir, and Utah Lake. Simulated storage results were also produced for individual owners and users in all three reservoirs. PROSIM results are graphically compared with historical reservoir volume data in Figures 3-4 and 3-5. Simulated reservoir volume results agreed very well with recorded historical data.

3.4 Water Supply Results

PROSIM produced simulated historical diversions for 108 ditches and 108 separate water users. Combined diversions for all individual and lumped users are compared with the historical demands/diversions in Figure 3-6. The simulated diversions agreed well with the historical diversions data that were used as the user demands.

3.5 Conclusions Regarding the Historical Simulation

The PROSIM simulation of the historical scenario leads to two important conclusions about the use of the model. First (and most importantly), this simulation has demonstrated that PROSIM is capable of accurately replicating the processes that influence flows, reservoir storages, and diversions on the Provo River system. Based on this analysis, the basic hydrology and the water rights and institutional arrangement modeling appears thorough and accurate. These results indicate that simulation of future scenarios using this model should yield results that can be used for future water resources planning and operational decision-making purposes.

The second conclusion from the historical modeling is that the accuracy and predictive value of PROSIM results may be decreased if either of the following two conditions exist:

1. Operating policies are used on the Provo River system but are not included in the institutional arrangements modeled by PROSIM.

2. Operational decisions are made on the river system based upon hydrological or institutional variables that are not included within PROSIM.

In the first case, if an operating rule is not included in PROSIM, the model cannot replicate the influences of that rule. The second case is somewhat more complicated. If a reservoir operator follows a certain policy at most times, but changes his operations during certain critical conditions, PROSIM will not accurately simulate those conditions unless the alternate operating policy is included in the model. Also, the decision variable that triggers the switch from one policy to another must be included in PROSIM. Frequently the critical condition trigger may include runoff or demand forecasts which are not currently included in PROSIM.

Future simulations are ordinarily made assuming constant operating policies, in order to test those policies. Where operations depend upon changing operational policies, or data outside of the model, PROSIM will not be capable of accurately simulating those operations until those changes and outside data are included. PROSIM was specifically designed to be flexible. Therefore, adding new capabilities or parameters is generally quite straight-forward.

4.0 ANALYSIS OF FLOWS, STORAGES, AND WATER SUPPLIES UNDER
PROPOSED DEMANDS SCENARIO

PL102-575 directs the District to perform hydrologic analysis of the Provo River system under "proposed project demands." This section describes the methods used to analyze the system under proposed demands and briefly presents the results of that analysis in terms of streamflows, reservoir levels, and water supplies throughout the system.

4.1 Description of Modeling Data and Assumptions

The Provo River system was analyzed under proposed project demands using PROSIM. Two separate types of modeling conditions were developed to represent the Proposed Demands Scenario. These modeling conditions are the hydrological setting and the operational setting. Because the modeling conditions and assumptions directly affect the simulation results, the scenario setting must be fully understood in order to understand the results. The hydrological and operational settings are described briefly below.

4.1.1 Hydrological Setting

The hydrological setting for the Proposed Demands Scenario includes all of the natural inflows, meteorology, land use, and return flow responses developed during the hydrologic analysis studies described in Sections 2.3 and 2.5. The hydrological data from the period 1950 through 1989 is used, along with future demands, operating rules, and facilities, to represent future conditions on the Provo River system. The only change to the hydrological setting involved adjustment of the return flow delay patterns associated with applied water in the Heber Valley.

The Heber Valley return flow delays were adjusted as part of the environmental analysis conducted for the Wasatch County Water Efficiency Project (WCWEP), another part of the CUPCA studies. Precise tracking of groundwater levels and the impacts associated with irrigation changes was required for WCWEP. The USGS's finite-difference groundwater model MODFLOW (USGS, 1988) was applied to the Heber Valley. The Heber Valley return flow functions in PROSIM were calibrated to be consistent with MODFLOW output of return flow delay rates, volumes, and patterns. Additional discussion of this recalibration is provided in Thurin and White, 1995.

4.1.2 Operational Setting

The operational setting used in modeling the Proposed Demands Scenario is complex. Only with a reliable computerized representation of the operational setting of the Provo River system is it possible to define and evaluate each of the operational parameters that affect the system. The primary operational parameters or assumptions used to define this scenario are divided into three classifications: demands, system storage rules, and reservoir operations. Each of these is described below. As was the case for the Historical Scenario described in Section 3.1.3.1, the Proposed Demands Scenario used the direct flow water rights information developed in the Provo River water rights analysis study and in the Weber River water rights analysis study, as documented in CUWCD, 1993b and CUWCD, 1993e.

4.1.3 Demands

The specific demands data developed to simulate the operation of the Provo River system under this scenario were designed to represent anticipated future, steady-state, full-demand conditions. Municipal and industrial withdrawals were set at their maximum levels under current water rights and reservoir ownership. Irrigation demands were not adjusted from their historic levels, even though development has significantly decreased the acreage of lands being irrigated, and this trend is likely to continue in the future. Irrigation diversions in excess of water rights were not permitted because this practice is expected to terminate in the future as full M&I diversions begin.

Specific demands assumptions for the Proposed Demands Scenario are listed in Table 4-1.

Table 4-1

Proposed Demands Scenario

Demands Assumptions

CUP demands are similar to the volume of demand satisfied in USBR operations studies and average 107,500 acre-feet per year.

PRP demands are set at 100,000 acre-feet per year.

Utah Lake demands are equal to historical releases, limited to 302,000 acre-feet, and reduced by the estimated historical yield of CUWCD’s Utah Lake water right purchases.

Weber River below Gateway demands are set at 21,000 acre-feet per month during the irrigation season.

Other demands are based on historical diversions, modified to account for the above Jordanelle and Deer Creek reservoir demands.

4.1.4 System Storage Rules

System Storage is a water storage concept developed as part of the Utah Lake Distribution Plan (DWR, 1994). System Storage consists of sufficient water (585,000 acre feet maximum) stored in and above Utah Lake, to satisfy the storage rights of Utah Lake water users. (Utah Lake storage rights are generally senior to those of the upstream reservoirs with the exception of storage of the direct flow waters that were applied historically to the lands inundated by Deer Creek Reservoir.) Thus, it represents all water in storage that could conceivably be called upon by the Utah Lake water users. System storage may be converted to priority storage (for exclusive use) by upstream reservoir owners once the total system storage exceeds the "conversion line" shown in Figure 4-1. The PROSIM conversion line is less than the State Engineer's conversion line because the Utah Lake water rights owned by CUWCD have been deducted.

System Storage in one reservoir may be exchanged for priority storage owned by PRP or CUP in Utah Lake at any time. In PROSIM, System Storage in Jordanelle and Deer Creek reservoirs is identified and reserved for either PRP or CUP at the time it is stored. The following explanation details how PROSIM simulates the accounting of System Storage so that it is stored for the exclusive use of either PRP or CUP.

PROSIM simulates the storage of System Storage above Utah Lake by allocating the volume of water stored to either the Provo River Project (PRP/SS) or the Central Utah Project (CUP/SS), depending upon which owner stores the water. Once stored, the System Storage cannot be converted to priority storage by an entity other than the one storing it, unless it is subsequently exchanged. The System Storage is still subject to call by Utah Lake, but it is dedicated to conversion by the storing owner.

Conversion of System Storage occurs according to priority of water rights, with PRP converting surplus System Storage before CUP, and exchanging PRP Utah Lake storage before CUP exchanges its Strawberry Reservoir water in Utah Lake. In the current simulation of the Proposed Demands Scenario, all System Storage held in Deer Creek and Jordanelle reservoirs is converted to priority storage each year.

Because it is critical to the water supply of the CUP, an emphasis has been placed on the storage of "Olmsted power water." The Olmsted power rights permit the storage of surplus Provo River flows by CUP and PRP. But due to the Utah Lake Distribution Plan, it is not necessarily clear at the time water is available for storage, whether it is actually surplus to the needs of the Utah Lake water users. Therefore the Olmsted power water is stored as System Storage, and subsequently converted, exchanged, or released to calls by Utah Lake.

Significant System Storage assumptions used in modeling the Proposed Demands Scenario are listed in Table 4-2.

Table 4-2

Proposed Demands Scenario

System Storage Assumptions

Utah Lake Distribution Plan is assumed to be in effect.

Olmsted power right allows CUP to store Provo River flows less than 429 cfs as CUP system storage.

PRP stores 5,000 acre-feet per year of Provo River water as PRP system storage. (PRP is entitled to an average of 5000 AF/yr over a 10-year period with an annual maximum of 10,000 AF.)

Storage of Provo River water in Jordanelle and Deer Creek is limited by calls from Utah Lake when Utah Lake primary storage falls below 125,000 acre-feet.

System Storage conversion line is reduced by CUWCD’s Utah Lake water right purchases, which are left in Utah lake.

System Storage conversion is permitted every month. Strawberry/ Jordanelle exchange is permitted in June - October.

4.1.5 River, Reservoir, and Project Operations

A large number of Provo River system operations are modeled in the PROSIM simulation of the Proposed Demands Scenario. These include such operations as direct flow water rights diversions; individual owner and user reservoir accounting, calling, and exchange procedures; and CUP and PRP operating rules. The details of these and other operations, and how they are simplified and simulated in PROSIM, are documented in the draft Technical Memorandum #3-Provo River Water Rights Analysis and draft Technical Memorandum #6-Weber River Water Rights Analysis, CUWCD, 1993b, and 1993e. The individual assumptions will not be repeated here, except in the abbreviated list presented in Table 4-3.

Table 4-3

Proposed Demands Scenario

River, Reservoir, and Project Operations Assumptions

Instream flow requirements are in place above Hailstone, below Jordanelle, below Deer Creek, and in the winter below Olmsted. When possible, reservoir releases to meet IFRs are recaptured as priority storage in a downstream reservoir.

CUP recaptures 5,140 acre-feet of return flow from CUP agricultural deliveries to Heber Valley in Deer Creek Reservoir.

PRP recaptures 9,000 acre-feet of return flow every year from foreign water delivered to Utah County in Utah Lake. (PRP may recapture return flows from the delivery of Weber and Duchesne imports under Water Right 55-262.)

Head of River Reservoirs are stabilized with an active storage of 5,172 acre-feet. HOR storage capacity of 8,842 acre-feet is transferred to Jordanelle.

The monthly volume of releases from Strawberry Reservoir to Utah Lake (for exchange to Jordanelle) is set to maximize CUP yield in critical years. The annual volumes range from 12,000 to 103,000 acre-feet, and average 29,000 acre-feet.

Loss rate of 4% is applied to deliveries from Jordanelle Reservoir.

Jacob Welby Exchange is in place between SLCWCD and CUP.

CUP/PRP exchanges are in place to limit storage of PRP water in Jordanelle and CUP water in Deer Creek. The PRP/CUP exchanges identified in the DC/JOA control the transfer of water between the two reservoirs. PRP water is stored in Jordanelle on a temporary basis as per the DC/JOA to facilitate these exchanges.

Flood control operations, which may limit spring storage levels in Jordanelle, are not modeled.

Wasatch County Water Efficiency Project is not modeled.

4.2 Streamflow Results

Simulated streamflow results under the Proposed Demands Scenario appear reasonable and consistent with expectations. Key results are tabulated below.

Table 4-4

Key Simulated Streamflow Results in cfs

Proposed Demands Scenario

Location	Minimum Flow	Average Flow	Maximum Flow	Comments
Hailstone Gage	14	321	2,682
Jordanelle Outflow	125	342	2,373	IFR = 125 cfs
Inflow to Deer Creek	144	371	2,211
Deer Creek Outflow	108	450	2,476	IFR = 100 cfs
Below Olmsted	5	126	1,897	Winter IFR = 25 cfs
Provo City Gage	0	118	2,112	Winter IFR = 25 cfs

PROSIM-produced 40-year hydrographs from the Proposed Demands Scenario are presented in Figures 4-2 through 4-4.

4.3 Reservoir Contents Results

Simulated reservoir contents results under the Proposed Demands Scenario were developed for the Head of River, Jordanelle, Deer Creek, Echo, East Canyon reservoirs, and Utah Lake. Key results are tabulated below.

Table 4-5

Key Simulated Reservoir Storage Results in Acre-Feet

Proposed Demands Scenario

Reservoir	Minimum Storage	Average Storage	Maximum Storage	Inactive Storage
Head of River (lumped)	11,400	13,100	15,000	9,960
Jordanelle	37,500	239,700	314,000	3,000
Deer Creek	20,400	116,100	152,400	3,000
Utah Lake	262,800	668,800	1,296,300	160,000

Reservoir storage hydrographs for Jordanelle, Deer Creek, and Utah Lake are presented in Figures 4-5 through 4-7.

4.4 Water Supply and Transbasin Diversion Results

Simulated water supply and transbasin diversion results under the Proposed Demands Scenario appear reasonable and consistent with expectations. Key results are tabulated below.

Table 4-6

Key Simulated Average Annual Diversion Results in Acre-Feet

Proposed Demands Scenario

Diversion or Water User	Demand	Diversion	Maximum Shortage	Comments
Weber-Provo Canal	N/A	59,500	N/A
Duchesne Tunnel	N/A	33,200	N/A
Wasatch Division Direct Flow Rights (lumped)	98,600	95,500	12,000	Includes some demands that exceed rights. The total of water rights limited by demand equals 96,000 acre-ft/year.
Central Utah Project	107,500	107,500	0
Provo River Project	100,000	96,600	68,500
Provo Division Direct Flow Rights (lumped)	44,400	38,600	20,100	Includes some demands that exceed rights. The total of water rights limited by demand equals 38,800 acre-ft/year.
Utah Lake Users	196,700	196,700	0
Strawberry-Utah Lake	N/A	28,600	N/A

PRP and CUP demands and simulated diversions are compared in Figures 4-8 and 4-9. The shortages shown on Table 4-6 for Heber Valley and Provo Division direct flow water users are due primarily to historical demands that exceeded users’ rights. Other simulated diversions closely match user demands.

4.5 Conclusions Regarding the Proposed Demands Scenario Simulation

The PROSIM simulation of the Provo River system under historical hydrological and proposed demands and operating conditions has provided useful information on future Provo River water resources conditions. However, the simulated results are only as good as the assumptions used in developing the model and the scenario. If a different set of demands were applied, or a different priority was used for a critical water rights assumption, the simulated results might have been significantly different. In interpreting these results, it is also important to keep in mind that PROSIM is 100 percent efficient, whereas real-world river operations are not. In other words, while PROSIM is capable of allocating every drop of water on the river, in actual practice there is significant waste or inefficiency in operating the system. Thus PROSIM's results may tend to be somewhat "best case" approximations.

With this in mind, the most important conclusion reached from the simulation of the proposed demands scenario is that all of the Central Utah Project demands are met throughout the simulation period. The average annual "design" yield of 107,500 acre-feet per year is satisfied, with a minimum remaining storage of 46,100 acre-feet in Jordanelle.

Additionally, minimum instream flow requirements of 25 cfs at Woodland, 125 cfs between Jordanelle and Deer Creek, and 100 cfs from Deer Creek to Olmsted are satisfied at all times. The 25 cfs, winter IFR from Olmsted to Utah Lake is also satisfied throughout the simulation.

Reservoir storage levels, water supply yields, and minimum streamflow conditions could be lower in drier hydrological conditions than were observed in the 40-year study period. In particular, the historical drought period observed in the 1930s would be expected to effectively empty Jordanelle Reservoir.

5.0 SUMMARY OF CURRENT AND FUTURE USES OF THE MODEL

This Hydrologic Model Analysis was conducted to develop a modeling tool that would assist in the analysis of future impacts associated with the completion of the Central Utah Project and to provide ongoing assistance to the CUWCD in its management of its Provo River system water resources. As described in the following sections, the Provo River Simulation Model is currently being used to meet these objectives.

5.1 Use of PROSIM in the WCWEP and DRP EISs

The first application of PROSIM after development and calibration was in the Wasatch County Water Efficiency Project and Daniels Replacement Project Environmental Impact Statement (WCWEP/DRP EIS). The EIS (CUWCD, 1996) concerns the effects of two separate, but linked, proposals on the Provo River system: an agricultural water conservation project and a project to eliminate an environmentally harmful transbasin diversion. Both proposed projects have the potential for significant environmental benefits. However, due to the interdependent nature of the river system, they also have the potential to cause inadvertent adverse impacts on other water users and other environmentally sensitive areas. In addition, because the system (and demands upon the system) are changing so rapidly, there is no baseline against which to measure the impacts. Thus the function of PROSIM is not only to estimate the project impacts, but also to provide a "yardstick" or "no-project" condition against which to compare them.

In the development of this multidisciplinary EIS, the PROSIM model was used in a number of ways. First, the model was used to design project alternatives that produced acceptable water resources impacts. The PROSIM surface water model was linked and calibrated with a groundwater model of the potential water conservation impact area. Thus PROSIM calculates diversions, stream flows, and reservoir levels, while the MODFLOW finite difference groundwater model uses these results to simulate potential impacts upon groundwater levels and wetlands. The MODFLOW results for groundwater outflow are used by PROSIM as input to downstream surface water return flows. PROSIM was used to prepare specific hydrological information needed by EIS discipline leaders in their analysis of potential water quality, wetlands, aquatic resources, and threatened and endangered species impacts.

5.2 Providing Input on Water Supply Decisions

PROSIM also is being used on an as-needed basis by CUWCD staff to analyze environmental, water supply planning, and operational decisions. Requests from agencies, companies, or individuals outside of CUWCD for simulation of a particular scenario using PROSIM should be submitted to CUWCD staff. District staff will review the request and meet with the requesting party to clearly define the scenario assumptions and how those assumptions will be simulated in PROSIM (i.e., develop a scope of work). Once agreement on the scope of work is reached, District staff will then execute a Task Order Agreement with the requesting party that specifies the scope of work, a schedule, and the obligations of each party. District staff will use PROSIM to simulate the particular scenario, compare results with baseline simulation results, and provide a summary of results to the requesting party.

5.3 Future Use of PROSIM

A number of potential future uses, modifications, and upgrades to the Provo River Simulation Model are envisioned. In addition to its continued use in providing input to water supply decisions, it is likely that PROSIM will be used on other CUPCA studies of the Provo River. PROSIM could also be used to provide information while establishing operating rules for Jordanelle Reservoir and to forecast the reliability of future water supplies under drought conditions.

Extending the hydrologic database to include the period 1930 through 1949 would probably be the most helpful modification to the model. This would be extremely useful because the historical drought of record occurred during this period, and because other studies of the Provo River and Jordanelle and CUP operations include this period. Another useful modification would include the development and simulation of updated future Provo River demands.

PROSIM also could be used in conjunction with a water supply forecasting system. If this modification were made, the model could be used with real-time snowpack and reservoir contents data and forecasted runoff, to predict the likelihood that Jordanelle Reservoir will be able to deliver its full requested supply. A range of future potential hydrologic conditions could be applied in the model to develop a probability function for meeting full demands over the next one to three years.