Upper Sabine Basin Water Supply Study

Executive Summary

In May 2002, the Sabine River Authority of Texas (SRA) authorized KBR to update and expand investigations of various methods and costs for supplying future water needs in the Upper Sabine Basin. This report documents the analysis of SRA demands in the Upper Basin and summarizes the alternative supply strategies that were investigated for meeting those demands through year 2050.

Key Findings

The key findings associated with this study are summarized below:

· Currently, existing water supplies available to the SRA in the Upper Basin include the SRA allocations of Lake Tawakoni and Lake Fork. The yield in these reservoirs is anticipated to decrease in the future due to sedimentation.

· The Upper Basin is expected to have demands for water from SRA that exceed the current SRA supply within the next 10 to 20 years.

o Demand Scenario No. 1. Demands associated with existing SRA contracts and requests for additional supplies, year 2050 new supply needed: 42.5 MGD.

o Demand Scenario No. 2. Demands associated with existing SRA contracts and requests for additional supplies and additional needs identified by Senate Bill 1 Regional Planning, year 2050 new supply needed: 83.4 MGD.

· A system yield permit that includes Lake Fork, Lake Tawakoni, and Toledo Bend Reservoir with upstream diversions to the Longview / Kilgore / Henderson area would provide 4 MGD (Million Gallons per Day) of additional supply under projected (conservative) 2050 sedimentation conditions. The Texas Commission on Environmental Quality’s permitting process encourages system yield permits.

· Short-term Supply Alternatives

o Lake Cherokee. No additional supply available under its current operation.

o Dallas portion of Lake Fork. Dallas is not expected to use its full allocation of Lake Fork water until 2018. This alternative provides the potential to delay construction costs associated with any of the following long‑term supply alternatives, but has considerable contracting issues to resolve between SRA and the City of Dallas.

· Long-term Supply Alternatives

o Water Conservation. Water conservation is an integral element of SRA’s commitment to provide adequate supplies of high-quality water to municipal, industrial, agricultural, and recreational users of Sabine Basin water. Water conservation is accounted for in the demand projections used in this study.

o Dallas “In-basin“ Portion of Lake Fork. According to the Lake Fork water right, 10.6 MGD of the Dallas allocation cannot be transferred out of the Sabine Basin. This supply could be acquired by SRA through contractual negotiations and used in the Upper Basin. This supply could also be reserved to maintain lake levels in Lake Fork for recreational uses. There are significant contracting issues to resolve between SRA and the City of Dallas before this water can be considered a viable option for meeting future demands.

o Groundwater Development. The Senate Bill 1 Regional Plans identify approximately 45 MGD of potential available supply in the Carrizo Wilcox Aquifer upstream of the Longview/Kilgore/Henderson area. There are significant issues that must still be addressed before groundwater can be considered a viable option for meeting future demands. These issues include water quality, impact on surrounding well performance, and regulatory issues.

o Prairie Creek Reservoir. The maximum reservoir yield of 26.5 MGD (reservoir with high-flow scalping diversions) is not sufficient to meet either of the year 2050 Upper Basin demand scenarios.

o Toledo Bend Reservoir Pipeline. A pipeline conveyance project from existing supplies in Toledo Bend Reservoir can be implemented in stages to meet increasing demands through 2050. This project provides flexibility for construction dates of segments to be adjusted to meet a variety of potential future demands.

· To meet projected year 2050 demands, Prairie Creek Reservoir, groundwater development, and/or a pipeline from Toledo Bend Reservoir will be needed.

· The only alternative that alone can meet the needs associated with the two demand scenarios is a pipeline from Toledo Bend to the Longview/ Kilgore/Henderson area along with a pipeline from Lake Fork to Lake Tawakoni.

· Regardless of which identified short or long-term supply alternative is selected by SRA, there will remain a projected need to deliver water from Lake Fork to Lake Tawakoni by year 2015.

Analysis of Demand and Existing Supply

A survey was performed by the SRA of its existing customers, entities that have requested water from SRA, and other retail water suppliers in the Upper Basin. SRA Upper Basin demands have been grouped into two categories: 1) Existing Contracts and Requests; and 2) Existing Contracts, Requests and Additional Demands from Regional Planning.

Existing supplies available to the SRA in the Upper Basin include the SRA allocations of Lake Tawakoni and Lake Fork. The yield in these reservoirs is anticipated to decrease in the future due to sedimentation. Table ES-1 and Figure ES-1 summarize the supplies, demands, and need for additional supplies in the Upper Basin.

Table ES-1. Additional Supplies Needed for Demand Scenarios (MGD)

	Permitted	2000	2005	2010	2020	2030	2040	2050
SRA Lake Tawakoni Supply	42.5	42.5	42.4	42.2	41.9	41.5	41.2	40.9
SRA Lake Fork Supply	50.7	46.2	45.8	45.5	44.8	44.0	43.3	42.6
Existing Supply in Lake Tawakoni & Lake Fork	93.2	88.7	88.2	87.7	86.6	85.6	84.5	83.5
Demand Scenario No. 1
Demands associated with Contracts & Requests		35.0	73.4	85.0	102.7	113.0	118.6	126.0
Additional Supply Needed		0.0	0.0	0.0	16.0	27.5	34.1	42.5
Demand Scenario No. 2
Demands associated with Contracts, Requests and Regional Planning		35.0	80.4	93.8	128.3	149.0	157.1	166.9
Additional Supply Needed		0.0	0.0	6.1	41.7	63.4	72.5	83.4

As part of this study, a water availability model was created to assess the potential benefit of the Sabine River Authority obtaining a system yield permit that includes Lake Fork, Lake Tawakoni and Toledo Bend Reservoir with upstream diversions in the Longview / Kilgore area. This analysis revealed that 4 MGD of additional supply (beyond the SRA portion of the permitted amount) would be available under year 2050 sedimentation conditions and 12 MGD would be available under year 2000 sedimentation conditions.

Alternative Future Supplies

Short-term supply alternatives analyzed included Lake Cherokee and the Dallas portion of Lake Fork. Lake Cherokee does not have any additional supply available under its current operation, which limits drawdown as necessary for power plant operation. Dallas is not expected to use its full allocation of Lake Fork until 2018. Prior to that, a portion of that supply could be reallocated to satisfy SRA Upper Basin needs. Obtaining an agreement with Dallas could potentially satisfy the demands for additional supply through 2015, after which a long-term supply would be necessary.

Long-term alternatives to meet the 2050 projected demands of the Upper Basin considered in this study include:

· The Dallas “in-basin” portion of Lake Fork.

· Groundwater from the Carrizo-Wilcox and Queen Cities Aquifers.

· Prairie Creek Reservoir.

· Toledo Bend Reservoir supplies conveyed via pipeline to the Upper Basin.

According to the Lake Fork water right, 10.6 MGD of the Dallas allocation cannot be transferred out of the basin. If an agreement were made with Dallas, this supply would become available to satisfy a portion of SRA’s future demand. This supply could also be reserved to help maintain lake levels in Lake Fork for recreational uses. The actual cost of this supply and ability to negotiate contracts for its transfer to the SRA are not known at this time; therefore, discussions should continue with the City of Dallas, but it cannot be expected to be a part of the solution to the SRA’s needs at this time.

Groundwater development was analyzed as a long-term supply alternative that has potential implementation benefits since well development could be staged as supplies are needed. The Regional Plans indicate approximately 240 MGD of available supply in the Upper Basin from the Carrizo Wilcox and Queen Cities Aquifers. Of this, approximately 45 MGD was identified upstream of the Longview / Kilgore / Henderson area based on review of the performance of existing wells and the location of potential wellfields relative to demands. Issues associated with this alternative include: water quality considerations related to discharge of groundwater into surface streams, bed and banks permitting requirements, and legal and political issues such as formation of groundwater conservation districts and other opposition from local government and private property owners. Since the estimated cost for this supply is projected to be relatively low, the SRA should conduct additional analyses to confirm the availability, quality, impact on surrounding wells, and likely cost of the supplies. If these detailed feasibility studies prove to be promising, then further investigation of the public receptivity to this alternative should be explored further. Revision to the charter of the SRA may be required to allow significant development of groundwater resources in the Basin. These significant issues must be addressed before groundwater can be considered a viable option for meeting future demands.

Development of Prairie Creek Reservoir was recommended as the most viable alternative in the Comprehensive Sabine Watershed Management Plan in 1999. The reservoir yield was previously estimated at 19,700 acre-feet per year (17.6 MGD) if operated alone, and 29,685 acre-feet per year (26.5 MGD) when supplemented with high flow scalping diversions. While the estimated cost is reasonable, significant issues must be addressed related to the environmental and construction permitting of such a reservoir project. Since the available supplies from this project are limited and do not meet the projected demands but for a short period, development of other supplies will be necessary and should be investigated first.

The Toledo Bend Reservoir supplies are currently available and can be conveyed to the Upper Basin with limited environmental impacts or regulatory requirements. A pipeline from Toledo Bend Reservoir can also be implemented in stages in order to meet increasing demands through 2050. This alternative also provides flexibility to allow construction dates of segments to be adjusted in order to meet a variety of potential future demands. The recommended pipeline routing is shown in Figure ES-2. Various staging and supply options were investigated for this option which indicate that Toledo Bend water could be delivered to the Upper Basin for a cost ranging from $0.70 – 1.33 per 1000 gallons delivered. This cost does not include the cost of Toledo Bend raw water supplies. This cost is higher than other potential options, but has the advantage of much less uncertainty and risk associated with its implementation. If additional participation in the use of Toledo Bend water can be developed to expand the pipeline capacity, the SRA cost can be reduced significantly. Therefore, this option is the recommended approach to meeting the projected Upper Basin water supply needs.

In developing pipeline alternatives, an important element was the ability to phase construction and develop a plan that is flexible enough to meet changing demands through 2050. A total of five pipeline alternatives were evaluated to meet the following demands for additional supply in order of increasing magnitude of supply:

TB 1. Existing contracts plus requests for additional supply, assuming 10 MGD can be obtained from the Dallas in-basin Lake Fork allocation, resulting in year 2050 additional required supply of 32 MGD.

TB 2. Existing contracts plus requests for additional supply, resulting in year 2050 additional required supply of 42 MGD.

TB 3. Existing contracts, requests for additional supply and projected Regional Planning demands assuming 10 MGD can be obtained from the Dallas in-basin Lake Fork allocation, resulting in year 2050 additional required supply of 73 MGD.

TB 4. Existing contracts, requests for additional supply and projected Regional Planning demands, resulting in year 2050 additional required supply of 83 MGD.

TB 5. Entire Longview / Kilgore / Henderson contract demands, requests for additional supply, and projected Regional Planning demands, resulting in year 2050 additional required supply of 97 MGD.

Table ES-2 summarizes the costs associated with the long term-supply alternatives considered in this study.

Table ES-2. Comparison of Long-Term Supply Alternatives

Alternative	Supply Available (MGD)	Total Construction Cost	50 Year Life Cycle Analysis *				100 Year Life Cycle Analysis *
Alternative	Supply Available (MGD)	Total Construction Cost	Average Deliveries (MGD)	Cost per 1000 gallons delivered	Average Water Sold (MGD)	Cost per 1000 gallons sold	Average Deliveries (MGD)	Cost per 1000 gallons delivered	Average Water Sold (MGD)	Cost per 1000 gallons sold
Prairie Creek Reservoir	17.6	$ 63,787,000	11.2	$ 0.71	17.6	$ 0.45	14.4	$ 0.35	17.6	$ 0.28
Reservoir With Scalping	26.5	$ 84,204,000	15.6	$ 0.69	26.5	$ 0.41	21.0	$ 0.34	26.5	$ 0.27
TB 1	32	$144,226,000	12.3	$ 1.33	30.0	$ 0.54	22.3	$ 0.61	30.0	$ 0.45
TB 2	42	$145,912,000	18.9	$ 1.05	40.0	$ 0.50	30.6	$ 0.51	40.0	$ 0.39
TB 3	73	$217,782,000	34.8	$ 0.87	60.0	$ 0.50	53.9	$ 0.50	65.0	$ 0.42
TB 4	83	$217,781,000	42.7	$ 0.80	70.0	$ 0.49	62.9	$ 0.48	75.0	$ 0.41
TB 5	97	$283,477,000	70.5	$ 0.71	70.0	$ 0.71	83.8	$ 0.47	75.0	$ 0.49
Ground water	45	$ 47,031,000	18.9	$ 0.37

TB # represents Toledo Bend Pipeline alternatives.

Groundwater unit pricing based on 30-year life cycle analysis.

* Unit costs for Toledo Bend Alternatives do not include the cost of Toledo Bend raw water.

Lake Fork to Lake Tawakoni Pipeline

A pipeline from Lake Fork to Lake Tawakoni is not an alternative to be compared to the others, but is required by year 2015 to meet Upper Basin demands regardless of which alternative(s) is (are) selected. While capacity may be available in the pipeline currently being designed and constructed for the City of Dallas, costs have been developed for a 42-inch diameter pipeline which would be dedicated to the SRA demands only in order to provide a “worst case” alternative in terms of estimated costs. This pipeline would be sufficient to meet the year 2050 average demand at Lake Tawakoni that must be met by Lake Fork of 25 MGD. Table ES-3 shows the total construction costs and unit costs to transport water sold from Lake Fork but delivered from Lake Tawakoni.

Table ES-3. Lake Fork to Lake Tawakoni Pipeline Summary

Total Construction Cost	50 Year Life Cycle Analysis				100 Year Life Cycle Analysis
Total Construction Cost	Average Deliveries (MGD)	Cost per 1000 gallons delivered	Average Water Sold (MGD)	Cost per 1000 gallons sold	Average Deliveries (MGD)	Cost per 1000 gallons delivered	Average Water Sold (MGD)	Cost per 1000 gallons sold
$30,979,000	9.7	$ 0.48	25.0	$ 0.18	16.8	$ 0.22	25	$ 0.15

Recommended Actions

The recommended implementation activities and the potential amounts of additional long-term supply that could be made available are summarized below.

· Initiate application with TCEQ for a system permit between Lake Fork, Lake Tawakoni and Toledo Bend Reservoir to allow upstream diversions from Toledo Bend Reservoir in the Longview / Kilgore / Henderson area. (4 MGD of new supply.)

· Pursue additional partnerships for use of Toledo Bend Reservoir supplies in order to increase the capacity of pipeline and pumping facilities and reduce the cost of the resulting water conveyance. (Up to 83 MGD of new supply.)

· Continue negotiations with Dallas to allow SRA to use a portion of the capacity of the Dallas pipeline from Lake Fork to Lake Tawakoni. If not successful, initiate detailed planning and begin right-of-way acquisition for a separate 42-inch diameter/ 25 MGD SRA pipeline.

Other alternatives to be considered if issues associated with them can be resolved include:

· Continue negotiations with Dallas to allow SRA to acquire Dallas in-basin water. (10.6 MGD of new supply.)

· Retain the Prairie Creek Reservoir as a future element in the SRA’s Upper Basin Plan, but defer further investigations of this option pending development of further studies related to use of Toledo Bend Reservoir supplies (No new supply at this time but up to 26.5 MGD if re-initiated at a later date.)

· Conduct feasibility studies for conjunctive use of groundwater in selected areas of the Upper Basin. Evaluate impact on existing wells, water quality, and use of bed and banks to transfer supplies to demand areas. (Up to 45 MGD of new supply.)

· Obtain agreement for temporary use of Dallas Lake Fork supplies on an interim basis in order to delay construction costs associated with long-term alternatives.

1.0 Introduction

In May 2002, the Sabine River Authority of Texas (SRA) authorized KBR to update and expand investigations of various methods and costs for supplying future water needs in the Upper Sabine Basin. This report documents the analysis of SRA demands in the Upper Basin and summarizes the alternative supply strategies which were investigated for meeting those demands through year 2050.

1.1 Current Upper Basin Supplies

Existing water demands in the Upper Basin are provided for through a combination of groundwater and surface water supplies. Groundwater supplies are generally used by local municipalities and water supply corporations. Surface water supplies in the Upper Basin include 1) direct diversions from the Sabine River; 2) the yield from small reservoirs located on tributaries to the Sabine River; and 3) two large reservoirs owned by the SRA and located in the upper reaches of the Upper Basin, Lake Fork and Lake Tawakoni.

The 1985 Update of the Master Plan for the Sabine River and Tributaries in Texas (1985 Master Plan Update) included development of proposed future reservoirs in both the Upper and Lower Basins. Several of the proposed reservoirs are located along the main stem of the Sabine River. One such project is Waters Bluff Reservoir, located in Smith, Upshur and Wood Counties. The yield of this project, 324,000 acre-feet per year, could meet the projected need in the Upper Basin well beyond 2050. However, since the initial feasibility studies were conducted several factors have come into existence which reduce the potential for construction of this reservoir in the foreseeable future. These factors include numerous land and ownership features which would be inundated by the proposed reservoir, including mitigation banks established in the area, the Little Sandy National Wildlife Refuge (a non-development conservation easement), and portions of the site which are designated as a Priority 1 bottomland hardwood area by the United States Fish and Wildlife Service. Additional issues complicating development of this site include the presence of prehistoric cultural sites, and the scenic and recreational qualities of this segment of the Sabine River. Finally, development of this project would also require a formal act of Congress to override the Little Sandy easement.

Several more recent studies relevant to future water supplies in the Upper Basin are summarized below.

1.2 Comprehensive Sabine Watershed Management Plan

This plan was prepared for the Sabine River Authority of Texas in conjunction with the Texas Water Development Board by Freese and Nichols, Brown & Root and LBG-Guyton in 1999. The plan further updated the 1985 Master Plan Update. The 1999 plan projected that the Upper Basin needed approximately 93,000 acre-feet per year (83 MGD) of additional supply by 2050. The most viable source identified within that study was a staged development of Prairie Creek Reservoir. The firm yield of the reservoir was expected to meet projected demands through 2023 and as further supply was needed, “scalping” diversions from the Sabine River were proposed to supplement the yield of the reservoir. However, these diversions would not provide enough additional supply to meet all of the needs through 2050. Another option suggested in this study was to supplement the supply from Prairie Creek Reservoir with a pipeline from Toledo Bend Reservoir.

Additional related recommendations from this plan included: water conservation; pursuing negotiations with the City of Dallas to allow for selling of water in Dallas’s Lake Fork contract that must stay in the Sabine Basin; beginning the permitting process for Prairie Creek Reservoir; reevaluating the water use demand projections; reviewing the future Water Availability Model of the Sabine River Basin to determine the current supply available for additional diversions and existing contracts; re-evaluating the need, timing, and sizing of a transmission pipeline from Toledo Bend Reservoir; pursuing discussions with various customers regarding reducing their contracted amount in order to free up those supplies for other needs; initiating discussions with Wood County regarding the possibility of converting the Wood County Lakes to water supply; and encouraging the Cities of Kilgore and Canton to work with the Texas Water Development Board (TWDB) regarding the possibility of a future “Aquifer Storage and Recovery” project.

1.3 Other Studies

The Water Availability Model (WAM) of the Sabine River Basin was developed for the Texas Natural Resources Conservation Commission (TNRCC), now Texas Commission on Environmental Quality (TCEQ), by Brown & Root in 2001 and updated in June 2002. That study estimated the water availability for existing water rights and computed the firm yields for existing reservoirs in the Sabine River Basin.

Additional regional water planning under Senate Bill One has been performed throughout the state as part of the process of creating a state water plan. Specifically, parts of designated Regions C, D and I are located within the Upper Sabine Basin. These regional water plans analyzed expected demands and supplies in each Region and identified shortages requiring additional supplies. The source for additional supplies in each Region included both groundwater and surface water. In this study, the majority of shortages that have been identified to be met by surface water are assumed to be provided by SRA.

A Groundwater Availability Model (GAM) of the Carizzo-Wilcox Aquifer was developed for the Texas Water Development Board and issued as a draft report in September 2002. This GAM assesses the impact of projected groundwater use through 2050 on existing water levels and spring flows in the Carrizo-Wilcox and Queen City Aquifers. The GAM does not address water quality issues in the aquifer. The results of the draft GAM have been considered in the evaluation of local groundwater supplies as further described below.

1.4 Scope of Work

The scope of work for this study consists of an evaluation of meeting Upper Basin customer requests through short-term use of committed but currently unused water supplies, and an evaluation of additional long-term supply alternatives.

Phase 1, the customer contract assessment, consists of the following tasks:

Determine the demands through year 2050 using data collected by the SRA from surveys of Upper Basin water users and water providers, as well as the official Regional Water Plans for this area.
Identify the customers who are not currently using their full supply and determine the amount of supply that could be available on a short-term basis.
Determine if any existing customers with demands significantly below their contract would be willing to renegotiate their contract.
Define a schedule that documents the amount of water needed in the Upper Basin if existing unused supplies are used temporarily to meet customer requests.

Phase 2, the water supply source assessment, consists of the following tasks:

Determine raw water facilities for reallocated water.
Determine a short and long-term water supply plan.
Prepare a new water availability model to determine the firm yield of Lake Fork and Lake Tawakoni under 2050 conditions. Additionally, use this model to assess the potential benefits of a “system yield” permit.
Prepare a schedule that illustrates the potential phasing in of new water supplies to meet the identified demands.

2.0 Current Conditions

In order to determine the additional supply needed within the Upper Basin, an evaluation of existing supplies and projected demands was performed as described in this section.

2.1 Projected Demands

As part of this study the SRA conducted a survey of its existing customers, entities which have requested water from SRA, and other retail water suppliers in the Upper Basin. The entities surveyed provided estimated demand data, by decade, of SRA supplied water. A summary of these demands is shown in Table 1.

Table 1. SRA Upper Basin Demands by Customer Type (MGD)

	2000	2005	2010	2020	2030	2040	2050
Existing Customer Demand Not Exceeding Current Contracts ¹	34.2	67.7	73.6	75.0	78.1	79.0	80.0
Existing Customers Demand Exceeding Current Contracts ²	0.1	2.2	7.0	22.7	29.3	33.4	39.3
Demands from Requests for Water by New Customers ³	0.7	3.5	4.3	5.0	5.6	6.2	6.7
Additional Demands from Regional Planning Projections ⁴	0.0	7.0	8.9	25.7	35.9	38.4	40.9
Total Demand	35.0	80.4	93.8	128.3	149.0	157.1	166.9

1. Existing customers provided demand data representing the total use of SRA water, assuming any additional requests could be met. “Existing Customer Demand Not Exceeding Current Contracts” has limited that demand to the current contract amount. Existing contracts total approximately 93.2 MGD.

2. “Existing Customer Demand Exceeding Current Contracts” represents the demands associated with requests for water which are above and beyond the current contract amount.

3. “Demands from Requests for Water by New Customers” includes demands of new customers which have made requests to the SRA for water.

4. “Additional Demands from Regional Planning Projections” are those demands from the Region D and Region I Plans which are to be met using surface water supplies that have not been identified as met by sources other than SRA, and are not already represented in a request to SRA.

The demands have also been grouped into the broad geographic regions around Lake Fork, Lake Tawakoni, and the downstream demand in the Longview / Kilgore / Henderson area as shown in Table 2.

Table 2. SRA Upper Basin Demand by Geographic Area (MGD)

	2000	2005	2010	2020	2030	2040	2050
Tawakoni	13.6	31.0	37.6	47.6	54.6	59.7	65.0
Fork	1.0	2.6	3.1	3.1	4.1	4.1	4.6
Longview/Kilgore/Henderson	20.4	46.8	53.1	77.7	90.2	93.3	97.3
Total All	35.0	80.4	93.8	128.3	149.0	157.1	166.9

Figure 1 provides a visual summary of the demands in the Upper Basin. Appendix A in this report includes a technical memorandum which provides further details of the projected demands and estimated supply from existing sources in the Upper Basin.

The identified future demands have been grouped into two categories: 1) “Existing Contracts and Requests”, and 2) “Existing Contracts, Requests and Regional Planning”. Because the demand from Regional Planning includes demands that are not associated with any particular entity (for example, Gregg County Manufacturing) and therefore are less likely to have contracts executed in the near term, the demands have been grouped in this manner.

Existing contracts total approximately 93 MGD, and the future anticipated demand associated with these contracts is approximately 80 MGD as was shown in Table 1. Requests for additional water supplies by current and new customers total approximately 57 MGD, and the future 2050 demand associated with these requests is approximately 46 MGD (as calculated from Table 1, by summing the second and third rows). Thus if contracts were executed for all known requests, the total contracted amount would be approximately 150 MGD (93 + 57), and the year 2050 demand would be approximately 126 MGD (80 + 46). The difference between year 2050 demand and contracts plus requests is 24 MGD (13 + 11). Additional demand estimated during Regional Planning is approximately 41 MGD in 2050.

2.2 Existing SRA Supplies

For the purposes of this study, the Upper Basin has been defined as that portion of the Sabine River Basin upstream of the headwaters of Toledo Bend Reservoir. The only existing SRA water supply sources in the Upper Basin are Lake Tawakoni and Lake Fork. The authorized diversion amount and the year 2000 and year 2050 estimated yields are shown in Tables 3 and 4 under various conditions.

Table 3. Firm Yield of Lake Tawakoni and Lake Fork (acre-feet per year)

Model Criteria			Total Yield		SRA Portion of Yield
Operations	Return Flows ¹	ACE ²	Tawakoni	Fork	Tawakoni	Fork	Total
Permitted	-	-	238,100	188,660	47,600	56,800	104,400

Firm Yield	Yes	Original	238,100	177,400	47,600	53,410	101,010
Firm Yield	Yes	2000	238,100	171,900	47,500	51,750	99,350
Firm Yield	Yes	2050	229,000	158,500	45,780	47,720	93,500
Firm Yield	No	Original	235,300	176,300	47,040	53,080	100,120
Firm Yield	No	2000	227,000	170,900	45,380	51,450	96,830
Firm Yield	No	2050	219,000	158,000	43,780	47,570	91,350

1. Return Flows, option “Yes” represents anticipated return flows as determined in the WAM. Option “No” represents no return flows as used by the TCEQ for permitting of perpetual water rights.

2. ACE (Area-Capacity-Elevation) represents the reservoir sedimentation condition used for the analysis, i.e. 2050 represents that an estimated year 2050 sedimentation condition was used in determining firm yields.

Figure 1

Figure 1. SRA Upper Basin Supply and Demand
Table 4. Firm Yield of Lake Tawakoni and Lake Fork (MGD)

Model Criteria			Total Yield		SRA Portion of Yield
Operations	Return Flows ¹	ACE ²	Tawakoni	Fork	Tawakoni	Fork	Total
Permitted	-	-	212.6	168.4	42.5	50.7	93.2

Firm Yield	Yes	Original	212.6	158.4	42.5	47.7	90.2
Firm Yield	Yes	2000	212.6	153.5	42.5	46.2	88.7
Firm Yield	Yes	2050	204.5	141.5	40.9	42.6	83.5
Firm Yield	No	Original	210.1	157.4	42.0	47.4	89.4
Firm Yield	No	2000	202.7	152.6	40.5	45.9	86.5
Firm Yield	No	2050	195.5	141.1	39.1	42.5	81.6

The SRA portion of supply from these reservoirs has been fully allocated. However, the current level of use by these customers is on the order of 25 percent of the allocated amount. Thus from a short-term perspective, there is additional water that could be used on an interim basis from these reservoirs. In order to use this additional water on an interim basis, the SRA must have a long-term supply mechanism that can be used to ultimately guarantee meeting all demands associated with existing contracts plus any additional contracts which the SRA might provide.

The future supply associated with Lake Fork and Lake Tawakoni is expected to decrease due to sedimentation which occurs in the reservoirs. Tables 3 and 4 reflect the reduction in yield over time due to projected sedimentation rates from the Water Availability Model (WAM) of the Sabine River Basin. The sedimentation rate for Lake Fork from that study was based on a comparison of reservoir area-capacity from the original condition to a resurvey done in 2001. Based on this comparison, the Lake Fork sedimentation rate was more than two times the sedimentation rate for Lake Tawakoni and significantly higher than previous estimates. While this high calculated sedimentation rate does not impact the year 2000 yield, it does reduce the year 2050 yield. If future resurveys of Lake Fork demonstrate that the sedimentation rate is in fact more similar to Lake Tawakoni, the SRA portion of Lake Fork year 2050 yield would increase by approximately 2 MGD.

2.3 Future System Yield

A system operations permit between Lake Tawakoni, Lake Fork and Toledo Bend Reservoir could theoretically be developed which allowed diversions of Toledo Bend inflows to be made in the Longview / Kilgore / Henderson area and would create some additional supply in the Upper Basin. This additional supply would potentially offset the reduction in supply from Lake Tawakoni and Lake Fork due to sedimentation. Tables 5 and 6 summarize the Upper Basin supply which would be available under the following operation scenarios:

Firm Yield - Individual yields of Lake Tawakoni and Lake Fork.
Firm Yield Plus - Modified system operation which does not allow diversions/releases from Lake Tawakoni or Lake Fork to exceed the permitted diversion amounts in any given year.
System Yield - System operation which allows diversions/releases from Lake Tawakoni and Lake Fork to exceed the permitted diversion amounts.

The SRA portion of the yield of the various scenarios is based upon the following:

Firm Yield – Yield pro-rated based upon SRA share of permitted diversion amount.
Firm Yield Plus – Diversions/releases out of Lake Tawakoni and Lake Fork pro-rated based upon SRA share of permitted diversion amount, and additional diversion at downstream control point allocated entirely to SRA.
System Yield – Non-SRA portion of Lake Tawakoni and Lake Fork diversions and releases held constant with other scenarios, and remainder allocated to SRA.

Tables 5 and 6 indicate the potential for a SRA system yield that is slightly higher than the currently permitted supply from Lake Fork and Lake Tawakoni. This will be discussed in additional detail in the following section. The diversions at SR-LV represent the diversions available from the Sabine River at the Longview / Kilgore / Henderson area. This portion of the system yield would not be available to meet demands in the Lake Tawakoni and Lake Fork area.

Table 5. SRA Upper Basin Yield Under Various Scenarios (acre-feet per year)

Model Criteria			Total Diversions or Releases by Location				SRA Diversions or Releases by Location
Reservoir Operation	Return Flows	ACE	Tawakoni	Fork	SR-LV *	Total	Tawakoni	Fork	SR-LV *	Total
Permitted	-	-	238,100	188,660	0	426,760	47,620	56,800		104,420

Firm Yield	Yes	Original	238,100	177,400	0	415,500	47,620	53,410	0	101,030
Firm Yield	Yes	2000	238,100	171,900	0	410,000	47,620	51,754	0	99,374
Firm Yield	Yes	2050	229,000	158,500	0	387,500	45,800	47,720	0	93,520
Firm Yield	No	Original	235,300	176,300	0	411,600	47,060	53,079	0	100,139
Firm Yield	No	2000	227,000	170,900	0	397,900	45,400	51,453	0	96,853
Firm Yield	No	2050	219,000	158,000	0	377,000	43,800	47,569	0	91,369

FY Plus	Yes	Original	238,100	177,400	19,277	434,777	47,620	53,410	19,277	120,307
FY Plus	Yes	2000	238,100	171,900	19,093	429,093	47,620	51,754	19,093	118,467
FY Plus	Yes	2050	229,000	158,500	18,070	405,570	45,800	47,720	18,070	111,590
FY Plus	No	Original	235,300	176,300	15,332	426,932	47,060	53,079	15,332	115,471
FY Plus	No	2000	227,000	170,900	15,332	413,232	45,400	51,453	15,332	112,185
FY Plus	No	2050	219,000	158,000	15,332	392,332	43,800	47,569	15,332	106,701

System	Yes	Original	238,100	161,660	57,000	456,760	47,620	37,670	57,000	142,290
System	Yes	2000	235,100	150,160	57,000	442,260	44,620	30,014	57,000	131,634
System	Yes	2050	226,600	134,660	47,000	408,260	43,400	23,880	47,000	114,280
System	No	Original	229,600	151,160	57,000	437,760	41,360	27,939	57,000	126,299
System	No	2000	224,000	148,660	47,000	419,660	42,400	29,213	47,000	118,613
System