|Table of Contents||Section 5 - Comparison of Existing Supply and Projected Demand|
To adequately manage the water resources in the Sabine Basin and plan for future growth, there needs to be an understanding of the existing water supply, projected demand, and anticipated need. The existing supply consists of water supply reservoirs, diversions from the Sabine River and it tributaries, ground water, and imports from outside the Basin. Projected water demands are the expected water use requirements developed from the TWDB’s 1996 Consensus Projections as discussed in Section 2.0. The anticipated need is based on the difference between the supply and the demand.
The Sabine Basin has a vast resource of existing water supply in the Toledo Bend Reservoir. However, this supply is not easily accessible to other areas with need such as the Upper Basin. Therefore, the comparison of existing supply and demand was evaluated on a county by county basis. Supplies from surface water reservoirs, river diversions, and importation were attributed to different counties based on the existing water rights and contracts. Unpermitted additional yield of existing reservoirs was considered unassigned supply in the county of the reservoir. Ground water supply was estimated from the year 2000 ground water projections, since these projections better reflect existing ground water resources that are currently used or planned for future supply. The projected water demands for each decade are identified for the Basin and county by the TWDB. Further discussion of potential ground water resources is included in Section 8.0.
The total water supply was assumed to meet only the need of the county, unless there was unassigned supply available in the county. This was because it was assumed that a water right holder would be reluctant to reduce its existing contracted supply. Also, water supply sources such as Lake Murvaul have stipulations that the water can only be used for county needs. A summary of the supply, demand and projected need is presented in Table 5.1. Details of the distribution of water supply within the Basin are included in Appendix E.
The supply/demand analyses addresses the projected TWDB needs only and does not include demands for environmental flows. Based on this analysis, the results indicate that in the year 2050 the Lower Basin has an available future supply of over 755,700 AF/Y, and the Upper Basin has an expected need of approximately 94,000 AF/Y. This need is largely assigned to three counties: Harrison, Rusk and Wood. The projected need in Harrison County is attributed to manufacturing growth; the need in Rusk County is primarily for power; and Wood County’s increased water requirement is largely due to mining and power. Hopkins County indicates a need of nearly 2,100 AF/Y, which is attributed to livestock demands. The unassigned 11,860 AF/Y in Hunt County is the portion of Dallas’s contract in Lake Tawakoni that must remain in the Sabine Basin. This water does not have to remain in Hunt County, and is available for use where needed in the Upper Basin.
As shown on Table 5.1, the projected need in these counties will occur sometime after year 2000 and before 2030. The projected need in Wood County shows a sudden increase in water requirements by 2010 due to power and mining. Since there are no known plans for power or mining in this county in the immediate future, this need probably will not occur until after 2010. Harrison County does not show a need until after 2020. Summaries of the projected need in the Upper Basin and projected surplus in the Lower Basin by decade are presented on Figures 5.1 and 5.2, respectively.