Section 5
Regional, County, City,
Water User Group, and Major Provider Plans
5.1 Regional Water Planning Process
The South Central Texas Regional Water Planning Group (SCTRWPG) has employed a planning process (Figure 5.1-1) focused on the development of a Regional Water Plan to meet the needs of every water user group in the region for a period of fifty years. Given the history of sharp and divisive conflict concerning water planning in this region, the planning process has provided extraordinary opportunities for participation by water user groups in providing input to achieve the goal of a plan that will “provide for the orderly development, management, and conservation of water resources…” 31 TAC 357.5(a). To build consensus among the constituencies represented by the members of the SCTRWPG, the planning process has emphasized the coordination and careful integration of technical information with information provided through public participation.
Figure 5.1-1. Planning Process
Conflict over the past several decades in this region has focused on how to manage the Edwards Aquifer so as to meet the needs of many water user groups. Central to progress in resolving this conflict, and thus in achieving the formulation of a water plan acceptable to all constituencies represented in the SCTRWPG, is the assurance that all of the different competing strategies for meeting water needs will be given consideration. It has thus been central to the viability of the planning process itself that the evaluation of water supply options and combinations of these options in the context of a regional plan receive extraordinary attention.
To this end, the SCTRWPG has employed a planning process that ensures evaluation of virtually all the water supply options or management strategies that have been proposed or discussed in the past, together with several new ones that have never before been subjected to technical evaluation. To achieve confidence by all constituencies in the planning process, it has been necessary to evaluate the options both on a stand-alone basis (Volume III—Technical Evaluations of Water Supply Options) and in various combinations in the context of alternative plans (Volume II—Technical Evaluations of Alternative Regional Water Plans). Given the fact that some of the proposed strategies for regional management are at odds with one another, it has been important to look at a series of alternative regional water plans. By formulating five alternative regional water plans, the SCTRWPG has carefully considered many diverse management strategies. In keeping with logical and acceptable planning methods, the SCTRWPG has taken the best components of these alternative plans and developed a Regional Water Plan (Volume I – Executive Summary and Regional Water Plan).
5.1.1 Water Supply Options
The SCTRWPG completed the technical evaluation of some 61 water supply options identified for potential inclusion in alternative plans and ultimately the Regional Water Plan (see Volume III, Introduction for a description of procedures used to identify and evaluate water supply options). These options can be generally categorized by source of water as follows:
· Local/Conservation/Reuse/Exchange
· Edwards Aquifer Recharge
· River Diversions with Storage
· Existing Reservoirs
· Potential New Reservoirs
· Carrizo and Other Aquifers
Table 5.1-1 summarizes key information regarding some 79 water supply options (including variations of the 61 originally identified for consideration) for which technical evaluations were completed. In Table 5.1-1, the water supply options are categorized in accordance with the manner in which the water might be used within the context of a regional plan and ranked by unit cost of supply. Additional summary information in Table 5.1-1 includes quantity of water, land impacted, time to implement, and qualitative measures of environmental sensitivity, public acceptability, and reliability. Comprehensive documentation of the technical evaluation of these water supply options is included in Volume III.
5.1.2 Alternative Regional Water Plans
The SCTRWPG defined a Regional Water Management Alternative Plan (hereinafter referenced as an Alternative Regional Water Plan) as a combination of options and strategies that could meet the water needs of the entire South Central Texas Region. The SCTRWPG formulated five alternative regional water plans using the water supply options in Table 5.1-1 (and others identified through public participation) and authorized technical evaluation of each plan. Appendix B summarizes the procedures followed in the formulation of alternative regional water plans. The five alternative regional water plans are identified as follows:
· Planning Unit (PU) Alternative
· Environmental/Conservation (EC) Alternative
· Economic/Reliability/Environmental/Public Acceptance (EREPA) Alternative
· Inter-Regional Cooperation (IRC) Alternative
· Recharge & Recirculation (R&R) Alternative
Technical evaluations and comparisons of these five alternative regional water plans are summarized in Volume II. Upon review and consideration of these five alternative plans, the SCTRWPG formulated the Regional Water Plan which is summarized at the regional, county, city, and water user group level in Section 5.2. General procedures and assumptions for technical evaluation of the five alternative plans and the Regional Water Plan are enumerated in Appendix B.
In Volume III, the technical evaluations of the water supply options are presented as if each would be a stand-alone, individual management strategy. These stand-alone options were often modified in the formulation of alternative regional water plans. In many cases, only a portion of the potential water supply of an individual option was needed to satisfy the projected water needs of water users of the region. In other cases, a similar option evaluated at one location on a stand-alone basis was included in an alternative regional water plan at another location. Incorporating such modifications and refinements, the Regional Water Plan and the alternative regional water plans were individually evaluated using technical procedures and assumptions similar to those for the evaluations of water supply options.
In order to facilitate and expedite the technical evaluations of alternative regional water plans, the Guadalupe–San Antonio River Basin Water Availability Model (WAM)[1] and the Edwards Aquifer Model (GWSIM4)[2],[3] were enhanced and computationally linked. Enhancements to GWSIM4 include program logic and data development for simulation of Critical Period Management Rules under development by the Edwards Aquifer Authority, Edwards Aquifer pumpage transfers from irrigation to municipal use, and the southern Bexar County aquifer storage and recovery program being developed by the San Antonio Water System. Enhancements to the WAM include the addition of program logic to facilitate daily computations necessary for application of Consensus Environmental Water Needs Criteria (Appendix B, Volume III) in the simulation of new reservoirs and river diversions with storage. In addition, GWSIM4 and the WAM may now be computationally linked so that options and alternative plans involving diversions of springflow and other streamflow to the outcrop of the Edwards Aquifer for recharge enhancement and increased pumpage from the aquifer may be simulated efficiently.
In the process of evaluating alternative regional water plans, consideration of seasonal and peak day water demands was essential to ensure that sufficient water treatment and distribution capacities would be included. Daily variations in water supplied by the San Antonio Water System during 1996 were assumed representative of typical urban areas during drought. For planning purposes, it has been assumed that regional water treatment and distribution facilities would be developed to serve multiple user groups with water from multiple sources, thereby realizing economies of scale. Considering the dependable annual supply and transmission capacity associated with each of the various water supply options comprising an alternative plan as well as the daily variations in water demand, small reservoirs providing balancing storage were sized and located near regional water treatment facilities in Bexar, Comal, and Hays Counties.
[1] HDR Engineering, Inc., “Water Availability in the Guadalupe – San Antonio River Basin,” Texas Natural Resource Conservation Commission, December 1999.
[2] Klemt, W.B., Knowles, T.R., Elder, G.R., and Sieh, T.W., “Ground-water Resources and Model Applications for the Edwards (Balcones Faulty Zone) Aquifer in the San Antonio Region, Texas,” Texas Water Development Board Report 239, 1979.
[3] Thorkildsen, D. and McElhaney, P.D.., “Model Refinement and Applications for the Edwards (Balcones Fault Zone) Aquifer in the San Antonio Region, Texas,” Texas Water Development Board Report 340, 1992.