5.2.7 Special Water Resources
The Texas Water Development Board has designated Canyon Reservoir and the Medina Lake System as special water resources located within the South Central Texas Regional Water Planning Area (Region L). This designation is pursuant to TAC 357.5 (g) & (h) as surface water supplies from these reservoirs may be obligated to meet demands outside of Region L. Water rights to Canyon Reservoir are held by the Guadalupe-Blanco River Authority (GBRA) which is headquartered in Guadalupe County. Water rights to the Medina Lake System are held by the Bexar-Medina-Atascosa Counties Water Control & Improvement District #1 (BMA) which is headquartered in Medina County. TAC 357.5 (h) requires that “the regional water planning group for the regional water planning area which contains the special water resource shall protect the water rights, water supply contracts, and water supply option agreements associated with the special water resource(s) so that supplies obligated to meet demands outside the regional water planning area shall not be impacted.” Present and potential obligations of supplies from these special water resources to meet demands outside Region L are summarized in the following paragraphs.
5.2.7.1 Canyon Reservoir
There is only one current contractural obligation with an entity located outside of Region L for water supply from Canyon Reservoir. This upstream diversion contract is between GBRA and the City of Kerrville and represents a commitment of up to 26 acft/yr from the firm yield of Canyon Reservoir for irrigation use in Kerr County. The South Central Texas Regional Water Plan includes approximately 300 acft/yr from Canyon Reservoir to meet projected needs for the City of Blanco located in Blanco County in the Lower Colorado Regional Water Planning Area (Region K). Pursuant to a Memorandum of Understanding (MOU) between GBRA and the Commissioners’ Court of Kerr County, the South Central Texas Regional Water Planning Group (SCTRWPG) recognizes a potential commitment of approximately 2,000 acft/yr from the firm yield of Canyon Reservoir for the calendar years 2021 through 2050. Subject to and conditioned upon the Texas Natural Resource Conservation Commission (TNRCC) granting, in whole, GBRA’s application to amend the Canyon water right, this MOU states:
Upon
request from Kerr County, at any time after
January 1, 2021 and prior to December 31, 2050, GBRA will support and
assist Kerr County in obtaining from the TNRCC permits to divert water from the
Guadalupe River or its tributaries at one or more diversion points within Kerr
County for use within the County, up to a total diversion of not to exceed
6,000 acft/yr, pursuant to GBRA’s then-standard agreement for “upstream sales
of water from storage.”
GBRA’s hydrology studies have indicated that a commitment of 2,000 acft/yr is necessary to allow permits for 6,000 acft/yr to be issued by TNRCC for diversion in Kerr County. No additional supplies from Canyon Reservoir are specifically reserved for entities within the Plateau Regional Water Planning Area (Region J) at this time.
5.2.7.2 Medina Lake System
The South Central Texas Regional Water Plan does not specifically include any supplies from the Medina Lake System to meet present or projected needs for water user groups within Region L or any adjacent planning regions. Simulations using the Guadalupe—San Antonio River Basin Water Availability Model (GSA WAM) indicate that there would be no dependable surface water supply from the Medina Lake System in a repeat of the drought of record if operated in accordance with its current Certificate of Adjudication (19-2130C). It is recognized, however, that the Medina Lake System may supply up to an authorized 66,750 acft for municipal (20,144 acft), irrigation (45,856 acft), and domestic and livestock (750 acft) uses in many years. Most of these supplies are contractually committed to irrigators in Region L and to the Bexar Metropolitan Water District (BMWD). The South Central Texas Regional Water Planning Group (SCTRWPG) recognizes that some supplies from the Medina Lake System may be committed to Region J pursuant to a March 1997 Memorandum of Understanding (MOU) between BMA, BMWD, Bandera County, and the Springhills Water Management District.[1] This MOU indicates that BMA will make up to 5,000 acft/yr available to Bandera County when Medina Lake exceeds 1,035 ft-msl (BMA datum) and up to 1,000 acft/yr when Medina Lake falls below this level. It is assumed that interests upstream of Medina Lake will obtain the necessary water rights permit(s) for diversion from the Medina River and/or its tributaries and will mitigate any associated impacts upon recharge of the Edwards Aquifer within Region L.
[1] Memoram of Understanding to Facilitate Regional Cooperation for the Maximization of Beneficial Development of the Water Resources Available from Medina Lake Pursuant to BMA’s Certificate of Adjudication No. 19-2130 and to Settle and Compromise Issues and Disputes Among the Parties, March 19, 1997.