The Alliance Water Regional Authority opened the $340 million Carrizo Water Treatment Plan, which will give San Marcos and other Hays County cities access to the Carrizo-Wilcox aquifer.
According to Alliance Water Executive Director Graham Moore, San Marcos is Alliance Water’s largest customer, with a 35.86% share. That percentage is proportional to San Marcos’s financial commitment to Alliance Water, board representation and the amount of water San Marcos gets per “drop of water [developed]” from this plant.
“This helps offset our dependence on some other water sources,” Paul Kite, assistant director of Water/Wastewater for San Marcos said. “It helps give us that ability to put that water into our portfolio, to be able to attract businesses and [know] that we are not necessarily in a shortage- we’ve done our planning and our due diligence as a city to prepare citizens and businesses for the future.”
Kite said San Marcos started receiving water from this plant in August. In October 2025, San Marcos will officially receive approximately 2,460 acre-feet of water a year from this plant.
According to Moore, Alliance Water encompasses about nine construction projects at different stages of completion. While the water treatment plant, booster, pump station and some pipelines are not fully completed, they are in a state of “beneficial use,” meaning they can still operate and provide water despite the contracts not being finalized. This is how San Marcos has been receiving water from the plant before the project’s official completion.
Moore said key projects, such as this water plant, have been the primary focus for Alliance Water since 2018. These projects are part of Phase 1b, which will deliver approximately 6,700 acre-feet of water per year (about six million gallons per day) to all customers. The phase is scheduled for official completion in October 2025.
Phases 1c and 1d are expected to be completed in 2027, and provide 16,800 acre-feet of water per year (15 million gallons a day).
According to Kite, San Marcos will receive 5,379 acre-feet of water as part of phases 1c and 1d. These phases will also include a second water take point connected to a tower, which Kite said will benefit San Marcos in several ways.
“Right now it comes to the surface water treatment plant, mixes in the clear well with our surface water and then it’s pumped out, so you have some limits on what you can do,” Kite said. “But a straight delivery point to a water tower that we can baseline and just constantly feed, rather than continuously having to pump is more economical, and it just applies overall more stability within the system.”
Kyle will be able to ease water restrictions during the winter months due to lower water demand. Additionally, starting in February, the city will begin receiving water from the Carrizo plant, according to Tim Samford, Kyle’s assistant director of water utilities.
Kite said San Marcos does not plan to lift any water restrictions unless there’s significant rainfall to relieve Edwards Aquifer and Canyon Lake.
In May, San Marcos approved a three-year agreement (2024-26) to lease 500 acre-feet per year of water rights to the Edwards Aquifer Authority to Kyle. That deal will not be affected by Kyle’s access to the Carrizo water treatment plant.
“It’s a little far out, and we continue to refine our water model and projections, so our intent is not to renew [the deal] and allow this supply that’s coming along with Alliance to fulfill what we’re going to need,” Samford said.
Alliance Water, initially known as The Hays-Caldwell Public Utility Agency, was founded in 2007. However, according to Moore, the initial discussion of finding a water source among the customers began in 2003, and a feasibility study to use the Carrizo-Wilcox aquifer was completed in 2005.
From 2007 to 2018, Alliance Water established its board of directors, some infrastructure design and contracts. Moore said it also took years to accumulate water rights leasing and groundwater conservation district approval to produce water.
“Our customers at that point in time realized they didn’t need the water immediately, and so they didn’t want to spend,” Moore said. “It’s very capital intensive, and so there was a desire to wait until closer to the time when that water is needed to invest that money.”
Detailed design started in 2018, and the first contractors were brought on in 2021 to start building the infrastructure. Moore said the entire design portion was collaborative with all Alliance Water customers.
“It was through the entity, Alliance Water, we were tasked with finding engineers, having everything designed and then soliciting contractors to actually build all the infrastructure, and then we own that infrastructure, on behalf of the sponsors,” Moore said.
