A. The Brackish Groundwater Resource Opportunity.
According to the Texas Water Development Board (“TWDB”), more than 2.7 billion acre-feet of brackish groundwater exists within the State of Texas. Texas has numerous aquifers capable of producing both fresh and brackish groundwater, including 9 major and 21 minor aquifers recognized by the TWDB. Among the major aquifers, the Gulf Coast aquifer has the largest volume of brackish water with approximately 522 million acre-feet and the Mesilla Bolson aquifer in west Texas has the smallest with approximately 0.5 million acre-feet. Of the minor aquifers, the Queen City and Sparta aquifers contain the largest volume of brackish water with approximately 246 million acre-feet and the Lipan aquifer contains the smallest with approximately 1.3 million acre-feet.
The growing interest in development and use of brackish groundwater is reflected in the 2012 State Water Plan, where five regional water planning groups included a total of 39 brackish groundwater desalination projects, which would produce over 181,000 acre-feet per year of new water supplies in year 2060. Of course, the State Water Plan only includes projects (deemed “water management strategies”) which seek state funding or require state permits, and hence private sector development of brackish groundwater projects are not reflected in the plan.
In terms of water quality (or salinity), the major aquifers and the minor aquifers are estimated to contain nearly equal volumes of brackish water, but the volume of brackish water in the range of 1,000 to 3,000 milligrams per liter (“mg/l”) of total dissolved solids (“TDS”) in the major aquifers is almost twice as much as that in the 3,000 to 10,000 mg/l range and a little less than twice as much as in the minor aquifers. However, the TWDB figures on salinity by aquifer are merely “very generalized estimates and may not represent site-specific conditions.” There remains a lack of water-quality data and irregular distribution of that data, particularly for some aquifers in the State.
Because water quality data is dependent upon wells, data gaps exist, particularly in the minor aquifers, due to the lack of wells or lack of water-quality analyses of existing wells. In the past, because water with concentrations of more than 3,000 mg/l of TDS was considered unusable, very few wells were drilled in these areas and exploratory wells which encountered such water were often plugged and abandoned without water samples being collected and analyzed. In other words, as LBG-Guyton Associates concluded in 2003, “the water-quality database is probably biased toward lower TDS measurements.” Plus, water-quality data, including TDS measurements, were collected over nearly a century by many different people using different methods, thereby undermining the reliability of the data.11 Furthermore, there are natural variations in water quality even within the same aquifer due to mineral composition, geochemical processes, groundwater flow velocity, residence time, long-term historical changes in recharge rates, and location of recharge and discharge areas....
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