Ensuring a Safe, Sustainable Future Water Supply--Case Study
Ensuring a Safe, Sustainable Future Water Supply
May 3, 2011
By the year 2060, water usage in Texas will exceed the available water supply due to rapidly
increasing population growth.Existing sources of water supply are inadequate to sustain future
demands for farming, ranching, recreation, and the environment.An additional 8.5 million acrefeet per year of new water supplieswill be needed. Ensuringa sustainable water supply in a semiarid climate is challenging and exacerbated by unpredictable factors such as climate change
associated with global warming. How will stakeholders meet future demand?
New technologies must be identified and developed to supply increased demand. This study
focuses on several innovative technologies in various stages of planning and implementation by
the Texas Water Development Board. This study also briefly examines technologies emerging in
other countries that will help ensure a safe, sustainable future water supply.
Meeting Future Demand
Ensuring a safe, sustainable water supply to meet the demand required for the projected
population for the year 2060 will entail development and implementation of many options.
Strategic water management practices which advocate usingexisting sourceswisely, capturing
and storing water, and reusing wastewatermust be implemented and followed. Innovative
technologies must be identified and developed. After suffering the most severe drought in the
history of Texas (1954-1956), the Texas Water Development Board (TWDB) was founded in
According to the TWDB, plans to meet the projected demand of 8.5 million acre-feet per year of
new water supplies necessary to keep up with expected population growth for 2060 include:
60 % --Conventional water sources
16 % --Desalination, brackish groundwater desalination, reuse and reclamation, rainwater
harvesting, and aquifer storage and recovery
A single source will not be adequate to supply demand. We must develop a diverse combination
of technologieswhich includes desalination, brackish groundwater desalination, rainwater
harvesting, aquifer storage and recovery (ASR), reuse, and emerging technologies.
Desalination is the process of removing dissolved salts from saline water to produce
freshwater. Texas has an infinite, drought proof-supply of seawater along its 370 miles of
coastline. Although Texas does not currently have a seawater desalination plant, optimization of
existing technology has decreased the cost associated with desalination, making it a costeffective alternative source of water.
Twoprocesses are currently used, the thermal process and the membrane process. The thermal
process involves heating saline water to the boiling point, then condensing and collecting the
water vapor. Membrane processes such as reverse osmosis and electrodialysis separate salts from
water using a permeable membrane.Both processes generate toxic by-products (salts and brine)
which must be disposed of, adding to the cost of producing freshwater from saline water.
Brackish Groundwater Desalination
Seawater typically contains greater than 35,000 milligrams per liter of Total Dissolved Solids
(TDS). The higher the concentration of TDS, the more pressure required to push the water
through membranes, which increases the cost of production. Brackish groundwater contains a
significantly lower concentration of TDS,making it less costly to process than desalination of
seawater. Almost every aquifer in Texas contains brackish groundwater. Approximately 2.78
billion acre-feet are available for desalination.Currently, 38 brackish groundwater desalination
plants, many of which are small-scale facilities and pilot plants, are operational.
While past studies estimated volumes, they failed to assess groundwater quality. In 2009 a
program was funded and implemented todevelop better tools to assess parameters, characterize
and map brackish groundwater aquifers, and develop flow models to determine aquifer
Rainwater harvesting is the forgotten practice of capturing, storing, and using rainwater. One
inch of rainfall that falls on a 2,000 square foot roof yields 1,000 gallons of harvestable water.
Average household systems can collect as much as 32,000 gallons per year even in a semi-arid
region. Rainwater collected is suitable for use in landscape irrigation, household use, and may
be suitable for drinking with minimum treatment. Large-scale systems are being developed by
Aquifer Storage and Recovery
During periods of heavy rain, appropriated surface water can be collected for subsequent
retrieval and injected, via well used for both injection and recovery, into a geologic formation
capable of underground storage (Class V aquifer).Stored water can be retrieved in dry or drought
years to help meet demand.Today, more than 75 ASR wells are operational in the United States,
compared to only three in 1968.Texas is lagging behind other states with only 67 Class V
aquifers in use today. Feasibility studies using different water supply sources, in addition to
different types of aquifers, show the technology is viable but many regulatory and legal barriers
Reuse and reclamation of wastewater is drought-proof and a key component in ensuring future
water supply. Texas is expected to nearly double its reuse capacity by 2060.Domestic or
municipal wastewater can be reclaimed and treated to a quality suitable for either direct or
indirect reuse. In direct reuse, effluent is piped directly from wastewater treatment plant to point
of use. Indirect reuse is when effluent re-enters a river, stream, or aquifer and is retrieved for
subsequent use at a different point in the system.Reclaimed water is commonly used for
industrial and power plant cooling water.
Reusing treated wastewater effluent from wastewater treatment plantsafter further treatment at an
integrated membrane facility in close proximity to industrial users, can supply industrial users
with water suitable for use as process and boiler water. Reuse of this water releases the surface
water for currently used for industry to meet other needs.
The atmosphere contains 0.001% of the Earth’s total water reservoir volume of 350 million cubic
miles. Water-from-air technology converts the humidity in the atmosphere to liquid water using
refrigeration methods that cool the air below its “dew point” Site-specific designs for tropical
coastal sites with access to deep, cool ocean waters that are used as a coolant produce freshwater
from saline water without pumping salts back into the ocean. Solar powered desalination units
and solar powered atmospheric generation units are currently under development. These
processes do not require fossil fuel to operate, and do not produce toxic by-products that require
disposal. Units can be either small-scale or large-scale.
Identifying and developing new technologies, along with a strategic water management plan that
includes using existing sources wisely, is absolutely essential in ensuring a safe, sustainable
water supply. Humankind cannot continue to squander our most precious resource.Future
generations will ultimately suffer if our misuse continues unchecked. There is no substitute for
Texas Water Development Board [homepage on the Internet]. (TX): n.d. [cited 2011 Apr. 4].
Available from: http://www.twdb.state.tx.us.
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Warair [homepage on the Internet]. n.d. [cited 2011 Apr. 3]. Available from:
DeSalWave[homepage on the Internet]. n.d. [cited 201 Apr. 4]. Available from:
Texas Water Development Board (USA) Ship Channel Wastewater Reclamation and Reuse
Feasibility Study Final Report. Austin (TX): 2005 Oct.