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Farm districts preserve fresh groundwater with recycled wastewater The Watsonville, California, recycled water facility, completed in , purifies wastewater from the city of Watsonville for use by farmers in the Pajaro Valley.
Mapping Central Coast Saltwater Intrusion. Water managers ask two central questions about saltwater intrusion, said Rosemary Knight, the Stanford geophysicist who is leading the research. They want to know where the salt is and how long until it hits a water supply well.
The answer for the Central Coast is not as simple as textbook hydrology suggests, Knight explained. To understand the variability, Knight and her colleagues went on an expedition. Traditionally, saltwater intrusion is measured by piecing together data from a string of individual wells. Gaps in the data exist where there are no wells. Instead, the researchers used new mapping techniques that yield a high-definition image. They surveyed, meter by meter, 40 kilometers 24 miles of coastline between Santa Cruz and Monterey, placing pairs of electrodes on the beach and measuring the electric charge between them, which detects the intensity of salt concentrations.
The maps, which are now being submitted to scientific journals for peer review, are a snapshot in time, a picture of saltwater intrusion when the measurements were taken. Continuous monitoring would be ideal, but Knight knows that the clearer image from the electrode survey will help managers improve their computer models, to show where the salt might travel next and how quickly it will move.
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Google Analytics Cookies. Other external services. These wells create a high potentiometric surface, which allows for the pumping of groundwater below sea level landward of a groundwater ridge created.
In some instances, barrier wells have been set up near the shore to pump out salt water and recharge a fresh water gradient toward the sea. In all of these cases, hydrologic studies and water quality monitoring are essential to help better understand the movement and interaction of fresh water and salt water in the subsurface, and determine the best method to manage saltwater intrusion.
Potentiometric surface mapping of an aquifer can provide important information determining the direction of groundwater flow within a confined aquifer. Plotting water level elevations on a map and contouring the results determines this. The contoured surface is known as the potentiometric surface, which is actually a map of the hydraulic head in the aquifer. Monitoring well networks allow continuous observation of the saltwater interface, after management strategies have been put in place.
This provides early warnings of saltwater intrusion and tracks the effectiveness of the strategy. Overall, proper groundwater monitoring techniques and groundwater management, combined with groundwater conservation are needed to keep saltwater intrusion under control, and ensure fresh water supplies are sustained for future generations.
Alley, William M. Geological Survey Circular: Anning, David. Southwest Hydrology. Atwater, Richard. Barlow, Paul M. De Breuck, W. Doremus, Dale. Driscoll, Fletcher G. Johnson Division, St. Paul, Minnesota pp Edwards, Brian D.
Geological Survey Fact Sheet Freeze, Allan R. Groundwater: Groundwater Source Evaluation. Hibbs, Barry, and Mercedes Merino. Hinrichsen, Don. Ocean Planet in Decline. Accessed: November 7, McNew, Elizabeth R. Reed, T. Geological Survey Scientific Investigations Report Freshwater-Saltwater Interactions Saltwater intrusion is a major concern commonly found in coastal aquifers around the world.
Deep recharge well creates groundwater ridge. Sampling Biases in Conventional Monitoring Wells. Page Two. Page Three. Page Four. Fracture Network Characteristics. Dissolved Phase Plume. In that area, a widespread network of surface-water canals is used to transport fresh water from inland water-storage locations during the dry season to coastal regions, where the water is recharged through the canals to the underlying aquifer to slow saltwater intrusion in the aquifer.
In addition to conventional methods, scientific and innovative strategies are now being used to control or manage saltwater intrusion along the Atlantic coast. These include aquifer storage and recovery systems and desalination systems.
Aquifer storage and recovery ASR is a process by which water is recharged through wells into a suitable aquifer, stored for a duration, and then extracted from the same wells when needed 8.
Typically, water is stored during rainy and wet seasons and pumped during dry seasons. Desalination is a water-treatment process that produces freshwater by removing dissolved salts from saline or brackish waters by using a membrane-based process called reverse osmosis.
Desalination systems are increasingly being adopted in the United States. One of the exciting aspects of the increased use of desalination systems is that it changes the perspective on saline or brackish water from that of a potential water problem a contaminant to that of a potential water source. The desalination plant in Cape May, New Jersey is capable of producing 2 million gallons treated water output per day and was installed at a total cost of USD 5 million in 9.
Despite the regulatory and non-regulatory efforts to manage salt intrusion, there are several challenges and opportunities associated with this problem. Some of the issues that need immediate attention are,. Because of increasing awareness of the critical role of ground-water in sustaining coastal populations, ecosystems, and economies, the time is right to review some of the essential water-management issues and scientific principles related to ground-water and to identify some of the management challenges that lie ahead.
As coastal populations and ground-water use increase, new monitoring and research efforts will be needed to characterize the occurrence and hydrodynamics of saline ground-water in different types of coastal terrains.
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