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The investigation of water utility strategies to address various impacts (see Figure 2) yielded useful results for dissemination about preparing for future impacts. Detailed information from over thirty utilities in the USA was collected and is summarized in Table 2.

Table 2

Summary of adaptation measures implemented by some water supply utilities in the USA

 Challenge (threat/impact)  
Region/UtilitySWISLRDroughtOver-pumpingDescriptionSolutions (adaptation measures)Source
Arizona – Tucson Water    Water shortages Conservation and wastewater recycling. Wastewater is treated to secondary standards and stored in the aquifer (artificial storage and recovery – ASR). Megdal & Forrest (2015)  
California – City of Long Beach  Increased salinity. Area most threatened by present or future increases in groundwater demand. SWI threatens area's economy as high-value, salt-sensitive crops are grown. Developed groundwater management plans. Installed barrier (injection) wells (using potable water). Johnson (2007), Hodges et al. (2014), Nico Martin (2014) 
California – Monterey, Salinas Valley   Sudden increase in salinity. Groundwater levels appear stable, yet seawater intrudes (up to 5 to 8 km [3 to 5 miles] inland) and replaces fresh groundwater that has been pumped out. Provided reclaimed water for irrigation as potable water offset to slow SWI rate. Capture and diversion of surface water to offset pumping within the basin. Barlow & Reichard (2010)  
California – Oceano Community Services, District and Cities of Arroyo Grande, Grover Beach and Pismo Beach   Water shortages, land subsidence Implemented drought response plans/water conservation; maximized surface water deliveries, optimized surface water delivery infrastructure, regional coordination, improved groundwater monitoring (frequency, more transducers), sentry well improvements. Future plans to increase surfacewater storage, develop a groundwater model, increase surface water deliveries, look into recycling water, and enhance conjunctive use of groundwater. Heimel et al. (2012)  
California – Pajaro Valley Water Management Agency   High chloride levels Adopted basin management plan, proposing several conservation projects to reduce pumping by 90% and halt SWI. Carollo Engineers (2012)  
California – Palo Alto   High chloride levels were documented in studies due to groundwater over-abstraction in the first half of the 20th century (Iwamura 1980). Recent USGS study concluded that modern SWI is the result of mineral dissolution of marine sediments (Metzger 2002). Conducted studies and diversified supply sources. Todd Engineering (2005)  
California Department of Water Resources   Water shortages, land subsidence Installed salinity barriers on two rivers and other measures – increased conservation, surface water curtailments, increased oversight of groundwater use, increased real-time data and information, etc. Hodges et al. (2014), Croyle (2015) 
Florida – Boynton Beach   Action taken because of up-coning of saline waters. Adjusted wells to make them shallower (from 60 to 40 m [200 to 120 feet]). Installed monitoring wells as a pre-emptive measure. Using of existing water treatment facilities (east and west) to provide source options. Interdepartmental Climate Change Group (2009)  
Florida – City of Dania Beach   One of the main factors causing the salinity impacting drinking water sources has been development. History of salt issues tied to drainage canals now facilitates SWI into the aquifer. Moving wellfield away from the coast. Purchased water from nearby utilities. Bloetscher et al. (2010), Trimble et al. (1998), Interdepartmental Climate Change Group (2009) 
Florida – Dunedin   Water supply does not currently suffer from salinity issues, but in the 1990s there was a need for it to be addressed. The worst salinity conditions were seen prior to the construction of the RO plant, where water was pumped and treated at each well location, then distributed to nearby areas. Connect City wells by a raw water main, install an RO (reverse osmosis) water plant and add more wells to the system to spread out pumpage. Improved water management, together with drought restrictions, public education on water conservation, and the implementation of a reclaimed water system. Diaz et al. (2016)  
Florida – Hillsborough County    Salt intrusion into groundwater through channels. Tide gates installed at two channels of a creek. Diaz, Seckinger & Associates (1974, 1975), Deyle et al. (2007), GPI Southeast Inc. (2012) 
Florida – Miami    Extensive canal system has allowed salt water to intrude vertically in addition to the high permeability of the aquifer (groundwater) 1940s: Construction of salinity control dams. Todd (1974), Interdepartmental Climate Change Group (2009) 
Florida – Miami-Dade County Salt water movement northwestward from Tamiami Canal towards center of pumping in Miami wellfield. Salt water was detected at a depth of 50 feet and some wells were no longer usable. Installed salinity barriers (control gates at canals). Kohout (1960), Trimble et al. (1998), Interdepartmental Climate Change Group (2009) 
Florida – Peace River Manasota Regional Water Supply Authority, Lakewood Ranch    Tidally influenced surface water. Does not currently have a salinity problem, but is definitely at risk. Without a dam or salinity barrier, salinity levels could definitely increase with rising sea levels. Adaptive management portfolio:
  • Proactively planning and engineering solutions,

  • increased pumping capacity,

  • additional off-stream storage,

  • alternate sources, and

  • moving the intake further upstream.

Conductivity was modeled and correlated to tide-level-related water quality to anticipate changes in water quality since Peace River flows are tidally influenced. 
Morris et al. (2015)  
Florida – Putnam, Flagler and St. Johns County    Diminished yields/crop failure in row crops. Wells depths between 100 and 130 m (300 and 400 feet), with diameters between 150 to 200 mm (6 to 8 inches). 1960s: magnets installed on pipes (paramagnetism) to remove salt from water. Recently installed modern remedy: tile drainage implementation. Cooper et al. (1964), Munch et al. (1979), SJRWMD (2015)  
Florida – St. Johns County   High chloride area, coastal location and agricultural use of groundwater Implemented water conservation programs, created well field optimization program, back-plugged certain wells, developed alternative wellfields, modeling/studies on salinity. 
Georgia – Brunswick-Glynn Joint Water & Sewer Commission (BGJWSC)   Salinity problem near downtown is not the typical lateral encroachment of saltwater, but one of trapped saline water in a formation that migrates upward from the Lower Floridan aquifer (Fernandina permeable zone) to the Upper Floridan aquifer. Closure of saline wells and pumped from an alternative source. Installation of real time water level and water quality monitoring equipment to serve as an early warning system. Reductions of groundwater withdrawals. ARCADIS Geraghty & Miller Inc. (1999), Barlow (2003), NOAA (2011), Barlow & Reichard (2010), USEPA (2015a, 2015b, 2015c, 2015d), USGS (2015) 
Georgia – City of Savannah   Tidally influenced surface water. Water sources impacted by high salinity levels. Dredging has increased this vulnerability. Reduced withdrawals. Implementation of a regional SWI plan. ARCADIS Geraghty & Miller Inc. (1999), Barlow (2003), GAEPD (2006), CDM (2011); Roehler et al. (2013)  
Louisiana – Mississippi River (at Alliance in Plaquemines)   Salt water wedge moved up the Mississippi river and was going to affect the water quality at intakes Constructed a salt water sill in 1988, 1999, 2012 (a new sill will be needed approximately every 5 years). Rainey (2012), Soileau et al. (1990), USACE (2015)  
 Challenge (threat/impact)  
Region/UtilitySWISLRDroughtOver-pumpingDescriptionSolutions (adaptation measures)Source
Arizona – Tucson Water    Water shortages Conservation and wastewater recycling. Wastewater is treated to secondary standards and stored in the aquifer (artificial storage and recovery – ASR). Megdal & Forrest (2015)  
California – City of Long Beach  Increased salinity. Area most threatened by present or future increases in groundwater demand. SWI threatens area's economy as high-value, salt-sensitive crops are grown. Developed groundwater management plans. Installed barrier (injection) wells (using potable water). Johnson (2007), Hodges et al. (2014), Nico Martin (2014) 
California – Monterey, Salinas Valley   Sudden increase in salinity. Groundwater levels appear stable, yet seawater intrudes (up to 5 to 8 km [3 to 5 miles] inland) and replaces fresh groundwater that has been pumped out. Provided reclaimed water for irrigation as potable water offset to slow SWI rate. Capture and diversion of surface water to offset pumping within the basin. Barlow & Reichard (2010)  
California – Oceano Community Services, District and Cities of Arroyo Grande, Grover Beach and Pismo Beach   Water shortages, land subsidence Implemented drought response plans/water conservation; maximized surface water deliveries, optimized surface water delivery infrastructure, regional coordination, improved groundwater monitoring (frequency, more transducers), sentry well improvements. Future plans to increase surfacewater storage, develop a groundwater model, increase surface water deliveries, look into recycling water, and enhance conjunctive use of groundwater. Heimel et al. (2012)  
California – Pajaro Valley Water Management Agency   High chloride levels Adopted basin management plan, proposing several conservation projects to reduce pumping by 90% and halt SWI. Carollo Engineers (2012)  
California – Palo Alto   High chloride levels were documented in studies due to groundwater over-abstraction in the first half of the 20th century (Iwamura 1980). Recent USGS study concluded that modern SWI is the result of mineral dissolution of marine sediments (Metzger 2002). Conducted studies and diversified supply sources. Todd Engineering (2005)  
California Department of Water Resources   Water shortages, land subsidence Installed salinity barriers on two rivers and other measures – increased conservation, surface water curtailments, increased oversight of groundwater use, increased real-time data and information, etc. Hodges et al. (2014), Croyle (2015) 
Florida – Boynton Beach   Action taken because of up-coning of saline waters. Adjusted wells to make them shallower (from 60 to 40 m [200 to 120 feet]). Installed monitoring wells as a pre-emptive measure. Using of existing water treatment facilities (east and west) to provide source options. Interdepartmental Climate Change Group (2009)  
Florida – City of Dania Beach   One of the main factors causing the salinity impacting drinking water sources has been development. History of salt issues tied to drainage canals now facilitates SWI into the aquifer. Moving wellfield away from the coast. Purchased water from nearby utilities. Bloetscher et al. (2010), Trimble et al. (1998), Interdepartmental Climate Change Group (2009) 
Florida – Dunedin   Water supply does not currently suffer from salinity issues, but in the 1990s there was a need for it to be addressed. The worst salinity conditions were seen prior to the construction of the RO plant, where water was pumped and treated at each well location, then distributed to nearby areas. Connect City wells by a raw water main, install an RO (reverse osmosis) water plant and add more wells to the system to spread out pumpage. Improved water management, together with drought restrictions, public education on water conservation, and the implementation of a reclaimed water system. Diaz et al. (2016)  
Florida – Hillsborough County    Salt intrusion into groundwater through channels. Tide gates installed at two channels of a creek. Diaz, Seckinger & Associates (1974, 1975), Deyle et al. (2007), GPI Southeast Inc. (2012) 
Florida – Miami    Extensive canal system has allowed salt water to intrude vertically in addition to the high permeability of the aquifer (groundwater) 1940s: Construction of salinity control dams. Todd (1974), Interdepartmental Climate Change Group (2009) 
Florida – Miami-Dade County Salt water movement northwestward from Tamiami Canal towards center of pumping in Miami wellfield. Salt water was detected at a depth of 50 feet and some wells were no longer usable. Installed salinity barriers (control gates at canals). Kohout (1960), Trimble et al. (1998), Interdepartmental Climate Change Group (2009) 
Florida – Peace River Manasota Regional Water Supply Authority, Lakewood Ranch    Tidally influenced surface water. Does not currently have a salinity problem, but is definitely at risk. Without a dam or salinity barrier, salinity levels could definitely increase with rising sea levels. Adaptive management portfolio:
  • Proactively planning and engineering solutions,

  • increased pumping capacity,

  • additional off-stream storage,

  • alternate sources, and

  • moving the intake further upstream.

Conductivity was modeled and correlated to tide-level-related water quality to anticipate changes in water quality since Peace River flows are tidally influenced. 
Morris et al. (2015)  
Florida – Putnam, Flagler and St. Johns County    Diminished yields/crop failure in row crops. Wells depths between 100 and 130 m (300 and 400 feet), with diameters between 150 to 200 mm (6 to 8 inches). 1960s: magnets installed on pipes (paramagnetism) to remove salt from water. Recently installed modern remedy: tile drainage implementation. Cooper et al. (1964), Munch et al. (1979), SJRWMD (2015)  
Florida – St. Johns County   High chloride area, coastal location and agricultural use of groundwater Implemented water conservation programs, created well field optimization program, back-plugged certain wells, developed alternative wellfields, modeling/studies on salinity. 
Georgia – Brunswick-Glynn Joint Water & Sewer Commission (BGJWSC)   Salinity problem near downtown is not the typical lateral encroachment of saltwater, but one of trapped saline water in a formation that migrates upward from the Lower Floridan aquifer (Fernandina permeable zone) to the Upper Floridan aquifer. Closure of saline wells and pumped from an alternative source. Installation of real time water level and water quality monitoring equipment to serve as an early warning system. Reductions of groundwater withdrawals. ARCADIS Geraghty & Miller Inc. (1999), Barlow (2003), NOAA (2011), Barlow & Reichard (2010), USEPA (2015a, 2015b, 2015c, 2015d), USGS (2015) 
Georgia – City of Savannah   Tidally influenced surface water. Water sources impacted by high salinity levels. Dredging has increased this vulnerability. Reduced withdrawals. Implementation of a regional SWI plan. ARCADIS Geraghty & Miller Inc. (1999), Barlow (2003), GAEPD (2006), CDM (2011); Roehler et al. (2013)  
Louisiana – Mississippi River (at Alliance in Plaquemines)   Salt water wedge moved up the Mississippi river and was going to affect the water quality at intakes Constructed a salt water sill in 1988, 1999, 2012 (a new sill will be needed approximately every 5 years). Rainey (2012), Soileau et al. (1990), USACE (2015)  

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