AWWA ACE58273

The aquifer systems in Florida, particularly those along the coastal areas, are susceptible to waterquality degradation through lateral intrusion and upconing. Surficial and intermediate aquifer systems'water supplies are often impacted by the upconing of brackish or salt water from the Floridan aquifersystem through over pumpage of wellfields. Lateral intrusion of seawater can also occur through overpumpage and the failure to maintain a positive potentiometric divide between the wellfield and theocean. Other contaminant sources such as irrigation wells, abandoned wells, drainage canals, landfills,etc., can also provide the potable water supply with major ions, which can complicate a safe-yieldanalysis with regards to changes in water quality. By periodically tracking major ions (Ca, Mg, Na, K,Cl, CO3, HCO3, and SO4) and their relationship to one another through the history of wells andwellfields, a better understanding of the water supply, the source water protection, and the safe yieldcan be determined.The case study involves the tracking of water quality over time for the City of Palm Bay. Chlorideconcentrations in several wells have nearly tripled since their construction and initial testing. By usingmajor ion analyses and Piper trilinear diagrams the degradation of the water supply in the surficialaquifer system was attributed to water from the Floridan aquifer and not lateral intrusion of seawater.The actual sources of the Floridan aquifer water contaminating the surficial aquifer water supplyinclude irrigation water from Floridan aquifer wells by both residential and commercial users, surfacewater drainage from agricultural areas west of the city, leakage of water from improperly abandonedFloridan aquifer wells, and some upconing from the intermediate and Floridan aquifers. Themovement of major ion facies from an initial condition towards Floridan aquifer type water is evidentin the Piper diagrams indicating the contaminant source for both the eastern and western wellfields.Water quality changes in the western wellfield indicate slightly different conditions due to wellfielddesign differences and potentially different hydrogeological conditions. By understanding changingwater quality conditions over time, one can better provide for source water protection and optimizewellfield operation in order to provide a sustainable potable water supply. Includes 11 references, figures.

Product Details

Edition:

Vol. - No.

Published:

06/15/2003

Number of Pages:

10

File Size:

1 file , 540 KB