The aquifer systems in Florida, particularly those along the coastal areas, are susceptible to water
quality 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 aquifer
system through over pumpage of wellfields. Lateral intrusion of seawater can also occur through over
pumpage and the failure to maintain a positive potentiometric divide between the wellfield and the
ocean. 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-yield
analysis 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 and
wellfields, a better understanding of the water supply, the source water protection, and the safe yield
can be determined.
The case study involves the tracking of water quality over time for the City of Palm Bay. Chloride
concentrations in several wells have nearly tripled since their construction and initial testing. By using
major ion analyses and Piper trilinear diagrams the degradation of the water supply in the surficial
aquifer 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 supply
include irrigation water from Floridan aquifer wells by both residential and commercial users, surface
water drainage from agricultural areas west of the city, leakage of water from improperly abandoned
Floridan aquifer wells, and some upconing from the intermediate and Floridan aquifers. The
movement of major ion facies from an initial condition towards Floridan aquifer type water is evident
in 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 wellfield
design differences and potentially different hydrogeological conditions. By understanding changing
water quality conditions over time, one can better provide for source water protection and optimize
wellfield operation in order to provide a sustainable potable water supply. Includes 11 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 540 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 10 |
| Published : | 06/15/2003 |
