Water into Salt: Salt Water Intrusion in South Florida

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SaltwaterIntrusionBy Beth Kelly

[Graphic: Saltwater intrusion by Florida’s Water.] Shrinking lakes and streams endanger the entire framework of our society. And while the wildfires and drought currently plaguing California and other Western states have managed to catch mainstream media attention, the contamination of natural aquifers has gone largely unreported outside local news. As other states encounter the effects of increasingly shallow aquifers, however, the tremendous urgency of the situation will inevitably come to light. But will it be too late?

A major issue in densely populated south Florida — which includes major cities like Miami and Fort Lauderdale — seawater intrusion into the Biscayne aquifer has caused the loss of a number of water wells in the area. Saltwater has already spread 6 miles inland in Broward County and is likely to continue creeping westward, impacting the drinking water from underground sources that supply ninety percent of South Florida. Some methods of combating this issue, such as desalination and wastewater reuse, are being implemented to remedy the problem, but both present the problem of cost and energy inefficiency.

In general, shallow, permeable water table aquifers are at the highest risk of contamination. One such shallow aquifer is the Biscayne, which lies under Dade, Broward and Palm Beach counties. An overpumping of the Floridan and Biscayne aquifers has lowered the aquifer levels and artesian pressures, reducing surface water flow from the springs to rivers and lakes. Many new technologies enable the direct analysis of groundwater, such as fiber optic chemical sensors, which can be utilized even in the harshest of environmental conditions to detect a variety of pollutants. But while we may have developed more advanced methods of measuring environmental impact, we still need to work on ways in which to ameliorate causal issues at the root of these problems.

Restoration of the Everglades would also do much to improve the freshwater situation for South Florida, but unfortunately is a long-term project that will take decades to advance. Diminished springs and their reduced river flow have increased pollution from fertilizer and surface nutrients. Overpumping has made aquifers susceptible to intrusion, increased the potential for sinkholes and damaged wetlands. The overpumping of groundwater causes the water table to drop, which leads to more and deeper wells being drilled. Saltwater from the ocean underlies the freshwater in underground aquifers and will move into a space where freshwater is depleted, migrating inland and upward towards the surface. The deep wells then bring up brine instead of freshwater, and other springs and traditional sources of freshwater become contaminated by saltwater.

Moreover, the freshwater that is used for agriculture is contaminated by fertilizer as it runs off the fields back into rivers and streams. Water that is pumped from the wells is not restored to the aquifers, but runs off, eventually joining the ocean where it contributes to sea level rising, exacerbating the contamination.

Saltwater intrusion is driven over decades by climate change, that in turn is driven by global warming due to the emission of greenhouse gases from over consumption of fossil fuels. Although the effects of climate change and sea-level rise are inextricably linked in south Florida, climate change is not acknowledged as an ongoing phenomenon wreaking havoc with the environment. What can be done in the face of this issue is to treat the problems at the level of freshwater resources.

Overpumping, pollution, and waste have led to water problems now because water has always been considered an infinite resource – nor should water be treated as a profit-making commodity. Instead, wasteful practices could be redressed by setting reasonable market prices. If users are charged a market price for consumption at the wellhead, they would adopt less wasteful practices or seek low-cost technologies and methodologies for water use reduction.

South Florida is not the only place where saltwater intrusion has been the cause of freshwater scarcity. In Cape May, NJ, groundwater extraction has lowered water tables by up to 30 meters. With the water table reduced to below sea level, this contamination has caused the closure of over 120 water supply wells due to contamination since the 1940s.

The South Florida megalopolis is made up in part by recovered freshwater swampland not far from rising sea level. According to water.org, every day, more than 2,000 people die of diarrheal disease caused by inadequate drinking water, sanitation and hygiene – a public health burden which South Florida is spared as part of the developed world. In the face of climate change and rising sea levels, and a past expectation of infinite freshwater supply, maintaining freshwater supplies will remain challenging while simultaneously mitigating environmental damage to the unique springs and estuaries surrounding the Everglades.


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