Who Wants to Do Without Water?

There is a continuing absence of consideration for regional aquifer sustainability by the water management districts that are tasked with protecting this public resource. The Floridan Aquifer, both upper and lower, from the Panhandle through peninsular Florida is over-tapped.

There should be no more discussion about increased groundwater extractions. The only discussion should be focused on how to expeditiously reduce groundwater pumping and how to increase aquifer levels and spring flows.

The above quote is from Dr. Robert Knight’s latest article in the Gainesville Sun and deals with the projected increases demanded by the cities of Jacksonville and Gainesville.  These increases, if effected, will further reduce the springs of the Santa Fe River, as well as other local nearby water sources.

You can read the original article at this link to today’s Sun, or continue here for a reproduction, graciously permitted to OSFR by  Nathan Crabbe and his newspaper.

Robert Knight: Jacksonville and Gainesville play roles in water imbalance

By Robert Knight
Special to The Sun
Published: Sunday, April 26, 2015 at 6:01 a.m.
Last Modified: Friday, April 24, 2015 at 5:26 p.m.

 

The law of conservation of mass dictates that in a closed system, any substance (mass or energy) is conserved over time. In other words, “Nothing comes from nothing.”

Water on earth is one of the substances that is governed by this natural law. Fresh water that recharges the Floridan Aquifer is conserved. Inputs must equal outputs, less any change in stored groundwater.

Prior to the drilling of wells into the Floridan Aquifer, recharge from rainfall (inputs) and spring flows (outputs) were in general balance. Aquifer levels were higher and spring flows greater than today.

Since the introduction of groundwater supply wells in the 1880s, Floridan Aquifer levels and resulting spring flows have declined due to the increasing groundwater extraction. This is an example of the law of the conservation of mass.

While nearly all water use in North Florida is supplied by groundwater from the Floridan Aquifer, some uses have a greater impact on aquifer levels than others. In terms of public water supplies, a comparison can be made between Gainesville’s and Jacksonville’s net groundwater consumption rates.

Gainesville Regional Utilities pumps about 22 million gallons of groundwater each day. An estimated 70 percent of this pumped and used groundwater is ultimately recharged back to the Floridan Aquifer through injection wells and groundwater recharge wetlands. The net effect of GRU’s 65,000 customers on reduced spring flows and aquifer storage is about 7 million gallons each day, for a gross per capita net consumption of about 100 gallons per day.

In contrast, a very minor fraction of the average 100 million gallons per day of groundwater extracted by JEA (formerly Jacksonville Electric Authority) is returned to the Floridan Aquifer. Instead, this used water flows directly or indirectly into the Lower St. Johns River and out to tide. Based on the conservation of mass principal, JEA’s groundwater use reduces both the level of water in the Floridan Aquifer and the discharge of North Florida springs by about 100 million gallons each day, for a gross per capita water use of about 330 gallons per day for JEA’s 305,000 water customers.

Both JEA’s and GRU’s net groundwater uses are negatively impacting lake levels near Keystone Heights and spring flows in the Suwannee, Santa Fe and Ichetucknee Rivers. But the magnitude of these effects is very different, with about three time’s greater impact per person in Jacksonville than in Gainesville.

Both of these city utilities need to acknowledge their roles in declining groundwater levels and reduced surface water flows and levels. Both of these cities need to make significant reductions in the magnitude of their impacts by mandating increased water conservation and by increasing the recharge of clean water to the Floridan Aquifer.

While GRU is actively pursuing options for water conservation and groundwater recharge, the city recently requested and received a water use permit that allows a groundwater pumping increase of about 10 million gallons per day.

On the other hand, JEA appears to be making limited efforts to increase water conservation or recharge of used water to the Floridan Aquifer. In a recent report by JEA’s consulting engineers, the authors concluded that an additional 20 million gallons per day of groundwater supply would be needed over the next 20 years to satisfy Jacksonville’s increasing thirst. Increased water conservation and groundwater recharge were not ranked high enough to be pursued as viable options for supplying JEA’s increased water demand.

The law of mass conservation tells us that GRU’s and JEA’s plans to extract a combined 30 million gallons per day of additional groundwater from the Floridan Aquifer will further reduce aquifer and lake levels, and spring flows. Yet state-financed studies across north and central Florida have determined that the area’s lakes, rivers and springs are already significantly impacted by excessive groundwater withdrawals.

My question for leadership at the Suwannee and St. Johns River Water Management Districts is: Who’s lake and who’s spring will supply that additional groundwater to GRU’S and JEA’s customers? There is a continuing absence of consideration for regional aquifer sustainability by the water management districts that are tasked with protecting this public resource. The Floridan Aquifer, both upper and lower, from the Panhandle through peninsular Florida is over-tapped.

There should be no more discussion about increased groundwater extractions. The only discussion should be focused on how to expeditiously reduce groundwater pumping and how to increase aquifer levels and spring flows.

Robert Knight is director of the Howard T. Florida Springs Institute in Gainesville.

This post rendered with LFS.