Post by jonsdigs on Apr 10, 2007 12:15:39 GMT -5
Sinkholes drain upper Peace
04/08/07
Charlotte (FL) Sun Herald
Agency's fix doesn't address aquifer level
BARTOW -- A section of the upper Peace River went dry this week. Its entire flow drained down a series of sinkholes and crevices in a 10-mile stretch between Bartow and Fort Meade.
Most of the flow swirled down a 20-foot-wide funnel-shaped hole called "Dover Sink" over the past couple of weeks.
By Thursday, the river didn't even make it that far. Now, one has to hike several miles upstream along a dry, sandy riverbed littered with the carcasses of dead fish, to find the river's end.
That's where a smaller hole is now big enough to swallow the river's flow.
In the river's flood plain, a half-mile-wide area forested with old cypress trees, there are more crevices, enough to make hiking treacherous. They take water only when the river is at flood stage.
But in a couple of them, water could be seen coursing rapidly through as if in an underground brook.
It's the fifth time in the past seven years that the river's flow disappeared underground.
Some 10 million gallons per day has been draining from the river into a karst limestone layer that forms the top of the Intermediate Aquifer in that area ever since the 1940s.
That's when excessive pumping primarily for phosphate mining drew down a deeper aquifer, known as the Floridan, by some 60 feet, according to U.S. Geological Survey reports.
Karst limestone is a sedimentary rock formation in which freshwater, over millions of years, had dissolved holes.
In the dry bottom of the upper Peace River this week, the karst limestone appeared to have as many holes as Swiss cheese.
Sinkholes are created when the limestone roof caves in to an underground cavity.
In Central Florida, the formation of sinkholes has been accelerated by man's withdrawal of water, which diminishes the hydraulic support for the limestone layer, according to USGS studies.
Also, surface water, which is slightly acidic, dissolves limestone, which is alkaline. So, the river's water can increase the erosion of the limestone over time.
The Southwest Florida Water Management District is responsible for maintaining water resources for both public supply and the ecosystem.
The district, in its most recent 20-year comprehensive plan, calls for degraded water resources to be restored "to a naturally functioning condition."
Because of the connection between surface and underground waters in Florida's geology, protecting them both is "imperative," the plan states.
Establishing minimum levels for ground waters is an "important tool" for accomplishing that goal, the plan states.
But the water district's proposed fix for the upper Peace River contains no plan for restoring the level of the aquifer near Bartow.
The district also has no plan to establish a minimum level for the aquifer in the upper Peace area, said Mark Barcelo, a hydrological section manager for the water district.
Instead, the district is planning to spend $80 million raising the level of Lake Hancock, located 10 miles upstream.
More water could then be released from the lake during dry spells to keep the river flowing despite the amount draining down the sinkholes, Barcelo said.
The district also envisions building concrete berms in the river's channel to keep its flow from draining down certain, larger sinkholes, he said.
The only aquifers for which the district is setting minimum levels are along the coast, where they are threatened by saltwater intrusion, Barcelo said.
"We have set a minimum aquifer level where the aquifer itself is a concern," he said.
However, Barcelo said the district doesn't consider the aquifer under the upper Peace an important water body.
It's the Peace River that is the concern, he said.
Barcelo said the district's Southern Water Use Caution Area program, which discourages new well water permits within an eight-county region, has also served to help protect the aquifer under the upper Peace.
He also said, since water withdrawals for phosphate mining peaked in the late 1970s, the aquifer has recharged, to a degree.
It now averages between 40 and 50 feet below its historical levels, instead of 50 to 60 feet below.
Full Article
04/08/07
Charlotte (FL) Sun Herald
Agency's fix doesn't address aquifer level
BARTOW -- A section of the upper Peace River went dry this week. Its entire flow drained down a series of sinkholes and crevices in a 10-mile stretch between Bartow and Fort Meade.
Most of the flow swirled down a 20-foot-wide funnel-shaped hole called "Dover Sink" over the past couple of weeks.
By Thursday, the river didn't even make it that far. Now, one has to hike several miles upstream along a dry, sandy riverbed littered with the carcasses of dead fish, to find the river's end.
That's where a smaller hole is now big enough to swallow the river's flow.
In the river's flood plain, a half-mile-wide area forested with old cypress trees, there are more crevices, enough to make hiking treacherous. They take water only when the river is at flood stage.
But in a couple of them, water could be seen coursing rapidly through as if in an underground brook.
It's the fifth time in the past seven years that the river's flow disappeared underground.
Some 10 million gallons per day has been draining from the river into a karst limestone layer that forms the top of the Intermediate Aquifer in that area ever since the 1940s.
That's when excessive pumping primarily for phosphate mining drew down a deeper aquifer, known as the Floridan, by some 60 feet, according to U.S. Geological Survey reports.
Karst limestone is a sedimentary rock formation in which freshwater, over millions of years, had dissolved holes.
In the dry bottom of the upper Peace River this week, the karst limestone appeared to have as many holes as Swiss cheese.
Sinkholes are created when the limestone roof caves in to an underground cavity.
In Central Florida, the formation of sinkholes has been accelerated by man's withdrawal of water, which diminishes the hydraulic support for the limestone layer, according to USGS studies.
Also, surface water, which is slightly acidic, dissolves limestone, which is alkaline. So, the river's water can increase the erosion of the limestone over time.
The Southwest Florida Water Management District is responsible for maintaining water resources for both public supply and the ecosystem.
The district, in its most recent 20-year comprehensive plan, calls for degraded water resources to be restored "to a naturally functioning condition."
Because of the connection between surface and underground waters in Florida's geology, protecting them both is "imperative," the plan states.
Establishing minimum levels for ground waters is an "important tool" for accomplishing that goal, the plan states.
But the water district's proposed fix for the upper Peace River contains no plan for restoring the level of the aquifer near Bartow.
The district also has no plan to establish a minimum level for the aquifer in the upper Peace area, said Mark Barcelo, a hydrological section manager for the water district.
Instead, the district is planning to spend $80 million raising the level of Lake Hancock, located 10 miles upstream.
More water could then be released from the lake during dry spells to keep the river flowing despite the amount draining down the sinkholes, Barcelo said.
The district also envisions building concrete berms in the river's channel to keep its flow from draining down certain, larger sinkholes, he said.
The only aquifers for which the district is setting minimum levels are along the coast, where they are threatened by saltwater intrusion, Barcelo said.
"We have set a minimum aquifer level where the aquifer itself is a concern," he said.
However, Barcelo said the district doesn't consider the aquifer under the upper Peace an important water body.
It's the Peace River that is the concern, he said.
Barcelo said the district's Southern Water Use Caution Area program, which discourages new well water permits within an eight-county region, has also served to help protect the aquifer under the upper Peace.
He also said, since water withdrawals for phosphate mining peaked in the late 1970s, the aquifer has recharged, to a degree.
It now averages between 40 and 50 feet below its historical levels, instead of 50 to 60 feet below.
Full Article