Water bodies, watersheds and storm water

Keystone Heights area lakes

Keystone Heights is a rural town located on a high sand ridge in southwestern Clay County. One of the area’s most distinguishing features is its numerous lakes, which were created by the collapse of a layer of limestone that lies beneath the lakes’ sandy bottoms and often a layer of clay. Called karst terrain, this geologic feature of the Keystone Heights area is natural.

In recent years, Keystone Heights’ lakes have been severely impacted by prolonged drought conditions, as were many lakes across Florida. Though the impacts to the lakes are visually dramatic and detrimental to real estate values and recreation, lake level fluctuations are a natural occurrence. Water levels can vary over time from short-term, storm-related rises to long-term fluctuations caused by rainfall trends.

Lake levels can change seasonally and annually. During periods of below-normal rainfall, lake levels drop, at times becoming so low that boating access becomes limited. Lake levels may continue to decline for several years, impairing the use of docks and affecting lakeside businesses.

Lake levels generally rebound, at times leading to water levels so high that lakeside property owners may experience too much water.

In Keystone, many lake bottoms are made of sandy, permeable soils that allow significant downward leakage of water. Blue Pond and lakes Lowry, Magnolia, Brooklyn and Geneva are interconnected by streams, known as Alligator Creek. The lakes in the Alligator Creek chain all leak downward into the Floridan aquifer system.

When Alligator Creek ceases to flow into Lake Brooklyn, the lake’s level rapidly falls. Lake Brooklyn exhibits large fluctuations in water levels as water drains to the aquifer during dry periods and as water is replenished faster than it drains during wet periods.

The Keystone Heights lakes receive water by directly capturing precipitation, from stormwater runoff, by groundwater seepage from surficial aquifer systems recharged by rainfall percolation, and from streams fed by seepage from groundwater and flow from other lakes. Rainfall is the only source of water for all of these flow paths to lakes.

Accomplishments

These three pools of water combine to make one large lake (Lake Brooklyn) during times of higher water levels. This photo was taken in July 2002 at the height of a drought.

This photo of Lake Brooklyn from 2005 shows how the lake had risen due to increased rainfall in the area.

The St. Johns River Water Management District has been involved in numerous efforts to bring greater understanding and has dedicated significant staff and financial resources to the Keystone Heights’ lakes issue, including in at least nine regional studies.

The District’s key contributions to the area have included:

• Providing funds for an independent consultant to investigate the causes of low lake levels in the Keystone Heights lakes. The consultant completed the study in 2002 and generated a report offering a broad range of ideas to increase water levels in Lake Brooklyn, primarily by increasing streamfall when rainfall does occur. The report identified ideas that were technologically feasible, but the ideas were not screened based on economic or environmental feasibility.
• Cooperatively funding water resource investigations by the U.S. Geological Survey, as well as surface geophysical investigations
• Coordinating and providing $32,000 in cost-sharing funds to initiate a project, in coordination with the Suwannee River Water Management District and DuPont, that recaptures a portion of DuPont’s Florida mine surface discharge and directs it to the Keystone Heights lakes watershed
• Monitoring surface and groundwater levels

The Alligator Creek basin is one of the most heavily instrumented small basins in the District. The District routinely measures surface water levels every hour, when conditions permit, in Blue Pond, Lake Lowry, Lake Magnolia and Lake Geneva. Lake Brooklyn and Brooklyn Bay are measured weekly when low water conditions will not accommodate a permanent gauge.

In addition, the District has five gauging stations on Alligator Creek that monitor stream flow:

Water levels in Lake Brooklyn were above average in April 1996.

This photo from 2009 shows a healthy inflow of water to Lake Brooklyn from Alligator Creek.

• Alligator Creek inflow to Lake Lowry
• Seep spring inflow to Lake Lowry
• Alligator Creek outflow from Lake Lowry
• Alligator Creek outflow from Lake Magnolia
• Alligator Creek inflow to Lake Brooklyn

Also, daily discharge data are available for the inflow to and outflow from Lake Lowry.

Over the years, the District has installed 71 monitoring wells in the Keystone Heights area. While some wells were short-term, project-related wells to support many hydrologic investigations performed by the U.S. Geological Survey, the University of Florida and District staff, several are permanent additions to the District’s monitoring well network. The cost to install these wells totals approximately $274,000. In addition, surface and groundwater data collection in the Keystone Heights area costs about $45,000 annually and is reported monthly in the Keystone Heights area hydrologic conditions reports.

Other efforts include requiring local mining operations to reduce their dependence on groundwater supplies through the District’s consumptive use permitting process. In addition, local projects have been permitted by the District to improve flow to the Alligator Creek system. Permit applications such as these involve considerable staff time, including site visits by senior hydrologists and regulatory scientists and permit review by department and division directors.

While options have been permitted to increase water levels in Lake Brooklyn, some future efforts may be difficult, perhaps impossible, to permit due to the potential for adverse environmental impacts that some proposed options present. The District cannot be involved in efforts that would result in negative impacts.

For more information

To learn more about lake levels in the Keystone Heights area, contact Geoff Sample at (904) 448-7904 or gsample@sjrwmd.com.

Updated on 2-12-2010