Potentiometric Surface Map - September 2007

Sources of Nitrate and Estimated Groundwater Travel Times to Springs of the Santa Fe River Basin, 2013. AMEC

Potentiometric Surface Map - September 2007Springsheds Boundaries Delineated

2013 AMECStudy

Boundary

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Sources of Nitrate and Estimated Groundwater Travel Times to Springs of the Santa Fe River Basin, 2013. AMEC

Estim

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Aquifer Confining Layers in Alachua County

Aquafer Vulnerability and Stream-to-Sink Basins

Karst Landscapes

http://www.nwfwmd.state.fl.us/water-resources/springs/learn-about-springs/

Flow pathways connecting surface sources to aquifer

Unconfined Semi-Confined Confined

“indirect” flowpath

Surface runoff and subsurface pathway to aquifer via sinkholes

“restricted” flowpath

Mostly surface runoff and surficial aquifer

with limited connection to aquifer

“direct” flowpath

Vertical leaching directly to aquifer

Nitrate Concentrations in upper Floridan Aquifer September 2012

Springsheds Study Area Land Use

Sources of Nitrate and Estimated Groundwater Travel Times to Springs of the Santa Fe River Basin, 2013. AMEC

Sources of Nitrate and Estimated Groundwater Travel Times to Springs of the Santa Fe River Basin, 2013. AMEC

Estimated Nitrate-Nitrogen Loading by Land Use

http://www.alachuacounty.us/Depts/epd/WaterResources/GroundwaterAndSprings/SFRSBWG%20Presentations/130926_Nitrate%20Study%20in%20the%20Santa%20Fe%20Springs%20Restoration%20Focus%20Area_Katz.pdf

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Gro

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Gro

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Mill Creek Sink Dye Trace Study

http://www.alachuacounty.us/Depts/epd/WaterResources/GroundwaterAndSprings/Reports%20and%20Maps%20Documents/Mill%20Creek%20Sink%20Dye%20Trace%202005%20REPORTCmplt.pdf

Mill Creek & Lee Sink Dye Trace Study• Dye released July 26, 11:34• Dye first detected in Hornsby spring August 8 (13 days later)• Distance between Mill Creek sink and Hornsby Spring 6 miles• Groundwater flow rate between Mill Creek Sink and Hornsby Springs 2,440 ft/day• Lee Sink day trace travel rate 1,382 ft/day

http://www.alachuacounty.us/Depts/epd/WaterResources/GroundwaterAndSprings/Reports%20and%20Maps%20Documents/Mill%20Creek%20Sink%20Dye%20Trace%202005%20REPORTCmplt.pdf

http://www.alachuacounty.us/Depts/epd/WaterResources/GroundwaterAndSprings/Reports%20and%20Maps%20Documents/Mill%20Creek%20Sink%20Dye%20Trace%202005%20REPORTCmplt.pdf

Cover-subsidence sinkholes -Cover-subsidence sinkholes tend to develop gradually where the covering sediments are permeable and contain sand. In areas where cover material is thicker or sediments contain more clay, cover-subsidence sinkholes are relatively uncommon, are smaller, and may go undetected for long periods.

Cover-collapse sinkholes - Cover-collapse sinkholes may develop abruptly (over a period of hours). They occur where the covering sediments contain a significant amount of clay.

Two Types of Sinkhole Formation

US Geological Service

Stormwater Basins in Karst Landscapes- prone to sinkhole formation -

Alternative - Dispersed Treatment Train:• Provides treatment near source thereby reducing

volume and contaminant loads in attenuation pond.• Shallower pond depths lower hydraulic head

pressure and allow for greater soil thickness between bottom of pond and underlying limestone.

• Increases treatment surface area for soil, plant, and microbial interaction to improve water quality.

• Distributes risk among multiple treatment cells each of which has lower potential for solution/sink formation.

Can We Achieve 0.35 mg/L Nitrate-Nitrogen?

Loadings to Lower Santa Fe Springsheds

Sources of Nitrate and Estimated Groundwater Travel Times to Springs of the Santa Fe River Basin, 2013. AMEC

Back of Envelope Calculation 1:How much N Fertilizer can you lose per hectare and stay below

nitrate standards?

• Loss of 30 kg/ha in one years worth of recharge (assume 12 in ~0.3 m3/m2)= 10 mg/l (Class I drinking water standard)

• Loss of 1 kg/ha in one years worth of recharge (assume 12 in ~0.3 m3/m2)= 0.35 mg/l (Class III springs nitrate standard)

Land use Assumed Average Leaching

concentration

Hectares of Native Vegetation per hectare of land use (assuming

no denitrification)

Hectares of Native Vegetation per hectare of land use (assuming 30% denitrification)

Forage1 0.85 mg/l 1.4 ha 0.7 ha

Planted Pine3 1.0 mg/l 1.9 ha 1 ha

Residential4 2.0 mg/l 5 ha 3 ha

Citrus2 7.5 mg/l 20 ha 14 ha

Poultry1 10 mg/l 28 ha 19 ha

Row Crop1 25 mg/l 70 ha 47 ha

Dairy1 42.5 mg/l 120 ha 84 ha

For every hectare of intensive land use within a springshed how much native area (leaching at 0 mg/l) do you need to achieve 0.35 mg/l ?

Back of Envelope Calculation 2:

1Graetz et al, 2008; 2Graham et al, 2000 3Harper et al.,20074Tucker et al, 2013 fertilizer, no septic tanks

Past and Projected Nitrate Loads

Sources of Nitrate and Estimated Groundwater Travel Times to Springs of the Santa Fe River Basin, 2013. AMEC

Gronberg, J.M., and Spahr, N.E., 2012, County-level estimates of nitrogen and phosphorus from commercial fertilizer for the Conterminous United States, 1987–2006: U.S. Geological Survey Scientific Investigations Report 2012-5207, 20 p.

Nitrogen Fertilizer Use in Alachua County 1987-2006

1985 1990 1995 2000 2005 2010 -

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

Farm Non Farm Linear (Non Farm)

Year

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