Nitrate Sourcing and Ground Water Age for the Springs of Merritt’s Mill Pond Kevin DeFosset NWFWMD

HISTORICAL NITRATE CONCENTRATIONS JACKSON BLUE SPRING

DISCHARGE MEASURMENTS JACKSON BLUE – SPRING CREEK

July 2007 Discharge Measurements Measurement Section Discharge (cfs) Spring Crk ds Hwy Jackson Blue39.1 Merritt's Mill Pond16.9 Shangri-La3.9 Twin Caves1.6 Hole in the Wall1.3 Heidi Hole0.2 Gator Hole0.9 Springs Total7.9 Merritt's Mill Pond16.9 Springs Discharge7.9 Miscellaneous Discharge9

RECENT NITRATE CONCENTRATIONS MERRITT’S MILL POND SPRING

Magnesium, Barium, and Strontium Concentrations Merritt’s Mill Pond

Range of Nitrogen Isotope Values for Inorganic and Organic Nitrogen Sources NO 3 Concentrations vs. Delta 15 N-NO 3

SF 6 age 3 H/ 3 He Jackson Blue Shangri-La Twin Caves17.3Modern44 Hole in the Wall14Modern46.4 Heidi Hole Gator Hole9Modern>55 Dating Ground Water with SF 6 Stable, atmospheric gas Primarily of anthropogenic origin Record of atmospheric input over time Dating Ground Water with Tritium and Helium Tritium results from atmospheric nuclear bomb testing Record of atmospheric input over time Helium is decay product and helps to refine age Atmospheric gases (N, Ar, Kr, Xe, Ne, He) needed for age determination.

What can be said? Based on available data, ground water sources other than Jackson Blue Spring contribute between 11 and 46 percent of the discharge of Merritt’s Mill Pond. Elevated levels of nitrate exist at all springs in Merritt’s Mill Pond. Artificial fertilizer is the predominate source of nitrate for the springs of Merritt’s Mill Pond. The waters feeding Merritt’s Mill Pond are of mixed age.

COMPARISON OF HYDROLOGIC CONDITIONS EARLY 2008 – CURRENT Date Measurement Value DISCHARGE, cfs (USGS Gaging Station) 2/1/ /12/ WATER LEVEL, ft msl (NWFWMD Monitoring Well) 2/1/ /12/200884