Climate control of decadal-scale increases in apparent ages of eogenetic karst spring water

JOURNAL OF HYDROLOGY

卷:540

Article

Martin, Jonathan B.¹  Kurz, Marie J.^1,2  Khadka, Mitra B.¹ 

[1] Univ Florida, Dept Geol Sci, 241 Williamson Hall,POB 112120, Gainesville, FL 32611 USA

[2] UFZ Helmholtz Ctr Environm Res, Dept Hydrogeol, Permoserstr 15, D-04318 Leipzig, Germany

关键词: Groundwater recharge;    Groundwater remediation;    Florida karst;    Springs;    Water age;    Atlantic multidecadal oscillation;   

DOI  :  10.1016/j.jhydrol.2016.07.010

来源: Elsevier

【 摘 要 】

Water quantity and quality in karst aquifers may depend on decadal-scale variations in recharge or withdrawal, which we hypothesize could be assessed through time-series measurements of apparent ages of spring water. We tested this hypothesis with analyses of various age tracers (H-3/He-3, SF6, CFC-11, CFC-12, CFC-113) and selected solute concentrations [dissolved oxygen (DO), NO3, Mg, and SO4] from 6 springs in a single spring complex (Ichetucknee springs) in northern Florida over a 16-yr period. These springs fall into two groups that reflect shallow short (Group 1) and deep long (Group 2) flow paths. Some tracer concentrations are altered, with CFC-12 and CFC-113 concentrations yielding the most robust apparent ages. These tracers show a 10-20-yr monotonic increase in apparent age from 1997 to 2013, including the flood recession that followed Tropical Storm Debby in mid-2012. This increase in age indicates most water discharged during the study period recharged the aquifer within a few years of 1973 for Group 2 springs and 1980 for Group 1 springs. Inverse correlations between apparent age and DO and NO3 concentrations reflect reduced redox state in older water. Positive correlations between apparent age and Mg and SO4 concentrations reflect increased water-rock reactions. Concentrated recharge in the decade around 1975 resulted from nearly 2 m of rain in excess of the monthly average that fell between 1960 and 2014, followed by a nearly 4 m deficit to 2014. This excess rain coincided with two major El Nino events during the maximum cool phase in the Atlantic Multidecadal Oscillation. Although regional water withdrawal increased nearly 5-fold between 1980 and 2005, withdrawals represent only 2-5% of Ichetucknee River flow and are less important than decadal-long variations in precipitation. These results suggest that groundwater management should consider climate cycles as predictive tools for future water resources. (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

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