Insights into quick flow in a karst aquifer: Usefulness of infrequently collected geochemical data from wells
- Univ. of Nevada, Reno, NV (United States). Nevada Bureau of Mines and Geology
Highly variable chemical characteristics (e.g., hardness) can indicate that a portion of a karst aquifer sampled by a well is subject to a quickflow component where water flow is rapid and water quality changes rapidly in response to precipitation events. Typically, karst aquifer monitoring for both water level and geochemistry is conducted at frequent intervals (hourly, daily) due to the nature of rapid geochemical and hydrologic changes in association with storm events. Quarterly monitoring data are available at the U.S. Department of Energy Oak Ridge Y- 12 Plant in Oak Ridge, TN, and these data are evaluated to identify quickflow portions of the aquifer. Values of P{sub CO{sub 2}} near atmospheric suggest rapid recharge of fluids, and 12 of 99 well waters exhibited P{sub CO{sub 2}} near atmospheric. Waters saturated with respect to dolomite must have relatively long residence times because attainment of saturation requires tens to hundreds of years. Repeat sampling of waters shows that both supersaturation and undersaturation with respect to dolomite occurs in 46 wells, indicating that relatively old waters diffusing from the rock matrix into conduits during baseflow experience periodic flushing by more rapidly recharged waters. Undersaturation with respect to calcite indicates active dissolution and may suggest short residence times because calcite saturation can be expected to occur on the order of days. Evaluation of a{sub Mg}/a{sub Ca} ratios in the waters allows identification of portions of the aquifer where flow occurs from a dolomite to a limestone, and vice versa. In addition, 30 well waters exhibited coefficients of variation of hardness >10%. Hence, quickflow was identified in association with numerous well waters even though only quarterly monitoring data were available.
- Research Organization:
- Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-84OS21400
- OSTI ID:
- 39786
- Report Number(s):
- Y/TS--1264; ON: DE95009058
- Country of Publication:
- United States
- Language:
- English
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