HR: 1340h
AN: H23F-1490    [Abstracts]
TI: Aerial Variation of Water Quality in the Alluvial and Sparta Aquifiers of Arkansas
AU: * Steele, K F
EM: ksteele@uark.edu
AF: University of Arkansas, Department of Geosciences 113 Ozark Hall, Fayetteville, AR 72701 United States
AU: Kim, B
EM: bxk03@uark.edu
AF: University of Arkansas University of Arkansas, Environmental Dynamics Program 113 Ozark Hall, Fayetteville, AR 72701 United States
AU: Fugitt, T D
EM: todd.fugitt@mail.state.ar.us
AF: Arkansas Soil & Water Comm., 101 East Capitol Suite 350, Little Rock, AR 72201 United States
AB: Because of the importance of the alluvial and Sparta aquifers for irrigation and domestic water supplies in Arkansas, the Arkansas Soil and Water Conservation Commission is expanding the monitoring network for these aquifers. The sediments composing the aquifers generally grade upward to sand, silt and clay, but there are discontinuous lenses of these sediments throughout the aquifers. The production zones, composed of coarse-grained sand and gravel, are at the base of the aquifers. The alluvial wells are 42-46 m deep and the Sparta wells are 135-185 m deep. The objective of this project was to determine the spatial variability of water chemistry from the alluvial (two sites) and Sparta (one site) aquifers on relatively small scale using irrigation wells less than 1.3 km from monitoring wells. Preliminary data indicate that there is considerable variation of concentrations for Ca, Mg, Na, K, Fe, HCO3, Cl, and SO4. These concentration variations may be shown by the mean concentration and the 95%confidence level for each parameter at each site. Examples for one of the alluvial sites are given below. All units are mg/L. Calcium (130±20), Mg (26.5±3.4), Na (25.2±2.4), K (1.57±0.13), Fe (4.6±2.0), HCO3 (397±104), Cl (22.8±7.2), and SO4 (63±29). Approximately 30% of the values of the parameters either exceed or are lower than the 95% confidence level. Also about 30% of the wells have two or more parameter values that exceed or are lower than the 95% confidence intervals. Manganese, Pb, Cu, Zn, Br, F, and PO4 concentrations were low and exhibited minor variations. It is hypothesized that heterogeneous distribution of minerals and organic carbon and the character of discontinuous sedimentary lenses that affect ground-water residence time contribute to the variation in water chemistry. The results of this study indicate caution should be used in drawing isoconcentration maps for these aquifers. Information of the type obtained from this study can be used to determine the required well density and selection of contour intervals for constructing isoconcentration maps.
DE: 1806 Chemistry of fresh water
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: Fall Meeting 2005