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Bacterial quality._____________________________________ Use of water._____________________________________________________ Conclusions-______________________________________________________ 43 Selected references.________________________________________________ Page FIGURES 4-6. Graphs Continued 6. Eleven Point River near Raven den Springs and Strawberry River near Poughkeeps^'e (Sharp County)-______.___.___-.________ B8 7. Flow-duration curves for continuous-record gaging stations.________________________________________ 8. Map showing dissolved-solids content and hardness as CaCO3 at sampling stations during periods of low flow. _ 23 9. Dissolved-solids and temperature-duration curves for Spring River at Imboden and Black River ner.r Corning (Clay County)-_-___-__._-_____________ 10. Diagram showing well-numbering system._____________ 26 11-14. Maps showing: 11. Thickness of deposits of Quaternary age ________ 27 12. Configuration of the water table in deposits of Quaternary age, spring 1966____-_-___-_-_-__ 13. Configuration of the water table in deposits of Quaternary age, fall 1966_-__-___-14. Water-level declines in deposits of Quaternary age, spring to fall 1966_________-_._____._-31 15. Hydrographs of wells 19N-2E-9dbd, 18N-lE-34abd, and 15N-lW-llddd-__-__-______________-_-______-_ 16. Map showing areas of potential development of ground water from the Wilcox Group and the Nacato?.h Sand. _ 33 17. Map showing dissolved-solids and combined iron and manganese content of water from selected wells in the Coastal Plain__-___-_____________________ 18. Map showing dissolved-solids content and hardness as CaCOa of water from selected wells in th^ Interior Highlands. __________________________ 40 TABLES Page TABLE 1. Low-flow characteristics of streams___-_-___-______-_ B9 2. Magnitude and frequency of floods at continuous-record gaging stations.___-____-____-___-_-__-_____-__ 3. Selected chemical analyses of water from streams.______ 16 4. Inventory of information on the quality of surface water in the vicinity of Randolph and Lawrence Counties, Ark__-___________________________-___-________-5. Specific capacity of selected wells in deposits of CJ uaternary age___________________________________________ 6. Chemical analyses of water from wells in Quaternary and Tertiary deposits of the Coastal Plain.._________ 7. Chemical analyses of water from wells in Paleozoic rocks of the Interior Highlands.

GROUND-WATER ISSUESMississippi depends heavily on its abundant ground-water resources. Aquifers capable of yielding large volumes of water that is suitable for most uses have led to the nearly exclusive use of ground water for public and industrial water supplies. Ground water constitutes 86 percent of the water used for public supply and serves the water-supply needs of about 2.3 million people in Mississippi (93 percent of the population). Groundwater is the source of supply for 54 percent of all the freshwater used in the State. In 1985, 49 percent of the total ground water withdrawn was for irrigation, 20 percent for fish fanning, 19 percent for public supply, and 12 percent for self-supplied industrial uses. The major issues related to ground water in Mississippi are: Declining water levels; Decreasing supplies; Saltwater encroachment in some coastal areas; and Effects of oil-field brines and agricultural chemicals on water quality.