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USGS1989

Effects of the 1986 drought on streamflow in Alabama, Georgia, North Carolina, South Carolina, Tennessee, and Virginia

A severe drought in the Southeastern United States during 1986 resulted in the lowest flows of record for many streams. Minimum flows in many streams occurred in mid-summer, several months earlier in the year than the minimums that occurred during notable regional droughts of 1954 and 1981. Streamflow data for 370 continuous-record gaging stations in Alabama, Georgia, North Carolina, South Carolina, eastern Tennessee, and southern Virginia were analyzed to determine the severity and areal extent of this drought. Minimum average streamflows for periods of 1, 7, 30, 60, and 90 consecutive days were evaluated to estimate the frequency of recurrence of the 1986 drought and generalized areas of similar recurrence intervals were delineated for the 7-day and 30-day minimum average flows. Flows in parts of Georgia, North Carolina, and Tennessee receded to rates estimated to occur on the average of once in 50 to 100 years. A much larger area that extended from central Alabama to central North Carolina experienced flows with estimated recurrence intervals of 20 to 50 years. In addition to the continuous-record station data, discharge measurements and observations of zero flow were made at 694 non-recording stream sites in Alabama, Georgia, South Carolina, and eastern Tennessee during the 1986 drought. These measurements were used in conjunction with the continuous-record station flow data to estimate minimum 1986 drought flows at the non-recording sites.

Alabama, Georgia, North Carolina, South Carolina, ↗

USGS1983

Storage requirements for Georgia streams

The suitability of a stream as a source of water supply or for waste disposal may be severely limited by low flow during certain periods. A water user may be forced to provide storage facilities to supplement the natural flow if the low flow is insufficient for his needs. This report provides data for evaluating the feasibility of augmenting low streamflow by means of storage facilities. It contains tabular data on storage requirements for draft rates that are as much as 60 percent of the mean annual flow at 99 continuous-record gaging stations, and draft-storage diagrams for estimating storage requirements at many additional sites. Through analyses of streamflow data, the State was divided into four regions. Draft-storage diagrams for each region provide a means of estimating storage requirements for sites on streams where data are scant, provided the drainage area, mean annual flow, and the 7-day, 10-year low flow are known or can be estimated. These data are tabulated for the 99 gaging stations used in the analyses and for 102 partial-record sites where only base-flow measurements have been made. The draft-storage diagrams are useful not only for estimating in-channel storage required for low-flow augmentation, but also can be used for estimating the volume of off-channel storage required to retain wastewater during low-flow periods for later release. In addition, these relationships can be helpful in estimating the volume of wastewater to be disposed of by spraying on land, provided that the water disposed of in this manner is only that for which streamflow dilution water is not currently available. Mean annual flow can be determined for any stream within the State by using the runoff map in this report. Low-flow indices can be estimated by several methods, including correlation of base-flow measurements with concurrent flow at nearby continuous-record gaging stations where low-flow indices have been determined.

Georgia↗