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Techniques for estimating 7-day, 10-year low-flow characteristics for ungaged sites on streams in Mississippi

January 1, 1994

Mississippi State water laws require that the 7-day, 10-year low-flow characteristic (7Q10) of streams be used as a criterion for issuing wastedischarge permits to dischargers to streams and for limiting withdrawals of water from streams. This report presents techniques for estimating the 7Q10 for ungaged sites on streams in Mississippi based on the availability of baseflow discharge measurements at the site, location of nearby gaged sites on the same stream, and drainage area of the ungaged site. These techniques may be used to estimate the 7Q10 at sites on natural, unregulated or partially regulated, and non-tidal streams. Low-flow characteristics for streams in the Mississippi River alluvial plain were not estimated because the annual lowflow data exhibit decreasing trends with time. Also presented are estimates of the 7Q10 for 493 gaged sites on Mississippi streams.

Techniques for estimating the 7Q10 have been developed for ungaged sites with base-flow discharge measurements, for ungaged sites on gaged streams, and for ungaged sites on ungaged streams. For an ungaged site with one or more base-flow discharge measurements, base-flow discharge data at the ungaged site are related to concurrent discharge data at a nearby gaged site. For ungaged sites on gaged streams, several methods of transferring the 7Q10 from a gaged site to an ungaged site were developed; the resulting 7Q10 values are based on drainage area prorations for the sites. For ungaged sites on ungaged streams, the 7Q10 is estimated from a map developed for. this study that shows the unit 7Q10 (7Q10 per square mile of drainage area) for ungaged basins in the State. The mapped values were estimated from the unit 7Q10 determined for nearby gaged basins, adjusted on the basis of the geology and topography of the ungaged basins.

Citation Information

Publication Year 1992
Title Techniques for estimating 7-day, 10-year low-flow characteristics for ungaged sites on streams in Mississippi
DOI 10.3133/wri914130
Authors Pamela A. Telis
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Water-Resources Investigations Report
Series Number 91-4130
Index ID wri914130
Record Source USGS Publications Warehouse
USGS Organization