Low-flow characteristics of streams in North Carolina

Ten low-flow hydrologic areas were defined for North Carolina by relating topography, geology, mean annual runoff, and other features to low-flow frequency characteristics for 122 continuous-record streamflow stations and 396 partial-record streamflow stations. Regression equations relating low-flow characteristics to mean annual discharge were developed for five of the hydrologic areas covering 40% of the State, and statistical summaries of low-flow characteristics are given for all 10 hydrologic areas. Low-flow characteristics selected for analysis were the low-flow 7Q10, which is the annual minimum 7-day consecutive low flow, which on average will be exceeded in 9 out of 10 years--or stated another way, the probability is 10% that the 7-day consecutive low flow in any year will be less than the 7Q10; the low-flow W7Q10, which is similar to the low-flow 7Q10 except that it takes into account only the months from November through March; the low-flow 7Q2; and the low-flow 30Q2. Low-flow 7Q10's ranged from zero in some hydrologic areas in the Coastal Plain and Piedmont physiographic areas to a maximum value of 1.06 cu ft/sec/sq mi for a station in the western Piedmont and mountains physiographic area.