Low-flow characteristics and profiles for the Deep River in the Cape Fear River basin, North Carolina

An understanding of the magnitude and frequency of low-flow discharges is an important part of protecting surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized for 7 continuous-record gaging stations and 23 partial-record measuring sites in the Deep River Basin in North Carolina. Records of discharge collected through the 1995 water year are used. Flow characteristics included in the summary are (1) average annual unit flow; (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, similar to 7Q10 discharge except only flow during the months of November through March is considered; and (5) 7Q2 low-flow discharge. The potential for sustained base flows in the upper half of the basin is higher than that for streams in the lower half of the basin. Much of the decrease in base-flow potential in the lower part of the basin is attributed to the underlying rock types of the Triassic basin. Soils in the lower part of the basin consist of clays which limit the infiltration of water into surficial aquifers for later release to streams during drought conditions. Correspondingly, many streams in the lower part of the basin have minimal (defined as less than 0.1 cubic foot per second) or zero 7Q10 discharges.

Drainage area and low-flow discharge profiles are presented for the Deep River. The drainage-area profile shows downstream increases in basin size. At the mouth, the drainage area for the Deep River is 1,441 square miles. Low-flow discharge profiles for the Deep River include 7Q10, 30Q2, W7Q10, and 7Q2 discharges in a continuous profile with contributions from major tributaries included.