Hydrology and Water Quality of Forested Lands in Eastern North Carolina
More than 100 site years of hydrology and water quality data spanning 25 years (1976-2000) were compiled from research and monitoring studies on forest stands with natural vegetation and tracts managed for timber production. A total of 41 watersheds located on poorly drained to very poorly drained soils on flat divides between coastal streams were included ranging in area from 7.3 to 6070 ha. Hydrology and nutrient concentration data from the study sites are used to examine how variation among sites may be related to soil type, drainage intensity, vegetation, and physiographic setting. The median annual hydrologic response (outflow as a percentage of precipitation) among the sites was 31%, with an interquartile range of 26-35%. Nutrient concentrations in forest outflow were generally low for most study sites compared with typical values for other land uses. Mean seasonal concentrations of nutrient fractions in drainage from 75% of the study sites were <1.8 mg/L for total N (TN), <0.08 mg/L for total P (TP). Concentrations of Org-N, TN, and TP were all consistently higher in drainage from organic soils compared with mineral soils for both paired comparisons and the overall data base. TN exports from 75% of the study sites were less than 6.5 kg/ha/yr, predominantly as Org-N and TP exports from all forest sites was <0.36 kg/ha/yr.