Interactions of hydrology and water chemistry in two coastal plain streams in a forested watershed.

摘要

The goal of this study was to compare and contrast the annual seasonal changes in hydrology and water chemistry of Mayfield Creek and Talladega Branch, two low-order streams located within the same forested watershed. Mayfield Creek and Talladega Branch, third-order and first-order streams, respectively, are Coastal Plain streams located in west central Alabama. Samples for water chemistry analysis, as well as instantaneous discharge measurements, were collected weekly from both streams from January--December 2009. Dataloggers also collected continuous stage measurements at both streams. These data were used to estimate annual flux of nutrients from the streams.;Mayfield Creek and Talladega Branch showed significant differences in discharge due to stream size; average annual values were 0.308 and 0.120 m3/s, respectively. Mean annual concentrations of NH4 -N and NO3-N were significantly higher in Mayfield Creek, while DON and DOC values were higher in Talladega Branch. NH4-N levels for Mayfield Creek and Talladega Branch (43.11 and 36.07 mug/L, respectively) were consistently higher than nitrate levels (15.45 and 5.06 mug/L) in both streams.;Similar seasonal changes in hydrology and nutrient concentrations were observed in both streams. Annual flow patterns were typical of streams in the eastern U.S., having low flow conditions during the dry, summer months and high, winter baseflow during the wet, winter months. All nutrient concentrations peaked in the spring or summer months, likely due to the concentrating effect of low, summer baseflow. NO3-N, SRP, DOC, and DON concentrations showed a positive linear relationship with discharge during high flow conditions in both streams, while NH4-N did not increase with increasing discharge, implying that the stream itself, rather than the terrestrial environment, is likely the source of NH4-N to these streams.;Annual estimates of DOC flux for Mayfield Creek and Talladega Branch, 30,602.4 and 19,456.8 kg C/year, respectively, were higher than fluxes reported for other coastal plain streams of similar size. DIN flux was similar to values reported for other systems. However, the dominant form of DIN exported from these streams is NH4-N rather than NO3-N, which typically predominates.