INITIAL FINDINGS FROM A NETWORK OF STREAM GAUGES ON HEADWATER STREAMS IN THE NORTH CAROLINA PIEDMONT

The network of USGS gauges on large streams in the United States is well established and provides important data to those interested in discharge and stream responses to precipitation events. However, headwater streams are rarely gauged despite the fact that they are ecologically important and experience an undiluted signal for discharge variability. We have created a network of 17 stream gauges on headwater streams in the Piedmont of North Carolina including gauges on streams draining suburban areas, farm land, and forested land. At each site, we installed a stilling well with a Hobo depth sensor and a conductivity meter. We found that gauging headwater streams presents unique problems including difficulties estimating peak discharge, measuring very low flows, and creating accurate ratings curves. Having collected nearly a year of data at all sites and roughly three years of data at a subset of sites, we can start to understand the behavior of headwater streams in the area.

Many of the streams we studied were very flashy with peak flows as much as five orders of magnitude higher than base flow. Predictably, streams draining more developed drainage basins tended to be flashier than forested drainage basins. However, forested drainage basins also exhibited flashy behavior during the winter months indicating that vegetation plays a large role in slowing water flowing and utilizing shallow groundwater. We also find that stream temperature is significantly impacted by land use with suburban drainages often one full degree warmer than more natural drainages. Regardless of land use, most drainages are efficient enough that rate of precipitation is a stronger indicator of discharge than amount of precipitation. Overall, while we have just begun to examine the very large dataset being collected, it is clear that headwater streams are very responsive to precipitation and land use changes. In fact, headwater streams may be the most impacted by development in the Piedmont because of their immediate response to precipitation events.