Station Research

Below you'll find details and figures on specific areas of the research performed at the WCHRS.

Most groundwater wells in the WCHRS are located near streams, so water tables are generally shallow (<2 m). Seasonally, the groundwater table is lowest in the early fall and highest in spring. (Lord et al. 2012)

SEE FIGURE 2

Sediment types are different in the three reaches, reflective of the geomorphic processes that formed the landscape. The hydraulic conductivity (aka permeability) of the sediments ranges from 9x10 -6 cm s -1 to 6x10 -4 cm s -1. Though there is no statistically significant difference in the average hydraulic conductivity between the three reaches, the Gribble Gap (GG) site has less variability in hydraulic conductivity than Cullowhee Creek (CC) and Long Branch (LB). (Hiatt et al. 2011)

SEE FIGURE 3

The relationship of groundwater to streams in the WCHRS varies substantially from the headwaters, where it is most complex, to the downstream Cullowhee Creek floodplain. Along Cullowhee Creek, the groundwater flows towards the (gaining) stream during all the seasons. In the Gribble Gap headwaters, stream reaches alternate between gaining and losing over short distances; the relationship also varies seasonally. At the Long Branch site, the stream is gaining and receives most groundwater input through the fan deposits that abut the southern channel bank. (Ferri et al. 2013)

SEE FIGURE 4

Most of the monitoring and studies at the WCHRS have focused on physical aspects of hydrology. However, some preliminary work on water chemistry has been completed to understand basic water chemical patterns, how hydrogen and oxygen isotope traits of vary with water types in the station and to understand the influence of present-day land use. In general, the water chemistry is similar throughout the station with a few outliers. There is most chemical variability in the headwaters, Gribble Gap. Also, reflective of the groundwater interaction with stream water, the groundwater (GW) pH is most similar to stream water (SW) at Cullowhee Creek and least similar at Gribble Gap. (Lord et al., 2012)

SEE FIGURE 5 & 6

As indicated above, few studies of been completed to directly evaluate the effects of current land use on water quality. However, a preliminary research project, carried out in a course, Geol 305 Soils & Hydrology, by Dunlap, Freeman, Howard, and Wood (2014, WCU, unpublished) showed perennial streams that drain developed campus property have significantly higher conductivity values than Cullowhee Creek and other tributaries that drain the minimally developed land. Their data are based on sampling Cullowhee Creek, and tributaries, up and downstream at six sites during baseflow and stormflow conditions during spring 2014.

SEE FIGURE 7

The southern Appalachians receive abundant rainfall; Cullowhee typically receives 127 to 140 cm of rainfall each year. In spite of this and the generally low-density population, droughts do cause groundwater wells to go dry, leaving residents without a water supply.

Learning more about where and when groundwater recharge happens in the region is important to support the high population growth rates as well as sustaining streams. Most groundwater recharge occurs during the periods of the fall and winter months when active vegetation isn't using much of the fresh rainwater in the soil for growth. Even during the winter months, not all rain results in groundwater recharge.

A preliminary study in the Long Branch and Gribble Gap watersheds showed that some rains likely prompt groundwater recharge (see A in Figure 8), but that a 5 mm rainfall in November did not likely result in groundwater recharge (see B in Figure 8) (Ferri, 2014, unpublished geology senior thesis, WCU)

SEE FIGURE 8