The Western Carolina Hydrologic Research Station (WCHRS) is located on the campus of Western Carolina University in Cullowhee, North Carolina.
The natural setting of the station and the land use history, is typical of much of
the Southern Appalachians, specifically in western North Carolina.
The research station is located within the Cullowhee Creek watershed and includes
part of the Long Branch watershed and the entire Gribble Gap headwaters basin.
The groundwater studies are focused at stream reaches in three different geomorphic
zones: Gribble Gap Creek (0.44 km 2) a colluvial reach, flows into Long Branch (4.39 km 2) an alluvial-colluvial reach, which flows into Cullowhee Creek (62 km 2) an alluvial reach.
The research station is equipped with about 45 groundwater wells, 3 rain gage sites,
9 soil moisture sites on 3 slopes, 6 stream gages, and one sampling lysimeter. For
more information on locations and equipment, explore the Research Station Facilities.
What is studied at the station?
There are three primary scientific research objectives for the site:
- Determine how the interaction of groundwater and stream water vary with their geomorphic
(aka landscape) setting. Fundamental to this question is the underlying hypothesis
that the geomorphic setting of streams is predictive of hydrologic processes, including
the interaction of groundwater and stream water (Walsh et al. 2010; Hiatt et al. 2011). This is important to understanding the quantity of water resources as well as the
quality in both streams and groundwater.
- Document where and when recharge of groundwater occurs in the watershed, especially
as it relates to different bedrock and soil types, landscapes, and land covers.
- Understand the influence of historic land uses and ongoing changes in land cover today
on water resources and quality. Though the focus of research is on questions related
to watershed hydrology, interdisciplinary questions, especially related to ecosystems,
are also studied. Most of the specific questions studied are relevant to regional
problems. A goal of the studies is to provide improved scientific understanding to
guide sound environmental management.
Specific areas of 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
GROUNDWATER AND STREAMS
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
WATER QUALITY AND LAND USE
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
SEE FIGURE 7
WHEN DOES GROUNDWATER RECHARGE OCCUR?
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
WCHRS is a part of a state-wide NCDEQ Groudwater Study. Data from two groundwater
wells on the campus of Western Carolina University is periodically collected and you
can visualize and download that data here. We also have a gauge on Long Branch that we are hoping to get online soon.
NASA's Integrated Precipitation Hydrology Experiment (IPHEX) also has paired tipping
bucket rain gages set on the roof of WCU's Health and Human Science Building. This
site is adjacent to our sites at Gribble Gap and Long Branch. These data are here and are listed in the table as 'WCU' (Gauge Number: NASA0028).