The Panola Mountain Research Watershed: 37 Years of Research at a
Forested Headwater Catchment in the Piedmont of the Southeastern United
States
Abstract
The Panola Mountain Research Watershed (PMRW) is a 41-hectare, forested
research catchment within the Piedmont Province of the United States
(U.S.), located about 25 km southeast of Atlanta Georgia (33˚ 37’ 54”
N, 84˚ 10’ 20” W). Annual precipitation (P) averages 1,250 mm
(<1% as snow) and annual runoff averages 358 mm, resulting in
a runoff ratio of 0.29 (based on water years 1986–2015; annual range
0.13–0.50). The PMRW is seasonally water limited which results in water
deficits and long-term actual evapotranspiration (ET) is about 75% of
potential ET. Recharge of storage occurs predominantly in
September–March when ET is lower. The U.S. Geological Survey (USGS)
initiated research at the PMRW in 1985. Early focus on the effects of
acid deposition transitioned to investigating processes affecting
streamflow generation and water quality as part of a network of five
diverse U.S. watersheds in the USGS Water, Energy and Biogeochemical
Budgets Program (1991–2016). Current research is funded by the USGS
Ecosystems’ Climate Research and Development Program and is focused on
the effects of droughts and climatic change on ET, soil moisture,
groundwater recharge, and streamflow generation. Collaboration with many
Universities have occurred throughout the study. Long-term monitoring
includes P, streamflow, groundwater, soil moisture, and meteorological
parameters and water quality sampling of P, streamwater, and soil water.
Thirty years of monthly water budgets (including actual ET and watershed
storage components) and 31 years of atmospheric deposition and
streamwater solute fluxes are published in USGS ScienceBase and include
supporting data. The PMRW has long water residence times despite its
small size, with a volume-weighted mean streamwater transit-time of
~4.7 years but can be >10 years during dry
years. The PMRW has a large dynamic (>500 mm) and total
(~1,000 mm) watershed storage with a hydrologic
persistence of 19-months, which is evident from the water budget
response to recurring hydrologic droughts. The dominant flowpath of
hillslope recharge to the riparian area and stream is through bedrock.
Storm-streamwater quality response was controlled by riparian (not
hillslope) groundwater. We welcome opportunities for collaborative
studies, cross-site comparisons, and data sharing.