When the USGS began work at Sleepers River in 1991,
it augmented the traditional hydrologically-based research at Sleepers
River with a significant biogeochemical component. Research
has centered on the problem of understanding streamflow generation
mechanisms and biogeochemical cycling in low-order catchments.
Well established isotopic, chemical and hydrometric techniques are
used, but also less proven multi-isotopic techniques (e.g., combinations
of Pb, Sr, and carbon isotopes), which provide complementary information
on water source and flow paths. As the project progressed,
riparian processes became the potential key to the stream response.
There seems to be a disconnection between processes on the hillslope
and the dynamics of the stream that points to regulation in the
riparian areas. Most of Sleepers River research is done in
a headwater forested catchment where hydrologic flow paths are investigated
at scales ranging from a linear small hillslope transect (McGlynn
and others, 1999) to a larger hillslope (K. Kendall and others.,
1999) to the entire 41-ha catchment (Shanley and Kendall, 1992).
The analysis (Smith and others, 1997) was extended to larger nested
catchments including the entire Sleepers River Watershed (111 km2),
and are actively investigating how streamflow generation mechanisms
change as basin size increases and land cover shifts from forested
to agricultural fields (Shanley and others, in press). A National
Scientific Foundation grant to McDonnell and others (1999-2002)
has enabled focused study of these hillslope - riparian relations.
Scientist sampling for organic carbon fractions
at site W-3 in Sleepers River, Watershed, April 2001.
Baseline data are collected at a small agricultural catchment,
which is used as an end member for the scale / land use research.
The site would be ideal for more rigorous investigations of the
effects of agriculture on runoff and water quality. Some initial
attempts in this vein compare nitrate dynamics at the main Sleepers
River gage (a NAWQA indicator site) are compared to other sites
in the Connecticut River NAWQA (see p. 60-61 in 1997 NRC review
"Water Research in the U.S. Geological Survey"). The small
catchment has tile drains, and at the Spring AGU meeting in Boston
USGS hydrologists presented an analysis of storm response before
and after their installation (Smith and Shanley, 1998).
During snowmelt of 2000 and 2001, movement of mercury
(Hg) at Sleepers River was monitored. In 2000, 10 different stream
sites were sampled that represent a wide range of catchment
size and land cover. Not only were samples analyzed for Hg but for
major ions and dissolved organic carbon (DOC) to help understand
the factors that control Hg movement. Because Hg behaved similarly
at all sites, in 2001 sampling was restricted to just 3 sites, but
with increased temporal frequency. The strong Hg-DOC relation found
in 2000 was investigated by collecting a subset of samples for organic
carbon fractionation and methyl-Hg determination.
The Energy aspects of WEBB have been
led by CRREL. Rae Melloh of CRREL is using radiation
and snow water equivalent data to validate SNTHERM,an energy balance
model that takes into account internal snowpack processes such as
layering and snow grain metamorphism. We will collaborate
with CRREL and use the output of SNTHERM as input to the topographically-based
model TOPMODEL to predict stream response to snowmelt.
Sampling of mercury at a agricultural catchment
on Sleepers River at site W-2 in Sleepers River Watershed, April
The WEBB program is committed to continuing several
high-quality historic data sets including (1) streamflow at
W-3 (8.3 km2) and W-5 (111 km2) operated continuously since
1959 and providing excellent winter record; (2) (jointly with
CRREL) precipitation, temperature and relative humidity at
13 sites (hourly since 1959); (3) seasonal snow depth and water
equivalent at 13 sites (weekly since 1959); and (4) seasonal
ground frost depth at 5 sites / land use types (weekly since 1983).
We operate 5 additional stream gages (2 reestablished and
3 new), and collect full meteorological data including radiation
at 3 sites, as well as soil moisture, soil temperature, and groundwater
levels. We collect an average of 1000 samples per year for
oxygen-18 and major ion analysis, and a selected subset for
less standard determinations such as 87Sr/86Sr, 13C, and dual
isotopes of nitrate.
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