HR: 09:45h
AN: H51G-08    [Abstracts]
TI: The Impact of Flow on Spatial Variability of Streamwater Chemistry in a Boreal Catchment
AU: * Buffam, I
EM: ishi.buffam@sek.slu.se
AF: Swedish University of Agricultural Sciences, Department of Forest Ecology, Ume$\aa$, 90183 Sweden
AU: Laudon, H
EM: hjalmar.laudon@sek.slu.se
AF: Swedish University of Agricultural Sciences, Department of Forest Ecology, Ume$\aa$, 90183 Sweden
AU: Bishop, K
EM: kevin.bishop@ma.slu.se
AF: Swedish University of Agricultural Sciences, Department of Environmental Assessment, Uppsala, 75007 Sweden
AU: Temnerud, J
EM: Johan.Temnerud@nat.oru.se
AF: \"{O}rebro University, Man-Technology-Environment Research Centre, \"{O}rebro, 70182 Sweden
AU: M\"{o}rth, M
EM: magnus.morth@geo.su.se
AF: Stockholm University, Department of Geology and Geochemistry, Stockholm, 10691 Sweden
AB: Spatial variability in water chemistry is one defining characteristic of stream ecosystems. An infrequently studied aspect of this variability is the impact of flow regime: for instance, does the variation in water chemistry within a watershed differ between times of baseflow and flood? We examined this issue in Krycklan, a largely forested till-underlain boreal catchment in Northern Sweden, with an emphasis on changes occurring during the annual spring flood. Utilizing 15 stream sites ranging in catchment size from 0.07-68 km$^{2}$ and in catchment wetland coverage from 0-40%, the between-site variance in several water parameters was compared between times of stable, relatively low flow and times of dramatically changing, high flow during spring flood. Distinctly different patterns were observed for different solutes. While dissolved organic carbon (DOC) varied widely between streams at baseflow (5-40 mg/l) and was positively correlated with catchment % wetland area, these differences were subdued during peak flood (DOC range 15-25 mg/l), and as such variability was lower. Conversely, differences in inorganic cation concentrations (electrical conductivity ranged from 15-30 $\mu$S/cm) were amplified during the spring flood, resulting in increased spatial variability. Much of the change in variability hinged on the contrasting behavior of streams draining catchments with high % wetland compared to forested catchments: wetland streams had lower concentrations of cations at baseflow, and were also diluted more dramatically than forest streams during the flood. Hydrological flowpaths were explored using isotopic and chemical signatures of streamwater and catchment source waters. Much of the observed patterns in spatial variability could be explained by divergent flowpaths within wetland and forest catchments during spring flood, and by differing source areas for DOC vs. cations.
DE: 1806 Chemistry of fresh water
DE: 1821 Floods
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
DE: 1890 Wetlands
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting