HR: 11:15h
AN: H22B-04    [Abstracts]
TI: Concentration-Discharge Relationships Across Temporal and Spatial Scales
AU: * Godsey, S E
EM: godseys@eps.berkeley.edu
AF: Univ. of California - Berkeley, Department of Earth & Planetary Science 307 McCone Hall #4767, Berkeley, CA 94720-4767 United States
AU: Kirchner, J W
EM: kirchner@eps.berkeley.edu
AF: Univ. of California - Berkeley, Department of Earth & Planetary Science 307 McCone Hall #4767, Berkeley, CA 94720-4767 United States
AB: Hydrochemically diverse catchments in the USGS Hydrologic Benchmark Network exhibit power-law concentration-discharge relationships for the major base cations and silica. These 59 catchments exhibit diverse land cover and geology, and vary in size from ~6 to 6000 km² with mean annual runoff between <1 and ~400 cm/year. At each of these catchments, concentrations typically decrease by a factor of approximately two to five while discharge increases by several orders of magnitude. These power-law relationships, with typical log-log slopes of -0.05 to -0.3, would not be expected in a kinetically-limited system where a constant chemical weathering flux is diluted by a variable water flux, even if a very large amount of subsurface storage is available. These observations imply that stream water solute concentrations are not directly controlled by kinetically-limited chemical weathering and solute mobilization processes. Furthermore, similar concentration-discharge relationships are also observed between mean annual concentration and annual discharge, implying that even on inter-annual time scales, kinetically-limited chemical weathering and solute mobilization processes do not directly regulate solute fluxes in streams. Similar power-law concentration-discharge relationships are observed at most sites, regardless of spatial scale. The slopes of the concentration-discharge relationships are not significantly correlated with catchment area or other landscape attributes. The observed concentration-discharge relationship is a general phenomenon across a wide range of temporal and spatial scales, as well as geologic and hydrologic environments, and therefore demands a general explanation. Simple mixing models are unable to reproduce the observed concentration-discharge relationships. We explore several new models to explain the observed patterns.
DE: 1806 Chemistry of fresh water
DE: 1879 Watershed
DE: 1886 Weathering (0790, 1625)
SC: Hydrology [H]
MN: Fall Meeting 2005