HR: 16:00h
AN: H34C-01 INVITED     [Abstracts]
TI: Disturbed Landscapes as Natural Laboratories For Testing Hydrological and Biogeochemical Models
AU: * Kirchner, J W
EM: kirchner@seismo.berkeley.edu
AF: University of California, Department of Earth and Planetary Science, 307 McCone Hall, Berkeley, CA 94720-4767 United States
AB: Disturbances like fire, urbanization, and deforestation can profoundly change the hydrological and biogeochemical functioning of catchments. Here I argue that precisely because disturbances alter catchments so dramatically, they can provide important opportunities to test our prevailing theories for how catchments function. Typical catchment models are calibrated -- often extensively so -- to mimic catchment behavior. Such models can become mathematical marionettes that will dance to the tune of the calibration data, whether or not the underlying theory is correct. To test whether models are getting the right answers for the right reasons, we need to test them against data sets that exhibit markedly different behavior from that which the models are already calibrated to. Catchment data collected before and after disturbances can provide just this kind of validation test for hydrochemical theory. I illustrate this approach by using data from catchment deforestation experiments to test a simple geochemical theory for cation mobilization in catchment soils. When calibrated using only pre-disturbance data, the theory correctly predicts chemical changes in streamflow that extend far beyond the range of the calibration data. Because disturbances can dramatically change catchment behavior, they can also reveal hydrological and geochemical mechanisms that would otherwise remain hidden. I present analyses of water and nutrient fluxes from deforested catchments to illustrate how catchment response to disturbances can clarify our views of catchment processes.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1804 Catchment
DE: 1806 Chemistry of fresh water
DE: 1834 Human impacts
DE: 1879 Watershed
SC: Hydrology [H]
MN: Fall Meeting 2005