HR: 11:30h
AN: H31G-05 INVITED     [PDF]
TI: Hillslope Hydrological Modeling in a Boreal Forest - Tools for Assessment of Logging Impacts on Runoff Generation and Nitrogen Loads
AU: * Koivusalo, H
EM: Harri.Koivusalo@hut.fi
AF: Laboratory of Water Resources, Helsinki University of Technology, P.O.Box 5300, Espoo, 02015 HUT Finland
AU: Kokkonen, T
EM: Teemu.Kokkonen@hut.fi
AF: Laboratory of Water Resources, Helsinki University of Technology, P.O.Box 5300, Espoo, 02015 HUT Finland
AB: Advance in runoff generation models requires measurements of water quantity and quality both at the outlet of a catchment and along hillslopes residing within a catchment. Predicting response of streamflow volumes to land-use changes is challenging, but it is even more demanding to produce realistic estimates of surface and subsurface runoff components and solute fluxes within a catchment. This work, which is part of the FEMMA project, presents development and application of a deterministic hillslope hydrological model, which combines hydrological, biological, and solute transport computation schemes. The model simulates canopy processes, snow accumulation and melt, soil and ground water movement, and nitrogen transport. Here the modeling system is applied to two coniferous-forested catchments (56 and 29 ha) located in Eastern Finland. One of the catchments was partially clear-cut (35 %) while the other one was left as a control. Measured meteorological, snow, streamflow, and nitrogen concentration data cover a nine-year period starting five years before the treatment. The model parameterization is based on spatial data on topography, soil types, soil depths, and location of treated areas with respect to the stream network draining the catchment. Spatial data analysis condenses information on catchment physical properties for identification of one or several typical hillslopes, which are assumed to represent the behavior of the entire catchment. Results derivable directly from the measured data suggest that timing and volume of streamflow changed soon after loggings were completed. In the modeling exercise these changes are attributed to increased melt intensity and absence of interception in the logged areas. Measured concentrations of nitrite-nitrate nitrogen showed changes only two years after the logging. This lag can result from slow initiation of felling waste decomposition and long residence of nitrates in mineral soils and wetland areas surrounding the stream. Sensitivity of modeled nitrate leaching to parameterization of decomposition and retention processes was assessed.
DE: 1860 Runoff and streamflow
DE: 1863 Snow and ice (1827)
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2003 Fall Meeting