HR: 0800h
AN: H31B-0360    [Abstracts]
TI: Measured and Modeled Water Balances For Three Snow Dominated Forested Catchments With Different Canopy Cover In The Inland Pacific Northwest
AU: * Hubbart, J A
EM: HubbartJ@missouri.edu
AF: University of Missouri - Columbia, School of Natural Resources 203-Q ABNR, Columbia, MO 65211, United States
AU: Link, T
EM: tlink@uidaho.edu
AF: University of Idaho, College of Natural Resources 975 West 6th Street, Moscow, ID 83843, United States
AU: Du, E
EM: enhaodu@vandals.uidaho.edu
AF: University of Idaho, College of Natural Resources 975 West 6th Street, Moscow, ID 83843, United States
AB: There is a need to better understand the dominant components of the catchment water balance in complex vegetated terrain to advance our understanding of basic hydrological processes and develop effective land management practices. A lack of paired or other detailed watershed studies in the inland Pacific Northwest has limited our understanding of this hydroclimatically, biophysically, and topographically complex region. Empirical analyses of long term data sets, and results from detailed investigations were used to assess impacts of contemporary timber harvest practices on the water balance components of the Mica Creek Experimental Watershed (MCEW). Measurements at the MCEW include precipitation, rainfall interception, snow water equivalent, sap flux, soil moisture, and streamflow. Results were applied to annual averages for the 2002 through 2005 water years directly following canopy removal. Of total precipitation (1401 mm/wy), 755 mm, 628 mm, and 475 mm/yr resulted in streamflow from clearcut, partial cut, and fully forested catchments respectively. Study results showed that canopy interception of rain was 17.2 % of rainfall for a full canopy, and 13.3 % for a partial cut (i.e. 50 % harvest) canopy. Canopy interception of snow was calculated as 43 % and 60 % for partial cut and full forest respectively. Based on sap flow measurements, transpiration was calculated to be 1.5 mm/day for approximately 200 days per year, or 300 mm/year. Based on these findings, estimates of evaporation (including sublimation) were 161 mm, 361 mm, and 470 mm/yr, and estimates of transpiration were 148 mm, 221 mm, and 296 mm/yr, for clearcut, partial cut, and fully forested catchments respectively. This suggests that water yield increased 30 % following clearcut harvest, and 20 % following partial cut harvest, and evaporation dropped to nearly 30 % of pre-harvest evaporation following clearcut, and nearly 60 % of pre-harvest evaporation following partial cut harvest. Soil evaporation was considered to be negligible, but nonetheless could be a source of error, especially for the clearcut catchments. Transpiration estimates for partial cut and fully forested catchments may also be somewhat lower than current estimates. The difference in Error ranged from 156 mm/wy between paired fully forested control watersheds, to 338 mm/year in the clearcut catchments. Errors may result from multiple processes including soil evaporation, spatial distribution of snow, storage changes, and transpiration estimate errors. Results of the empirical water balance components will be compared to modeled values using the Distributed Hydrology Soil Vegetation Model (DHSVM) and will result in improved understanding and modeling predictive power in this topographically and hydroclimatically complex region.
UR: http://www.cnr.uidaho.edu/micacreek/
DE: 1847 Modeling
DE: 1860 Streamflow
DE: 1876 Water budgets
DE: 1879 Watershed
DE: 1880 Water management (6334)
SC: Hydrology [H]
MN: 2007 Fall Meeting