HR: 1340h
AN: H13F-1384    [Abstracts]
TI: Exploring Hydrological Response Patterns at the Catchment Scale Using "Snapshots" Measurements
AU: * Szeftel, P
EM: pszeftel@interchange.ubc.ca
AF: University of British Columbia, Department of Forest Resources Management, Vancouver, BC V6T1Z4 Canada
AU: Weiler, M
EM: markus.weiler@ubc.ca
AF: University of British Columbia, Department of Forest Resources Management, Vancouver, BC V6T1Z4 Canada
AB: In the past few decades, a large variety of runoff generation processes at individual hillslopes have been intensively studied. On the other side, the watershed as a whole entity was observed, focusing on the hydrological response at the basin scale. In the present study, we propose a scale connecting, geographic aggregative approach, considering the studied watershed as a collection of contiguous hillslopes. By taking snapshots of the hydrological response of a watershed, we first have an insight into the spatial variability (for each hillslope) of water delivery to the stream network at the basin scale. Then, by comparing different snapshots, we can establish the temporal variability of the hillslopes' hydrological response through a wide range of discharge rates. Thus, the basin wide response patterns can be used to understand the different water delivery mechanisms in a watershed. Within a 17.4 km² snow-dominated watershed, salt dilution experiments were carried out along the whole stream network at 52 specific sites. Two main channels drain the watershed, each one splitting into two streams of same order at higher elevation, thus defining 4 distinct headwater catchments. The hillslope, smallest entity considered in the study, is defined by the drainage area between 2 contiguous spots along the stream network. At each site, discharge, temperature and electric conductivity were measured, which resulted in the longitudinal profiles of these variables along the whole stream network. We used three snapshots of the hydrological response of the watershed to analyze the hydrological variability at different discharge rates. The wet state is measured during the snowmelt season whereas the dry state has been observed in late summer. An additional intermediate state has been recorded earlier in the snowmelt season. First results show the non-linearity between discharge and drainage area on the two main streams of the basin. Irrespective of the wetness state of the watershed, headwaters generally produce more runoff than the flatter area closer to the outlet. Electric conductivity and temperature data allow us to identify the sources of water supplies within the 4 headwater sub-basins. It has been found that they react differently to snowmelt or rainfall inputs. Results found at the sites match observations at the sub-basin scale (climate stations, stream gages at the outlet of each of the 4 sub-basins). We also applied simple mixing analysis to calculate the electrical conductivity of the water draining from each hillslope. This information together with a detailed geological and pedological map provided interesting insides into the different water delivery mechanisms.
UR: http://www.forestry.ubc.ca/cottoncreek/index.htm
DE: 1804 Catchment
DE: 1829 Groundwater hydrology
DE: 1839 Hydrologic scaling
DE: 1856 River channels (0483, 0744)
DE: 1860 Streamflow
SC: Hydrology [H]
MN: Fall Meeting 2005