HR: 1400h
AN: H33B-08    [Abstracts]
TI: Shopping for Hydrologically Relevant Connectivity Metrics in Humid Temperate Forested Systems
AU: * Ali, G
EM: genevieve.ali@umontreal.ca
AF: Département de géographie, Université de Montréal, C.P. 6128, Succursale Centre- Ville, Montréal, QC H3C3J7, Canada
AU: Roy, A
EM: andre.roy@umontreal.ca
AF: Département de géographie, Université de Montréal, C.P. 6128, Succursale Centre- Ville, Montréal, QC H3C3J7, Canada
AB: Connectivity is often said to be crucial for hydrologic prediction as it relates to the functional connectedness between catchment elements. If connectivity is to serve as an effective diagnostic classification tool of hydrological behaviour, then it clearly matters (1) how it is measured, and (2) whether the spatial metrics are strongly correlated not only to catchment-scale antecedent moisture conditions but also to streamflow discharges in a given environment. Previous studies have advocated that connectivity in shallow soil moisture patterns induces threshold-like changes in runoff in semi-arid rangeland catchments but not in temperate humid forested catchments. We argue that in the latter environments, capturing critical spatial organization in soil moisture patterns depends on the way the chosen connectivity metric is built. We therefore tested several 2-D and 3-D connectivity measures (i.e. entropy, effective upslope area, integral correlation and connectivity scale lengths, source-to-stream connectivity, flow path connectivity) in a temperate humid forested catchment (Laurentians, Canada). Computations were based on continuous soil moisture patterns collected on 16 occasions at soil depths of 5, 15, 30 and 45 cm and then transformed into indicator patterns using either time- variable or time-invariant thresholds. Assessments of connectivity were variable depending on the computed metric, as just a few measures were significantly correlated with both antecedent moisture conditions and catchment discharges. Antecedent moisture conditions were strongly associated to high connectivity between source areas having a 40% or higher soil moisture volumetric content. Also, significant discharges at the outlet were generated when physically connected source areas had a soil water volumetric content greater than 30%. Topography-based connectivity metrics reflected changes in catchment macrostate and stormflow response better than omnidirectional methods, as well as source-to-stream connectivity metrics were more hydrologically relevant than metrics that did not consider the stream channel. These conclusions stress the importance of shopping for the right connectivity metric for hydrologic prediction, especially in humid forested environments that exhibit much larger variability in soil hydrologic properties than semi-arid rangeland catchments.
DE: 1804 Catchment
DE: 1866 Soil moisture
DE: 4435 Emergent phenomena
DE: 4460 Pattern formation
SC: Hydrology [H]
MN: 2009 Joint Assembly