Connectivity and runoff dynamics in heterogeneous basins

• Published in: Hydrological Processes
• Main Authors: Phillips, R. W., Spence, C., Pomeroy, J. W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2011
• Subjects: Subarctic
• Online Access: http://dx.doi.org/10.1002/hyp.8123; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fhyp.8123; https://onlinelibrary.wiley.com/doi/pdf/10.1002/hyp.8123

Abstract A drainage basin's runoff response can be determined by the connectivity of generated runoff to the stream network and the connectivity of the downstream drainage network. The connectivity of a drainage basin modulates its ability to produce streamflow and respond to precipitation events and is a function of the complex and variable storage capacities throughout the drainage basin and along the drainage network. An improved means to measure and account for the dynamics of stream network connectivity at the catchment scale is needed to predict basin scale streamflow. At a 150 km 2 subarctic Precambrian Shield catchment where the poorly drained heterogeneous mosaic of lakes, exposed bedrock, and soil filled areas creates variable contributing areas, hydrological connectivity was measured in 11 sub‐basins with a particular focus on three representative sub‐basins. The three sub‐basins, although of similar relative size, vary considerably in the dominant typology and topology of their constituent elements. At a 10‐m spatial resolution, saturated areas were mapped using both multispectral satellite imagery and onsite measurements of storage according to land cover. To measure basin‐scale hydrological connectivity, the drainage network was represented using graph theory where stream reaches are ‘edges’ connecting sub‐basin ‘nodes’. The overall hydrological connectivity of the stream network was described as the ratio of actively flowing relative to potentially flowing stream reaches. The hydrological connectivity of the stream network to the outlet was described as the ratio of actively flowing stream reaches that were connected to the outlet to the potentially flowing stream reaches. Hydrological connectivity was then related to daily average streamflow and basin runoff ratio. Improved understanding of causal factors for the variable streamflow response to runoff generation in this environment will serve as a first step towards improved streamflow prediction in formerly glaciated landscapes, especially in ...