Connectivity and runoff dynamics in heterogeneous basins

Abstract

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 small ungauged basins.

Recent climatic, cryospheric, and hydrological changes over the interior of western Canada: a review and synthesis

“…Here, the Precambrian Shield geological setting, abundant lakes, and thin glacial-fluvial soils are not particularly sensitive to changes in thermal regime, but changes in lake storage can rapidly change the runoff contributing area available for river discharge formation. The WECC observatory has a distinct threshold-response runoff regime (Spence, 2006) where increasingly large areas of the watershed connect and can contribute to runoff as lake storage increases (Phillips et al, 2011). Spence et al (2011) have documented sudden changes in streamflow regimes as the climate has changed.…”

Runoff generation in mountain catchments: long-term hydrological monitoring in the Rio Vauz Catchment, Italy

“…Data from piezometers located in Piramide and Emme hillslopes were used to assess the role of topography, soil depth and shape of the hillslopes in the variability and timings of shallow subsurface flow generation (Penna et al, 2015). Depths to water table data from LCC and the hillslope-riparian-hillslope transects in BCC were also used to quantify subsurface connectivity by a graph-theory approach (Phillips et al, 2011) and to study the effects of rainfall-runoff events and topographic characteristics on connectivity (Zuecco et al, in preparation). …”

Characteristics and Factors Influencing the Hysteresis of Water Area–Stage Curves for Poyang Lake

“…Hysteretic phenomena are often found in hydrology relationships [12] (e.g., runoff connectivity streamflow, discharge, and runoff storage). Phillips et al found hysteresis between runoff connectivity and streamflow in the Baker Creek Research Basin [13]. Wolfs et al used three approaches to develop discharge-stage curves affected by hysteresis [14].…”