Hierarchical controls on runoff generation: Topographically driven hydrologic connectivity, geology, and vegetation

Abstract

[1] Understanding the relative influence of catchment structure (topography and topology), underlying geology, and vegetation on runoff response is key to interpreting catchment hydrology. Hillslope-riparian-stream (HRS) water table connectivity serves as the hydrologic linkage between a catchment's uplands and the channel network and facilitates the transmission of water and solutes to streams. While there has been tremendous interest in the concept of hydrological connectivity to characterize catchments, few studies have quantified hydrologic connectivity at the stream network and catchment scales with observational data. Here we examine how catchment topography, vegetation, and geology influenced patterns of stream network HRS connectivity and runoff dynamics across 11 nested headwater catchments in the Tenderfoot Creek Experimental Forest (TCEF), MT. This study builds on the empirical findings of Jencso et al. (2009) who found a strong linear relationship (r 2 ¼ 0.91) between the upslope accumulated area (UAA) and the annual duration of shallow groundwater table connectivity observed across 24 HRS transects (146 groundwater recording wells). We applied this relationship to the entire stream network across 11 nested catchments to quantify the frequency distribution of stream network connectivity through time, and quantify its relationship to catchment-scale runoff dynamics. Each catchment's hydrologic connectivity duration curve (CDC) was highly related to its flow duration curve (FDC) and the slope of the relationship varied across catchments. The slope represents the streamflow yield per unit connectivity (Con yield ). We analyzed the slope of each catchment's CDC-FDC relationship or Con yield (annual, peak, transition, and base flow periods) in multiple linear regression models with common terrain, land cover vegetation, and geology explanatory variables. Significant predictors (p < 0.05) across 11 catchments included the ratio of flow path distances and gradients to the creek (DFC/GTC), geology, and a vegetation index. The order and strength of these predictors changed seasonally and highlight the hierarchical controls on headwater catchment runoff generation. Our results highlight direct and quantifiable linkages between catchment topography, vegetation, geology, their topology, and hydrologic dynamics.

Landscape analysis of soil methane flux across complex terrain

“…Continuous topographic metrics such as the topographic wetness index (TWI, a surrogate for water accumulation) could represent hydrologic influences on variables relevant for CH 4 fluxes (e.g., redox state, diffusivity of CH 4 and O 2 , and substrate availability). Here, we build on previous research from Tenderfoot Creek Experimental Forest (TCEF) that has demonstrated how topographic metrics can represent landscape structure and its influence on hydrologic processes (Jencso et al, 2009;Jencso and McGlynn, 2011) and carbon cycling (Riveros-Iregui and McGlynn, 2009;Pacific et al, 2010Pacific et al, , 2011. Our objectives were to determine how locally and distally mediated environmental conditions influence CH 4 fluxes, and to estimate the net seasonal CH 4 balance of the upper Stringer Creek watershed.…”

Topography significantly influencing low flows in snow-dominated watersheds

“…Studies of watershed topography on hydrological processes often include topics such as specific discharge (Karlsen et al, 2016), spatial baseflow distribution (Shope, 2016), transit time (McGuire and McDonnell, 2006;McGuire et al, 2005), and hydrological connectivity (Jencso and McGlynn, 2011). 65…”

“…As far as we know, no studies have quantified topographic controls on various flow magnitudes. Nevertheless, the relationship between topography and the mean transit time (McGuire and McDonnell, 2006), temporal specific discharge (Karlsen et al, 2016), and hydrological connectivity (Jencso and McGlynn, 2011) have been investigated. It is no doubt that topography is one 230 of the major contributors to hydrological variations (Price, 2011;Smakhtin, 2001).…”

HESS Opinions: The complementary merits of competing modelling philosophies in hydrology

“…It is well established that hydrological connectivity exhibits not only temporal but also spatial dynamics and that therefore source areas of flow generation vary over time (e.g. Lehmann et al, 2007;Spence et al, 2010;Jencso and McGlynn, 2011;Ogden et al, 2013). Adapting the spatial resolution of models to the spatial resolution of available observations offers considerable potential to improve the representation of process dynamics across the model domain.…”