Topographic Controls on the Extension and Retraction of Flowing Streams

Abstract

Flowing stream networks extend and retract as their surrounding landscapes wet up and dry out, both seasonally and during rainstorms, with implications for aquatic ecosystems and greenhouse gas exchange. Some networks are much more dynamic than others, however, and the reasons for this difference are unknown. Here we show that the tendency of stream networks to extend and retract can be predicted from down‐valley changes in topographic attributes (slope, curvature, and contributing drainage area), without measuring subsurface hydrologic properties. Topography determines where water accumulates within valley networks, and we propose that it also modulates flow partitioning between the surface and subsurface. Measurements from 17 mountain stream networks support this hypothesis, showing that undissected valley heads have greater subsurface transport capacities than sharply incised valleys downstream. In catchments where broad valley heads rapidly transition to sharply incised valleys, subsurface transport capacity decreases abruptly, stabilizing stream length through wet and dry periods.

Climate Change Causes River Network Contraction and Disconnection in the H.J. Andrews Experimental Forest, Oregon, USA

“…Similarly, connected length averages a loss of 21.4 m/yr in August, and is 9.2% shorter in 2009-2018 than the 1953-1962 August average. Network expansion and contraction exhibit threshold behavior, generally consistent with past studies (Ward et al, 2018a;Prancevic and Kirchner, 2019). When discharge at the Lookout Creek gage is greater than about 1 m 3 s −1 , the flowing and connected lengths are nearly constant at their plateau values (Figure 3B and Figure S27).…”

“…These services are associated with the frequency with which streams have surface flow (hereafter "flow permanence"), and any declines in flow permanence will effectively disconnect larger rivers from their headwaters and their functions. Flow generated in headwater streams is highly sensitive to changes in precipitation timing, magnitude, and duration based on a small number of empirical studies over short timescales (Godsey and Kirchner, 2014;Jensen et al, 2017;Zimmer and McGlynn, 2017;Prancevic and Kirchner, 2019). However, no observational studies have covered a sufficient period of record to evaluate if and how changing climate has altered flow permanence across river networks.…”

“…Evaluating how flow permanence has changed requires quantification of both the temporal variation (i.e., the frequency a given segment has surface flow) and spatial variation (i.e., the spatial connectivity of surface flow) (Covino, 2017;Wohl, 2017;Wohl et al, 2017). In headwater streams, flow permanence is controlled by the dynamic interaction of geologic setting with hydrologic forcing (Costigan et al, 2016;Prancevic and Kirchner, 2019). Climate change is primarily associated with changes to hydrologic forcing, such as altering the spatial distribution and within-year timing of precipitation.…”

Simulated response of an intermittent stream to rainfall frequency patterns

“…given the renewed interest in the study of the dynamic expansion and contraction of river networks and their ecohydrological significance (e.g., Prancevic and Kirchner ;, Van Meerveld et al 2019), this study could pave the way for the use of ISSHMs as effective tools to reproduce these important dynamics.…”

Forestland-peatland hydrologic connectivity in water-limited environments: hydraulic gradients often oppose topography

“…Most previous studies concerning water table dynamics in undisturbed landscapes have focused on high relief, humid regions with shallow water tables and/or hydrogeologic settings that promote predictable and steady local-scale flow systems (Jencso et al 2009, Goodbrand et al 2019, Prancevic and Kirchner 2019. Consequently, there is a general lack of understanding regarding the spatiotemporal distribution of groundwater recharge and discharge zones in more complex and dynamic landscapes.…”