Geomorphic controls on hyporheic exchange flow in mountain streams

Abstract

[1] Hyporheic exchange flows were simulated using MODFLOW and MODPATH to estimate relative effects of channel morphologic features on the extent of the hyporheic zone, on hyporheic exchange flow, and on the residence time of stream water in the hyporheic zone. Four stream reaches were compared in order to examine the influence of stream size and channel constraint. Within stream reaches, the influence of pool-step or pool-riffle sequences, channel sinuosity, secondary channels, and channel splits was examined. Results showed that the way in which channel morphology controlled exchange flows differed with stream size and, in some cases, with channel constraint. Pool-step sequences drove hyporheic exchange in the second-order sites, creating exchange flows with relatively short residence times. Multiple features interacted to drive hyporheic exchange flow in the unconstrained fifth-order site, where pool-riffle sequences and a channel split created exchange flows with short residence times, whereas a secondary channel created exchange flows with long residence times. There was relatively little exchange flow in the bedrock-constrained fifth-order site. Groundwater flow models were effective in examining the morphologic features that controlled hyporheic exchange flow, and surface-visible channel morphologic features controlled the development of the hyporheic zone in these mountain streams.

Hyporheic Flows Along a Channelled Peatland: Influence of Beaver Dams

“…For our study, the dam height threshold was between 0.67 m (height of dam 2) and 1.05 m (height of dam 1). Other studies have demonstrated how beaver, debris or other small dams ]0.5 m were sufficient to generate vertical hyporheic exchange (Kasahara and Wondzell, 2003;Hester and Doyle, 2008), which is consistent with our findings. Further, Hester and Doyle (2008) used a modeling exercise to demonstrate that enhanced hyporheic flow gradients translated into increased downwelling flux rates with larger dams.…”

“…For example, stream bed topography such as step-pool or riffle-pool sequences (natural or constructed) have been linked to the creation of enhanced zones of hyporheic exchange (Hill and Lymburner, 1998;Butturini et al, 2002;Kasahara and Hill, 2006). Other stream characteristics, such as stream meanders (Triska et al, 1993;, stream size and morphological channel constraints (Kasahara and Wondzell, 2003), downstream longitudinal gradients and secondary channels (Wondzell and Swanson, 1996), and flood induced channel changes (Wondzell and Swanson, 1999) have also been shown to be important in influencing hyporheic exchange. Additionally, sediment characteristics of the stream bed and banks can affect the rate of water exchange across the bed or bank interface, where higher permeability sediments are more conducive to greater hyporheic exchange (Packman and Salehin, 2003).…”

Buffered, lagged, or cooled? Disentangling hyporheic influences on temperature cycles in stream channels

“…Only one hyporheic discharge location exhibited a diel temperature cycle consistent with a long (greater than $100 m) hyporheic flow path (the extreme low point in Figure 9f). These results are consistent with modeling [Cardenas et al, 2004;Poole et al, 2008] and solute tracer studies [Haggerty et al, 2002;Gooseff et al, 2003Gooseff et al, , 2007 that show an inverse power law relationship between hyporheic flow path frequency and length in streams, and suggest that most hyporheic exchange in streams arises from short hyporheic flow paths [see also Kasahara and Wondzell, 2003].…”

Scaling down hyporheic exchange flows: from catchments to reaches

“…Confined aquifers are separated from the surface by aquitards with low hydraulic conductivities, which limit or prevent ground-surface water exchange with these aquifers (Winter, 1998). If the confinement is due to the presence of near-surface bedrock, the lack of alluvium limits vertical HE flows (Kasahara and Wondzell, 2003;Buffington and Tonina, 2009). Indeed, Gurnell et al (2016) 20 described GFE patterns with consideration of the permeability of confining layers, with GSE being prevented or limited to local interactions in confined bedrock and colluvial channels or in confined alluvial channels depending on the local structure of the local sediment (e.g., coarse or fine particles) and to rock structure (e.g., continuous or discontinuous confinement) (Gurnell et al, 2016, Table 7.5).…”