Relative contributions of transient and steady state infiltration during ephemeral streamflow

Abstract

[1] Simulations of infiltration during three ephemeral streamflow events in a coarsegrained alluvial channel overlying a less permeable basin-fill layer were conducted to determine the relative contribution of transient infiltration at the onset of streamflow to cumulative infiltration for the event. Water content, temperature, and piezometric measurements from 2.5-m vertical profiles within the alluvial sediments were used to constrain a variably saturated water flow and heat transport model. Simulated and measured transient infiltration rates at the onset of streamflow were about two to three orders of magnitude greater than steady state infiltration rates. The duration of simulated transient infiltration ranged from 1.8 to 20 hours, compared with steady state flow periods of 231 to 307 hours. Cumulative infiltration during the transient period represented 10 to 26% of the total cumulative infiltration, with an average contribution of approximately 18%. Cumulative infiltration error for the simulated streamflow events ranged from 9 to 25%. Cumulative infiltration error for typical streamflow events of about 8 hours in duration in is about 90%. This analysis indicates that when estimating total cumulative infiltration in coarse-grained ephemeral stream channels, consideration of the transient infiltration at the onset of streamflow will improve predictions of the total volume of infiltration that may become groundwater recharge.

Ecohydrology: Processes and Implications for Rangelands

“…There is an extensive body of work examining the ecohydrological influence of grazing, and specifically its influence on soil infiltration. Much of this work was conducted in the USA in the 1970s and 1980s and has been summarized in several review papers (Gifford 1978;Wood et al 1978;Wood and Blackburn 1981;Blackburn et al 1982;Trimble and Mendel 1995). The findings consistently show that, irrespective of grazing systems, light-to-moderate grazing generally has little adverse effect on the ecohydrology of rangelands and may even have a positive effect, whereas heavy grazing generally significantly decreases soil infiltrability.…”

“…The headwaters section of a river typically has steep gradients, and the river bed contains rocks or boulders with little accumulation of fine sediments, whereas the middle and lower reaches are characterized by extensive alluvial deposits and wide floodplains (e.g., Nile, Platte, Euphrates, Ganges) (Vannote et al 1980;Wiens 2002). These deposits are typically heterogeneous, with coarse sediments that can capture, store, and transmit large volumes of water interspersed vertically and horizontally with fine sediments that have a lower storage capacity and low transmissivity (Blasch et al 2006;Morin et al 2009). In humid-to-semiarid landscapes, rainfall is sufficient to generate runoff and groundwater that sustain river systems, and the rivers are gaining water, albeit seasonally.…”

“…The importance of soil infiltrability has long been recognized (Smith and Leopold 1941) and has been the focus of considerable research in the last half century or more. It is influenced by many factors, including management practices; for example, overgrazing that results in a loss of vegetation cover and an increased exposure of bare soil can dramatically reduce soil infiltrability (Blackburn et al 1982;Snyman and du Preez 2005).…”

Use of heat to estimate streambed fluxes during extreme hydrologic events

“…[Healy and Ronan, 1996]. VS2DH is a modification of VS2DT [Healy, 1990], which was developed for simulating solute transport in variably saturated porous media such as ephemeral streambeds or through the vadose zone [Blasch et al, 2006;Constantz et al, 2001]. Recent studies have also shown the effectiveness of using heat to model energy transport in order to derive hydraulic properties of alluvial aquifers and wetlands [Su et al, 2004;Burow et al, 2005].…”

Geomorphology as a first order control on the connectivity of riparian ecohydrology

“…Another important source in many semiarid rivers is snowmelt from surrounding mountains that is concentrated in a spring flood, the magnitude of which depends on the snowpack accumulated in the mountains over the winter; and this, too, is subject to major interannual variation in magnitude. (Blasch et al, 2006;Morin et al, 2009).…”