Quantify the Pore Water Velocity Distribution by a Celerity Function

Abstract

Celerity and velocity of subsurface flow in soil porous medium are intimately linked with tracer transport, while only few current studies focused on their relations. This study conducted theoretical analyses based on a pore bundle model, under which celerity in unsaturated flow is equivalent to maximum velocity. Furthermore, under 3 models Brooks-Corey model and unmodified and modified Mualem-van Genuchten models, we used a celerity function to derive breakthrough curves aiming to quantify the advective tracer transport for 5 typical soil textures. The results showed that the celerity under near-saturated conditions can be 5 up to 100 times larger than the saturated hydraulic conductivity, and a small volumetric fraction (<15%) of pores contributed more than half of the specific discharge. First arrival time and extensive tailing of the breakthrough curves were controlled by maximum velocity and velocity distribution, accordingly. As the kinematic ratio in the Brooks-Corey model remained constantly for each specific soil, we used it to quantify the ratio of maximum tracer velocity over average tracer velocity. We also found that a bimodal soil hydraulic function (for a dual-permeability model) may result in similar soil hydraulic conductivity functions for different parameter sets, but their celerities are different. The results showed that the proposed celerity function can assist in investigating subsurface flow and tracer transport, and the kinematic ratio could be used to predict the first arrival time of a conservative tracer.

Short high-accuracy tritium data time series for assessing groundwater mean transit times in the vadose and saturated zones of the Luxembourg Sandstone aquifer

“…MRT values are in general almost four times lower than 𝜏 𝑝𝑓 ones. A potential explanation for this difference is that MRT would reflect water celerity, i.e., the speed at which the water infiltration signal is transmitted through the vadose zone to the springs, while 𝜏 𝑝𝑓 relate to water velocity, i.e., the movement of water molecules (McDonnell and Beven, 2014;Scaini et al, 2017;van Verseveld et al, 2017;Shao et al, 2018;Worthington and Foley, 2021).…”

An Experimental Study on the Hydromechanical Behaviours of the Evolution of Postearthquake Landslide Deposits

“…The coarse-textured gravelly soil gathered from the landslide site has a loose porous structure, which enables preferential flow to run through certain pathways [39]. In order to prove the occurrence of preferential flow in the soil, the relationship between soil density and porosity was verified via a special device (Figure 7(a)).…”

A Study of Velocity-Celerity Relationships during Leakage from Soil Columns under Natural Rainfall Events

“…Rasmussen et al (2000), in their investigation of unsaturated infiltration in a peat soil column, introduced the ratio of celerity to velocity (c/v) as the kinematic ratio (k). Researchers such as McDonnell and Beven (2014) and Shao et al (2018) had surveyed and compared celerity and velocity formulas for various flow environments, along with the c/v values.…”

“…They also noted that its value is independent of water content changes. Furthermore, c/v has been employed to identify flow types in streams (R.H. & E., 2021) and to predict the arrival time of conventional tracers, effectively the maximum velocity (Shao et al, 2018). Thus, the kinematic ratio c/v serves as a critical indicator for understanding the relationship between celerity and velocity.…”