Relating in situ hydraulic conductivity, particle size and relative density of superficial deposits in a heterogeneous catchment

Abstract

11Estimating the permeability of superficial deposits is fundamental to many aspects of catchment 12 science, but can be problematic where insufficient in situ measurements are available from pumping 13 tests in piezometers. Consequently, common practice is to estimate permeability from the material 14 description or, where available, particle size distribution using a formula such as Hazen. In this 15 study, we examine the relationships between particle size, relative density and hydraulic 16 conductivity in superficial deposits in Morayshire, Northern Scotland: a heterogeneous environment 17 typical of many catchments subject to previous glaciations. The superficial deposits comprise 18 glaciofluvial sands and gravels, glacial tills and moraines, raised marine sediments, and blown sands. 19Thirty-eight sites were investigated: hydraulic conductivity measurements were made using 20 repeated Guelph Permeameter measurements, cone resistance was measured in situ with a Panda 21 dynamic cone penetrometer; material descriptions were made in accordance with BS5930:1999; and 22 disturbed samples were taken for particle size analysis. Overall hydraulic conductivity ( independent predictors of log K and together gave a relationship with an R 2 of 0.80. Material 28 description using the largest fraction (e.g. sand or gravel) had little predictive power. Therefore, in 29 heterogeneous catchments, the permeability of superficial deposits is most strongly related to the 30 finest fraction (d10) and relative density of the material.In situ Guelph permeameter 31 measurements at outcrops with good geological characterisation provide an easy and reliable 32 method of determining the permeability of particular units of superficial deposits. 33

A constant head well permeameter formula comparison: its significance in the estimation of field-saturated hydraulic conductivity in heterogeneous shallow soils

“…It is also worth noting that other studies have multiplied the Guelph permeameter values (calculated using the Richards solution) by 2 to obtain similar Ks values to the auger hole method (Noshadi et al 2012), which they attribute to air entrapment (Bouwer 1978, p. 45). considering its wide use in the UK and the dependency on soil descriptions for predetermined α* values (Lilly 1994;Marshall et al 2009;MacDonald et al 2012). In this study the high silt content in the floodplain (G4) suggests an α* value of 0.04 cm would be significantly lower than the Kfs values of the AH method (as shown in Fig.…”

“…the Glover solution, overestimates Kfs when compared to the Richards equation, but according to Talsma (1987) the CHWP method using the Glover solution underestimates Kfs in comparison to the AH method (Talsma 1987). Even though the Richards equation provides the lowest Kfs of all the solutions in most studies, it is the main solution used to estimate in situ Kfs in the UK (Ragab and Cooper 1993;Lilly 1994;Chandler and Chappell 2008;Marshall et al 2009;MacDonald et al 2012). It is also worth noting that other studies have multiplied the Guelph permeameter values (calculated using the Richards solution) by 2 to obtain similar Ks values to the auger hole method (Noshadi et al 2012), which they attribute to air entrapment (Bouwer 1978, p. 45).…”

“…Measurements of field-saturated hydraulic conductivity, for example, have been used to investigate land cover effects on the dominant stormflow pathways (Elsenbeer et al 1999;Bonell et al 2010), water flow modelling and solute transport for drainage investigation (Noshadi et al 2012), development of class pedotransfer functions (Lilly 2000) and estimating permeability of superficial deposits for characterising groundwater/surface water interactions (MacDonald et al 2012).…”

Mapping suitability for open-loop ground source heat pump systems: a screening tool for England and Wales, UK

“…'Glacial Deposits', 'River Terrace Deposits' or 'Blown Sand') rather than lithology. Permeability within these classes can vary hugely (Bricker & Bloomfield 2014;MacDonald et al 2012), and their productivity will also depend on the lithology of the deposit, areal extent (which is often small) and saturated thickness, making it difficult to distinguish between deposits that form aquifers and those that do not. There are also currently no superficial deposits maps available at the scale of 1:250000.…”

Groundwater, flooding and superficial deposits in the Findhorn catchment

“…Transmissivity (T) is approximately 50 m 2 d -1 . The pumping tests indicate high variability in permeability in the superficial deposits across the floodplain (MacDonald et al, 2012). Measured transmissivity (permeability integrated over depth) varies by over three orders of magnitude, from less than 1 m 2 d -1 to > 3000 m 2 d -1 .…”