Combination of Measurement Methods for a Wide-Range Description of Hydraulic Soil Properties

Abstract

Established measurement methods for hydraulic soil properties cover a limited soil moisture range. Simulations of soil water dynamics based on such observations are therefore rarely representative for all conditions from saturation to drought. Recent technical developments facilitate efficient and cheap collecting of soil water characteristics data, but the quantitative benefit of extended measurement campaigns has not been adequately tested yet. In this study, a combination of four methods to measure water retention and hydraulic conductivity at different moisture ranges was applied. Evaporation method, dewpoint psychrometry, hood infiltrometer experiments, and falling head method for saturated conductivity were conducted at two experimental sites in eastern Austria. Effects of including the particular methods in the measurement strategy were examined by visual evaluation and a 1D-modelling sensitivity study including drainage, infiltration and drought conditions. The evaporation method was considered essential due to its broad measurement range both for water retention and hydraulic conductivity. In addition to that, the highest effect on simulated water balance components was induced by the inclusion of separate conductivity measurements near saturation. Water content after three days of drainage was 15 percent higher and the transpiration rate in a drought period was 22 percent higher without near-saturated conductivity measurements. Based on relative comparisons between different combinations, we suggested combining evaporation method and hood infiltrometer experiments as the basis for representative predictions of soil water dynamics.

Why We Should Include Soil Structural Dynamics of Agricultural Soils in Hydrological Models

“…Saturated hydraulic conductivity (K s ) is often determined in the field using single or double ring infiltrometers or using hood infiltrometer [28]. Recently, Weninger et al [29] evaluated the combination of different measurement methods to parameterize SHP to predict soil water dynamics. The authors concluded that a combination of field and lab measurements (e.g., hood infiltrometer in combination with the evaporation method) may provide a basis for representative predictions of soil water dynamics.…”

The Impact of Poplar Short Rotation Coppice on Topsoil Physical Properties and Related Water Conditions

“…For a sustainable management of SRC plantations, the water availability in the soil needs to be considered. Soil hydraulic properties such as water storage depend on soil structure, and on soil hydraulic properties, both are affected by land use and land management which dynamically change over the course of the season [13,14,16,17]. The impact of SRC on soil hydraulic properties can be determined by relating the water retention and hydraulic conductivity functions through hydraulic functions [17] using a combination of field and laboratory experiments.…”

Soil Hydraulic Properties Determined by Inverse Modeling of Drip Infiltrometer Experiments Extended with Pedotransfer Functions

“…The accurate modeling of water flow and budgeting of solute and heat transport in the vadose zone based on a numerical solution of the Richards equation depends on precise knowledge of the fundamental soil hydraulic properties (SHPs): water retention [θ( h )] and hydraulic conductivity [ K ( h )] (Groh et al, 2018; Weninger et al, 2018). Direct measurement of K ( h ) is laborious, therefore K ( h ) is most commonly indirectly derived by using the measured saturated hydraulic conductivity, the θ( h ) function, and an empirical parameter related to tortuosity and connectivity, which, in its turn, exhibits a very large spatial variability (Durner et al, 1999).…”

“…Direct measurement of K ( h ) is laborious, therefore K ( h ) is most commonly indirectly derived by using the measured saturated hydraulic conductivity, the θ( h ) function, and an empirical parameter related to tortuosity and connectivity, which, in its turn, exhibits a very large spatial variability (Durner et al, 1999). Consequently, any method to directly quantify K ( h ) represents an improvement of modeling quality, but this is predominantly neglected (Weninger et al, 2018; Weller et al, 2011).…”

“…Direct measurement of K(h) is laborious, therefore K(h) is most commonly indirectly derived by using the measured saturated hydraulic conductivity, the q(h) function, and an empirical parameter related to tortuosity and connectivity, which, in its turn, exhibits a very large spatial variability (Durner et al, 1999). Consequently, any method to directly quantify K(h) represents an improvement of modeling quality, but this is predominantly neglected (Weninger et al, 2018;Weller et al, 2011). Both soil heterogeneity at different scales, from millimeters to kilometers, and the large amount of required data restrict the use of pedotransfer functions for the determination of SHPs and especially the soil water retention function [q(h)] (Graham et al, 2018). Methods to measure SHPs, including pressure plates and in situ techniques like internal drainage experiments, are commonly laborious and costly.…”