TDR technique for estimating the intensity of effective non rainfall

Abstract

A b s t r a c t. The objective of this paper is to present a method for determining diurnal distribution of the intensity of effective non rainfall water flux. It was found that the application of TDR technique for the determination of diurnal dynamics of effective non rainfall water flux requires temperature correction of sensed volumetric moisture contents. Without temperature correction the error of estimated non rainfall water flux can be as much as 26%. In addition, the effect of temperature changes on the soil surface was determined in 0.5, 1, 2, 3, 4, and 5 hours periods. It was found that the intensity of effective non rainfall water flux was determined to the greatest extent by the rate of temperature drop during the period of 3 h preceding the non rainfall water flux determination. The agreement of non rainfall water flux calculated with the method proposed and that obtained by the collector was better for dew than for hoarfrost periods.K e y w o r d s: TDR technique, effective non rainfall water flux, impermeable barrier INTRODUCTIONKnowledge of the physical processes that affect the efficiency of water infiltration into the surface horizon of soil is important in the formulation of input data for mathematical models describing the movement of water (Jacobs et al., 2002;Reinhard and Reinhard, 2005). Knowledge of the run of processes of that type is important, as water is a source of nutrients for animals and plants (Kidron, 2005;Kolev et al., 2012). In such considerations one should take into account the role of dew, hoarfrost, condenzation of water vapour contained in the soil air, and adsorption of water from the atmosphere. In regions with arid climate the effect of those processes on the water balance of the top horizon of soil may be greater than that of atmospheric precipitation (Agam and Berliner, 2006). As an example, the contribution of dew and hoarfrost in the annual water balance of the surface horizon of soil in a semi-desert area situated in Nevada, USA, amounts to 31 mm year -1 (Malek et al., 1999). With regard to the phenomena considered here, the contemporary methods for the determination of the diurnal dynamics of the intensity of water infiltration can be classified in four groups: methods consisting in measurements with the use of dew and hoarfrost collectors, lysimetric methods, models employing empirical mathematical formulae, and phenomenological models. The first group includes eg the Duvdevani dew gauge, the Cloth Plate Method and the Hiltner Dew Balance. The Duvdevani dew gauge is one of the first devices for the measurement of the dew balance (Duvdevani, 1947). The measured volume of dew deposit should be treated as an estimate and it cannot be compared with absolute values. The Cloth Plate Method is also a method in which the measurement is taken manually. The apparatus is equipped with a glass plate with dimensions of 10 x 10 x 0.2 cm, to the centre of which highly absorbing synthetic fabrics are attached, with dimensions of 6 x 6 cm (Kidron, 1998). In their study, Zangvil ...

Atmospheric water infiltration intensity in non-rainfall periods under conditionsof varied soil moisture

“…The application of the TDR technique and the introduction of temperature correction ensures that soil moisture can be determined with high accuracy (up to 0.001 m 3 m -3 ). The method of determination of the temperature correction is elucidated in the papers by (Janik et al, 2014;Oates et al, 2017;Skierucha, 2009). When the LP/ms probe is placed horizontally, we found that it was possible to register the volume of soil moisture in the top soil layer (2 cm).…”

“…However, due to varied weather conditions, the values of E P in the successive series were different. The values of E R were determined with the use of the knowledge of the dynamics of volumetric moisture of soil in isolated spaces (Janik et al, 2014). The application of the TDR technique and the introduction of temperature correction ensures that soil moisture can be determined with high accuracy (up to 0.001 m 3 m -3 ).…”

“…Ultimately, it was possible to construct for successive short time steps (chosen at will) water budget equations for soil volumes 2-17. The only unknown in the equations is the value of E R , and on this basis it can be calculated from the formula (Janik et al, 2014):…”

“…On that day, the value of E R without the temperature correction is 0.017 mm day -1 , while after the temperature correction the resulting E R is 0.049 mm day -1 ((0.049-0.017)/0.049 100=65%). Therefore, in the case of calculations of this type, the application of temperature correction is necessary (Janik et al, 2014;Skierucha, 2005). During experiment D 1 , the value of E P varied on individual days because the atmospheric conditions were different.…”

“…In non-rainfall periods, soil is also supplied with water from the atmosphere (Jacobson et al, 2015;Kidron et al, 2014;McHugh et al, 2015;Tomaszkiewicz et al, 2015). This is an effect that comes about due to the formation of dew, hoarfrost, soil-water vapour condensation and atmospheric water adsorption (Alishaev, 2013;Janik et al, 2014;Zhang et al, 2015). The importance of these processes in the water balance of the soil surface layer is demonstrated not only in arid (desert) areas, but also in humid regions (Cassity-Duffey and Cabrera, 2016).…”