Analysis of Non-Rainfall Periods and Their Impacts on the Soil Water Regime

Rainfall and evaporation belong to the basic components of the hydrological cycle. Rainfalls are a decisive natural source of water in the soil. For water replenishment in the natural environment, it is important not only the sum of the rainfall for the balanced period but also the time distribution. In the case of long non-rainfall periods, the soil profile is dried. In the sufficiently long non-rainfall period, the water reserves in the unsaturated zone of the soil profile change and the actual evapotranspiration is reduced. There is a meteorological and then dry soil formation. For the design of adaptation measures, it is necessary to quantify the mentioned hydrological processes. These were investigated in the central area of the Eastern Slovak Lowland between 1970 and 2015. Significant non-rainfall periods, their periodicity and statistical characteristics have been identified. In the course of significant non-rainfall intervals during the vegetation periods the water reserves in the root layer of the soil were analysed up to a depth of 1 m, the actual and potential evapotranspiration, the evapotranspiration deficit, the groundwater level and the air temperature. The longest non-rainfall periods exceeded 30 days

The importance of volume changes in the determination of soil water retention curves on the East Slovakian Lowland

Estimation and application of water retention curves in heavy soils have own specifics. The reason for these specific properties is the composition of the high clay texture. This is manifested by volume changes of soil depending on moisture. Up to 40% change in the volume compared to the saturated state was recorded in the conditions of the East Slovakian Lowland. The results described in this work are based on research work carried out in the East Slovakian Lowland and represent an analysis of selected 42 samples out of a total of 250 samples in which laboratory measurements of soil water retention curves and volume changes were performed. Selected samples represent the localities Senné and Poľany. Volumetric changes were measured in a laboratory by measuring the dimensions of soil samples. Appropriate changes in the volume of soil samples should be measured when determining moisture retention curves. Neglecting this physical effect leads to a distorted determination of the water retention curves in heavy soils. In the laboratory measurement of water retention curves points, changes in the volume of the sample were measured in the range of 0.24–43.67% depending on the soil moisture potential during drainage. In the case of neglecting the effect of shrinkage during the drainage of samples, a certain error is occurring in the calculation of the volumetric moisture. The range of this error was 1–13% of volumetric moisture

Quantification of Evapotranspiration by Calculations and Measurements Using a Lysimeter

Evapotranspiration is one of the key elements of water balance in nature. It significantly influences the water supply in the unsaturated zone of a soil profile. The unsaturated zone is a water source for the biosphere. The aim of this study is to measure, calculate and analyze the course of actual evapotranspiration, precipitation and dew totals as well as the totals of water flows at the lower boundary of unsaturated zone and the change in water content in specified soil volume. The measurements are used for verifying the results of numerical simulation. The methods used in the study were chosen based on the hypothesis that dynamics of water supply changes in the unsaturated zone is the result of the interactions between atmosphere, soil and plant cover. The elements of water balance were quantified by the methods of water balance, lysimeter measurements and numerical simulation on the model HYDRUS-1D, version 4. The abovementioned parameters were quantified for the East Slovakian Lowland, with an hourly time step during the years 2017, 2018 and 2020. The measurements have shown that evapotranspiration exceeded precipitation during all monitored periods, specifically by 22% in 2017, by 14% in 2019, and by 10% in 2020. The deficit was compensated for by capillary inflow from the groundwater level and the water supply in the unsaturated zone. A verification by measurement has shown that numerical simulation is imprecise in relation to the quantification of water flows at the lower boundary of the unsaturated zone. This inaccuracy is manifested in the higher value of the actual evapotranspiration, which is on average exceeded by 11%. The performance of the mathematical model is assessed as satisfactory for the analysis of the soil water regime

Development of evapotranspiration and water supply of clay-loamy soil on the East Slovak Lowland

With regard to optimization of the factors of field crop harvest formation in semi-arid areas the phenomenon of soil drought is of key importance. This article deals with the problem of soil water management in connection to soil fertility in the area of East Slovakian Lowland, characterized by the complexity of its agro-ecologic conditions. In clay-loamy soils of the corresponding area, soil water content at the level limited by the threshold point and field water capacity ensures that the average value of actual evapotranspiration intensity varies between 2.69 and 3.89 mm per day-1. Time development of soil water storage and evaporation deficit depends on optimized system of soil water management necessary for plant production.The East Slovak Lowland Semi-arid region Evapotranspiration deficit Critical soil moisture

Evaluation of precipitation measurements using a standard rain gauge in relation to data from a precision lysimeter

The construction of modern lysimeters with a precise weighing system made it possible to achieve an unprecedented accuracy of precipitation measurement. This study compares two methods of measuring precipitation in the conditions of the humid continental climate of the Eastern Slovakian Lowland (Slovakia): measurement using a standard tipping-bucket rain gauge vs. precision weighable lysimeter. Data from the lysimeter were used as a reference measurement. The comparison period lasted four years (2019–2022). Only liquid rainfall was compared. The rain gauge was found to underestimate precipitation compared to the lysimeter. Cumulative precipitation for the entire monitored period captured by the rain gauge was 2.8% lower compared to lysimeter measurements. When comparing hourly and daily totals of precipitation and precipitation events, a very high degree of agreement was detected (r2 > 0.99; RMSE from 0.22 to 0.51 mm h–1). A comparison based on precipitation intensity showed a decreasing trend in measurement accuracy with increasing precipitation intensity. This tendency has an exponential course. With increasing intensity of precipitation, increasing intensity of wind was also recorded. In order to correct measurement errors, simple correction method was proposed, which helped to partially eliminate the inaccuracies of the rain gauge measurement

Geometric Factor as the Characteristics of the Three-Dimensional Process of Volume Changes of Heavy Soils

During simulation of a water regime of heavy soils, it is necessary to know the isotropy parameters of any volume changes. Volume changes appear in both vertical and horizontal directions. In vertical directions, they appear as a topsoil movement, and in horizontal directions as the formation of a crack network. The ratio between horizontal and vertical change is described using the geometric factor, rs. In the present paper, the distribution of volume changes to horizontal and vertical components is characterized by the geometric factor, in selected soil profiles, in the East Slovakian Lowland. In this work the effect of soil texture on the value of the geometric factor and thus, on the distribution of volume changes to vertical and horizontal components was studied. Within the hypothesis, the greatest influence of the clay soil component was shown by the geometric factor value. New information is obtained on the basis of field and laboratory measurements. Results will be used as inputs for numerical simulation of a water regime for heavy soils in the East Slovakian Lowland

Changes in crack width on the surface of heavy soils during drought, determined by precise measurement and calculation

In heavy soils, changes in humidity incur soil volume changes. In the horizontal plane, these are manifested by cracks formation and in the vertical plane by the movement of the soil surface. Cracks have a significant impact on hydrodynamics of the soil profile. The work is based on the hypothesis that soil volume changes depend on both the content of clay particles in soil and soil volumetric moisture. The aim of the work is to measure and analyze the changes in the width of the cracks and their reaction to the changes in volumetric soil moisture. One of the objectives of the work was to design a simple tool for accurate measurement and calculation of the crack width on the soil surface. For the study of crack width, a soil profile in an area on the East Slovakia Lowland was selected. The profile was examined under conditions of extreme drought, at the turn of July and August 2022. Crack width varied between 1.0 cm and 3.3 cm. The calculation procedure was evaluated as satisfactory for estimating the change in crack width on the soil surface