Instability driven flow and runoff formation in a small catchment

Two anomalous phenomena were observed in a small catchment: 1) In some situations, the water supplied by rain caused a pronounced decrease in the soil water content. 2) In these periods, the soil water movement could be explained only by assuming an irregularly oscillating outflow of soil water into lower horizons. In these situations a large volume of water flows through the soil; therefore on the hydrological scale, this phenomenon forms a great part of the outflow from a watershed. These phenomena are described in the frame of the instability driven flow theory and explained as consequences of the porous soil body's capacity to become conductive as a result of a very little change of its moisture. Therefore the soil profile can attenuate or amplify the rainfall pulses during their transformation to the outflow below the soil profile. If the soil water content is lower than the threshold value, the rainfall pulses can be suppressed down to zero. If the soil profile contains more water, the soil does not attenuate the rainfall pulses, it can even amplify them by adding the released soil water. This is the mechanism of rapid growth of rising hydrograph limb during a storm event. The rapid transport of the soil water can occur in any part of the porous soil body regardless of the pore size and can be caused by any rainfall event with any intensity, duration or total volume

Preface to the special issue on biohydrology dedicated to the memory of Dr. Louis W. Dekker

Publisher PD

Impact of secondary succession in abandoned fields on some properties of acidic sandy soils

Abandonment of agricultural lands in recent decades is occurring mainly in Europe, North America and Oceania, and changing the fate of landscapes as the ecosystem recovers during fallow stage. The objective of this study was to find the impact of secondary succession in abandoned fields on some parameters of acidic sandy soils in the Borská nížina lowland (southwestern Slovakia). We investigated soil chemical (pH and soil organic carbon content), hydrophysical (water sorptivity, and hydraulic conductivity), and water repellency (water drop penetration time, water repellency cessation time, repellency index, and modified repellency index) parameters, as well as the ethanol sorptivity of the studied soils. Both the hydrophysical and chemical parameters decreased significantly during abandonment of the three investigated agricultural fields. On the other hand, the water repellency parameters increased significantly, but the ethanol sorptivity did not change during abandonment. As the ethanol sorptivity depends mainly on soil pore size, the last finding could mean that the pore size of acidic sandy soils did not change during succession

Extent and persistence of soil water repellency induced by pines in different geographic regions

This work was supported by the Slovak Scientific Grant Agency VEGA Project Nos. 2/0054/14 and 2/0009/2015, the Slovak Research and Development Agency Project No. APVV-15-0160, and it results from the project implementation of the “Centre of excellence for integrated flood protection of land” (ITMS 26240120004).Peer reviewedPublisher PD

Vliv preferenčního proudění na pohyb vody a transport kadmia v půdě

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Evaporation from soils of different texture covered by layers of water repellent and wettable soils

Water repellent soils are able to channel water deep into the soil profile by fingered flow, minimising water storage in the water repellent top layer where water is most susceptible to evaporation. To date, the effect of water repellent or wettable surface layer on evaporation from wet sublayer has only been reported for coarse materials, and an increase in water repellency led to a greater delay in water evaporation. The objective of this study was to assess the effect of water repellent vs. wettable top layers with different thickness on water evaporation from coarse and fine texture subsoils that were pre-moistened. Clay loam soil samples were taken from Pinus pinaster woodland of Ciavolo, Italy, and sandy soil samples from Pinus sylvestris woodland of Sekule, Slovakia. Evaporation from soil samples was determined from the loss of weight in laboratory conditions. Water in the clay loam soil from Ciavolo was held for a longer period due to slower evaporative loss than in the sandy soil from Sekule, and the impact of the water repellent layer on the loss rate over time is related to its thickness. Over 550 hours, about 90% of the initial stored water was evaporated from the uncovered clay-loam soil sample from Ciavolo. In the same time, the 0.3, 1, and 2 cm-thick duff layers, respectively, saved about 23, 34, and 58 % of water from evaporation, and evaporation of 90% of water took over 780, 1100, and 1450 hours. It means that the clay loam soil cover with the 0.3, 1, and 2 cm-thick duff layers resulted in prolonging the evaporation by 10, 23, and 37.5 days, respectively. As to the sandy soil from Sekule, 98% of water was evaporated from the uncovered soil sample over 240 hours. In the same time, the 0.3, 1, and 2 cm-thick water repellent soil layers, respectively, saved about 7, 45, and 59 % of water from evaporation, and evaporation of 98% of water took over 330, 606, and 774 hours. It means that the sandy soil cover with the 0.3, 1, and 2 cm-thick water repellent soil layers resulted in prolonging the evaporation by about 4, 15, and 22 days, respectively. It can be concluded that water repellent surface layers, created by pine trees, are able to delay evaporation significantly for both coarse and fine textured soils, which may be particularly beneficial for plants during hot and dry periods in summer

Instability driven flow and runoff formation in a small catchment

Two anomalous phenomena were observed in a small catchment: 1) In some situations, the water supplied by rain caused a pronounced decrease in the soil water content. 2) In these periods, the soil water movement could be explained only by assuming an irregularly oscillating outflow of soil water into lower horizons. In these situations a large volume of water flows through the soil; therefore on the hydrological scale, this phenomenon forms a great part of the outflow from a watershed. These phenomena are described in the frame of the instability driven flow theory and explained as consequences of the porous soil body's capacity to become conductive as a result of a very little change of its moisture. Therefore the soil profile can attenuate or amplify the rainfall pulses during their transformation to the outflow below the soil profile. If the soil water content is lower than the threshold value, the rainfall pulses can be suppressed down to zero. If the soil profile contains more water, the soil does not attenuate the rainfall pulses, it can even amplify them by adding the released soil water. This is the mechanism of rapid growth of rising hydrograph limb during a storm event. The rapid transport of the soil water can occur in any part of the porous soil body regardless of the pore size and can be caused by any rainfall event with any intensity, duration or total volume

Soil water repellency changes with depth and relationship to physical properties within wettable and repellent soil profiles

This study explored the effect of soil water repellency (SWR) on soil hydrophysical properties with depth. Soils were sampled from two distinctly wettable and water repellent soil profiles at depth increments from 0-60 cm. The soils were selected because they appeared to either wet readily (wettable) or remain dry (water repellent) under field conditions. Basic soil properties (MWD, SOM, θv) were compared to hydrophysical properties (Ks, Sw, Se, Sww, Swh, WDPT, RIc, RIm and WRCT) that characterise or are affected by water repellency. Our results showed both soil and depth affected basic and hydrophysical properties of the soils (p <0.001). Soil organic matter (SOM) was the major property responsible for water repellency at the selected depths (0-60). Water repellency changes affected moisture distribution and resulted in the upper layer (0-40 cm) of the repellent soil to be considerably drier compared to the wettable soil. The water repellent soil also had greater MWDdry and Ks over the entire 0-60 cm depth compared to the wettable soil. Various measures of sorptivity, Sw, Se, Sww, Swh, were greater through the wettable than water repellent soil profile, which was also reflected in field and dry WDPT measurements. However, the wettable soil had subcritical water repellency, so the range of data was used to compare indices of water repellency. WRCT and RIm had less variation compared to WDPT and RIc. Estimating water repellency using WRCT and RIm indicated that these indices can detect the degree of SWR and are able to better classify SWR degree of the subcritical-repellent soil from the wettable soil