Intensity Of Water Repellency Research Articles

Wettability of ash conditions splash erosion and runoff rates in the post-fire

Although the impact of ash on the hydrological and erosive response of burned soils has been studied in the last years, the effect of ash wettability on particle detachment by splash erosion has been rarely studied. In this research, we have studied the effect of wettable and water-repellent ash on the intensity of splash erosion after a prescribed burn in a Mediterranean shrubland. Runoff rates from wettable and water-repellent ash layers were also studied by rainfall simulation experiments (6mmmin−1 during 10min) at plot scale. Splash erosion experiments showed that the intensity of ash water repellency strongly conditioned the detachment and mobilization of ash and soil particles due to raindrop impacts in the post-fire. Although the intensity of water repellency and the amount of ash decreased through the experimental period, it was observed that splash erosion in originally water-repellent ash areas was about three times higher than in wettable ash areas. Plot-scale rainfall simulation experiments showed that runoff rates were much higher in water-repellent ash areas, where runoff rates increase with decreasing depth of the ash layer. In water-repellent ash areas, thick ash layers store a significant proportion of water that does not infiltrate soil, but contributes to relatively low runoff rates. In contrast, thin water-repellent ash layers are rapidly redistributed by rainfall, and the burned mineral soil surface is exposed. Pore clogging with fine water-repellent ash particles enhances runoff rates. During low or moderate intensity storms, patches of wettable/water-repellent ash arrange in a pattern that produces water infiltration/runoff generation areas, reducing the connectivity of water and sediments through the slope.

Basic soil properties as a factor controlling the occurrence and intensity of water repellency in rankers of the White Carpathians

Abstract Water repellency in soils is controlled by many different factors, basic physical and chemical properties might be considered the crucial ones. For the purpose of this study, 12 sites were selected and sampled (0–20 cm depth) in the White Carpathians. Repellency tests were conducted under laboratory conditions in triplicate using water drop penetration time (WDPT) test and the molarity of ethanol droplet (MED) test. Results of WDPT measurements showed that three samples were marked by slight to extreme water repellency. Regarding the relationship between WDPT/MED and tested soil properties, the highest value of correlation coefficient was calculated for soil organic carbon (r = 0.706; p < 0.05), suggesting there is a positive, statistically significant correlation between repellency severity and total carbon content. A negative relationship between repellency and soil reaction/silt/silt + clay contents of studied soils was found. Samples taken from the surface horizon of arable soils showed no repellency.

Fire-induced soil water repellency under different vegetation types along the Atlantic dune coast-line in SW Spain

Abstract The distribution and variation with soil depth of water repellency has been studied in fire-affected sand dunes under three different vegetation types (pine forest, shrubland and sparse herbaceous vegetation) in SW Spain. The persistence and intensity of water repellency at the exposed surface of soil was measured using the water drop penetration time test and the contact angle method, respectively, in surface samples (0–3 cm) collected at burned and unburned areas. The variation of water repellency with depth in burned areas was studied in soil profiles every 5 cm between 0 and 40 cm depth. None or slight soil water repellency was observed at unburned soil sites, whereas burned soil sites showed a high degree of repellency, especially under pines and shrubland. The spatial pattern of fire-induced soil water repellency was found to be associated to vegetation types, although it was modulated by soil acidity and the soil organic carbon content. Soil water repellency was generally higher at the soil surface, and decreased with depth. Dense pine forests and shrublands showed strong and/or severe water repellency in depth, but it was rare and limited to the first five centimeters under sparse herbaceous vegetation. The heterogeneity of moisture patterns under dense pine forests or shrublands showed the existence of wetting and water repellent three-dimensional soil patches.