Search results for "soil water"
showing 10 items of 840 documents
Improvement of FAO-56 Model to Estimate Transpiration Fluxes of Drought Tolerant Crops under Soil Water Deficit: Application for Olive Groves
2014
[EN] Agro-hydrological models are considered an economic and simple tool for quantifying crop water requirements. In the last two decades, agro-hydrological physically based models have been developed to simulate mass and energy exchange processes in the soil-plant-atmosphere system. Although very reliable, because of the high number of required variables, simplified models have been proposed to quantify crop water consumes. The main aim of this paper is to propose an amendment of the Food and Agricultural Organization (FAO) of the United Nations FAO-56 spreadsheet program to introduce a more realistic shape of the stress function, valid for mature olive orchards (Olea europaea L.). The mod…
Physical and hydraulic characterization of a clay soil at the plot scale
2010
Summary The soil physical and hydraulic properties have to be determined for interpreting and simulating many hydrological processes. An investigation was carried out to determine the physical and hydraulic characteristics of a clay soil at the plot scale. An intensive sampling of the surface soil layer of two plots of 4 × 11 m2 was carried out by measuring, for each plot, dry soil bulk density, ρb, and antecedent soil water content, θi, at 88 sampling points and field-saturated soil hydraulic conductivity, Kfs, at 176 sampling points. A wide range of Kfs values (0.7–5107 mm h−1) were measured by the Simplified Falling Head (SFH) technique. For each variable, the two plots yielded very simi…
High resolution remote estimation of soil surface water content by a thermal inertia approach
2009
Summary The spatial distribution of soil surface water content in a bare soil was evaluated by a thermal inertia approach from high resolution visible/near infrared (VIS/NIR) and thermal infrared (TIR) airborne data. Given that the relationship between the thermal inertia and the soil water content strongly depends on the accurate estimation of the soil thermal conductivity, two different empirical models were applied to estimate it. Remotely estimated water contents were tested with time domain reflectometry (TDR) measurements collected on a 110 × 90 m 2 bare field in coincidence with airborne over-flights. The thermal conductivity model by Johansen (1975) produced more accurate estimates …
Comparing different application procedures of the water drop penetration time test to assess soil water repellency in a fire affected Sicilian area
2019
Abstract The Water Drop Penetration Time (WDPT) technique was applied in two subsequent years (2016 and 2017) to check surface soil water repellency (SWR) in a Sicilian mountain area affected by a wildfire on June 2016. A total of 93 sites were sampled and from 3 to 100 droplets were used to characterize a site. The detected SWR varied with the severity of the wildfire, being practically absent in the unburnt control area and slight to extreme in the burnt areas. The percentage of extremely repellent sites increased with wildfire severity. SWR vanished one year after the passage of the fire in sites where fire severity was moderate but it persisted in the case of a severe wildfire. In gener…
Climatic changes in yield index and soil water deficit trends in China
2000
Long-term trends of the combined effects of evapotranspiration and precipitation effect surface hydrology and soil water and consequently natural and agricultural ecosystems. This paper analyses yield index and soil water deficit time series derived from water balance calculations for multiple cropping systems with FAO methodology. The analysis shows that yield index values have increased and soil water deficits have consequently decreased over much of China during 1954‐1993. The likely parameters contributing to this trend are precipitation changes north of 35 N and maximum evapotranspiration as well as available soil water trends south of this line. Increasing the assumed maximum soil wat…
Soil erosion susceptibility assessment and validation using a geostatistical multivariate approach: a test in southern Sicily
2008
A certain number of studies have been carried out in recent years that aim at developing and applying a model capable of assessing water erosion of soil. Some of these have tried to quantitatively evaluate the volumes of soil loss, while others have focused their efforts on the recognition of the areas most prone to water erosion processes. This article presents the results of a research whose objective was that of evaluating water erosion susceptibility in a Sicilian watershed: the Naro river basin. A geomorphological study was carried out to recognize the water erosion landforms and define a set of parameters expressing both the intensity of hydraulic forces and the resistance of rocks/so…
A Rainfall Simulator Laboratory Approach to Determine the Impact of Ash Depth on Runoff Generation and Soil Losses
2020
Ash cover the forest fire affected soil for some weeks or months and act as a key factor to determine the soil and water losses. Ash depth is researched here to determine how affect the soil detachment and the runoff generation. Seventy rainfall simulation experiments on paired 0.50 m2 plots (five plots with 0, 1, 2, 3, 5, 10, 15- and 30-mm ash depth), and repeated one week later) under thunderstorms of 48 mmh-1 for one hour were carried out under laboratory conditions. In the first experiment, after the bed of ash was applied, the results show that ash depth determines the runoff rates as they reduce the discharge from 23.1% to 13.9%. The sediment concentration increased from 23.8 till 38.…
ON THE USE OF SATELLITE THERMAL DATA FOR DETERMINING EVAPOTRANSPIRATION IN PARTIALLY VEGETATED AREAS
1992
Abstract The use of satellite data for determining daily evapotranspiration over completely vegetated areas has been analysed by different authors. However, if the soil surface is partially covered by vegetation the problem becomes more complicated, because in this case the value of the temperature measured by the satellite varies with the viewing geometry. In this work we have studied the influence of the satellite observation angle for crops with different cover degree, field geometry and ground emissivity. For this purpose we have used the simplified relation proposed by Jackson et al.LET d=Rnd−B(T3−T a)iwhere ET 4 and R nd are the daily values of evapotranspiration and net radiation res…
Effect of climate on surface flow along a climatological gradient in Israel: a field rainfall simulation approach
1998
Abstract A climatological gradient was selected in Israel to examine the effects of climate on surface flow and soil erosion. The gradient is composed of eight study areas located between the Dead Sea and the Galilee Mountains. Mean annual rainfall ranges from 100 mm year −1 in the driest site to 900 mm year −1 in the wettest site. Simulated rainfall experiments were performed in order to determine the main hydrological and erosional parameters. Data were recorded in 36 different plots after showers of 50 mm h −1 rain intensity and 45–60 min duration. In the arid sites ( −1 ) abundant runoff appeared on the soil surface very quickly, and the infiltration rates were very low. Erosion rates, …
Ecohydrological adaptation of soils following land abandonment in a semi-arid environment
2010
Representative land use types were selected in southeast Spain to investigate the redistribution of soil water in relation to vegetation development and land abandonment.Simulated rainfall experiments were performed during 2 days on each of the four selected surfaces: ploughed, a 3-year fallow field, a 12-year abandoned field with shrubs and a semi-natural field with Stipa tenacissima tussocks. Each experiment consisted of five runs of artificial rain. Soil moisture dynamics were measured by time domain reflectometry (TDR), as well as runoff and ponding on the plot surface. Also the movement of the wetting front was measured after each run.On the ploughed field, ponding and local runoff wer…