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The wetting pattern which occurs under surface drip irrigation is an important component for the optimum design of the system and for irrigation programming. The aim of this investigation was to devise a model which enables estimation of the 2D cross-sectional area of the wetting pattern which occurs under a surface dripper by an analytical method. The main parameters of the wetting pattern are the wetting diameter on the soil surface, the maximum wetted depth and maximum wetted width in the soil profile, and the depth of this maximum wetted width from the soil surface. In the laboratory experiments, water applications were carried out on two soil textures (clay loam and clay) with homogeneous soil profiles at two discharge rates over 125 min and 170 min periods. The sizes of the parameters of the wetting pattern were measured as consecutive series over 5-min intervals during the water application period. The general/main shape which represents the wetting patterns which occur under different irrigation conditions was defined and mathematically modelled. When the results were evaluated statistically, a correlation of 0.9128 was found between the momentary rates of change of the maximum depth of the wetting pattern predicted by the model and those measured in the experiment. The correlation between the momentary variations of accelerations of the same parameter was 0.9205. In addition, the size of the wetting pattern showed an increment in reducing velocities during the water application period. The results indicate that the model devised in this investigation can be used in the prediction of the cross-sectional area of the wetting pattern which occurs under a surface dripper. [ABSTRACT FROM AUTHOR]

The main purpose of this review is to find the diversity in research studies of subsurface irrigation systems in the past two decades. Two periods of five years were selected to reflect the research studies at the beginning and the end of the comparing periods range. A statistical sorting was used to investigate the distribution of papers according to objectives, types of irrigation systems, research methods, and limitations of the studies. Results showed that the measurements and evaluations were the most presented objectives of the selected papers for both periods. Furthermore, almost 90 percent of the recent papers used multiple research methods, unlike the papers published in the former period which only 56 percent of them used multiple methods. Also, more than 90 percent of the recent papers used a single irrigation system. In conclusion, knowledge of subsurface irrigation systems had been advanced in the former studies mostly by analyzing the measurements and evaluations of the traditional irrigation systems. Unlike the former period, the advancement in knowledge has been produced in the current period by introducing new subsurface irrigation systems and more concentration by the order of measurements, evaluation, and designing, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to analyze differences in experimental and calculated model study of the processes of movement of soil water under low head ponding and gravity infiltration. In the forecast of the water regime two kinds of hydrological information were used – experimental and pedotransfer functions (PTFs). The experimental information: the hydraulic conductivities (HC) in saturated conditions were determined in the field conditions, unsaturated conductivity function was calculated (van Genuchten-Mualem model) using HC and water retention curves (WRC), WRC were investigated in laboratory condition with the help of capillarimeters, sand-kaolin boxes and by the centrifuge method. PTFs included: regional PTF, based on the data of the original database for the soil hydrological properties of the study area relying on the soil density and soil organic content, PTF based on particle size distribution, based on field capacity and wilting point as a predictors, and PTFs based on physico-mechanical properties, specifically Atterberg limits. The spatial distribution of moisture indicates that after infiltration under low head ponding, the soil water content variation is rather high (at depths of 50 and 60cm the quartiles were about 2-3 and 6-12%), but in the case of gravity infiltration the quartiles were about 2 and 5%. This points to the presence of preferential flows. The best forecast of the real-mode soil water regime gave experimental hydrological information: no systematic errors in the high min-max range of modeling errors. Among PTFs the modeling results were placed in the following order: regional PTFs work better (>) than PTFs based on the field capacity and wilting point >PTFs based on Atterberg limits> PTF based on particle size distribution. The statistical analysis of the modeling errors by Williams-Klute nonparametric statistical criteria is evidence that models describe best gravity filtration. [Copyright &y& Elsevier]