Erosion Processes Due to Sprinkler Irrigation

The study and analyses of erosion have shown that the main factors determining erosion processes under equal soil and climatic conditions are the intensity and structure of artificial rain and the ground slope. The main factor, artificial rain intensity, depends mainly on the soil infiltration rate. In sprinkle irrigation, the soil infiltration is preceded by interaction between the soil and the rainfall drops. Failure to observe this interaction has often caused irrigation erosion problems due to the impact drops on the soil. It has been proved that the bigger are rainfall drops and their intensity, the bigger are the damages to soil structure. The most important factors on which depends the degree of erosion are erosion resistance and slope of the soil surface. Bulgarian soils are classified in a seven-degree scale, based on Qcritical - erosion-safety discharge. This paper deals with the feasibility to choose irrigation equipment suitable for agricultural crops and having appropriate characteristics of the irrigation sprinklers in dependence of soil resistance and land slope. Both analytical and experimental approaches have been used in solving the problem. Nomograms, aiming at determining the required parameters of irrigation equipment in order to prevent soil erosion, are presented. They are created on the base of experimental approaches for sprinkler equipment characteristics. The intensity and structure of the artificial rain in relation to the nozzle and the working pressure head of the sprinklers, on one side, and the soil erosion stability in relation to the difference in the land slope and rain intensity, on the other, have been studied. The analysis of nomograms allows following conclusions about the application of three classes irrigation equipment in the erosive-safe area of land with high slope:  High pressure sprinklers set with the appropriate blendes are to be applied to terrains of soils with medium to high degree of erosion resistance regardless of the slope. In the set with nozzles the field of application is the same as by 2-3 degree of erosion resistance, but the limit of the slope is 7 %.  The erosion-safe area of medium pressure sprinklers application is wider as they can be used in soils of low erosion resistance (1-2 and 2) by limiting the slope to 3-5 %. For soils with moderate resistance (2-3) the slope limit is 3-7 %, and for soils with high resistance (above 3), the sprinklers are applicable on steep slopes