Toprak Erozyon Çalışmaları İçin Bir Yapay Yağmurlama Aletinin Tasarım Prensipleri ve Yapay Yağış Karakteristikleri

Abstract

Bu araşt ı rman ı n amac ı , Ankara Üniversitesi Ziraat Fakültesi Toprak Bölümü Ara ştı rma Laboratuvar ı nda kurulan bir yapay yağmurlama aletinin tasar ı m prensipleri ve teknik özelliklerini tan ı mlamak ve oluşturulan yapay yağışları n karakteristiklerini incelemektir. Yapay yağ murlama aletinin ana parçalar ı aç ı klanm ış olup damla oluşturucuları n detay ı ve uniform bir ya ğış elde edebilmek amac ı yla damla oluşturucular ı n uygulama tank ı içerisindeki yerleşim plan ı verilmiştir. Yağış karakteristikleri olarak intensite, damla büyüklüğü, damla düşme h ızı ve kinetik enerji incelenmi ştir. Yağ murlama havzası ndaki yağış intensitesinin dağı l ı mı uniformite katsay ı sı Cv ile değerlendirilmiştir. Cv değerleri çoğunlukla %80'nin üzerinde bulunmuş ve yağmurlama havzas ı nda yağış dağı l ı mı n ı n uniform olduğu saptanm ışt ı r. Farkl ı su yüklerinde, 3 mm ve 5 mm'lik uç çap ı na sahip damla oluşturucularla damla büyüklükleri ölçülmüştür. 5 mm'lik damla olu şturucularla daha büyük damlalar elde edilmi ştir ve su yükünün art ı rı lmas ı yla her iki uç çap ı nda damlaları n büyüklüklerinde azalma olmuştur. Bu koşullar alt ı nda yapay yağmurlama aletinin damla büyüklükleri 4.38 mm ile 5.25 mm aras ı nda değişmektedir. Damla çap ı ve düşme yüksekliğinden yararlan ı larak damla düşme h ı zları hesaplanm ışt ı r. Damla büyüklükleri ve ili şkili damla dü şme h ı zları çok fazla bir değişim aral ığı göstermediği için, yağış kinetik enerjisindeki de ğ işimlerin doğrudan yağış intensitesine bağ l ı olduğ u görülmüştür. Yağış intensitesi ve kinetik enerjisi aras ı nda doğrusal bir bağlant ı kurulmuşt

Keywords

• Yapay yağ murlama aleti
• damla olu şturucu
• intensite
• damla büyüklüğ ü ve düşme h ı z ı
• kinetik enerji

Design Principles of a Rainfall Simulator and Characteristics of Simulated Rainfalls for Soil Erosion Studies

Abstract

The objectives of this research are both to describe design principles and technical properties of a rainfall simulator constructed at the Research Laboratory of Soil Science Department, Agricultural Faculty of Ankara University, and to examine characteristics of simulated rainfalls. Main elements of the simulator were explained. Details of drop formers and a plan of drop formers within the application tank at which a uniform distribution of simulated rainfall was well attained were giyen. As rainfall characteristics, intensity, drop size, drop fall velocity and kinetic energy were investigated. Uniform intensity distributions of rainfalls in the catchment basin were evaluated by the uniformity coefficient Cv . Cv values were mostly found more than 80%, and uniform rainfall distribution was determined in the catchment basin. At different water height in the application tank, drop sizes were measured with drop formers having 3 mm and 5 mm tip diameter. Bigger drops were obtained with 5 mm drop formers, and drop sizes at either tip diameters were getting smaller with increasing water height. Under these conditions, drop sizes of the simulator were between 4.38 mm and 5.25 mm. Using drop diameters and fall heights of drops, drop fall velocities were estimated. Since drop sizes and related fall velocities did not signifı cantly change, it is observed that changes in kinetic energies of rainfalls were directly dependent upon the changes in rainfall intensities. A linear relationship was established between rainfall intensity and kinetic energy.

Keywords

• Rainfall simulator
• drop former
• intensity
• drop size and fall velocity
• kinetic energy

References

1. Al-Durrah, M. M. and J. M. Bradford, 1982. The mechanism of raindrop splash on soil surfaces. Soil Sci. Soc. Am. J., 46:1086-1090.
2. Brakensiek, D. L., W. J. Rawls and W. R. Hamon, 1979. Application of an infı ltrometer systems for describing infiltration into soil. Trans.of the ASAE, 22(1): 320-325.
3. Cruse, R. M. and W. E. Larson, 1977. Effect of soil shear strength on soil detachment due to drop impact. Soil Sci. Soc. Am. Proc., 41:777-781.
4. Erpul, G., D. Gabriels, and D. Janssens, 1998. Assessing the drop size distribution of simulated rainfall in a wind tunnel. Soil and Tillage Research, 45:403-409.
5. Erpul, G. and M. R. Çanga, 1999. Effects of subsequent simulated rainfalls on runoff and erosion. Tr.J. of Agriculture and Forestry 23:659-665.
6. Gabriels, D. and M. De Boodt, 1975. A rainfall simulator for erosion studies in the laboratory. Pedologie, 2:80-86.
7. Ghadiri, H. and D. Payne, 1977. Raindrop impact stress and breakdown of soil crumbs. J. Soil Sci., 28:247-258.
8. Ghadiri, H. and D. Payne, 1981. Raindrop impact stress. J. Soil Sci., 32:41-49.

9. Giley, J. E. and S. C. Finkner, 1985. Estimating soil detachment caused by raindrop impact. Trans.of the ASAE, 28:140-146.
10. Gunn, R. and G. D. Kinzer, 1949. The terminal velocity of fall for water droplets in stagnant air. J. Meteorol., 6:243-248.
11. Hamon, W. R. 1979. Infiltrometer using simulated rainfall for infiltration research. Infiltration Research Planning Workshops, Part I, State of the Art Reports, USDA-SEA, ARM-NC-4:54-60.
12. Hudson, N. W. 1971. Soil conservation. B.T. Batsford Limited, London.
13. Laws, J. O. 1940. Recent studies in raindrops and erosion. Agric. Engineering, 21(11):431-433.
14. Laws, J. O. 1941. Measurements of the fail velocity of waterdrops and raindrops. Trans. Amer. Geophys. Union, 24:452-460.
15. Laws, J. O. and D. A. Parsons, 1943. The relation of raindrop size to intensity. Trans. Amer. Geophys. Union, 24:452-460.
16. Meyer, L. D. and D. L. McCune, 1957a. Development of rainfall simulator for run-off plots. Paper to Amer. Soc. Agr. Eng., Dec. 15-18th ., Journal series paper 1197, Purdue Agric. Expt. Sta.
17. Meyer, L. D. and D. L. McCune, 1957b. Rainfall simulator for runoff plots. Agric. Engineering, 39:644-648.
18. Meyer, L. D. 1958. An investigation of methods for simulating rainfall on standard run-off plots, and a study of the drop size, velocity and kinetic energy of selected spray nozzles. USDA-ARS Div. E.S. and W. Man. Branch, Special Report No. 81.
19. Meyer, L. D. 1960. Use of the rainulator for soil erosion research. Soil Sci. Soc. Am. Proc., 24(4):319-322.
20. Meyer, L. D. 1965. Symposium on simulation of rainfall for soil erosion research. Trans.of the ASAE, 8(1):66-67.
21. Meyer, L. D. and W. C. Harmon, 1992. Interrill runoff and erosion: Effects of row-side slope shape, rain energy and rain intensity. Trans.of the ASAE, 35(4):1199-1203.
22. Moldenhauer, W. C. and D.C. Long, 1964. Influence of rainfall energy on soil loss and infiltration rates: 1). Effect over a range of texture, Soil Sci. Soc. Am. Proc., 28:813-817.
23. Moldenhauer, W. C. and J. Koswara, 1968. Effects of initial clod size on characteristics of splash and wash erosion. Soil Sci. Soc. Am. Proc., 32(6):875-879.
24. Mutchler, C. K. and W. C. Moldenhauer, 1963. Applicator for laboratory rainfall simulator. Trans.of the ASAE, 6:220-222.
25. Mutchler, C. K. and L. F. Hermsmeier, 1965. A review of rainfall simulators. Trans.of the ASAE, Vol. 8, No.1.
26. Nearing, M. A. and J. M. Bradford, 1985. Single waterdrop splash detachment and mechanical properties of soils. Soil Sci. Soc. Am. J., 49:547-552.
27. Nearing, M. A., J. M. Bradford, and R. D. Holtz, 1986. Measurement of force vs. time relationship for waterdrop impact. Soil Sci. Soc. Am. J., 50:1532-1536.
28. Onstad, C A , J K. Radke, and R. A. Young, 1981. An outer portable rainfall erosion laboratory. Proceedings of Florence Symposium: Erosion and sediment transport measurement, June 1981, International Association of Hydrological Sciences (IAHS) Publ., No.133:415-4220.
29. Poosen, J. and H. Mucher, 1990. The hydrological response of soil surfaces to rainfall as affected by cover and position of rock fragments on the top layer. Earth Surface Processes and Landforms, 15:653-671.
30. Rose, C. W. 1960. Soil detachment caused by rainfall. Soil Sci. 89:28-35.
31. Sharma, P.P., S.C. Gupta, and W.J. Rawls, 1991. Soil detachment by single raindrops of varying kinetic energy. Soil Sci. Soc. Am. J., 55:301-307.
32. Shultz, J. P., A. R Jarrett,. and J. R. Hoover, 1985. Detachment and splash of a cohesive soil by rainfall. Trans.of the ASAE, 28(6):1878-1884.
33. Slattery, M. C. and R. B. Bryan, 1994. Surface seal development under simulated rainfall on an actively eroding surface. Catena, 22:17-34.
34. Taysun, A. 1985. Doğal ve yapma yağışı n karşı laşt ı r ı lmas ı , yağış benzeticiler ve damla düşme h ı z ı tayin aletleri. T.C. Tar ı m Orman ve Köyişleri Bakanl ığı Köy Hizmetleri Gen. Md. Menemen Bölge TOPRAKSU Aras. Ens. Md. Yay ı nları , Gen. Yay. No:13.
35. Truman, C. C., Bradford, J. M. and Ferris, J. E. 1990. Antecedent water content and rainfall energy influence on soil aggregate breakdown. Soil Sci. Soc. Am. J., 54:1385- 1392.