The effect of irrigation water turbidity on measurement accuracy of water content by Theta prob device

Document Type : Research Paper

Authors

1 Ph.D. Student, Water Engineering Department, Zabol University, Zabol, Iran

2 Associate Professor, Water Engineering Department, Zabol University, Zabol, Iran

Abstract

One of the methods of indirectly measuring amount of soil moisture is using Theta prob device. Since it is based on the constant dielectric of soil, factors affecting the physical and chemical properties of soil have a great impact on the accuracy of the device measurement. The aim of this study is the effect of irrigation water turbidity on measurement accuracy of water content of the soil by Theta prob device. Because of this, three different soil texture (silty loam, sandy loam and loam) were on different levels of irrigation water turbidity. The levels of irrigation water turbidity include 10, 1000, 2000 and 3000 NUT. The result indicated that factors of soil texture and irrigation water turbidity in significant level (P<0.01) have impact on measurement of humidity accuracy by ML2 Model of Theta prob device. Increasing the level of irrigation water turbidity in each of three soil texture leads to reducing the accuracy of device measurement and most errors were observed in loam which has highest percentage of clay. Also, the result showed that specific calibration of the device functions (special linear and special nonlinear) is more accurate compared to other calibration functions which indicate necessity of special calibration for all soils are tested.

Keywords

Main Subjects


Barzegar, A. (2008) Advanced soil physics (3th ed.). Ahvaz: shahid chamran university press (In Farsi).
Birchak, J. R., Gardner, D. G., Hipp, J. E., and Victor, J. M. (1974) High dielectric constant microwave for sensing moisture. Proceedings of the IEEE, 62: 93-98.
Butler, D. and Karunaratne, N. (1995) The suspended solids trap efficiency of the roadside gully pot. Water Research, 29:2, 719-729.
Cosh, M. H., Jackson, T. J., Bindlish, R., Famiglietti, J. S., and Ryu, D. (2005) Calibration of an impedance probe for estimation of surface soil water content over large regions. Journal of Hydrology, 311(1), 49-58.
Namdar Khojasteh, D., Shorafa, M., and Fazeli, M. (2012) The effects of amount and type of clay minerals on soil dielectric constant for easuring water content with Time Domain Reflectometry. Journal of Water and Soil Conservation. 18(3): 85-101. (In Farsi)
Dobson, M. C., Ulaby, F. T., Hallikainen, M. T., and El-Rayes, M. A. (1985) Microwave dielectric behavior of wet soil-Part II: Dielectric mixing models. Geoscience and Remote Sensing, IEEE Transactions on (1), 35-46.
Friedman, S. P. (1998) A saturation degree-dependent composite spheres model for describing the effective dielectric of unsaturated porous media. Water Resources Research, 34: 2994-2961.
Fuchs, S., Haritopoulou, T., Schaefer, M., and Wilhelmi, M. (1997) Heavy metals in freshwater ecosystems introduced by urban rainwater runoff – monitoring of suspended soilds, river sediments and biofilms. Water Science and Technology, 36:8-9, 277-282.
Gaskin, G. and Miller, J. D. (1996) Measurement of soil water content using a simplified impendence measuring technique. Journal of Agricultural Research, 63: 153-160.
Gong, Y., Cao, Q., and Sun, Z. (2003) The effects of soil bulk density, clay content and temperature on soil water content measurement using time-domain reflectometry. Hydrol Process. 17: 3601–3614.
Jafari Haghighi, M. (2003) Methods of soil analysis (1th ed.). Tehran: Zoha press (In Farsi).
Kargas, G. and Kerkides, P. (2008) Water content determination in mineral and organic porous media byML2 theta probe. Journal of Irrigation and Drainage, 57(4), 435-449.
 
Miller, J. D. and Gaskin, G. (1977) The development and application of the theta probes soil water sensor. MLURI. Technical note.
Roth, K., Schulin, R., Flühler, H., and Attinger, W. (1990) Calibration of time domain reflectometry for water content measurement using a composite dielectric approach. Water Resources Research, 26(10), 2267-2273.
Salamati, N. and Moazed, H. (2008) Study of the effects of irrigation water turbidity on physical and hydraulic properties of soils. Scientific Journal Management System, 9(2): 113-125. (In Farsi) 
Sarani, N. and Afrasiab, P. (2012) Effect of soil texture on moisture measurement accuracy with Theta probe ML2 in Sistan region. International conferance on chemical, ecology and environmental sciences (ICEES'2012), March 17-18, 2012 Bangkok.
Sun, Z. J., Young, G. D., McFarlane, R., and Chambers, B. M. (2000) The effect of soil electricalconductivity on moisture determination using time domain- reflectometry in sandysoil.Canadian. Journal of Soil Science 80(1): 13–22.
Topp, G. C., Davis, J. L., and Annan, A. P. (1980) Electromagnetic determination of soil watercontent: Measurement in coaxial transmission lines. Water Resources Researches, 16:574-582.