Ecology, Environment and Conservation Paper

EVALUATION OF KRIGING AND CO-KRIGING METHODS IN ESTIMATING SOIL SATURATED HYDRAULIC CONDUCTIVITY BY USING SOIL TEXTURE (CASE STUDY: FATH ALI IRRIGATION AND DRAINAGE NETWORK, ARDABIL, IRAN)

Yaser Hoseini

Abstract

The direct measurement of soil hydraulic properties is time consuming and expensive and partly due to the non-homogeneity of the soil and laboratory errors is unreliable. Instead, Soil hydraulic properties can be achieved by quickly replacing data such as soil texture, soil bulk density and by using functions. Kriging and co-kriging are such methods which are used for the Soil pedotransfer functions estimating (PTFs). In this study, kriging and co-kriging methods were used to estimate the saturated hydraulic conductivity of the soil by using the properties of the particle size distribution percentage. among the geostatistical methods, Ordinary cokriging has the Best fitting. The best fitted variogram in this method was Exponential model with the nugget effect of zero and the sill of 156 meter that represents the strength of the spatial structure of the region and the full impact of the structural components on variogram model for the region. The data was prepared from 175 soil profiles related to soil and land reform studies of Ardabil Agricultural Organization .The results showed that all of kiriging methods have low accuracy and between the kriging methods (Universal, ordinary simple) Universal kriging with the regression coefficient of (R2 =0/54) and error (RMSE =9/74) on the estimating of saturated soil hydraulic conductivity has highest accuracy. In the Ordinary Cokriging method the accurate estimate was estimated with the regression coefficient of (R2=0/ 93) and error (RMSE =3/21). So Cokriging method in determining the rate of saturated hydraulic conductivity of the soil with high accuracy. However, co-kriging has higher accuracy than kriging methods.