Application of gamma-ray in research of soil water movement

Based on previous discussions on the accuracy of measured soil water contents and the spatial resolutions by the gamma-ray approach, this paper focused on the applications of the approach in the soil water movement studies. The basic principle and the methodology for measuring the unsaturated soil hydraulic parameters with one dimensional experiment setup both in the lab and fields are given first. Then several systems which have been developed in the past decade for the study of one and two-dimensional soil water movement in the lab were described briefly in conjunction with their practical applications. Moreover, the application of the approach in detecting the soil moisture variation by a large scale lysimeter with a weighing system was introduced. All the applications given here were implemented with computerized systems in data acquisition, control and processing. It was shown that in measuring the soil water content, under the condition that the ray strength rate through the soil sample was more than 104, the gamma-ray approach was able to present good results with an error of less than ±2% in the lab and 3%～5% in the field respectively, where the measurement point separation was 2.5 cm in the lab and 5.0 cm in the field correspondingly.