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| Application of cosmic-ray fast neutron method to measure soil moisture:A case study of Liudaogou basin in Shaanxi |
| Wang Qiuming1, Wang Sheng2, Fan Jun1,2 |
| 1. Northwest Agriculture & Forestry University College of Resources and Environment,712100, Yangling,Shaanxi, China;2. State Key Laboratory of Soil Erosion and Dry Land Farming on the Loss Plateau,Northwest Agriculture & Forestry University,712100,Yangling,Shaanxi, China |
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Abstract As an important component of water resources, soil moisture plays a crucial role in the energy exchange between soil and atmosphere, and is also an important part of every ecosystem. The soil moisture has a significant effect on the soil erosion process; therefore, it is very momentous to obtain the soil moisture content accurately and continuously. As we all know it is very difficult to measure region-scale soil moisture but now soil moisture at a horizontal scale of around 300 m can be observed by the cosmic-ray fast neutron probe, which makes this method available to fill the gap between small scale oftraditional point measurement and large scale of remote sensing measurement. We compared soil moistures form COSMOS and TDT to verify the accuracy of COSMOS and provide a method to measure the soil moisture in wind-water erosion crisscross region. In this study, the domestic cosmic-ray soil moisture observing system (COSMOS) was used to observe soil moisture of slope field in Liudaogou basin of Shaanxi Province during the period of 21 May 2014 to 31 October 2014. TDT probes were set in 5 cm and 15 cm deep in the soil of all plots. Main results are presented as follows. COSMOS soil moisture was mainly affected by precipitation and could reflect sensitivity on the precipitation. The results of the COSMOS soil moisture well reflected the variation trend of soil moisture at the field scale, and had a linear correlation with the average of the results measured by TDTs in two depths of three experimental plots. The R2 was 0.76 and the root mean square error was 0.022 cm3 / cm3. We found the correlation coefficient of COSMOS soil moisture and TDT soil moisture in 0 -10 cm were greater than those in 0 -20 cm from the comparison between the results measured by TDT in two depths of all experimental plots and COSMOS. Based on this, we can consider that the average soil moisture measured by COSMOS was more consistent with the water content of the soil near the surface. And we found the correlation coefficient of COSMOS soil moisture and TDT soil moisture in slope land was slightly worse than alfalfa and abandoned land from the comparison between the results measured by TDT in 0 -20 cm of all experimental plots and COSMOS. In conclusion, COSMOS can be used to measure and record field soil moisture during a period and provide more reliable ground data for the region-scale soil moisture and runoff prediction. It can also provide verification data for the remote sensing inversion of soil moisture. It can be applied to continuous observations of soil moisture in slopes of loess plateau and small watersheds, and provide data for soil erosion prediction.
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Received: 02 February 2015
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