Research On Soil Moisture Monitoring Technology And Movement Law

Soil moisture, as the important factor of hydro-ecosystem, is the key condition tomaintain a good hydro-ecosystem. So its dynamic monitor is necessary. Contemporary andadvanced sensor technology provides a convenient method to monitor soil moisture, but itcan‘t be well applied because the developers and users in technology and application aredisjointed. Soil moisture is mainly monitoring artificially, which is time-consuming andbody-exhausting. Simultaneously, contemporary and advanced sensor technology provides amore powerful method for researcher to study soil moisture. Further research on soilmoisture‘s movement law is very important to the rational use of water resources based onautomatic technology.In this paper, soil moisture monitoring technology‘theory, characteristic and problems inapplication are analyzed, applicability in Jinghuiqu irrigation district is evaluated, soilmoisture monitoring system based on wireless transmission technology is built up andevaluated, soil moisture dynamic characteristics in bare land is studied, coupled water,vapor, and heat model‘s construction and calculation is achieved, and soil moisture movementmode is summarized. The main achievements are as follows.(1)Discussing the theory on TDR,TDT,FD and SWR to monitor soil moisture,summarizing the characteristics of different sensors, which shows that, sensors based on TDRand TDT‘s precision and cost are higher than sensors based on FD and SWR‘s, and sensorsbased on FD and SWR‘s precision is equivalent to sensors based on TDR and TDT‘s by fieldcalibration.(2)Analyzing sensor‘s structure and spatial scale of measuring soil, summarizing thesensor‘s installation methods on vertical profile type, ladder type and single point type, aswell as problems in application.(3) Evaluating the applicability with TDR, FD and SWR in Jinghuiqu irrigation district.Results show that, three kinds of sensors‘stability,sensitivity and accuracy are fine, sensorson TDR can be directly used without field calibration, while sensors on FD and SWR needfield calibration. And significance to measure soil moisture with three kinds of sensors isanalyzed by One-way ANOVA, which shows that, there are no significant difference on threekinds of sensors.(4) Designing the overall structure of soil moisture monitoring system based on wirelesstransmission technology, finishing the hardware installation of soil moisture monitoring system with eight vertical monitoring points, conceiving the software architecture,completing the establishment of database and the development of software, and evaluatingmonitoring system s fuction.(5)Analyzing soil moisture‘s diurnal and annual variations between0and500cm belowthe earth. Diurnal variation shows, without anthropogenic interference，only in rainfall, soilmoisture has large changes and the degree of change reduces and appears hysteresis with thedepth increasing. Annual variation shows, soil vertical profile is classified as four layers,which are active layer(0~20cm), relatively active layer(20~50cm), transition layer(50~200cm),and relatively stable layer(200~500cm). Among them, soil moisture in active layer andrelatively active layer is relatively stable from December to late-March, slow decline fromlate-March to mid-May, Alternately increasing and decreasing from late-May tomid-September, Continuous decline from late-September to the end of November. Soilmoisture in transition layer is increasing after decreasing from December to late-March, hassome fluctuations from early April to Mid-August and slow decline from late-August to theend of November. Soil moisture in relatively stable layer shows sinusoidal trend with smallamplitude.(6)Achieving the coupled water, vapor, and heat model‘s construction, determining thewater and heat parameters based on test and theory, and solving the model by hydrus-1D.Analog values are approximately equal with observations, which shows that the model canreflect the actual situation in the field.(7) Calculating soil moisture flux caused by water potential gradient and temperaturegradient, and summarizing soil moisture‘s diurnal movement mode by analyzing soil moistureflux in the process of rainfall， as well as annual movement mode by analyzing soil moistureflux in the year.