Resource-saving has become a global issue in the 21st century. This study examined the Mie irrigation scheme and analyzed the water-saving effects of its volumetric water charge system which is generally expected to save water used for rice field irrigation. The results showed that 1) the system saved water by reducing the required diversion volume from the water source in the periods with average river water level; and 2) the volume of water usage markedly increased in the periods of low water when the water saving effects of the volumetric water charge system was most anticipated. For the latter phenomenon, following reasons can be given; 1) some features of the fee structure, such as basic rate, low excess charge and long calculation period of one year, and in addition to that, 2) the supplemental function of the Mie irrigation scheme.
This paper describes the classification of agricultural land use based on multi-temporal TerraSAR-X images taken during the vegetation season in Tokachi District, Hokkaido. Support Vector Machine (SVM) is becoming a popular alternative to traditional image classification methods because it performs accurate classifications using small training samples. Nevertheless, some parameter tunings are required. Thereby the approach was adopted after retrieving the most appropriate parameters in this study. Using the sixteen TerraSAR-X images acquired between May 2 and November 5, 2009, the overall accuracies for all classes are 92.9% and 91.7% for HH and VV polarization respectively. In addition, the almost perfect agreements (κ>0.80) were achieved by using the 4 scenes (acquired on June 4, June 26, July 7 and July 18) for both polarizations. However, more scenes (6 scenes for HH, 8 scenes for VV) were required in order to discriminate maize fields.
A diurnal rainfall pattern generator which can statistically reproduce observed characteristics of heavy rainfall in target areas was developed. The data are obtained as hourly data, and it is possible to generate a lot of heavy rainfall with different patterns of internal structure. We can set any given value as a generation period, and the generator composed of four procedures as follows: 1) to decide the monthly event frequency, 2) to generate total rainfall amounts for each event of daily rainfall, 3) to disaggregate the total rainfall amount into hourly data, and finally, 4) to rearrange disaggregated data series by performing autocorrelation correction. An important purpose of the final step is to correct the autocorrelation relation of disaggregated hyetographs. In this process, a hyetograph with autocorrelation relation was newly generated by each rearrangement. The hyetographs were used as a reference pattern to rearrange the hourly data. Parameters in each step were estimated by using long-term rainfall data collected from the target area to reproduce observed characteristics. Here, we set 100 years as the generation period and 305 events were generated. The data were compared with observed data to verify accuracy of the method. The verification results demonstrated that the characteristics of heavy rainfall were reproduced with good accuracy, so these data showed availability as input rainfall data for any analysis such as flood simulation.
Recently, trenchless rehabilitation methods for aging irrigation pipes are often used. In this method, a new pipe is inserted into an aging pipe. Therefore, the rehabilitated pipeline consists of the outer aging pipe and the inner rehabilitated pipe. However, the mechanical influences of the damaged outer pipes on the inner rehabilitated pipes are not clear. In the present study, in order to reveal the influences, model experiments were conducted under the different damage levels of the aging pipe and loading positions. Experimental results indicate that the deflection of the rehabilitated pipe increases according to the damage level of the aging pipe. In addition, the strain concentration occurs at the top and the bottom of the rehabilitated pipe due to the point contact of the edge of the aging pipe. It is also found that the deflection and the strain distribution of the rehabilitated pipe under the eccentric load are significantly affected by the damage level of the aging pipe.
A ditch was dammed by a slope failure of a shoulder in the Kitsuregawa Hills located in eastern Tochigi Prefecture resulting in flooding of a paddy plot and the drought of the former ditch. In order to investigate the consequences on Inversiunio jokohamensis habitation, capture and environmental conditions were examined on 19 February, 2012. Furthermore a hearing investigation was also performed on 18 February and 9 December, 2012. The following information was acquired from these results. 1) Death rate for 10 days drying-up was estimated at 0.29. 2) A significant positive correlation was observed between survival rate and average substratum depth, with the highest survival rate for the deepest substratum depth. 3) The death rate in surface substratum was highest and the dead individuals were probably due to being frozen. This study suggested that mussel habitat and ditch ecosystem may degrade in ditches without maintenance in the future.
We estimated soil water content and daily water consumptive use on cabbage fields during the irrigation period for the past 49 years (1964 to 2012) using a soil tank model. The analysis was performed on soil with a thickness of 40cm, and was carried out for two different cases involving a field on which irrigation was practiced and another field that was not irrigated. We performed a multiple regression analysis by assuming the estimated daily consumptive water use as the objective variable, while the explanatory variable was meteorological conditions and soil water content. The degree of influence each explanatory variable had on the daily consumptive water use was evaluated by using a standard partial regression coefficient. It was shown that the degree of the influence that each meteorological element had on daily consumptive water use was the largest with the actual sunshine duration, and decreased in the order of temperature, the wind velocity, relative humidity, and precipitation. It did not vary whether irrigation was practiced or not. It was shown that when irrigation was carried out, the influence that soil water content had was smaller than the relative humidity. In addition, the influence by the soil water content when it was not irrigated was shown to be larger than the actual sunshine duration.