??In this study, a waveform of a self-excited pressure vibration that occurs in low-pressure pipeline systems was analyzed using a pressure-reducing valve. This analysis was conducted on the basis of field measurement data that was obtained for the condition in which the pressure-reducing valve is placed in the middle of the pipeline and a direct-acting constant-flow valve is installed at the end. On obtaining the intrinsic oscillation period from the transfer matrix and the oscillation period of the field measurement waveform from the spectral analysis, it was clarified that the theoretical period of the intrinsic oscillation of the pipeline approximates the shortest oscillation period based on the measurement data and provides an indication of the periodicity of the pipeline. Moreover, on verifying the cross-correlation function and the phase-shift time between the primary and secondary pressure of the pressure-reducing valve, it was clarified that they depend on each other and the secondary pressure propagates as the primary pressure via the pressure-reducing valve. In addition, the efficacy of the installation of the surge tank and air stick for controlling the pressure oscillation was theoretically and experimentally demonstrated. Based on these results, it was proposed that the occurrence of the self-excited pressure vibration be determined based on the intrinsic oscillation period by using the dimensions of the pipeline.
??Development and economic growth of cities in Northern Mongolia seriously depend on its national urban planning policy and also the accompanying social infrastructure. In addition, the city expansion might be restricted by water resources, as the area has only 300-400 mm of annual precipitation. In this research, despite of its inherent difficulty thus, development of Darkhan city in Northern Mongolia is simulated using a Cellular Automata Model for better decision-making in planning. The model is modified to accommodate to the locality of the city growth, in which ger that is a typical temporal residence of nomads is introduced as a part of the city. Population growth is assumed to be expressed by a logistic function with coefficients derived originally from an actual statistical record and fluctuated according to dynamically-changing water resources deficiency. The urban growth is regulated by these population dynamics as well as a potential of respective land for development that is given by the distances from a station, roads and a cluster of residence. Calibration is successfully executed and the fractal dimensions of the real urban area and simulated one become 1.56 and 1.60, respectively. The simulated results with several scenarios during 2008-2030 indicate that Darkhan might develop with fluctuation and attain to a certain magnitude, only if water demand increases gradually. Otherwise, Darkhan city, especially ger area might shrink due to water resources deficiency.
??Modelling is inevitable as far as strategic planning and decision making are of concern. However, natural systems such as hydrology tend to be complex when it comes to modelling. Coupled with many variables and numerous uncertainties, hydrological modelling presents an enormous task especially on distributed or semi-distributed models. This study applies Soil Water Assessment Tool (SWAT) 2012 model for long term daily streamflow simulation in Yasu River Basin. Automatic irrigation from the reach is considered in paddy fields. Two reservoirs along the main channel are included in the model. Simulation period ranges from the year 1990 to 2009 inclusive of a two year warm up period. Sequential Uncertainty Fitting Algorithm (SUFI-2) is used as optimization program for model calibration, validation, parameter statistical significance and uncertainty analysis. Calibration is conducted from 1992 to 2000 whereas validation is from 2001 to 2009. The performance of the model is determined by coefficient of determination (R2) and Nash-Sutcliffe (NS). SWAT provided a suitable platform for hydrological modelling of Yasu River basin with relatively good performance for streamflow simulation.
??Rainwater use and rooftop vegetation can be considered as one of the primal means for mitigating environmental problems encountered in urban areas, such as urban flooding and heat island. However, urban areas are too crowded for installing these facilities. In this paper, Rooftop vegetation with rainwater storage is created that is more flexibly than existing ones because of their less restriction on some constraints. It consists of two containers: an upper container for vegetation and a lower one for storing rainwater. Stored rainwater is supplied to the upper one by bottom irrigation system which consists of two kinds of fibrous sheets: one is horizontally placed on the upper container bottom for distributing the water into the soils and the other is connected vertically under the former for transporting the stored water to upper one. Some experiments are conducted for examining the ability of regulating soil moisture. Experimental results indicate that moisture movements to the upper in vertical fibrous decrease with increase in the distance from rainwater surface to the bottom of upper container, which affects moisture movements in horizontal sheet in quantity and the speed. Therefore, it is suggested that the present bottom irrigation can regulate soil moisture.
??We clarify the effect of volcanic activity on the succession of woody vegetation in relation to the growth environment and the effect on water infiltration rates on the peripheral slopes of Sakurajima Volcano, Japan. We selected ten plots (25 m2) on the peripheral slopes of the volcano located 7-15 km from the Minami-dake crater and conducted a field study. The results showed that the maximum tree height and diameter at breast height, the number of trees and tree species, breast height cross-sectional area, Fisher-Williams index of diversity, forest soil thickness, and water infiltration rate all increased with distance from Minami-dake. However, the thickness of the volcanic ash layer deposited since the 1914 Taisho eruption decreased with distance. The succession of woody vegetation and the water infiltration rate in these plots were not at the level of a climax forest. Overall, plots further from the crater had a better environment for vegetation growth. To prevent a decrease in the water infiltration rate from the volcanic activity of Sakurajima, it is essential to promote soil development by planting trees resistant to volcanic activity.
??In the downstream part of the water supply system using a long open channel, a supply-demand gap occurs in which the water supply amount is smaller than the demand amount. In the agricultural water section of Aichi Canal Project, the supply-demand gap is adjusted by the upstream and downstream water level control gates that control both the upstream water level and the downstream water level of the gate. The set-up method of downstream control water level of the gate enables switching between demand-oriented operation using level-reactive gate and supply-oriented operation using flow rate-reactive gate. As a result of simulation of water supply management using the upstream and downstream water level control gates, it became clear that the difference in the setting method of the gate downstream control water level affects the allocation function of the channel storage amount and the replenishment for supply-demand gap. When combining two types of downstream controlled water level setting methods, it is possible to switch to supply-oriented operation, based on demand-oriented operation, and the flow condition improvement effect is obtained.