Modifying Ben-Asher's model, a simple model to estimate evaporation using only maximum and minimum surface temperature (MST) was proposed based on energy balance on the ground surface and supposing periodic sinusoidal change in soil surface temperature. Non-saline and saline soil (Silty loam) columns were adjusted at initial moisture condition between air dry to field water capacity. Daily evaporation (Ed) and soil temperature of the columns were measured for 23 days under field condition. At higher water content above 15 % and 19 % for non-saline loam and saline loam, respectively, the observed evaporation (Ed obs.) and estimated evaporation (Ed est.) were in a good agreement. However, the MST model overestimated evaporation at lower water content. Evaporation from the saline loam was somewhat smaller than that of the non-saline loam. The MST model can apply to estimate evaporation over a large scale area under wet conditions, if it would be combined with an infrared satellite image.
The design and operation factors on the effluent ATU-BOD and N-BOD concentrations in sedimentation tank were investigated by using observed data in the rural sewerage facilities with biofilm process and activated-sludge process. The operational problems with occurrence of N-BOD were also studied on the basis of the results of BOD removal performance obtained from research data of the rural sewerage facilities with both processes. Regarding to effluent BOD concentrations in sedimentation tank with both processes, it was found that the biological nitrification reaction and nitrogenous compound had the considerable influence on the effluent N-BOD concentration in sedimentation tank. The effluent ATU-BOD concentration in sedimentation tank was assumed to be governed by first-order function with complete-mix system of biological treatment process in the rural sewerage facilities with both processes. It was recognized that the effluent ATU-BOD concentration in sedimentation tank with both processes were influenced by the design and operation factors such as influent ATU-BOD concentration, microorganisms (mixed liquor suspended solids/specific surface area of contact filter for fixed bed submerged filter), and average DO in reactor (contact aeration tank/aeration tank). The effluent ATU-BOD concentration in sedimentation tank with both processes were found to be predicted by the empirical formula of hydraulic retention time and the design/operation factors mentioned above. Consequently, it is important that the control in occurrence of N-BOD and operational countermeasure for decrease of ATU-BOD are effective to maintain BOD removal efficiency in the rural sewerage facilities with both processes.
The diagnostic method of rural area, composed by two parallel programs of local situation survey and damage-by-wildlife situation survey, is applied on a paddy agricultural settlement in Wakayama Prefecture. After that, local meetings are held where to share the results of surveys and discuss the improvement of countermeasure against wildlife. At the same time, questionnaire was conducted for participants of meetings, to examine the effectiveness to reach a consensus on the improvement of countermeasure. The influence of the method on improvements carried out after surveys in fact are also examined. The results are followed; the local situation survey with the intention survey to every resident is useful to make good grounds of proposing the better countermeasure. It is useful for constructing of local agreement, especially for corporative working system of countermeasure and improvement of land use. The damage-by-wildlife situation survey gives objective and visual data about wildlife behavior, and makes it possible for local people to learn weak points of present countermeasure. The combination of two surveys makes it possible to show the relationship between the situation of workers and land use in the settlement and damage by wildlife. It is useful for the consideration of comprehensive improvement of countermeasure. Corporative survey of residents, officers and supporters gives residents to learn about the settlement and effective countermeasure against wildlife, resulting in agreement for proposal countermeasure.
High accuracy model experiments were performed to study the influence of bearing capacity of a two-layered foundation consisting of sand in the lower layer and gravel in upper layer. The influence of the gravel layer on the bearing capacity of foundation was estimated. Results obtained from these two-layered model experiments were compared to a strain softening elasto-plastic FEM computational model to validate its effectiveness. It was revealed that the bearing capacity of two-layered foundation consisting of wet sand in lower layer decreased with the increase in thickness of gravel layer. It was clarified that the bearing capacity was decreased due to the cohesion in lower layer of model experiments and dried sand of FEM. Scale effect was estimated by some finite element analyses with same ratio between thickness of upper layer and width of loading plate. If the ratio between thickness of upper layer and width of loading plate was 0.5, the bearing capacity showed an increase from the bearing capacity without upper gravel layer when the width of loading plate was more than 1m and thickness of upper layer was more than 0.5m.
In Mongolia, meteorological conditions have great impact on nomad by inducing a severe hazard such as dzud. The frequency of dzud has been influenced not only by meteorological conditions, but also by socioeconomic conditions. By using long term meteorological data and mortality of livestock in Dornod prefecture located in the east Mongolia, we attempted to clarify how meteorological conditions can affect the magnitude of dzud. As a result, total snowfall amount has shown a positive correlation with mortality when it exceeds the average snowfall amount. In addition, the correlation becomes clearer when less rainfall in summer or lower temperature in winter occurred at the same time. On the contrary to this, meteorological conditions such as less rainfall in summer, lower temperature in winter and less snowfall in winter have no correlations with mortality only by itself. These results imply that while main factor of white dzud can be recognized as meteorological conditions, occurrence of drought, black dzuds, and cold dzuds might be decided not only by meteorological conditions but also by other socioeconomic factors in Dornod prefecture.
The authors conducted swimming experiments in the field using ice goby (Leucopsarion petersi) in order to study its swimming ability and the relationship between tail beats and swimming speed. The experimental equipment used was a stamina tunnel, which was installed at a local dry riverbed. During one swimming experiment, the relationship between swimming speed and time with swimming distance was considered; in the other, the movement of the tail beats of the ice goby was analyzed using a high-speed camera and the relationships of the movement of the tail beats with their amplitude and the tail beat frequency with swimming speed were considered. As a result, a swimming-curve-formula defining the relationship between swimming speed and swimming time was obtained for ice goby, who have a body length from 4 to 5 cm. The ratio of the amplitude of tail beats to the total length of the ice goby was a constant 0.13, even with increases in frequency or swimming speed. The ice goby swam with a tail beat frequency of from 5.8 to 35.4 times per second, at from 2.7 to 27.8 times its own total body length per second, and a positive correlation was found between the swimming speed and the frequency. This allowed us to obtain an experimental formula defining the relationship between swimming speed and the frequency of tail beats.
In the irrigation district in the lower Ili River basin, a crop rotation system which combines paddy rice and field crops is practiced. Upland crops use the groundwater which is raised by seepages from canals and rice cropped fields. However, excessive rising of groundwater level on upland cropped fields causes salinization. Therefore, it is necessary to control groundwater level appropriately and to perceive temporal and spatial characteristics of groundwater level fluctuation is quite important for adequate groundwater level control. This study analyzed temporal and spatial distribution of groundwater level fluctuation. The results are summarized as follows; (1) Groundwater level had risen sharply since 1970s when cultivation of paddy rice was officially introduced and was highest in 1980s when amount of irrigation water supply peaked. Recently, groundwater level showed the decreasing trend with decrease of amount of irrigation water supply. (2) Spatial distribution of groundwater level inclined with ground surface inclination during non-irrigation period while spatial distribution of the raised groundwater level was not uniform during irrigation period. (3) Agricultural land use and condition of drainage canals affected groundwater level fluctuation.
A series of hydropower projects have been planned in the Mekong River, and the influences of these developments of water resources and climate change on hydrological cycle are of particular interest to the Mekong riparian countries. In the Lao PDR, there are about 70 hydropower projects and several dams are under construction upstream of the Nam Ngum Dam (NN1). In this study, we explored the combined impacts of climate change and dam constructions on water management of the NN1 and available water resources in the Nam Ngum River. To assess dam operation and hydrological cycle, a distributed water circulation model and a reservoir operation model were applied to the basin. Furthermore, we used the future climate scenarios by the MRI-AGCM3.1S for the assessment of climate change impact. The results of the analysis show that inflows and reservoir storages of the NN1 during rainy seasons will decrease in drought years due to climate change and new dams in future. In addition, water releases for hydropower of the NN1 will increase owing to smoothing effects of flood discharges by the new dams. These results indicate that the consideration of combined impacts of climate change and water resources developments is of importance in projection of water resources in developing regions such as the Mekong River Basin.
In this study, we investigated the management of irrigation and paddy fields in the Fukuoka-zeki land improvement district of Ibaraki Prefecture, which is predominantly a rice paddy area managed by part-time farmers. The following points were clarified: 1) In branch canals with many beneficiary farmers, farmers keep the division works of branch canals in an open state and adjust the amount of intake water at the inlet of each paddy or the division work of tributary canals. 2) In the middle section of the main canal, farmers hasten the start of water intake for puddling to avoid conflicts with the upper section farmers. 3) The working dates of puddling and rice transplanting were fixed annually. On the other hand, harvesting was done in according to the rice growth because a lot of part-time farmers outsource the harvesting work. 4) In an area dominated by rice paddies managed by part-time farmers, there are many beneficiary farmers along each branch canal and most of them are absent during the day. Therefore, it is difficult to operate the division work of the branch canal depending on water demand. Thus, the delivery water requirement tends to increase.
This paper discusses the climate-dependency of three coefficients in general long wave radiation equations and the validity of the cloudiness factor in general equations, based on data at 18 high accuracy stations for long wave radiation fluxes. The following became apparent: (1) two coefficients of Brunt's formula for the air humidity correction factor under clear-sky conditions have a correlation coefficient of −0.98; (2) the coefficient of the Brunt's formula has a correlation with annual mean vapor pressure and is assumed to be climate-dependent; (3) the coefficient of the original cloudiness factor which is a linear function of a rate of short wave radiation under a clear sky to actual short wave radiation have a correlation with annual mean vapor pressure and annual mean air temperature and is also climate-dependent; (4) the cloudiness factor in general equations is considered as the fitting parameter which considers not only cloud radiation but the temperature difference between air and surface.
90 degrees V-shaped water cushion energy dissipator has the advantages with a compact, a cheap construction cost and easy maintenance. However, there was no experiment report of the effect of this energy dissipator. This paper presented the experimental dissipating effects of V-shaped water cushion depth in the steep slope channel (the upstream channel inclination and the downstream one was 1/33). By the patent formula, the depth of water cushion was 50% of the velocity head of the water rushing into the water cushion. In this case, the water was often splashed out to the outside of the channel without dissipating. From this study, when the depth was set to 60% of the velocity head, it became clear that the most jumping inhibiting effect was shown.
In recent years, concrete channels subjected to frost damage in cold snowy regions have been repaired in a variety of ways. In pre-repair diagnosis, it is important to understand the depth of frost damage deterioration in concrete structures. As channels are long irrigation facilities requiring a high level of watertightness, it is not possible to frequently perform core sampling or other testing techniques that are considered useful but involve local destruction. Against this background, there is a need to establish a diagnostic method based on an efficient and effective non-destructive testing technique. In this study, the depth of frost damage deterioration in the sidewalls of concrete channels was estimated based on the surface scanning method, which is a non-destructive testing technique involving the use of ultrasonic waves. The results suggested a high likelihood that the depth of concrete surface damage could be estimated by measuring ultrasonic pulse velocity based on this method in cases where there were no minute cracks or other forms of damage inside the concrete structure. Moreover, the problems to establish a diagnostic method of the depth of frost damage deterioration that used the ultrasonic waves became clear.
A distributed-parameter model was developed to simulate water and nutrient runoff from various point and non-point sources in an urbanizing watershed, Zuibaiji River Watershed. The model was calibrated and validated with field-measured data of the years 2009 and 2010 respectively. The performances of the model for simulating hourly runoff for the calibration and validation periods were good with the Nash-Sutcliffe simulation coefficients of 0.60 and 0.55 and the relative errors of 27% and 30% respectively. The model also simulated daily TN and TP concentrations reasonably well for both calibration and validation periods. It was implied that the runoff loads from septic tanks and livestock farms were dominant factors of nutrient sources in the watershed. The scenario analyses showed that reduction of runoff loads from septic tanks and livestock farms were effective as watershed management strategies.