Production of crushed stone and crushed sand used as aggregate for concrete is classified into two types, dry process type and wet process type. In the dry process type, a large amount of crushed stone powder is produced as a by-product. In 2009, crushed stone powder was standardized by JIS A 5041. However, there is no discussion on the utilization method and the specific surface area of the crushed powder satisfactory. In this study, we made many types of mortar with different mix proportion. The mortar was made from two types of crushed sands which were produced from dry process and wet process, and three types of crushed stone powders with different specific surface areas. The table flow tests were conducted to clarify the fluidity of these mortar. As a result, it was revealed that the difference in the specific surface area of the crushed powder influences the fluidity of the mortar, and in particular, the crushed stone powder having a large specific surface area deteriorated the fluidity of the mortal remarkably. Therefore, it was suggested that the upper limit which is 9%, of fine particles quantity in crushed sand (JIS A 5005) could be moderated.
The terminal pipelines of the Miyagawa irrigation network system are being clogged due to the accumulation of Asian clams. To counteract this clogging, the Miyagawa land improvement district conducts sludge discharge operations. In this study, the government-managed No. 1 main channel via a pond and the government-managed No. 2 main channel not via a pond were set as the study area. From the estimated growth curve, the growth of Asian clams in the pipeline was considered. As the result, it indicated the possibility that Asian clams were reproducing during all seasons excluding severe cold season. In addition, the water sampling were carried out in discharge operations. Some water qualities were analyzed. As the results, it was found that the pond had the effect of increasing Chl-a and DO. It was shown that Miyagawa irrigation network system provide the water quality environment suitable for the habitat of Asian clams within the pipeline. In addition, it was shown that total nitrogen, total phosphorus, and COD in the downstream increase until the middle of the irrigation period, due to the presence of Asian clams in the pipeline.
This report proposed a new definition of abnormal data in the estimation of evapotranspiration and described the applying result of the definition for the energy balance-Bowen ratio method. Namely, the abnormal data defined that the sensible heat flux (H) and the latent heat flux (lE) are α times of the applied heat flux (Rn-G) and the abnormal range of the Bowen ratio (Bo) derived mathematically. As a result, in Bo method, the definition of this abnormal data induces that Bo is equivalent to abnormal data generated in the vicinity of -1. Also, following result clarified by applying the definition to actual data, ①The evaporation rate required for water resource and irrigation planning can be obtained if α closed 1.0∼3.0 for Bo method. ②Abnormal ratio in Bo method is remarkably much in night time than day time which coincided with the many previous researchers' experiences. ③Proposed abnormal range covers all range previously proposed by researches when choosing adequate α.
This paper described the feature of lE (Latent heat flux) and H (Sensible heat flux) derived from the IABM (Inverse analysis of Bowen Ratio method), BO(Bowen ratio) method and Eddy covariance method and compared the feature among them. Above three methods are applied by the abnormal criteria that α×ABS(Rn-G)>ABS(H) and ABS(lE) as proposed by the previous research. ① The hourly changes of lE and H of the three methods are very well consistent with each other during crop growing season (α=1.0 in the IABM). ② Comparison of three set of daily data of the lE between the two methods among the IABM, BO and Eddy covariance methods shows they are very well consistent with each other. ③ Comparison of monthly change for the lE among the three methods describe very well their consistency with each other in case of α＝1.0. ④ The ratio of the abnormal data is remarkably many in the BO method than the Eddy covariance method and IABM. ⑤Monthly evapotranspiration required for water resources and irrigation planning can be estimated by the three methods sufficiently.
We conducted field surveys to clarify distribution of the wintering Nagoya Daruma Pond Frog (Pelophylax porosus brevipodus) and the environmental factors affecting wintering site of this species in a rice paddy field and an adjacent fallow paddy field in Kurashiki, Okayama Prefecture, western Japan, where the species inhabits at a high density. The majority of the wintering individuals (34 out of 35) were found in the fallow paddy field. A GLM was fitted using presence and absence of this species as the objective variable, whereas cover rate, plant height, soil pH, volumetric water content, gravimetric water content, degree of saturation, porosity, and topsoil hardness as the explanatory variables. The best model selected based on AIC consisted of soil hardness, cover rate, and the quadratic term of plant height, in which the negative effect of soil hardness was significant. The results insist on the importance of soil hardness and the presence of plants on the topsoil when creating wintering habitat for this frog species in rice paddy fields.
The nitrogen (N) removal equation for paddy fields can be used to estimate the N removal rate based on input N concentration and temperature. The objective of the present study was to focus on various temperature factors affecting the accuracy of the equation in estimating the N removal rate. The survey site was a wet paddy field in the Kanto region of Japan. It was always flooded and under non-vegetation, non-penetration conditions. The survey was carried out for about 2 years starting in January 2015. We looked at water temperature, soil temperature (at 10 cm beneath the surface) and the average integrated hourly temperature in terms of how they affect the estimation of N removal rates. The average integrated hourly temperature was determined by AMeDAS. The relationship between the calculated values and measured values were evaluated using the R2 value. It was found that the N removal rate correlated more strongly with the soil temperature at 10 cm beneath the surface and the average integrated hourly temperature than with water temperature. We introduced a temperature factor “D” to correct the removal rate. It was found that the most accurate estimation of the N removal rate was obtained when the average integrated hourly temperature was used along with a temperature correction coefficient D = 1.3.
High temperatures of the asphalt concrete pavements in summer contribute to the heat island phenomenon in the urban areas. The effective cool-pavement technologies are sought to mitigate the pavement environment. In this paper, developed heat-reflective pavements are constructed from open-graded asphalt concrete, in which voids in the upper part of the pavement are filled with a geopolymer, containing recycled materials as a fine aggregate. Crashed oyster shells and roof tile debris were used in this study. The temperature reduction of the pavement surfaces at an open site is measured in the summer. The results show that the maximum surface temperature of the pavements filled with geopolymer mortars containing oyster shell aggregates falls by approximately 11℃ compared to the asphalt concrete pavement.
Efforts undertaken to restore villages that were damaged due to tsunami over wide areas following the Great East Japan Earthquake were characterized by large-scale local measures such as relocation of villages to higher land and reorganization of land use. The restoration project diverted broad areas of farmland to development sites. If viewed as a spatial change of land use, it is merely the relocation of residential land to avoid tsunami damage. When farmland is used for a different purpose, it is necessary to preserve the land and/or give land in compensation. However, such measures were not taken in this case. The primary reason for this lapse is the maintenance of the policy of controlling the new paddy field reclamation and the lack of perspective while managing land use in the entire region. In this paper, we propose “selective paddy field reclamation” where the reclamation of fields is allowed only in cases where specified conditions for disaster restoration are satisfied to preserve farmland resources and effectively manage land use.
Groundwater is a most available water resource and its conservation and management are important problem. However, it is difficult to research the flow dynamics and water balance of aquifer because they are phenomena under the ground. In this paper, a lumped parametric hydrologic model was developed which includes surface, intermediate and aquifer region to understand a water balance in a coastal area in Shikoku Island. At first, basic data sets were established from rainfall, river flow, pumped up amounts for various purposes such as domestic, industrial or agricultural use which were collected by public agencies and by us to be used for the calculation of daily groundwater level by the model. Model parameters were optimized as to minimize the cumulative error between the calculated and measured levels. As a result, the calculated levels coincided with measured one and it was concluded that the model could be available to know water balance in the area.
Continuous irrigation with running water (CIRW) experiments were conducted in paddy fields, to study the effects of CIRW using irrigation water of low temperature and low nitrogen concentration on grain nitrogen (protein) concentration and percentages of chalky grains. Under CIRW conditions, the grain protein content was lower with decrease in the distance from the inlet, and the average water temperature during 20 days after heading had a positive correlation with the grain protein content. Moreover, the percentages of chalky grains were higher as the grain protein contents were lower. These results indicate that CIRW using irrigation water of low temperature and low nitrogen concentration could reduce nitrogen absorption of rice, which may decrease the quality of rice. Our results suggests that to investigate the effects of CIRW on the quality of rice, it is necessary to study not only the influence on the temperature environment, but also the influence on the nitrogen environment in a paddy field.
Because of the humid climate in Japan, it is sometimes difficult to demonstrate the effect of irrigation on crops under natural rainfall conditions. To evaluate the effect of irrigation on Japanese persimmon, a field observation was conducted for two years at a farmland in Sado island, which is one of the famous production areas of the fruit. We revealed that irrigation could do the following: 1) minimize the probability of producing small fruits, which cannot be supplied to the market and 2) increase the proportion of larger fruits (fruits larger than L size would increase by approximately 10%) in the period when the Japanese persimmon trees experienced water stress due to low amount of precipitation in the early cultivation period or due to drought conditions lasting more than 1 month in summer. Since Japanese persimmon trees have wide root zones, irrigation water supplied from a drip tube located 1.2 m away from the trunk would be used effectively by the plant. In addition, we can expect adequate size of fruits in the drought years if irrigation water does not have a matric potential head less than > pF3.0. This value is consistent with the lowest matric potential head (or highest pF value) for normal growth, which is generally used in field irrigation planning in Japan.
The aim of this study is to predict the soil water condition and flux and evaluate applicability of a method to quantify water consumption in a frequent and small amount irrigated field. A numerical model was introduced using HYDRUS 2D/3D to predict the soil water movement under frequent and small amount irrigation. To verify the model accuracy and obtain input data for the numerical model, field measurement was performed in a greenhouse where cherry tomato was cultivated. The simulated result of soil water flux indicated that the downward soil water movement after irrigation occurred in the vicinity of surface layer and drainage of gravitational water did not occurred in deeper layer. The method to quantify the water consumption in one-dimensional crop field could apply to frequent and small amount irrigated field because the horizontal soil water movement was quite small compared to vertical soil water movement.
The reduction of energy for irrigation and drainage by reconstruction of two-step irrigation system with open-channel and booster pump stations in Niitsugo is calculated. 5,278 MWh (3,576 MWh as theoretical energy) is consumed in the existing system for irrigation and drainage. It is found that 1,465 MWh which is 41% of the theoretical energy will be reduced by merging pump stations and installation regulation tanks. The most effective measure is improving pipeline networks which contributes 70% of the reduction. Even if pump stations are merged in order to reduce labor, the reduction of energy for irrigation and drainage will be achieved in lowland paddy area like this case by means of combining other measures.
In Northeast Thailand, recent land use change by population and economic growth, expansion of food production and modernized agriculture were causes of frequent floods, serious droughts and water pollution. In this study, water resources and nitrogen load estimation model, which can include the spatial distribution of the population, land use, and differences of agricultural practice, was developed. Meteorological and hydrological data from 1987 to 2001 were collected for model simulation. Completely distributed TOPMODEL was employed for rainfall-runoff analysis. A conceptual nitrogen balance model, which has three nitrogen pools, was developed and combined with the rainfall-runoff model. The proposed model was applied to the Northeast Thailand, and simulated river discharge and nitrogen load in 1 km × 1 km resolution to check the model applicability. Calculated river discharge was in good agreement with observed data and seasonal variation (RMSE < 0.31 mm･d-1). Simulated nitrogen load was also in good agreement with the observed data (RMSE < 0.13 kgN･s-1). From the nitrogen load distribution, histogram of nitrogen load from different land use was also evaluated. And then, impact of fertilizer input on annual nitrogen load was evaluated.
With the aging of social infrastructure facilities, there are increasing cases of serious accidents and obstacles due to the inability to exert the functions expected at the time of initial design. In the accident case where pipes inserted into tunnels or pipelines are buckled due to external water pressure, it caused serious damages to the irrigation system. Typically, renewal pipes are inserted into the existing tunnels and pipelines to increase their structural integrity; inner-fill materials are filled inside the existing pipes to fill voids. The effects of these inner-fill materials have not been yet fully elucidated. This study aims to determine the effect of external water pressure on renewal pipe. Simulation buckling tests are conducted to determine the contribution of water pressure in causing unexpected pipeline accidents. Two types of buckling behavior, i.e., free and restrained, were observed. We tested the buckling strength of horseshoe-shaped renewal pipes.
The decrease in ammonia nitrogen (NH4-N) and increase in nitrate nitrogen (NO3-N) in batch tests of Iwate Andosol at a range of saturations were fitted with a first-order transformation equation. The first-order rate constant (µ) of nitrification decreased with decreasing soil water content. Simultaneously, column evaporation experiments were performed to investigate redistribution of NH4-N and NO3-N in the Andosol with nitrification and soil water flow. Most of the NH4-N in the column was depleted by nitrification, and the produced NO3-N was accumulated near the surface with the soil water flow. The rate of NH4-N decrease was higher in the early stages of evaporation, during which the soil contained higher amounts of water. Then, the results of column evaporation experiments were analyzed using µ obtained from the batch tests. When µ was given as a function of water content, instead of a constant value, the calculation more closely reproduced the experimental results, especially for early stages of evaporation. The amount of ATP in the soil was also measured for the batch tests and evaporation experiments to provide an index for soil microbial activity. Larger amounts of ATP were observed in soils with larger µ. This suggests that the first-order rate constant may be estimated from the amount of ATP, which is relatively easy to measure.
Crop transpiration rate is crucial for managing regional water resources and water productivity. In this study, we assessed crop water requirement, transpiration rate, and potential evapotranspiration rate using soil moisture data, sap flow data, and meteorological data, respectively, in a sugarcane field on Tanegashima Island, Japan. The transpiration rate measured using the heat pulse method (with a value of 1.3) was validated as correct by comparison with values obtained using the weighing and potometer methods. The maximum sap flow rate was calculated to be 548 cm3/d; in addition, the maximum transpiration rate was 6.7 mm/d. On the other hand, maximum soil moisture reduction rate was 4.3 mm/d for estimating crop water requirements. It was inferred that the decrease in soil moisture due to transpiration can be accounted for both by capillary supply a soil layer deeper than 50 cm and by water uptake from roots deeper than 50 cm depth. In addition, there was a high correlation between standard crop evapotranspiration and sugarcane transpiration, indicating a linear functional relationship.
It is essential to accumulate the case studies on the social relations formed in the process of recovering from the earthquake disaster in rural areas from a standpoint of not only considering disaster-prevention measures but also rethinking shrinking rural areas' value. This report represents the disaster restoration and revitalization model collaborating with urban residents in rural areas based on the case study on “Yamakoshi-Kogomo-furusato-kai” Group established after the Mid Niigata prefecture Earthquake in 2004 by the participant observation and interviews in FY2016. It was revealed that development of the struck houses, old elementary school site, etc. led to the interaction between urban and rural areas, the collaboration among settlements, and the interaction between disaster-affected areas, which were achieved by flexibility of the organization management and attachment of the people concerned.
Clogging of terminal faucets by Asian clams has been reported in the Miyagawa Irrigation Network, Mie prefecture. A previous research reported that the Asian clams inhabited the hollow of the pipe joint in the in-pipe survey of Government-managed No.1 trunk channel of the Miyagawa Irrigation Network. In this study, we conducted an in-pipe survey at Government-managed No.2 trunk channel, which had few clogging reports and different conditions such as flow velocity and pipe diameter, and analyzed the inhabiting condition of Asian clams. The results were compared with the previous research. The differences in the population due to the pipe gradient and joint shape of the pipeline were examined. As a result, regardless of the number of damage reports, it was confirmed that Asian clams were inhabiting in high density of about 6,000 clams/m2 at joints. It was found that Asian clams are hard to accumulate at the joint of downstream socket and where the pipe gradient exceeds 10 degrees.
Loach, Misgurnus anguillicaudatus, that inhabit paddy fields are an important food resource for higher-level consumers such as birds, and the quantity of the resource is of great concern for environmental conservation. In a previous study, we conducted an experiment to estimate Loach population size using a closed experimental paddy field, high density of sampling points in the field overall, removal of captured individuals, and DeLury’s linear model as well as the program CAPTURE, and reported that the estimated values were reasonably accurate and there was a possibility of a estimating the approximate population using limited data from rim-sampling points. In the present study, we set up fixed sampling points spaced at 2 m intervals near the paddy field rim where we could harvest Loach without stepping into the paddy, and examined the possibility of making simple population estimates using only those points’ data. We also examined the possibility of further reduction of the number of fixed sampling points for future general use. Our results indicate that those results are approximately proportional to the sub-area around the rim of the paddy field represented presumably by the sampled points. The result suggests that adequate estimates of Loach population may be obtainable at farms interested in implementing eco-friendly farming techniques.
Recently, irrigation systems using soil water sensors have been investigated for their potential to reduce irrigation management efforts and improve the quality of agricultural products. In order to introduce such systems, it is very important to identify suitable locations for sensor installation. The application of time stability concept-based methods may be useful for this. Therefore, in the present study, we measured the spatial distribution of the volumetric water content of surface soil (0-20 cm) using a FieldScout TDR 300 soil moisture meter and attempted to identify representative locations by applying time stability concept-based methods to measurements taken in an upland field and a paddy field. Prior to the measurements, the TDR 300 was calibrated to two specific field soils. As the result, we confirmed that it is possible to identify representative locations by calculating the root mean square error for each measurement location.