The delivery water requirement, a component of water requirements for paddy irrigation, supposedly influences the discharge characteristics of irrigated paddy fields. Combined with the drainage from paddy fields, it forms part of the return flow, which will be utilized by downstream water users. A return flow analysis based on field surveys was applied to a 321 ha Okazeki Irrigation Project, Kokai River basin, Japan, where intermittent irrigation at 3-day intervals is practiced. A 10-hectare consolidated sub-area was chosen for the water distribution study. Tank model simulations showed that the runoff was affected by the existence of the delivery water requirement, which was determined as 20 percent of the total water requirements, according to field surveys.

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The essential requirements of durability of protective coatings are the sulfuric acid resistance and interception of the sulfuric acid permeation of finish coating, and the adhesion stability of surface preparation compounds.
This paper presented the results of an investigation on the sulfuric acid resistance of specimens exposed to severe corrosion environment for 5 years. The results showed that some finish coatings had higher acid resistance but lower intercepting ability of acid. It was considered that there were some differences in the properties between acid resistance and interception ability required from this result. On the other hand, the blister generation was closely related to both water permeation and deterioration of surface preparation compounds resin.

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Water budgets in large-sized paddy fields with 3 different cultivation methods were measured in the Yokoyama district of Shiga Prefecture from 1995 to 1999, and these were compared to the water requirement plan in the district. Direct seeding culture in a flooded paddy field (DF), direct seeding culture in a well-drained paddy field (DW) and traditional transplanting culture (TC) were compared. The following results were obtained: i) At the early stage of irrigation, the direct seeding cultures (DF and DW) require more water than the TC. ii) The larger amount of water required in the DF was caused, to some extent, by a water distribution plan which was not suitable for the DF at seedtime. iii) After the early stage of irrigation, water demand for the DW tended to be much higher than that for the TC, while the DF was more variable than the others. iv) The water depth requirements in the TC and the DF seldom exceed the planned requirement. However, it would be necessary to enhance the planned water intake volume if an increase of the lot-management water requirement due to labor-saving is intended. v) The differences of cultivation types have no significant impact on effective rainfall.

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It is experimentally confirmed that montmorillonite suspensions exhibit marked thixotropic properties. Since it is sensitively affected by ionic species and concentration of solution, general models to quantitatively represent the shear-thinning behavior of montmorillonite suspension have not been proposed.
In this study, we measured viscosity of Na-montmorillonite suspensions composed of 0.01N (mol/l)-0.3N NaCl concentrarion and 1.4-2.2 % solid ratio, then checked two preparation methods of suspensions. On the basis of structure model by Moore (1959), which assumed that thixotropy depends on the balance of build-up and breakdown of links between clay particle, measured data were examined.
As a result, hysteresis appeared in all of the flow curves. Particularly, upward stages in flow curves showed the typical feature of thixotropy. In contrast to these general tendencies, anti-thixotropic loop was observed for 0.1N NaC1 concentration. It indicated that build-up of links occurred even at upward stages of shear stress, breakdown at downward stages. They proved to increase with solid ratio and NaC1 concentration for both of preparation methods.

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We conducted a questionnaire survey and interviews to clarify factors involved in the dumping of garbage at irrigation ponds and possible preventive measures, which involve problems of improvements in the environment for diversified utilization. We surveyed 204 ponds in Kyoto Prefecture; respondents were the farmers in charge of the ponds and the local managers such as representatives of the farmer's association. The main conclusions are as follows:(l) Common preventive measures such as setting up billboards are not effective when this is the only measure taken;(2) Patrol by residents is effective. However, this requires some devices and support to reduce the burden on residents;(3) Principal factors, that encourage the dumping of heavy garbage, are blind spots from residential section, and lack of cleaning and mowing of the area. Dumping might be prevented by removing these factors.

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Though farmland shows high productivity when collectively conserved, farmland evaluation seldom consider this point. However, in our country, it is insufficient to simply collect a quantity of farmland, but it is required that farmland possesses the conditions for being suitable for the maintenance and advance of agricultural production through repeated land readjustment. We developed the “road omission method type contour line field lot” as a form of field which satisfies such conditions. And, we have proposed the “ farmland management area” as plan unit based on the land use assuming the superscription field form.
In this paper, above, an application test of the farmland management area was carried out in a case district, and the following points were clarified.
1) It is possible to carry out farmland classification based on the field lot block where the road omission method type contour line field lot is applicable.
2) The management of land use, which is based on farmland classification that makes the farmland management area a unit, is effective for the maintenance of agricultural land resources.

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The effectiveness of imperfect irrigation planning in run-of-the river irrigation is discussed through a tropical region case study in Way Sekampung Irrigation Project, Indonesia, where the year is clearly divided into rainy and dry seasons. First, it clarifies that the yearly paddy cropping intensity under the present planning method, adopting a perfect irrigation system based on the 5-year probable low flow, is limited at 140% because of low flow during dry season. It also shows that the historical water deficits in this project has not resulted in reduction of harvesting area if the cumulative water deficit rate during droughts was less than 110%. Second, the water use for yearly paddy cropping intensities of 140% up to 180%, with an interval of 10% is simulated and compared with the 20 year historical river flow discharge to evaluate the occurrence of accumulated water deficit. It shows that the occurrence frequency of water shortage is 0.5 and 1.0 times a year at cropping intensities of 140% and 180%, respectively, and most of the water shortages have the cumulative water deficit rates of less than 110%. It concludes that imperfect irrigation planning is one of the feasible alternatives in run-of-the-river irrigation schemes as long as a stable water management system is established.

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This paper discusses the current problems of the irrigated agriculture in the left bank of the Kzylorda region, the lower Syrdarya River in Kazakhstan. After the collapse of the Soviet Union, Sovkhozes and Kolkhozes, which were the basic unit of agricultural production during the past Soviet Union period, have been restructured to cooperative farms or private farms. It was revealed that privatization process of the state farms was suffering from the following problems. 1) Reduction of productivity due to the lack of agricultural machines and fuel, 2) uncontrol (less control) of the rotational cropping-pattern resulting in the increase in the rice cropped area in the farmland cultivated by the private farmers, 3) increased risk on agricultural sustainability caused by the increasing rice mono culture, which may destroy the current water and salt management system in the farm, 4) malfunctions of water management organizations which were embodied into the Sovkhoz or Kolkhoz systems. These technical and social problems and their relations were identified and analyzed to give the priorities to the measures for the improved agricultural production in this region.

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In order to characterize surface water flow in the process of initial irrigation and drainage in paddy fields, a method of finite differences was developed incorporating effects of unevenness of ground surface on surface water flow. This method can reproduce the local water flow resulted from the unevenness of ground surface. The measured water levels at the observation point of the experimental fields agreed well with the calculated ones in the process of initial irrigation and drainage respectively.

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In this paper, a long-term runoff model including infiltration equation was developed to discuss the application of the model. By consideration of water budget among rainfall and evapotranspiration and infiltraion into the soil, increasing or decreasing process of infiltration by them was able to be described. Using the runoff model, daily discharge was simulated for experimental forest catchment. The results showed acceptable agreement between the observed and calculated discharge. By reference to the identified parameters of infiltration, the depth of soil which controls the subsurface runoff and evapotranspiration was discussed and the change in soil moisture of surface soil was calculated. As the result, it was shown that this runoff model was able to provide available information about some physical properties. Therefore, It was expected that it will be possible to evolute the effects of change in land use on the hydrologic cycle in catchments.

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The rainfed rice production in Northeast Thailand is unstable with low yield. In order to analyze the stability of the production quantitatively, it is important to establish the method to calculate water conditions in rainfed paddy fields and to simulate the rice production based on the conditions. At the first stage, this study aims at constructing a hydrologic model for expressing the water movement in a series of rainfed paddy field lots. In the hydrologic model, the ponding depth and groundwater level in a lot is expressed by using a two-story set of storage tanks. The model was examined by comparing the calculation results and observed data. Application results showed that the model could sufficiently represent the hydrologic processes of the paddy field lots in series.

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This paper deals with a method of real-time forecasting of flood drainage in a wide area which consists of pumping drainage districts (PDD) and gravitational drainage districts (GDD). The Back-Water Tank Model (BWTM) is used to forecast the discharge from each drainage division, and an unsteady flow numerical model is applied for forecasting the water level of the main channel joined up with drainage divisions. For forecasting the boundary condition of the down-stream end of the main channel, regression equations were used and the Kalman Filter technique was applied. This method was applied for the Sinkawa River in Niigata, so that, real-time forecasting with a lead-time of up to 6 hrs was tried for the heavy rainfall record in Aug. 1995. The results show that the inside water-level and discharge from the pump-station were forecasted simultaneously by the BWTM for the lead-time up to 6 hrs. Moreover, a real-time forecast was also completed in the GDD for the lead-time up to 6 hrs. For the long lead-time forecasting of pump drainage, however, sufficient accuracy was not kept every time. Joining the forecasted discharges of PDD and ODD inflowing to the Sinkawa River, the water level of the Sinkawa River could also be forecasted by the mathematical model. Even when the installation height of a local water-level recorder is not right, forecast accuracy was able to be maintained by adjusting the observed water-level at the present time.

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BOD removal performance in anaerobic filter tank was investigated using observed data on rural sewerage facilities with submerged biological filters. It was found that BOD removal in an anaerobic filter tank was assumed to depend on influent loading, influent BOD concentration, SS reduction, effluent SS concentration, and T N reduction. The multiple regression equation between BUD removal and five factors can be obtained from observed data. The predicted values of BOD removal in an anaerobic filter tank were approximately in agreement with the observed values. The deposited sludge on the bottom of an anaerobic filter tank have considerable influence on the effluent SS concentration from the anaerobic filter tank/influent BOD concentration in the anaerobic filter tank. The control of hydraulic loading rates in an anaerobic filter tank and effluent SS concentration from an anaerobic filter tank is effective in maintaining BOD removal efficiency in an anaerobic filter tank. The multiple regression equation between BOD removal and sludge thickness is effective in estimating the removal efficiency in an anaerobic filter tank. The BOD removal have limitation due to elution of accumulated biofilm in filters of anaerobic filter tank.

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In steady flow, unsteady flow equations must be satisfied since the steady flow is a special case of the unsteady flow. The purpose of this study is to develop a flexible method for the analysis of hydraulics of sprinkler irrigation systems and design of its laterals based on the unsteady flow principle. Any sprinkler irrigation system can be analyzed if an objective program is made in a simple way. The analyzing method-based on unsteady flow principle-is simple and we can apply it in the design of field irrigation systems. In steady state analysis, the role of wave speed is not an important issue, because there is no actual wave speed in the pipeline when the final state is achieved. Therefore, a pseudo wave speed is selected which is convenient for the calculation of steady state heads and discharges. An algorithm is developed for the efficient calculation of heads and discharges at each node and riser end. The results obtained by unsteady flow method (UFM) are compared with the results obtained by a step by step method (SBSM) and they are found almost same. In this paper, the development technique of the algorithm, the design of best lateral size, and the analytical results of a sprinkler irrigation system are presented.

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To create an optimum water conveyance and distribution system in the planning and design of a pipeline, it is necessary to choose a pipe diameter that satisfies geographical and hydrological binding conditions, yet is economical. Optimum performance throughout the entire pipeline system including key water facilities such as pressure regulating facilities and pump stations is another major consideration. For this purpose, we introduce some examples of trial calculations where the Cost Potential Method, the Linear Programming Method, and the Dynamic Programming Method were applied to a gravity flow pipeline that has no intermediary water facility. In addition, we suggest a method of handling facilities as dummy pipelines. We also introduce some examples of calculations for optimizing pipe diameters by applying the Linear Programming Method to a semi-closed pipeline having pressure regulating facilities and a pump-assisted gravity-flow pipeline having intermediary pumping stations.

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An intermediate reservoir consisting of pipelines serves as a main water facility. To minimize the construction cost of an entire system that contains an intermediate regulating reservoir, it isimportant to establish a regulating reservoir with an effective head which will have a large impact on the hydraulic gradient of the upstream and downstream pipelines. Two methods employing linear programming were used to select the optimum pipe diameter. In one method, the regulating reservoir was treated as a dummy pipeline. In the other method, the effective head was replaced by a length of pipeline. It became clear, however, that the optimization of the altitude for establishing the regulating reservoir could not be attained by simply constraining the range of HWL and LWL of the regulating reservoir. Consequently, as a way to work out the altitude for establishing the regulating reservoir, we used a method that takes into account the relation between LWL and the effective head as a constraint condition. Using this method, we were able to establish a feasible altitude for the regulating reservoir and to select the optimum pipe diameter.

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The 1997 Kagoshimaken-Hokuseibu Earthquake brought about damage to various structures, and agricultural facilities also suffered damage. Especially, damage by liquefaction was inflicted on the reclamation dikes in Izumi City. Sand boils at the bottom of water channels and in paddy fields, cracks and collapses in the pavement of the reclamation dikes, and deformation of revetments by liquefaction occurred at that time.
In this paper, the behaviors of the reclamation dikes and the surrounding ground during the earthquake are simulated by numerical analysis and liquefaction behavior in the disaster is clarified. Simulation using nonlinear dynamic effective stress analysis is carried out in order to consider the effect of deterioration of shear stiffness by the excess pore water pressure developed during the earthquake. Results of the finite element analysis are basically consistent with the observed performance of the reclamation dikes and the surrounding ground, and it is possible to reproduce the ground motion, the distribution of the pore water pressure and the deformation.

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The leveling of a paddy field is one of the important items in farming. The examinations were carried out on the role of rotary tilling/puddling works for soil movement. Main results obtained are as follows:
(1) Rotary tilling works has the effect of making a paddy field surface smooth, but doesn't have the effect of making a surface flat.
(2) A puddling works can be expected to have the effect of making the whole height of paddy field equal. If working number of times were increased to get equal level, the density of a tractor wheel tracks becomes higher than other parts. And as a result, puddling works often causes irregular surface of paddy field.

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Two kinds of furrow irrigation methods of upland field converted from paddy field have been performed. One of them is a temporary furrow irrigation for crop plants needed soil with good drainage and water holding, and the other is a full water furrow irrigation for crop needed soil with high moisture. However, lately, crop wanted to soil with high moisture is cultivated by repeating an intermittent flooded furrow irrigation in the fields with low groundwater level or difficulty in continuos flooding by low impermeable function of plow-soil depend on continuous cropping. Accordingly, to clear the present conditions of water usage of the intermittent flooded furrow irrigation, we studied the water management conditions in a case of an open culture of eggplant. The conditions of plow-soil, the irrigation interval, the soil moisture tension at the beginning of flooding, the irrigation requirement and the irrigation efficiency of upland field converted from paddy field were investigated.

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The spatial distribution patterns of the nitrogen and phosphate input/intake amounts in crop production within rural area are examined, based upon a cropping units distribution map that is obtained through remote sensing data analysis. As a result, it is clarified that the distribution patterns of nitrogen inputs (by chemical fertilizer and compost) differ with months and the distribution pattern of annual phosphate inputs is not similar to that of annual phosphate intakes by crops. The distribution pattern of nitrogen balance of annual inputs and intakes shows that many farmlands of over intake are widely found in the area, although a few farmlands of over input at more than 100kg·ha^-1·yr^-1 are scattered. The distribution pattern of phosphate balance of annual inputs and intakes indicate that many farmlands of over input at more than 100kg·ha^-1·yr^-1 are found in center to north-west portions within the area. It is considered that examinations on spatial distribution of nutrient inputs and intakes in the process of crop production are effective to study regional material flows for watershed environmental management.

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