The objective of this study is to understand characteristics of salinity intrusion and its relations with river fresh water discharge and tidal fluctuation in the Mekong River, through field measurements and numerical simulation. Field observations and calculations have been done for the Mekong River and the Tieu River which are considered the most vulnerable to salinity intrusion in the Mekong delta.
ADCP and TPM were used to measure river discharges, morphology and water qualities (salinity and turbidity) along the rivers. Though measurement term was in seven days, salinity intrusion particularities were found out. The mixing pattern of the Tieu River in dry season was identified as a strong mixing type. Tidal discharge was much larger than freshwater discharge. Based on observed data, numerical analysis was done. By correction of water level at Vam Giong, the suitable values are-41cm lower than observed ones. Referring to regressive curves, the averaged river discharge is proportional to the averaged water level difference. The salinity peak occurs one month earlier than the peak of water level difference and river discharge.

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The subject of this research is to clarify current situations and challenges of water markets for irrigation mainly in the State of New South Wales in Australia. This research takes an approach with observation of the actual condition towards the subject.
The background of the development of water trade has been examined to be proved to be a political factor, a natural factor, and an institutional factor. The market structure involving water trade for irrigation in the Murray Valley has been examined to clarify some characteristics of water market such as features of temporary trade and thin market of permanent trade. The conditions for successful water market, devaluation loss on water entitlement as asset, and consistency with the policy towards water market have been also discussed to add some new arguable points for the development of water market.

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BOD removal performance was investigated by using observed data in rural sewerage facilities with intermittent aerobic suspended-growth processes. It was found that the probability distribution of influent BOD concentration in aeration tank and effluent BOD concentration in sedimentation tank agreed with logarithmic normal distribution. The BOD removal reaction was assumed to be governed by first-order function with complete-mix system of biological treatment process. It was recognized that the BOD reaction rate was influenced by the temperature and aeration conditions in aeration tank. BOD removal was confirmed to be dependent on MLSS, hydraulic retention, temperature, and amount of aeration in aeration tank. The relationship between BOD removal and hydraulic retention time · MLSS cloud be modeled as the form of rectangular hyperbolas. On the base of the influent temperature and influent BOD load, the control of MLSS and amount of aeration in aeration tank is effective in maintaining stable BOD removal efficiency.

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This paper discusses a distributed rainfall-runoff model which is developed considering soil moisture content, and applied to the Daido river watershed, Japan. The watershed is represented by subdividing it into many uniform small cells in a grid as an approach for a distributed system. Cell-based soil moisture content and other physical factors influence the runoff generation process and water movement to and from the cell. The model comprises a soil moisture submodel in which the rainfall, evapotranspiration and infiltration interact to produce different runoff components and a tank submodel which transforms the generated runoff into discharge. It simulates water balance at each cell using single outflow path, and lumped assumption is taken for baseflow. Geographic information system (GIS) is used to obtain the spatially distributed data. Observed river flow hydrograph of the year 2001 is compared to model predicted one, and it is found that the developed model shows good performance in terms of the model efficiency criterion R². The model is verified thrice separately for each year of 1998, 1999 and 2000 to investigate the validity of the model parameters identified, and it is found that R² is in the acceptable range. Therefore, the developed distributed rainfall-runoff model would be dependable for discharge estimation.

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In Egypt, the major challenge facing the substantial requirements for rice (Oryza sativa L.) production is limited water resources. The experiment was conducted to determine the optimum irrigation frequency and tillage to maximize water use efficiency (WUE) and yield of rice. Two rice cultivars (Giza 177 and Sakha 101) were tested for the experiment. Four main tillage treatments were applied to both the rice cultivars: 1) chisel plough (2-passes) and wet leveling (T-1), 2) chisel plough (1-pass) and dry leveling (T-2), 3) moldboard plough, disc harrow and then dry leveling (T-3), 4) zero tillage (T-4). Rice crop was irrigated at four different intervals as sub-treatments: at every 3 days (i.e., continuous flooding)(I-1), 6 days (I-2), 9 days (I-3) and 12 days (I-4). As indicators for the performance of rice production; root volume, root/shoot ratio, grain yield and WUE were determined. Soil penetration resistance (SPR) and dry bulk density (BD) of post-harvest soils were also measured. Irrigation schedules and tillage types had profound effects on the crop and soil parameters. The main results are as follows:(1) irrigation interval of 6 days is recommendable for paddy rice in Egypt, (2) amounts of water can be saved through irrigation every 6 days with 8.6% for Sakha 101 and 13.7% for Giza 177 rice varieties compared with irrigation every 3 days, (3) based on grain yield, WUE and the ability to reduce soil compaction, the tillage practice T-3, recommended by Rice Research and Training Center (RRTC) in Egypt, is suggested to be reviewed in favor of T-1 which is commonly used by the rice farmers, (4) to increase rice productivity and water use efficiency, Giza 177 rice variety should be reviewed in favor of Sakha 101 variety.

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In order to clarify the effects of a pond on fish fauna, migration behavior and habitats of fishes were investigated in 2000 and 2001 at an artificial pond connected to the Yagawa River and paddy field-ditches in Kaminokawa Town, Tochigi Prefecture. It was observed that twenty three fish species captured in the Yagawa River, and fourteen fish species captured in the artificial pond in winter, and twenty one fish species captured migrated between three water zone, such as Yagawa River and artificial pond, artificial pond and paddy field ditches, paddy field ditches and paddy fields. From the results, pond utilization by fish fauna can be categorized into five types: 1) Full life cycle dependence, 2) Utilization in spawning and growing period, 3) Utilization in growing period and over yearing, 4) Temporal utilization in migration, and 5) Incidental intrusion. This implies that the pond as a permanent and stagnant water zone contributes to the conservation of many fishes as a source of fish species.

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The utility of floatable phosphorous adsorption concrete, developed for a new restoration technique on the environmental water such as closed and stagnant water area, was verified fundamentally in this research. This material was composed of Mg-Al-Cl forms a hydrotalcite compound, foamed glass, and special buoyant body. Horikawa, one kind of stagnant water in Matsue city, was selected for the experimental site, and put these materials into this river for three months. As for the fundamental experiments on this material, it was confirmed that any environmental pollutants haven't dissolved into the water, and this material has the ability of phosphorus removal due to the chemical and physical reactions. Moreover, one kind of plant was vegetated at the upper surface of this material. The growth of plants was evaluated and it was confirmed that vegetated plant had worked as the biological removal of nutrients. Furthermore, it was revealed that this material was stable against the external force, such as wind and wave forces. Therefore, this material, floatable phosphorous adsorption concrete could be considered to be useful as a new environmental restoration material in stagnant and closed water area.

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Paddy fields having good connection with dual-purpose-channel have been disappearing by land consolidation projects and urbanization. This study clarified how fish use such paddy fields in relation with rice farming to examine a future expected model of the area. As a result of investigation, the following became clear. 1) Paddy fields functioned as reproduction field for Misgurnus anguillicaudatus, Gnathopogon elongatus elongatus, Carassius spp., Cobitis biwae, and as growth field for fries which were born in other water area. 2) M anguillicaudatus used paddy fields as habitat through irrigation term, but G elongatus elongatus didn't use paddy fields after midsummer drainage. 3) The velocity of drainage water was almost the same velocity as that adult fishes were promoted to carry out ascending migration at water outlet. 4) It was suggested that increase of fish biomass in a paddy field is influenced by the structure of water inlet and outlet from which fish can escape easily.

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We examined electric arc furnace oxidizing slag that was heated at high temperatures to determine a quantitative relationship between the temperature and the phosphorous removal capacity, and the mechanism of phosphorous removal improvement. The phosphorous removal capacity was improved with heating of the slag. The slag heated at temperatures over 600°C yielded a removal capacity of over 90%. The calcium carbonate that accumulated on the surface of the slag grain was thermally decomposed to calcium oxide at temperatures above 600°C. The pyrolysis procedure provided large phosphorus removal component such as Ca ion and pH from the slag. The measured Ca ion concentrations were between 1 and 1.5 mmol/L, and the pH values were as high as 10.5 to a little over 11. Phosphorus removal is controlled by pH in case of this study. Heightening the pH value improved the capacity of the phosphorous removal. The mechanism of the phosphorous removal improvement was due to the elution process of removal factor from the slag and removal process controlled by pH.

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In Lake Kasumigaura, milky water has often been observed since 1998. To find the relation of this milky water to the bottom mud, we carried out turbidity measurement, X-ray analysis of suspended solids, and observation with transmission electron microscope. Tube shaped halloysite, 0.03-0.04 lAm in diameter and 0.1-0.2 sm in length, was the relatively major clay mineral of the bottom mud in this lake. As halloysite disperses well under high pH, it hardly sediments in the lake water with pH 8-9. The ratio of this halloysite to suspended solids tended to increase with time since other suspended solids sediment gradually. It was alsoconfirmed that halloysite has a nature that scatters light remarkably compared to allophane or montmorillon-ite. Therefore, dispersed halloysite was considered to cause the appearance of milky water in Lake Kasumigaura.

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This study was conducted to characterize the treated wastewater from the rural sewerage using the intermitted aeration OD process with the automatic control and the simultaneous coagulation. This process has been employed in O area in Ehime prefecture, in Japan and the treated wastewater has been used to irrigate farmlands in 0 area. Main findings are: 1) Most constituents in the treated wastewater had higher concentrations than the usual irrigation water in O area: river water and effluents from forests. Cations (K⁺·Na⁺·Ca²⁺·Mg²⁺), anions (Cl·SO₄²), and EC had low coefficients of variations, while SS ·COD·T-N·NH₄-N·NO₂-N·NO₃-N· T-P·PO₄-P had high coefficients of variations. 2) Composition of ion concentrations was different from that in the usual irrigation water. 3) The main part of T-N was nitrate. COD and T-N concentrations were lower than those of the treated effluents from the other OD process plant without automatic control and from contact aeration process plants with anaerobic tanks. 4) The T-P concentration was mostly lower than the design concentration: lmg· L^-1. However, this concentration can lead to eutrophication. 5) O-157 was not detected. The numbers of heterotrophic bacterium and coliform groups were equal to or smaller than those detected from the usual irrigation water.

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The irrigation pond supplied with the treated wastewater from the rural sewerage and the paddy field only using the pond water for irrigation were investigated. The increase of the water volume of th overflow water from the pond was very beneficial for irrigation. The overflow water had generally lower concentrations of many constituents than the treated wastewater, and the cation and anion balances in the overflow water scarcely reached to those of the treated wastewater. The concentrations of T-N·NH₄-N·NO₂-N·NO₃-N·T-P·PO₄-P were extremely lower in the overflow water than those in the treated wastewater. In almost all cases, COD and T-N concentrations were maintained under their irrigation water standard in Japan: 6mg·L^-1 and 1mg·L^-1 respectively. In terms of the safety for irrigation and the amenity for the inhabitants, the suitable water quality was maintained in the pond surface water. Without any special management in the paddy field, for example reducing fertilizer, any deteriorations of the soil chemical properties and the reduction of crop production were not found. In conclusion, for the area having the intention to use the treated wastewater, the utilization of irrigation pond can be very valuable.

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The irrigation pond supplied with the treated wastewater from the rural sewerage was investigated at the D pond in Ehime prefecture, in Japan. The movement of the treated wastewater in the pond was not uniform, and the treated wastewater mainly flew into 1-2m depths. The reason of this flow pattern was that water densities were higher in the treated wastewater than those in the pond surface water, and densities of the treated wastewater were corresponded to densities of the water in 1-2m depths. Because of high salt concentrations and low temperature, the densities of the treated wastewater were higher than those of the surface water of the pond. In the top 2m of the pond water, the increase in Cl^- concentration led to the increase in EC · T-P · Ca²⁺ ·Mg²⁺ ·K⁺ ·Na⁺ · SO₄^2- concentrations and the decrease of T-N ·NO₃-N concentrations. must be the tracer of the treated wastewater. In the treated wastewater, EC ·T-P ·Ca²⁺·Mg²⁺ ·IC ·Na⁺ · SO₄^2- concentrations were higher and T-N ·NO₃-N concentrations were lower than those in the inflows to the pond from the forests. These results showed that the movements of the treated wastewater had significant effects to the water quality distribution in the D pond.

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The impact of supplying the treated wastewater from the rural sewerage to a D pond on phosphorus and nitrogen release from sediments was investigated in Ehime prefecture, Japan. In the year when the larger volumes of the treated wastewater were supplied to the D pond, T-P·PO₄-P·NH₄-N·Org.-N concentrations of the bottom water were low. In the bottom water, while the increase in DO concentration led the decrease in T-P·PO₄-P·NH₄-N·Org.-N concentrations, the increase in NOx-N concentration resulted in decrease in T-P·PO₄-P concentrations when DO was smaller than 0.1 mg·L^-1. The increase in the volume of the treated wastewater mixed into the bottom water caused the increase in DO·NOx-N concentrations in the water. When the larger volumes of the treated wastewater were supplied to the D pond, the volume of the treated wastewater mixed into the bottom water was higher. These results suggest that supply of the large volume of the treated wastewater can reduce the phosphorus and nitrogen release from sediments because the bottom environment becomes to aerobic. By the treated wastewater supply to the D pond, the deepening the thermocline depth and the decrease in the temperature gradient in the thermocline were not clear.

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Deep ponding cultivation method (DPCM) is a farming method which is labor-saving and promotes sustainable agriculture. We examined the improvements of farmland infrastructure and institutions that are required to apply the method. Although DPCM, in which inundation is deeper than current farming methods, has been used as a means of protecting crops from cold weather damage, in recent years, some farmers have also introduced it as a means of saving labor, increasing yield, and weed control in cold districts. The investigator conducted a questionnaire and interview survey in the Tohoku and Hokkaido area, among farmers and land improvement districts which are using DPCM. The survey results showed clearly that the following four measures are fundamental for the success of DPCM:(I) Maintaining the height and width of the levee which maintains inundation depth.(2) Preventing water leakage through a levee.(3) Irrigation canal repair to fit in well with levee height increase.(4) Measures against drainage for bearing-capacity-of-soil improvement. Moreover, the new environmental function of DPCM was pointed out, and the possibility of future spread of the method was shown. The improvements in farmland infrastructures and institutions required to apply DPCM ware examined.

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Inadequate supplies of quality water in arid and semi-arid regions for irrigation lend saline water as valuable alternative resource. However, information on how saline water irrigation affects crop yield is scarce. A research was conducted to investigate the use of saline water for drip irrigation of sorghum (Sorghum bicolor (L)) on dune sand. A new drip irrigation scheduling model for saline water use was proposed. Irrigation intervals were daily and once in every two days. The amount of irrigation input was based on open-pan evaporation method. The electrical conductivity of the saline water used was 7.32dS/m. Crop evapotranspiration during the growing period was 580mm while the estimated actual amount of water inclusive of leaching was 734 and 794mm for threshold (ECe=8.4 and 6.8dS/m). Daily irrigation significantly increased grain yield by 25-32% compared with 2-day schedule. Water use efficiency (WUE) was higher in daily irrigation (0.30kg/m³) than 2-day schedule (0.22kg/m³). The study provides new and additional information on appropriate irrigation input regimes and intervals required when saline water is used for crop production.

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Soil erosion was estimated by photogrammetry using the digital camera. The precision was first assessed by comparing the measured data against photogrammetry under no rainfall condition. The assessment was based on the statistical parameters, the absolute error (AE) and relative error (RE), which are 0.0946 kg/m² and 8.59%, respectively. In the second step, the precision was assessed for under simulated rainfall on soil surface packed to two different dry bulk densities. At 1.20g/cm³ density, the AE and RE were 6.62 kg/m² and 1490%, respectively and corresponding values at 1.30 g/cm³ density were 0.675 kg/m² and 86.0%, respectively. The soil saturated with water and whose bulk density was 1.38 g/cm³, was subjected to rainfall of intensities of 40, 80, 120mm/h continuously for 1 hour. They had AE (RE) of 0.0313 (36.1%), 0.0183 (26.4%), 0.0268 kg/m² (29.8%), respectively, at each intensity.

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The purpose of this study is to demonstrate migration range of fish which reproduce in temporary water area and their dispersal range from temporary water area after growth, to conserve their habitat in permanent water area. The investigation method was marking of fish which migrated to temporary water area and dispersed from there, and recapturing marked fish afterward. As a result, 1) Migration and dispersal of Misgurnus anguillicaudatus ranged from 300m of the lower permanent channel to 100m of the upper permanent channel at connection of permanent channel and temporary water area. As for Gnathopogon elongatus elongatus, it ranged from 500m of the lower permanent channel to 200m of upper permanent channel from there. 2) The range of Cobitis biwae and Carassius sp. were not enabled to demonstrate, but Cobitis biwae migrated from upper permanent channel to temporary water area and reproduced, dispersed to upper permanent channel. Carassius sp. dispersed from temporary water area to deep pool of upper barrage. 3) Some Misgurnus anguillicaudatus and Gnathopogon elongatus elongatus migrated to temporary water area beyond aforesaid range of migration and dispersal.

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In Japan, in order to realize huge rice paddy plots, it is necessary to enlarge farm size of core farmers or farming groups by borrowing farm plots from retiring farmers of small farms (accumulation of cultivating rights), to consolidate small scattered leased farm plots and to constructhem as huge rice paddy plots. In this paper, Kawai district in Fukui prefecture was surveyed as the district where community farming was realized by setting up the farming group and huge rice paddy plots were constructed by land consolidation project, and it was clarified the characteristics and problems in constructing huge rice paddy plots in the project area where such a community farming was carried out. The result shows that 1) accumulation of cultivating right and consolidation of leased plots are relatively easy in case of community farming, and 2) as the result, huge rice paddy plots are realized more easily, 3) while this system has the problem that the price of rent for land owners tends to be expensive because most of farm lands in the project area are borrowed by the farming group, and so it causes decrease of full-time farm workers' income, 4) subsidies from central and prefectural government to the farming group in purchase of agricultural machines were effective for curing this problem, and so on. The effectiveness of such subsidies for high rent in order to inspire retirement of farmers of small farms was discussed.

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Swimming experiments of wild Japanese Dace (Tribolodon hakonensis)(length ranging from about 5cm to about 22cm) were carried out by installing a stamina tunnel (cylindrical pipe) in a fishway in the river. The burst speed of individual fish that swam for 1-5 seconds and the maximum instantaneous burst speed of individual fish that swam 50cm distance at a maximum speed were investigated. The results show:(1) the average burst speed of a Dace, which is when the fish swims at a speed of at least 10 times its own body length per second for a period of one to five seconds, was 19.5 times body length per second on average;(2) for both the burst speed and the maximum instantaneous burst speed, Dace had a tendency to swim in accordance with the flow velocity in the pipe; within conditions of a certain high velocity, the burst speed showed an upper limit; and the maximum instantaneous burst speed was 1.17 times faster when compared to the burst speed;(3) the burst speed and the maximum instantaneous burst speed were calculated for fish with a body length of about 5cm to about 19cm in conditions of a high velocity (175cm·s^-1), and the results were: mean burst speed: 246 cm·s^-1 (σ=±30cm·s^-1), mean swimming time: 2.89s (σ=±1.07s), maximum instantaneous burst speed: 291cm·s^-1 (σ=±59cm·s^-1), mean swimming time: 0.66s (σ=±0.46s);(4) and it was shown that these burst speeds were similar to the results of past on-site investigations at the fishway of the river, and it was speculated that when the velocity in the fishway was fast, the fish swam at speeds corresponding to the maximum instantaneous burst speed for only a very short time.

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In this paper, the lightweight thrust restraint for pipe bend acting internal pressure is proposed. In new proposed method, geogrid and anchor plate are attached behind the pipe. In order to investigate the effect of new method, lateral loading tests using model pipe having diameter φ90 were conducted in dry sand. And image analysis for model ground surface and DEM analysis in 2D were carried out to clarify mechanism of new method.
As the results, it is found that new method is significantly effective for lateral resistance. Judging from image analysis of ground face, it is clarified that soil mass above the soil block wrapped by restraint using geogrid is unification. In addition, it is clear that the shear surface occurs on the bottom of the soil block wrapped by restraint by DEM analysis.

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The Shiroishi plain lying west of Saga prefecture in Kyushu, Japan, is a plane paddy area on a reclaimed land with man-made creeks in various directions over the land. Of recent, it became apparent that water quality in the creeks has been deteriorated ever since the 1960s when water was reasonably clean. In around 1960 and 2000, the author investigated the nitrogen concentration in the creeks based on the nitrogen cycle model formulated by the author. The investigation proved that contamination of the creek water was mainly caused by increased quantity of gray water and attendant changes in treatment processes, modification on the operation and maintenance system of the creeks, and increased nitrogen concentration in the creeks attributable to changes in cropping patterns. To be more specific, the area of paddy field has been decreasing due to not only reformation of ill-drained paddy field into well-drained paddy field but also conversion from paddy field to upland field. Therefore, the expanding upland cropping, which requires more fertilizer, is obviously one of the major factors that increases nitrogen concentration in the creek water.

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In this paper, estimated value and 95% confidence interval of total effluent loading (flux) from a small forested catchment (12.82 ha) is discussed based on the 10 minutes stream chemistry and discharge data over about 7.7 months. Three LQ equations, i.e., linear LQ equation, power law LQ equation, and nonlinear LQ equation are tested in the effluent loading calculation. The indices discussed here are Cl^-, K⁺, Na⁺, and virtual index. Virtual index is generated from K⁺ data so as to have a strong nonlinear relation to discharge. Specifically, the ratios of the data set numbers, which include true value within the 95% confidence interval, to total data set numbers are evaluated. The data sets evaluated are extracted from the whole data by regularly-interval sampling. As results, in order to estimate the total effluent loading over specific duration, power law LQ equation should not be used. The linear LQ equation is adequate for this purpose though it requires 237 to 947 data to determine the LQ equation and 95% confidence interval properly. The desirable conditions of LQ equation to estimate the total effluent loading are good performance in being fitted with the nonlinearly scattered data in L-Q plot and good predictability of total loading comparing to true value. Both linear LQ equation and power law LQ equation don't satisfy these two conditions simultaneously.

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Real-time flood forecasting in basins where water resources are highly developed needs to take account of operations of water management facilities, like dams or head works etc., installed in the objective basins. A well-used simple forecasting system based on a single lumped model could not provide satisfying accuracy in forecasts in highly developed basins. For improving accuracy in real-time flood forecasting for the developed basins, real-time flood forecasting system including upstream dam operation was developed. The developed forecasting system is based on a diffusion wave flood routing model of a channel conveying the upstream dam release with inflow from adjacent areas. The observed data of the upstream dam discharge was given as inflow to the channel at its upstream end, and the inflow from the adjacent areas to the channel is forecasted by using the modified Variable Infiltration Capacity (VIC) model. The system was applied to real-time forecasting of flood flow into the Osakabe-gawa Dam Basin Reservoir located in the north part of Okayama Prefecture. The reservoir receives discharge from the Ohsa Dam located upstream. The forecasting accuracy of the system was compared with that of the simpler forecasting system based on a single VIC model without using discharge data from the upstream dam. The developed system showed better accuracy than the simpler system so that forecasts kept accuracy satisfactory to operational purposes for up to three hours ahead. The developed system is expected to demonstrate its advantage over the simple system for the basins including large subbasins from which discharge is controlled by water management facilities.

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The Ministry of Energy and Mines of Madagascar in cooperation with UNICEF embarked on a drinking water project in the Mahajanga region in 1999. In this study, the climatological parameters were used to assess the recharge potential of groundwater, and the hydrogeological parameters using pumping test data were evaluated. In addition, possible effects of the project on socio-economic aspects of rural development were explored. The results showed that 24 % of the 38-drilled boreholes was negative (no water or dry hole) and 76 % was positive. However, only 80 % of the positive boreholes had highly efficient pumping specific capacity. The failures observed in some of the boreholes highlight the importance of hydrogeological information in such a project. Use of such information may increase the efficiency of borehole specific capacity (i.e. stability of borehole specific capacity) as well as the number of operational boreholes in the area. Currently, at least 35 % of the population have access to safe drinking water and are thus free of waterborne diseases. Such access to water quality will lighten the Government's social responsibility and increase the agricultural productivity of the farmer.

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A carbon fiber is inert and high biocompatibility. It has a large specific surface area and strength as the contact medium. The tuft type of carbon fiber medium was introduced to the full-scale biofilm pilot plant. Examination items were investigated increasing contact medium by replacing to the carbon fiber for existing wastewater treatment plant, application as the additional plant for insufficiency nitrification water, and the application as the biofilm treatment in arid-lands. As the results in this study, it was possible to install three times existing contact medium. The increase in the amount of introducing contact medium showed that the treatment plant becomes downsizing. The performance of treatment was efficient because carbon fiber was able to maintain a lot of microorganisms even in low diversity conditions.

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Irrigation with used low quality water in arid and semiarid regions may damage soil structure due to clay dispersion. We investigated water retention of montmorillonite affected by salinity and sodicity, which are indicated by electrical conductivity (EC) and sodium adsorption ratio (SAR), respectively. Experiment was carried out with solutions of NaCl 2, 20, 50 mol m^-3, combined with SAR 5, 10, 20. When NaCl concentration was 2 mol m^-3, the clay showed high water retention at all SAR owing to low EC. At NaCl 20 mol m^-3, the sample SAR 5 showed significantly low water retention compared to SAR 10 because EC of the former solution was high. Water retention increased with increasing SAR when the system was in coagulative condition, and no difference was found in water retention if the system was in dispersion condition. In coagulative condition, both EC and SAR affected the water retention, and lower water content was observed at higher EC and lower SAR. For montmorillonite, this lower water retention might lead to an aggregated structure. Thus, combined effect of salinity and sodicity was found important for controlling physical properties of montmorillonitic soils.

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In present study, noise from Gomen-Nahari railway of Kochi Prefecture was investigated. Field measurements data and social survey data indicated that, although the railway noise levels are less than the standard value of 10 dB (A), about half of respondents reported annoyed. Furthermore, the frequency spectrum of this noise source possesses a prominent peak in the range of 400-3000 Hz, which is the frequency range that easily makes people feel annoyance. This study suggested that in small towns, when land use planning is made, from viewpoint of noise, it should not simply refer to the noise level standard; background sound level and noise source characteristic also should be considered.

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A verification of the effectiveness of the ecological canal was carried out from fiscal year 2001 to 2003. The verification was for the investigation research which was fulfilled to examine the durability. maintenance management method and other possible tasks on fascine bank protection work. It is found that the durability of fascine bank protection work endorsed as an embankment is estimated 2.5 to 3 years, and maintenance is necessary to reinforce it. In addition, it is found that special technology is not needed to carry out the reinforcement. It is simple and can be carried out with manpower. It is clarified through the investigation research that problems for maintenance are aging population and labor shortage. Therefore as a solution, the younger generation are needed to participate in the maintenance job and efforts such as providing public bulletin, information about nature should be made.

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From the viewpoint of management of the watershed water quality, a nitrogen mitigation function of paddy fields has recently received much attention. In order to quantitatively evaluate nitrogen removal rates, from June to December in 2003, we measured the water flow and nitrogen concentrations every week at the inlet and the outlet of an experiment paddy plot with gravity flow. The resultant average monthly nitrogen removal rates ranged from 0.025-0.116g m^-2 d^-1. The maximum and minimum values were measured on July and December, respectively. In July, the initial nitrate nitrogen concentration was 3.7mgL^-1 and the water temperature was 25.4°C. In December, the initial nitrogen concentration was 5.4mg L^-1 and the water temperature was 9.6°C. In addition, applying the measured data to the nitrogen-removal equations yet proposed, parameters such as removal coefficients were discussed. These values follow the published values. The results suggested that nitrogen removal rates in an experiment paddy plot with gravity flow did not show so much difference in the rates evaluated in plots with constant flow.

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The concentrations of soil CO₂, snowmelt, precipitation and soil temperature in a cedar forest area covered by seasonal snowpack have been monitored over a 2-year period from December 2003 to December 2005. This paper discusses effects of hydrological characteristics on annual cycles and profiles of the concentrations of soil CO₂. It is found that profiles of CO₂ concentration of the soil are mainly influenced with melt water entering the soil during the snow cover seasons, that the diffusion into the atmosphere from the soil is affected by the level of soil moisture. It is confirmed that the annual cycle of soil temperature causes the annual cycle of concentrations of soil CO₂. It is found that the soil CO₂ concentration is expressed by the logarithmical function with soil temperature within the limits of 5-20°C under conditions of the high concentration of soil CO₂, and that in addition the soil CO₂ concentration linearly increases with soil temperature within the range of <5°C

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Farmers' evaluations and expectations of an upland irrigation project in the Nansatsu district of Kagoshima prefecture were investigated for the administration to obtain basic knowledge to build consensus for an upland irrigation project. The differences and/or similarities between the perceptions of farmers as beneficiaries and project-promotion members as administration were analyzed based on the results of questionnaire survey.
Both farmers and project promotionmembers have the most interest in improving crop productivity associated with the irrigation project, but the former respects the investment efficiency less than the latter. There was a similar outcome in age-classified data. Project-promotion members have strong expectations about the organized effect, which means crop integration and farm-land collectivization for their successors by the upland irrigation project, whereas farmers have no interest in it. It is therefore important that the project-promotion members encourage the farmers to understand more about the organized effect to build consensus for the upland irrigation project.

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