In order to clarify the interactive effects of land use on the discharge of suspended sediment and its sources, for a two-year period (July 1997∼June 1999) we measured stream discharge and wash load concentration at the mouth and middle of the mainstream of the Nukibetsu River and from three of its tributaries passing through differing proportions of cultivated land, in southwestern Hokkaido, northern Japan. Wash load concentration at the mouth of the main stream increased during large discharge conditions caused by snowmelt and rainfall events. The annual yields of wash load transported from the Nukibetsu River watershed were estimated at 26, 900 Mg yr-1. The wash load discharged from the three tributaries in six months (July∼December 1998) increased with the proportion of cultivated land. The mineral properties of cultivated land soils, talus cone, fan, and flood plain deposits, and mineral analysis of total suspended sediments during rainfall events within catchment OH were analyzed by the X-ray diffraction method. Total suspended sediments included cristobalite, which was found in cultivated land soil. These results suggest that most of the wash load transported from the Nukibetsu watershed came from cultivated land.

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The relationships between inter-annual variation of the growth of terrestrial vegetation, climatic variation and atmospheric CO2 content were examined. The variation of vegetation activity expressed by NDVI variation was well correlated with that of air temperature and precipitation, although the relation to the air temperature and precipitation was different in the region. Air temperature-dominated region was distributed mainly in Northern Hemisphere, and rain-dominated region was widely recognized in the Southern Hemisphere. The time change of the NDVI anomaly was found to be very similar to that of annual mean atmospheric CO2 content, and plus NDVI anomaly was corresponding with plus atmospheric CO2 content anomaly. The annual amplitude of atmospheric CO2 at Point Barrow, Alaska, well synchronized to the anomaly of NDVI. In the warmest year in 1990, atmospheric CO2 on June and July, beginning of growing season, decreased compared with that of previous year. This suggests the existence of the causality or interaction between plant growth, atmospheric CO2 and climatic variations, however, there exists two relationships in inter-annual and seasonal scales. The one is global increases in atmospheric CO2 and NDVI, and the other is local absorption of CO2 in growing season by enhanced vegetation growth due to worm weather.

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River discharges for the Huaihe River Basin in China during the GAME HUBEX IOP, between May 1 to August 31 in 1998, are simulated by using a macro grid based hydrological model developed by the authors. Precipitation and evapotranspiration data with five miniute spatial resolution and hourly time resolution developed by Tanaka et al. are used for input data to the model. The data set was generated from the GAME HUBEX IOP observed data set with the SiBUC model. Simulated river discharge hydrographs show good agreements with the observed ones, but computed discharges are underestimated especially on lower reaches. This might be due to overestimation of evapotranspiration, or the effect of human activity on river flow regulation such as dam releases. Further study is needed to make the cause for the underestimation clear. A contribution of a channel routing model to estimate river discharge for a large river basin is also discussed.

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In this paper, we proposed a model that explains residents' activities at the waterside. The model was set up with the aid of the discrete choice model based on a random utility theory. In order to take residents' cognitive data of components on the waterside environment in the model, we proposed several data-handling ways as follows. They were ways 1) of taking individually cognitive data of components on the waterside environment in the utility function, 2) of using classified samples, and 3) of using the unobserved endogenous variables composed of some observed exogenous variables expressed the residents' cognition of the state for the waterside environment. The effectiveness of these proposed ways was shown by the results of the applications to the real waterside in urban area. And the applicability to estimation of the number of visitors and compensating variation with change in waterside environment was shown.

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A local linear approximation method (LL method) was developed as a simple flood forecasting method. The LL method can be considered as an extension of nearest neighbor (NN) method which was developed by Karlsson and Yakowitz (1987) for daily rainfall-runoff analysis. Both methods are also conceptually similar to local prediction method developed for forecasting chaotic time series. The NN method is based on the basic pattern recognition technique. Forecasts of the future daily flow are estimated as average of the recorded flows whose regressive time series patterns of rainfall and runoff are similar to the latest pattern. Such a similar pattern is called as a nearest neighbor. The LL method is based on an assumption of a linear relationship between the forecast and its pattern composed of regressive hydrological data. The forecast is estimated from the latest regressive data using the linear relationship defined by the data of the nearest neighbors and their succeeding records. The NN and LL methods are much simpler than a conventional flood forecasting system like a rainfall-runoff model combined with Kalman filtering technique. Appropriate dimension of a input data vector that is important for utilizing the NN and the LL methods was found by false nearest neighbor (FNN) algorithm. The FNN algorithm is much simpler than general methods like that using Akaike's Information Criterion (AIC). The NN and LL methods were applied to forecasting of flood discharge at Kuroki Dam basin, and the result showed the advantage of the LL method in the accuracy of forecasts around peaks. The overall forecasting accuracy was comparative to the conventional flood forecasting model that is Tank model combined with Kalman filtering technique.

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Japanese alluvial area has been an excellent agricultural zone but subjected to complex problems such as drainage, salinity and water quality due to its natural low-lying and flat characteristics. These problems are worsened by the modern economical development and severe relations between water supply and demand press the shortage of water for agricultural use continuously. Consequently, traditional water order in the coastal field which controlled skilfully the uprising of salt from salinized underground layer by the intrusion of seawater to surface layer is getting worse and remarkable risk of salt injury would be increased. The objective of this study is to present a proposal for necessary countermeasures to maintain agricultural productivity in the alluvial area. Two fields were selected near the Naruto Straits with salinity problem in underground layer originated from tidal river. In first case at the Magota River improvement project on western Awaji Island, it become clear that some device like upper and lower layer not to be mixed at construction works are necessary to avoid the uprise of saline groundwater in a range from the river mouth to upstream 600m. In second case at Kawauchi district on the most downstream of the Yoshino River, we considered it is necessary a high level of countermeasure that distributes sufficient fresh water as multipurpose use of irrigation water that include the customary salt exclusion water.

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We report on the characteristics of suspended sediment discharge in three small basins covered with volcanic ash soil, where upland farming is widespread. Despite a small runoff ratio in summer when the ground is permeable, high suspended sediment discharge is measured because of high erodibility of soil. On the other hand, high suspended sediment discharge is measured also during snowmelt because of impermeability of the frozen subsurface. The field measurements introduced the relationship between the flow rate (Q m3/s) and the suspended load (Qs m3/s), giving the magnitude of three or four orders larger that by the empirical equation; Qs=(4×10-8∼6×10-6) Q2. Furthermore, the concentration of suspended sediment in snowmelt season is higher than that in summer. It is suggested that the origin of suspended sediment is upland fields in the small basins, because the particle size distributions are similar. The suspended sediment includes much fine silt less than 0.1 mm in diameter and flows out in a way of wash load. The control for soil erosion is effective if the buffer zone is constructed between the upland field and the river, because suspended sediment is fine and does not settle easily on the river bed.

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Dams have played a central role in water and energy development in the last few centuries in various part of the world. At the same time, it also has increasingly recognized that dams also had negative impacts on human life and ecosystems on Earth. Recent argument on large dams on a global scale highlighted a sharper contrast between costs and benefits of large dams, involving a wide range of stakeholders. The World Commission on Dams (WCD) was established to review the development effectiveness of large dams and prepare internationally acceptable standards and guidelines on dams planning, construction and operation. Its final report was published in November 2001, including the global review of large dams, and recommendations for future decision making on development. The report received varied reactions from organizations involved in dam issues, but based on the information and materials produced through the process, coordinated follow-up was requested by the WCD stakeholders. At this request, the United Nations Environment Programme (UNEP) has been preparing the “Dams and Development Project (DDP)” which will assist each stakeholder in following up the WCD in sharing and exchanging information on large dams. As a country with many dams existing, under construction or planned, further discussions and dialogues among multi-stakeholders in Japan could be conducted based on the WCD materials and in association with future dialogues at the international level, particularly through DDP.

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