We have developed a new streamflow prediction model that takes into consideration social change, which can be used in developing countries. This new model can predict annual and seasonal streamflow using census data and area averaged rainfall data. The model needs the following social change factors: population, forest land, crop land, paddy land, irrigated area and major rice production. The model can estimate annual and seasonal streamflow with extreme accuracy during 1958-1990. Moreover, the model can predict annual and seasonal streamflow with good accuracy in the next six years. The case study watershed has a vast irrigated area in lower basin, which needs much water. The model is able to help to manage water resources in this target basin.

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The electrical conductivity of the extract of a saturated soil (EC_SAT) was defined as:
EC_SAT≡EC_1:χ, when χ=ερ_w/(1-ε)ρ_d
where EC_1:χ is the electrical conductivity of the extract of a soil sample at 1:χ soil-water ratio, ε is the porosity of the soil under actual field conditions, ρ_d is the density of soil particles and ρ_w is the density of water. The EC_SAT is not equal to the traditional index, the electrical conductivity of the extract of a saturated soil-past prepared by the standard procedure(EC_e), but both these indices have almost the same physical meaning. A comparative test on EC_SAT showed that it can be measured both in the field using TDR and in the laboratory by the dilution extract(DE)method with a reasonable degree of agreement between them. Although EC_SAT and EC_e have both merits and demerits, it can be said that EC_SAT is a more practical index than EC_e is, because the former can be measured not only in the laboratory without special apparatuses such as a vacuum pump but also in the field automatically and continuously; furthermore, it can be compared at first hand to the electrical conductivity of groundwater when water and salt movements in the soil profile are analyzed.

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A field in this study is located in the eastern part of Hokkaido Tomakomai City, and it is Lake Utonai where it registers for Ramsar Convention in 1991. In the Lake Utonai, the influence on ecosystem becomes a problem by the transportation of nutrient salts, and fine sediment from the inflow river. Because the depth of water is shallow, flow inside the lake takes an influence by the sea-land wind of the near Pacific coast geographically, and it is expected to take the influence of the groundwater around the lake. Firstly this report arranged about local characteristic and sediment characteristic of Lake Utonai, Secondly inspection by reproduction calculation considering effects of the groundwater flow and sea-land wind and estimated an accumulation point of a tracer particle by a water quality model with Lagrange technique. Furthermore, set ingredient correlation of flow direction and vertical direction by two-dimensional vertical flow analysis model. The lakebed change analysis that the amount of sedimentation of vertical direction was adopted more than that result is being enforced, and examined comparison and analysis with distribution area and sedimentation point of the fine sediment about Lake Utonai. In this result, confirmed local application in Lake Utonai, and the simulation model that developed in this study clarified a sediment tendency.

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This paper describes the use of satellite image interpretation for analysis of small-scale on-farm ponds in northeast Thailand based on field knowledge of hydrology and water uses. For the purposes, high spatial resolution satellite data, QuickBird, was employed to carry out image interpretations. The results show that 1)the type of ponds can be categorized visually from the viewpoint of the locations, 2)catchment location to the pond can be estimated from the intake point of water and the layout of the ponds, and 3)these methods can contribute to the evaluation of accuracy of DDM(Digital drainage matrix)processed from DEM. Through a series of image interpretations, the effectiveness of high resolution satellite imagery for field sciences and investigations was confirmed.

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In order to assess the effect of human activities, such as land use change and large-scale reservoir development on river flow regime, we have developed a hydrological circulation model using MIKE11 for the Chao Phraya River basin. We have tested the effectiveness of this model. River discharge and water level during 1956-1962 when large-scale development had not been carried out in the Chao Phraya River basin yet were simulated using MIKE11.This model was able to estimate the river discharge and water level with a high degree of accuracy. Comparisons with the actual measurements have proved the validity of our model.

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We investigated the applicability of the infiltration water sampling system using a suction-controlled flux sampler in various soils. When a glass filter was used in a sandy soil, the simulation results from HYDRUS-2D model indicated that once the matric potential above the filter (h_C) decreased rapidly by suction application, a zone of low water content was remained above the filter. When the next infiltration water approached the filter, the low water content zone was packed between the filter and the infiltration water. That was showing a lower h_C than the matric potential in the natural soil profile (h_L, h_R). This phenomenon was also observed when a glass filter was applied to loam and silt loam soils. In contrast, h_C was higher than h_L and h_R when using a porous plate and membrane filters, which have low permeability. These results indicated that appropriate selection of a sampling filter and boundary condition was required for better sampling, when a suction-controlled flux sampler was applied to various soils. Because the filter permeability and soil properties affected the criterion for suction control, their combination and the existence of low water content zone between the filter and soil should be considered.

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