The hydrologic conceptualization of virtual condition is relied on the behavior of monitored data at various monitoring gauges but there are frequently missing values in the monitoring database. Reasonably estimating these missing values is important for the complete analysis and modeling of hydrologic cycle. The linear regression and multi-variable interpolation of monitored data were often used to estimate the missing data or check the inadequate data of the hydrologic database. But in many instances, the relationships between the predicting and predicted variables are not truly linear, and the non-linear forms of their relationships are very difficult to be known. In this paper the Artificial Neural Network (ANN) based model is employed using the pre-construction period data to evaluate the inadequate data and missing data in the hydrologic dataset without understanding the detail relation between input and output data elements. Prediction results present that ANN method with highest coefficient of determination (R²) could be the desirable and preferred choice for evaluating the missing hydrologic data.

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Numerical experiments were performed to analyze the generation of a secondary discharge peak from a small watershed. A simple physically based three-dimensional infiltration simulation was adopted at the Minamitani valley head watershed (0.45 ha) in university forest in Aichi, the university of Tokyo. The parameters of hydraulic characteristics of topsoil were determined by sample tests and those of bedrock were sought to simulate the observed hydrographs and groundwater levels. Changing such numerical conditions as soil depth, bedrock depth and hydraulic conductivity showed that the secondary discharge peak from this watershed was generated when the value of soil or bedrock hydraulic conductivity was not changed vertically, or when a comparatively high permeable region was dominant in a watershed. The secondary discharge peak increased with increasing hydraulic conductivity, but the time of the secondary discharge peak did not change with increasing hydraulic conductivity. A secondary discharge peak was not generated in cases of high permeable regions in upper layers and low permeable region in lower layers. Soil water infiltration into bedrock functioned to suppress the secondary discharge peak under some conditions because the hydraulic conductivity of bedrock is commonly low. Increased soil or bedrock depth caused very stable base discharge whether or not the secondary discharge peak was generated. These results demonstrate the relationship among the physical conditions of the intended watershed and the conditions that generate the secondary discharge peak.

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The following are shown to be fundamental and essential flood damage mitigation measures in basins: (a)reduction of the damage by increase in the ability of flood control facilities (structural measures), (b) damage control by reduction or curbing of the damage potential (non-structural measures), and (c) integrated flood damage mitigation measures which comprise a combination of (a) and (b), this is based on the basic theory of flood damage mitigation measures in basins. Concrete examples to conduct post-evaluation of the effects of the implementation of the integrated measures under this fundamental theory of integrated flood damage mitigation measures are those taken in the Naka/Ayase river basin in Japan, the Bangkok metropolitan area, and the entire Chaophraya river basin in Thailand. All the target basins belong to gently flowing rivers on low-lying plains, where flood damage has increased due to the recent rapid progress of urbanization. As the results, the followings are shown: (1) as structural measures, appropriate measures have been planned against the cause of flooding by taking into consideration the hydraulic and hydrological characteristics of each basin, and these measures are being slowly but steadily implemented; (2) non-structural measures, which include curbing of the flood damage potential (adjustment and regulation of land use) as an important component, are implemented but under varying degrees of scale according to each country's situation; (3) based on the above-mentioned facts, the integrated flood damage mitigation measures can be estimated to be effective in the basins of gently flowing rivers on low-lying plains, which have undergone rapid urbanization.

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Water resources in XinJiang are composed of surface water, ground water and glacier. Mainly, the little amount of precipitations and melted-snow water from high mountains, which are limited in summer season, has sustained agriculture production of XinJiang. It is strongly thought by the agricultural development act that there is a lack of water resources since the population rate increases as well as the water resources decrease, beside with the climatic conditions becomes dry with time in XinJiang. Looking at the outflow of the rivers and the area of the lakes, we can see that the long time range is not always connected with the decrease of water resources in XinJiang. For that reason, this study explores the spatial and temporal characteristics of water resources from both sides: human activities and climatic factors, using Geographical Information System (GIS) technique and Landsat images of Lake Wulungu basin, Lake Ayding basin, Lake Bostan basin and Lake Ebnur basin. The observation data for the past 50 years of 26 rivers, the CRU TS2.0 data set, world climate data and each year statistical yearbooks of XinJiang were used as an input data for this study. As a result, some remarkable changes of water resources in XinJiang were produced. It is supposed that the influence of human activities was strong during the period from 1950s until the second half of 1980s. In opposition, the influence of climate is strong from the second half of the 1980s until present. Both aspects are important to consider the durability of agricultural production in XinJiang.

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Nitrogen dynamics in lotic ecosystems have been intensively studied in the light of eutrophication caused by anthoropogenic input of nitrogen. Natural abundance of ¹⁵N (δ¹⁵N) is a promising tool to elucidate in-situ processes in lotic ecosystems because δ¹⁵N can be a conservative tracer. However, many processes in intact ecosystems can exert isotope effects in different ways resulting in complex behavior of δ¹⁵N, which often makes our understanding origins and processes of nitrogenous compounds semiquantitative. Especially it is not easy to discuss quantitatively the effect of anthoropogenic N input in an intact ecosystem with δ¹⁵N data because endmembers of natural and anthoropogenic N compounds with respect to δ¹⁵N are not easy to define. Here, we summarized the existing isotopic data of inorganic N (ammonium and nitrate), the variability of with δ¹⁵N data, processes causing such variabilities in intact lotic ecosystems, and explore the possibility to use δ¹⁵N data for the better understanding of N dynamics.

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