Water from small glaciers and ice caps are sensitive against the ongoing global climate change. However, previous researches have been estimated current water resources from glaciers based on areaweight method of available mass balance observations. It is therefore difficult to estimate the future volume change of glaciers due to the lack of available data. This paper reports our latest effort to develop a global glacier model that can be coupled with global hydrological and land surface models by including individual glacier inventory data in a distributed way. Simulation result over European small glaciers showed that the newly developed model successfully replicates average mass balance obtained from available observation-based estimates, indicating the advantage of new model which includes detail location and area distribution of glacier inventories, comparing to the original glacier model assuming one large glacier within each 0.5-degree grid. Sensitivity test revealed that the calculation excluding small glaciers within 0.5-degree grid in a random manner shows similar mass changes, indicating the potential method to save calculation cost of the new model. Preliminary experiment using warming climate scenario by a climate model showed that the new model has lower climate sensitivity than that of the previous model due to the loss of small glaciers at low altitude.

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Mountain glaciers are one of key elements to indicate current climate change considering their contribution to sea-level rise and to water resource change through regional hydrological processes. This study estimated the area and location of tropical mountain glaciers in Bolivia using satellite imagery. Previous studies have produced datasets of global glacier information, but the area/location information of mountain glaciers in Bolivia is not stored in those datasets due to limited field measurement data. In this study, we developed a couple of satellite remote sensing measurement methods so that the area/location information of tropical mountain glaciers in Bolivia was obtained at a country-wide scale for the first time.

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The disappearing of glaciers in Himalaya alpine region, in where hundreds of millions of people rely on melting glaciers for water, has been reported by recent studies. However, the estimation of change in glacier mass still has a significant challenge because of a limited observational methodology to understand hydrological processes in Himalaya region. In this study, we estimate the ice loss rate for the Himalaya alpine region for the period January 2003 through December 2008, mainly using terrestrial water storage (TWS) variations observed by the Gravity Recovery and Climate Experiment (GRACE). To separate the effect of the other TWS components, simulated soil moisture, snow mass and river storage are calculated by using the Minimal Advanced Treatment of Surface Interaction and Runoff (MATSIRO) land surface model (LMS). The methodology using GRACE data and LMS result is similar to one of previous studies. In addition, we also use groundwater withdrawal data, and our estimated glacier mass change is compares with glacier model (HYOGA) results. Finally, it is estimated that the melting rate of the glacier mass over target region is approximately 4.7 Gt/year. Although we believe that our methodology is the newest comparing previous one, our estimated value is much underestimated than HYOGA results. Our methodological experience and information will be helpful to better understand glacier mass change.

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Cloud water content and solid precipitation over the arctic cryosphere affects the radiation characteristic on the land surface. Ground-based quantitative observation of the solid precipitation over the arctic cryosphere has however a significant problem in terms of capture rate for solid precipitation. In addition, the visible and infrared remote sensing is not useful since the scattering property of sun shine can not be used and the ground surface temperature falls significantly over the arctic cryosphere. Development study of observation system for solid precipitation over the arctic cryosphere is therefore needed. In this study, the microwave satellite retrieval algorithm for the cloud water content and snow physical quantity over the arctic cryosphere was constructed. Estimated snow grain size, snow depth and cloud water content by using this algorithm was in comparatively good agreement with the in situ data in Yakutsk, Russia. This conclusion suggests that this algorithm is useful for the quantitative observation method for cloud water content and solid precipitation over the arctic cryosphere.

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We incorporate a subgrid snow cover parameterization, Subgrid SNOW Distribution (SSNOWD) model, into the land surface model MATSIRO. SSNOWD assumes the subgrid snow water equivalent depth distribution following the lognormal distribution function, and accounts for the subgrid snow physical processes. The 29-year simulation is conducted forced by the observation and reanalysis based meteorological data. The results are compared with satellite based observational dataset and the intra- and inter-annual snow cover fraction variations are validated. The effects of incorporating SSNOWD on hydrological properties are also evaluated. The results show that SSNOWD improves the intra- and inter-annual variability of snow cover area in Northern Hemisphere especially in the accumulation season and the effect of those changes in snow cover on the other land surface properties are not negligible.

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The objective is to develop an estimation method of snowdepth distribution in mountainous areas. The existing SWE model shows underestimation of snowdepth in the Yoneshiro River catchment because of the observation error of snowfall. To improve the estimation, this study incorporates assimilation strategy of observed snow depth into snow water equivalent (SWE) model at regular intervals and determines the most accurate assimilation method in some methods proposed. Observed snowdepth and disappearance dates of snow cover obtained from thermometers on the ground are used for the validation. As results, the assimilation method can reduce the observation error of snowfall and the analysis shows high accuracy of snowdepth in high mountainous area.

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For better estimation of snow water equivalents for dam basins in cold snowy regions, snow depth distribution was investigated in relation to both elevation and aspect of slope using a high-resolution digital elevation model (DEM) created from an airborne laser scanning survey conducted on a certain day in the snowy period and another one in the snow-free period. Based on the results, a snow water equivalent estimation model was developed.The model was used to estimate snow water equivalents in six dams, and resulted in estimates with a higher level of accuracy than those based on snow surveys and existing models.

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This paper verificated Degree-Day method, one of the temperature-based snowmelt methods, over Japan with AMeDAS data. Snowmelt rate factor, which is parameter of the Degree-Day method, is optimized comparing observed snowdepth at AMeDAS point with estimated snow depth with SWE model and snow density estimation model. As a result, the optimized Degree-Day factor is able to estimate snowdpth with high accuracy at more than around 86% AMeDAS points. But snowmodel estimates snowdepth with less than 80% correlation factor at less than 1m maximum snowdepth and high temperature point. Moreover, we confirmed that maximum snowdepth and temperature have effect on snowmelt rate factor. Sensibility of correlation factor against temperature and precipitation showed same results.

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X-band multi parameter (MP) radar network has an advantage in accuracy of quantitative rainfall estimation (QPE) by dual polarization parameters. However, it has an disadvantage in detecting area by considerable signal attenuation by rain particles. Therefore, combined use of both kind of radars would be anticipated. In this study, we developed an algorithm to improve QPE by conventional C-band radars through the use of X-band MP radars. The algorithm utilized microphysical properties retrieved from X-band MP radar, and provided optimum coefficients of Z-R relationship from a rain event. The rainfall distribution made from C-band radar agreed fairly well with QPE by X-band MP radar. It could be helpful for providing seamless rainfall maps.

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In summer season, the frequency and amount of rainfall become large over the mountain slopes surrounding a basin. As one of the examples, the distribution and increase of rainfall over the slope of Mt. Kushigata on west side of Kofu Basin were investigated using X-band multi-parameter radar (X-MP radar) data. The rainfall amount estimated from June to September on 2009 using X-MP radar became large at the lower layer over the slope. On the case study on 27 July 2009, the increase of rainfall intensity at the lower layer was discussed from the growth of raindrops originated from the brightband falling through the low-level precipitating system formed over the slope. The results provide not only the more understandings of distribution and increase of rainfall over mountain slopes surrounding a basin but also the availability of the X-MP radar installed in a basin for the observation of rainfall associated with small-scale meteorological phenomena on a slope.

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Quantitative estimation of precipitation is important to management water resources and utilizes distributed hydrological modeling system. Coherent dual polarization radar is expected to advance river managements. In this study, the ability of the first operational dual polarization radar was reported, which had been installed in Kyusyu district. Using the coherent polarimetric information was the good countermeasure to the weakness of conventional weather radars such as attenuation problem of heavy rainfall, contamination of ground echo and electric power blockage of mountainous areas. The rain estimation algorism incorporated polarimetric information showed quite good accuracy comparing to the previous.

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In Japan, test operating of X-band polarimetric radar network started in July, 2010 by Ministry of Land, Infrastructure, Transportation and Tourism. Polarimetric radar has an advantage over conventional non-polarimetric systems because they measure some parameters related to raindrop shape. In this research, a retrieval method of raindrop size distribution (DSD) is developed to improve accuracy of rainfall estimation. The new developed DSD retrieving method was superior to previous method when heavy rainfall occurs. Then, the method was used to figure out the characteristics of DSD in a convective storm. After retrieving DSD parameters, rainfall estimation for non-polarimetric radar is directly estimated from the retrieved DSD parameters. Two methods are used, and both are evaluated using disdrometer, and it is shown that both are well estimated when compared with previous studies.

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The latest version of the TRMM (Tropical Rainfall Measuring Mission)/PR (Precipitation Radar) standard product (Version 7; V7) was recently released. This study focuses on heavy rain rate estimated in V7, which are more frequent than in the previous version (Version 6; V6). Surface reference technique is crucial for attenuation correction particularly of heavy rainfall, and becomes more reliable in V7, mainly because of ensemble of multiple SRT methods. Though the accuracy of clutter detection and the validity of Z-R relations are carefully examined, there are still possible rain estimates with extremely heavy rate of more than 300 mm/h. As hourly rain rate, 300 mm/h should be unexceptional, but the time scale of PR measurement may be shorter than 1 hour and these extremely heavy rain rate estimates should be investigated considering the time scale. Relations between heavy rain rates and surface temperature are analyzed with V7 and surface measurements. 99% rain rates in V7 generally increase with the increase of daily surface temperature, though daily rain amount by gauges tends to decrease when daily surface temperature becomes higher than 25 ^oC, which implies different time scales between PR and gauge measurements.

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Relationship between cloud droplet effective radius and cloud top height is investigated using CloudSat data product to evaluate the hypothesis of convection invigoration by atmospheric aerosols. The result shows negative correlation between the two, which supports the hypothesis. Since CloudSat is sensitive to precipitation particles, means to decrease the errors due to precipitation particles should be devised. Cloud droplet growth processes can be divided into two processes: condensation growth process and collision coalescence growth process. By using profiles which correspond to condensation growth process, influence of precipitation particles can be reduced. It is shown that by k-means clustering, CloudSat radar reflectivity profiles can be divided into two clusters. By using profiles in the cluster which is considered to correspond to condensation growth process, negative correlation between cloud droplet radius and cloud top height is confirmed.

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In order to improve the accuracy of strong rainfall nowcasting for a very short term usually of one hour, a new rainfall nowcasting method based on the image processing technique is developed. The key technique in this study are to evaluate the deformational errors between observed and predicted rainfall areas obtained by Japan Meteorological Agency (JMA) and to minimize errors of the JMA rainfall nowcasting in real time based on its evaluation. As a result of verification experiments for intense rainfall events, it is concluded that our new method remarkably improves the accuracy of rainfall nowcasting by considering complicated deformation processes of rainfall area, and the predictive value for one hour ahead forecasted by the new method is at least 10% greater than that by the original JMA rainfall nowcasting.

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The current study conducted numerical experiments using nonhydrostatic mesoscale meteorological model to clarify the mitigating e.ect of weather modification by cloud seeding on torrential rains. Based on simulated two heavy rain events in northern Kanto and Tokai regions of Japan, sensitivity analysis was performed by manipulating some conditions for cloud seeding implementation, i.e., area, height, time, etc., in incremental steps. Variations of rainfall distribution and convective cloud activity were examined to see the in.uence on the generation and development process of torrential rains. Results in some cases show a signi.cant decrease in areal average and/or regional maximum rainfall, especially noticeable in the case where cloud seeding was performed at a relatively high altitude. It suggests that weather modification by cloud seeding can weaken the development and convergence of torrential rains. In the case with such a decrease in regional maximum rainfall, a signi.cant increase of cloud ice was found in the upper part of the atmosphere, which seems to have caused the mitigation in the spatial and temporal convergence of precipitation particles falling to the ground.

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Meteorological characteristics of the formation and environment of the Niigata-Fukushima heavy rainfall on 28~30 July 2011 were studied. Line-shaped rainfall systems were observed by using synthetic radar and Xband MP radar on 29 July at 09~17 and on 30 July at 00~04. The purpose of this study is to classify these events and to reveal the reason why these occur and stagnate. It was found that the former event can be classified as Back Building type while the latter can be classified as Back Building composite type. The development environments were focused by the convergence, relative humidity, wind and temperature by using the Japan Meteorological Agency GPV mesoscale model dataset. Results indicate that convergence area, flow of high-humidity air at 950hpa and incursion of dry-low-temperature air generated the event on 29 July at 09~17. The event on 30 July at 00~04 was generated by the effect of cold air at 400hpa which flowed into high-humidity region.

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Recently, localized heavy rainfalls over heavily urbanized areas have caused severe damage in Japan. On 5 August 2008, a localized heavy rainfall caused a rapid increase in drainpipe discharge, which killed five people working in a drainpipe near Zoshigaya, Tokyo. This study investigated the effect of urban heating on this localized heavy rainfall by two ensemble experiments using a cloud-resolving model that included precise urban features. The first experiment (CTRL) considered realistic land cover, anthropogenic heat, and urban geometry. In the second experiment (WURB), to reduce only the urban heating and keep the urban geometry, the anthropogenic heat was ignored and the roofs, walls, and roads were covered by shallow water. The amount of rainfall was clearly reduced over Tokyo in the WURB experiment. The weaker surface heating in WURB reduced the near-surface air temperature and weakened the convergence of horizontal wind and updraft over the urban area, and resulted in the smaller amount of rainfall in WURB.

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Train operation is suspended to ensure safety when the precipitation observed by a rain gauge exceeds the train operation control criteria. This paper proposes a method to determine the rain gauge installation interval and the train operation control criteria suitable for hourly precipitation. Those are evaluated from the viewpoints of both safety and reliability of train operation, based on the spatial distribution of precipitation observed by rain gauges. This paper shows the combinations of the rain gauge installation interval and the train operation control criteria which can improve either safety or reliability when one is kept constant, or can improve both. For instance, in the case that the rain gauge installation interval is reduced from 10 km, which is the current standard interval adopted by many railway companies, to 5km, the train operation control criteria are raised by 17% and reliability can improve by 25% when safety is kept constant, and the train operation control criteria are raised by 8% and safety can improve by 19% when reliability is kept constant.

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To clarify the spatial characteristics of rain-gauge network over Japan, we studied some characteristics of rain-gauge network over Japan using available data observed by the Japan Meteorological Agency (JMA), the Water and Disaster Management Bureau under the Ministry of Land, Infrastructure, Transport and Tourism (WDMB-MLIT) and Local Government (L-Gov). Additional spatial analysis was also used available digital national land information (DEM, topographical slop, land use, surface geology, major road, natural park). As a result of spatial analysis using some digital national land information and observation blank zone, more than altitude 500m area couldn't be installed rain-gauge stations. Some observation blank zones have been topographical slop were rich in ups and downs. Rain-gauge stations weren't installed in only limited land use or surface geology. Moreover, many rain-gauge stations tend to be installed near the major road. Therefore, some observation blank zones could install rain-gauge stations.

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A new method to assess the causes of the changes in the extreme precipitation under changed climate was proposed. Previous methods have not explicitly considered the contribution of changes in the near surface atmospheric humidity to the changes in the extreme precipitation under changed climate, although the changes in the extreme precipitation can be affected by the changes in near surface atmospheric humidity through the changes in lifting condensation level. The new method can consider changes in near surface atmospheric humidity as well as the changes in atmospheric circulation and lapse rate of the ascending air parcel. The new method was applied to atmosphere-ocean coupled model output, provided for the Coupled Model Intercomparison Project Phase 5. It was confirmed that the new method can assess the regional difference of the contribution of the changes in near surface atmospheric humidity to the changes in the extreme precipitation with climate change.

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In this study, the frequency and the intensity of localized heavy rainfall enhanced by climate change was quantified using the outputs from super high resolution regional climate model (resolutions of 5km and 30minutes) provided by KAKUSHIN program. Since we are concerned with the localized heavy rainfall caused when the Baiu front hangs in a specific region, it is not easy to identify based on simple criterion of a certain threshold rainfall. Therefore, through the experiences of radar-based severe storm analysis, we counted the number of events, checked their location, and quantified their intensity by watching the images of precipitation for several accumulation time steps and meteorological variables based on several criterions developed in this study. As results, it was found that the frequency of localized heavy rainfall events has a tendency to increase significantly in the end of the 21st century and that they might occurs on the Pacific Ocean side of East Japan with obvious spatial pattern.

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Oxygen isotopic ratio in coral skeleton (δ18Oc) is an important parameter to reconstruct past climate in tropical region for several centuries. That is because δ18Oc physically reflects δ18O in sea water (δ18OSW) and δ18OSW is influenced by hydrologic balance such as precipitation, evaporation, and terrestrial runoff at the location. However, the quantitative relationship between δ18OSW and the hydrological balance has not been fully uncovered yet. We predicted δ18OSW with an isotope incorporated atmospheric general circulation model (A-GCM) and compared them with 32 coral records. The model successfully reproduced the δ18OSW recorded in the corals at many sites. We then analyzed what affected the δ18OSW variations. The comparison suggests that coral records represent past hydrologic balance information where interannual variability in precipitation is large. According to the model, the interannual precipitation variation is a dominant factor of the δ18OSW variation, but those of δ18O in both precipitation and in evaporation also have non-negligible influence.

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The discrepancy of bias-corrected monthly temperature and precipitation data simulated by multiple General Circulation Models (GCMs) are compared among the bias-correction methods. This study classifies previous methods into 2 groups. The methods in one group consider about the statistical characteristics of the change of GCM outputs from historical simulation to future simulation, while the methods in the other group do not. The difference of the bias-corrected data is not large in the validation using the historical GCM outputs and observed data. The difference in the future GCM outputs is, however, large among the two methods. The variance of the increment of bias corrected-data from historical period to future period among GCM outputs are also compared between the two methods. Our proposed method, which is one of the methods that consider the characteristics of the change, is better than other methods because the variance of our method is smaller than that of other methods.

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The projection of typhoon activity is one of the most important issues in risk management under climate change. In this study, we aim to project near-future typhoon activity, and to assess the expected damage cost associated with typhoon in the near-future climate change. Firstly, we have developed a Stochastic Typhoon Model combined with future typhoon characteristics based on General Circulation Model in order to estimate near-future typhoon activity. Further, to evaluate our model's reliability, the outputs of our model have been validated against the observed tracks and central pressure of typhoon in the Western North Pacific. The projected near-future typhoon activity shows the tracks of typhoon shift to the northeast and the typhoon of lower central pressure is increased in the near-future. These changes cause a decrease on annual damage cost in countries around the Asia-Pacific region except for Vietnam. The methodological experience in this study will be helpful to build risk management.

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In the inland of the Indochina Peninsula, i.e., in Cambodia, it is known that it rains even after the withdrawal of the Asian Summer Monsoon. The four requirements for the initiation of this rainfall have been proposed in the previous studies: (i) the existence of the very hot surface of Tonle Sap Lake, (ii) intrusion of cooler airmass from the southwest of the lake, (iii) strong nocturnal northeasterly, and (iv) abundant precipitable water in the atmosphere. In this study, the behavior and the mechanism of the third component was studied. It was shown that the mountain-valley circulation caused by the Annam Range strengthened the northeasterly during night at the inland (west side of the mountain) and it appeared as if northeasterly monsoon got stronger during night. Since this wind is a key to initiate the post-monsoon rainfall, it is notable that this wind is reproduced well by the GCM in the NCEP-FNL reanalysis model. This information could be used for the rainfall prediction in the further study.

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The demand of energy and food production will grow as rapid population increase. However, although it is closely related to food habitat change, water resource, and bioenergy boom, a comprehensive understanding integrated with food, water and bioenergy has been rarely documented. Our aim in this study is to investigate the effect of agricultural land and bioenergy potential in global scale using water resources model H08. We use five future food consumption scenarios, which are composed of 10 food categories. Two different land-cover types, abandoned land and fallow land, are defined as potential area for cultivation of food-producing and biofuel-producing crop. The estimated global bio-energy potential is 57-200 [EJ]. It is highly related to increased land demand for large-scale food production based on the scenarios. In particular, the cereals consumption for fodder production is significantly changed on the basis of the land-use scenario. It implies that future energy and food security will critically depend on livestock food consumption.

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Improvement in flood control and water availability by multipurpose dams has been called for as a part of the strategies for adapting to climate change. Improvement in the accuracy in flood forecasting is one such strategy. The runoff of a river depends on the moisture condition in the watershed. A runoff calculation method that takes into consideration the moisture condition in the watershed is useful in improving the accuracy and stability of flood forecasts. This paper quantifies a basin's storage by evaluating the long-term water cycle in the basin and proposes a method of calculating the runoff percentage using the resulting quantities. When the proposed method was applied to 25 floods in the subcatchments of five dams in the Ishikari River System, the calculations corresponded closely to measurements. The proposed method is thought to be effective for calculating general runoff.

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A lot of slope failures were generated by Typhoon No.17 in 1976 and Typhoon No.10 in 2004 in the upstream of the Nakagawa River located in southern Tokushima Prefecture. Shallow slope failures were generated in Typhoon 200410 while deep slope failures were generated in Typhoon 197617. In this study, the maximum value and time series of subsurface water storage on forest slopes were estimated using a distributed runoff model, and the reason why the form of slope failure is different was discussed. We found that: (1) the collapsing forest slopes have large capacity of subsurface water storage. (2) the ratio of groundwater storage to soil water storage became large on the slope where a deep collapse was generated. (3) the ratio of soil water storage to groundwater became large on the slope where a shallow collapse is generated. (4) rain-fall intensity and its waveform are related to the generation form of slope failure, too.

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The present study attempts to estimate watershed-scale storage changes and storage capacity only from hourly runoff data in Japanese mountainous watersheds, based on a methodology developed by Kirchner in 2009. The results showed that the methodology is applicable even in Japanese mountainous watersheds if we can assume that the rainfall-runoff processes of a watershed could be modeled by a simple storage function. We found this methodology is potentially useful for estimating storage capacity of a watershed from the annual maximum runoff and the minimum runoff. Finally, we suggested a ratio between the annual maximum runoff and the estimated storage capacity multiplied by a runoff record interval as "storage-runoff index" that could be potentially useful for watershed classifications.

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Significant seepage from rivers into groundwater sometimes causes difficulties in river flow management particularly in the sense of water environment and its conservation. Kurobe river which runs from Northern Alps of Japan into Japan Sea forms an alluvial fan in the range of 13km from the sea. NK-GHM which is a quasi-three dimensional hydrological cycle analysis model has been applied to clarify hydrological cycle in this area including seepage/discharge from/to the river. The model was tested by comparing with river flow rate, groundwater height and other observations and the model well described the observations.

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This paper presents a power-law model of Shreve's link magnitude for estimating flow regime and the mean annual discharge in river networks. The model takes into account the effects of climatic, geological and land use conditions within river basins. High predictability of the model for discharge estimation is confirmed by using discharge observation data from 109 large river basins in Japan. The results indicate that the effect of precipitation on flow regime estimation is apparent for high flow discharges, while that of geology become obvious for low discharges or a drought condition. As for the land use types, the results show that wastelands and city areas have large impacts on the mean annual discharge. Since the link magnitude system with climatic, geological and land use conditions provides flow regime information throughout river networks, it could be very useful for basin-wide environmental management.

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Pakistan suffered from a devastating flood disaster in 2010. This study investigated the potential of utilizing a rainfall-runoff-inundation (RRI) model for providing useful information for effective emergency response. The model was applied to the entire Indus River Basin (modeled area: 929,723 km² with 60 sec. (about 1.7 km) grid-cells, and its performance was evaluated based on the simulation results of river discharge and flood inundation. More specifically, a large-scale flood extending about 100 km apart from the main Indus River was focused for testing the model performance. Furthermore, by comparing different modelling settings including one- and two-dimensional kinematic and diffusive wave approximations and different treatments of embankment, the study discussed a suitable model structure to achieve the above objective with limited information. As a result, two-dimensional diffusive wave rainfall-runoff-inundation simulation without explicit considerations of embankment turned out to be the best combination for large-scale flood simulation for the case of the 2010 Pakistan flood.

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In order to clarify its physical meanings and obtain it as a simple and useful form, the rational formula is theoretically derived as an explicit analytical formula in this paper. The authors declare that the rational formula is derived from the basic formula of runoff in a hill under the assumption that the flow resistance of runoff takes the steady velocity such as saturated Darcy's law. Synthesized rational formula can be expressed by superposing the analytical linear formula of rational formula. Since given rainfall is expressed as a summation of unit step functions, which is the same form of the general rainfall data, derived analytical formulas can accept rainfall data with no modification. With this formula of synthesized rational formula, to investigate the effect of time-resolution of rainfall data for urban-runoff simulations, numerical simulations are conducted in the end of the paper. The results show that when the arrival time of flood is short, enough time-resolution is required to obtain fine calculation results.

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The authors have been developing Advanced GIS Delineation Data of the upper Kanda river basin by detailed land use recognition. When using distributed water circulation model, grid land use data of 100m or 10m-mesh division is typically used. However there has been no study conducted to verify the permeable area set by the 100m or 10m-mesh land use classification. In this study, we estimated the true permeable area ratio of 10m-mesh land use classification using the advanced GIS delineation. As a result, it was identified that the frequency distribution of permeable area ratio and the characteristic of spatial distribution of permeable area ratio by 10m-mesh.

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Recently, a particle filter (PF) that is one of the non-liner and non-gaussian filter has been proved to be a powerful tool for real-time runoff forecasting. In this paper, we implement the PF on Urban Storage Function (USF) model which incorporates urban runoff process such as the outflow from combined sewer system and leaked from water distribution pipes. USF model using the PF is applied to a virtual catchment where rainfall-runoff characteristics are known. The model parameters are updated with 1-minute river discharge data by the PF. The results show that USF model using the PF forecasted the amount of river discharge accurately.

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A real-time runoff prediction system based on the Kalman filter theory using a distributed runoff model incorporating dam reservoir operation is extended to apply a basin with multiple dam reservoirs. A reservoir operation modeled with a function of inflow, outflow and reservoir storage is represented by a linear function of state variables using the statistical linearization method, which is incorporated into an entire state update vector equation composed of river discharges, dam inflows, outflows and storages in a distributed hydrologic system. An application to the Kizu River basin with five dam reservoirs successfully shows updating of state variables, which realizes fully distributed forecasting.

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In this paper, the particle swarm optimization (PSO) is applied into automatic parameter calibration process of a distributed runoff model. As distributed runoff models require long simulation time compared with general optimization problems, the number of particles and repeat computation times should be selected property. We conducted sensitivity experiments for the number of particles and found that the PSO has to be applied in following conditions: i) to set the number of particles more than 100 in the case of calibrating about five parameters, ii) to conduct repeat computations about 25 times. Analyzed river discharge using identified parameters shows good agreement with the observed one.

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Rock breakdown by freeze and thaw action occurs at bare slopes in mountainous area in Japan. The quantitative estimation of the amount of sediment produced is indispensable because the sediment closely relates to sediment disaster. In relation to this, it is required to obtain the temperature and moisture profile. In this study, a concurrent numerical simulation of underground heat and water transfer was conducted and the characteristic of water flow during freezing was discussed. In the analysis, a physical model of the pore structure change due to freeze-thaw was used. If the pore structure change occurred, which did not accompany the increase of porosity, considerably small amount of water was supplied to the freezing layer. However, if the increase of porosity was considered, upward water flux occurred which was large enough to increase volumetric water content. Moreover, it was revealed that the water flux positively correlates with freezing speed and with the amount of temperature fall.

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Illegal dumping at the mountainside is one of serious problem in Japan. However, the conventional approaches to the groundwater pollution problem mainly focus on the urban area or flat land. In this study, it was investigated that the change of water content and solute transport caused by rainfall infiltration in the model slope by experiment and numerical analysis. The results show that the change of pore pressure was reproduced well by numerical analysis, and peak value of the concentration at the points near the source was also reproduced well. But, the calculated value of the concentration at the point far from the source was different from measured value.

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The cavity around underground waterside structure has been recognized as primary factor of cave-in in the road, seepage-failure of the river levee, etc. There are numbers of experimental studies on the mechanism of hollowing out. However, no research has yet been carried out to clarify the causal relationship with numerical description. In this paper, we developed a 2-phase groundwater flow model by incorporating Manning's law for intracavernous flow. Its applicability is shown by numerical experiments and actual scale calculations. These results show that the proposed model is effective for expressing time-dependent behavior of air and water during the cavity-detecting test.

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Mud transport in sand beds provides a better understanding of the knowledge involving the environment and sludge-ization of tidal flats. In this study, the permeability reductions due to mud deposition under different flow rates, porosities and mud properties are investigated through laboratory experiments, and the validities of previous models are confirmed. The filtration coefficient of mud in sand beds was determined, and a new experimental formula is proposed to estimate the amounts of residual mud in sand beds. This formula can estimate the amount with a relative error of 10%. Further, the previous models of permeability reduction were found to be impossible to represent the experimental data, thus a new model is proposed. The new model can estimate the permeability reduction with a relative error of 10%.

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It is important to apply proper dispersivity in unsaturated condition when solute transport near the soil surface is assessed. However data on unsaturated dispersivity are limited because dispersion in unsaturated condition is more complicated than in saturated condition. In the previous study, we tried to evaluate unsaturated-dispersivity by tracer experiment in the laboratory seepage tank. However, it was difficult to investigate clear results because observed values were scattered. In this study, numerical tracer simulation was conducted under unsaturated water flow condition. The numerical tracer simulation results were confirmed that longitudinal and transverse dispersivities have dependency on soil water content. When the water content is lowered, dispersivity becomes larger. The ratio of transverse dispersivity to longitudinal dispersivity was in the range of 1/1000-1/6000. Numerical results showed that longitudinal dispersivity may have almost constant value in the small scale as seepage flow tank used in this study.

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The continuous time random walk (CTRW) model, which is one of the method to evaluate contamination, has been noticed because it can describe the complex behavior of substances in heterogeneous porous media. However, how to determine its parameter values is not well understood. The purpose of this research is to relate the parameters of CTRW to the parameters used in ADE. We conducted numerical experiments and found that the flow rate, the retardation factor and the dispersion coefficient are respectively represented by Δx⁄Δt, <τ>, (Δx²⁄Δt)^β.

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Hot water flushing experiments in a two-dimensional sandbox (35 cm × 20 cm × 1 cm) were conducted using dyed salad oil in single and two-layered porous formations under saturated conditions. Based on a calibration relation between the dye concentration and the corresponding pixel brightness an image processing technique in conjunction with spatial moments was developed to quantify not only the spatial distribution of oil but the apparent retardation and dispersion coefficients both in longitudinal and lateral directions. The increase of flooding water temperature resulted in accelerated downward movement of oil because of the reduced viscosity at elevated temperatures. The results also revealed that the variation of the apparent lateral dispersion coefficient depended on the oil saturation within a pore space and exhibited an increasing tendency in a smaller size porous material due to the difference of intrinsic permeability.

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Examination of the effectiveness of Multipoint Temperature Logging as the investigation technology of leakage flow of basement of riverbank was performed by a model experiment and field measurement. Results of the model experiment showed that shape of restoration ratio of multipoint temperature can indicates the existence area of permeable layer and the vertical ground flow structure. And the results showed indicated that the faster the groundwater flows the higher the recovering rate of temperature becomes. Results of field measurement showed good agreement with the results of model experiment. Results of Multipoint Temperature Logging in field measurement showed that leakage flows in the riverbank and basement exit in multiple areas. And flowing groundwater often has vertical flow structures.

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It is predicted that global warming and climate change will affect both of global and regional water environment in future. Local downpours or serious drought may be brought in an unexpected region. It is suspected that these impacts finally affect on the groundwater flow and water quality. Therefore, investigation and analysis of the water budget and the material balance in basin-wide are important for conservation and utilization of the water resources. In this study, two-dimensional model of groundwater flow and quality was prepared for evaluation of groundwater environment in Kyoto basin. This model has good performance for simulation of groundwater level and it has acceptable performance for simulation of T-N concentration observed in Kyoto basin. So, this model was used for the impact assessment on the groundwater system in Kyoto basin by global climate change in future using of MRI-AGCM20 outputs.

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Hydrological meta-modeling for watershed management has been proposed. A physically-distributed, surface and subsurface fully-coupled fluid flow code GETFLOWS was used to derive the metamodel. The metamodel has been well-trained the mutual interaction between surface water and subsurface water flow, and has predicted the water resources indicator without time-intensive computation. The adequate accuracy of the computed indicators for an actual river basin has been attained by using the metamodel. We proposed here a combined-application of the surface and subsurface coupled fluid-flow modeling and the meta-modeling concept to the practical water resources management.

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In order to improve the hydrologic cycle in urban catchment with impervious area, we examine the infiltration capacity of two types of rainwater-infiltration inlet (RII) under actual rainfall conditions, and furthermore clarify the effects of the RIIs on increase of spring yield in urban catchment area. We measured water balance in a single RII and urban catchment area in which a small spring, named Kaga-Simizu Spring, is located and a lot of RIIs were installed. The results indicate that parts of RIIs may maintain large infiltration capacity even under heavy rainfall intensity. Ratio of infiltration to inflow in RIIs is evaluated to be 77.7- 91.3 %, showing high performance of RIIs as an infiltration measure. Yields in Kaga-Simizu Spring increase recently mainly due to installation of RIIs with higher infiltration capacity.

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Groundwater observation wells have been bored in 42 sites in Tokyo Metropolis by the Civil Engineering Support and Training Center of Tokyo Metropolitan Government. Large fluctuations of unconfined and confined groundwater levels in Tokyo were observed following the 2011 off the Pacific coast of Tohoku earthquake. In this study, the characteristics of unconfined and confined groundwater level fluctuation caused by the earthquake were investigated. As for the results, three and seven fluctuation patterns were identified for the unconfined and confined groundwater levels, respectively. The increase after short drawdown was a major pattern for the confined groundwater levels, whereas no change in pattern was observed for about 70% of the unconfined groundwater levels. The causes of those patterns were additionally outlined in this study.

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