Launched in 2012 by Potsdam Institute for Climate Impact research, the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP) aims to establish a long-term, community-driven process of cross-sectoral climate-impact model. The three scenarios provided by ISI-MIP2b were implemented into the H08 model, a global scale water resource model.
The different general circulation models (GCMs) had significant effects on the outputs of the H08 model such as ET and river discharge. The effects of the RCPs were consistent across the different GCMs and the simulations using RCP6.0 always produced clear increasing (surface runoff, subsurface runoff, discharge, ET) or decreasing (water recharge) trends as well as extrema values. Future research directions include: (1) a region based data analysis to better characterize the effect of different combinations of GCMs and RCPs, (2) a Bayesian change-point analysis to compare change-point models, and (3) the investigation of the targeted 1.5 °C increase on global water resources.

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Bio-Energy with Carbon Capture and Storage (BECCS) is considered a promising technology to achieve the two-degree target. To produce a massive amount of bio-energy, a vast area of land is required. The land requirement could be reduced by applying irrigation and enhancing crop yield. We investigated the sustainability and effects of irrigation for massive production of bio-energy by using the global hydrological model H08 and simple land use scenarios.

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Demand for water resources has been increasing over last decades. Growing population, anthropogenic and climate change impacts have increased pressure on the water resources. In case of Central Asian (CA) countries, this has not only food availability issue but also huge economical impact, as it threatens security of water resources availability and possibilities to grow. Most of the rivers in the CA are snow-glacier fed originating in high mountains of one country (upstream) and fully utilized in another (downstream). Such disparity in river usage causes upstream to consider heavy investments in hydropower dams that increase social and political tension between counterparts. Thus water resources have been one of the limiting factors in economical growth, as they heavily relies on cash crops.
Over stress of the water resources availability it is important to define water efficiency (crop to water demand) and water availability for agricultural crops. Available productive area and its water demands will assist for planning efficient water management techniques and investigate appropriate irrigation methods to maximize outcomes of the main and market oriented crops. Therefore knowing crop water requirement is important step to water resources management under climate change scenarios. Current research suggests that river flow is decreasing and traditional irrigation strategies could not cover today's irrigation area. The analysis of water consumption by various types of crops will be important in the future projections. In this research water demand and analysis of the possible water resources distribution in the case study of Zeravshan river basin to achieve positive water management nexus for both countries were analyzed.

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Drought indices are expected to use for evaluation of quantitative goal of a water plan and drought severity of a drought event. However, no index can provide such comparison of different hydro-climate regions with the same scale, such as comparison between Tokyo Metropolitan area and California. From this viewpoint, we investigated the effectiveness of PDSI by applying to a drought event in the Tone River system for the purpose of comparison of quantitative goal of a water plan and drought severity of a drought event.

In addition to PDSI, deviation of storage rate and rainfall in the unit of month are applied as other indices. Considering river intake reduction rate as drought severity, we analyzed correlations between these three indices and drought severity. The results shows no correlation for any index and suggest any index are not appropriate for drought index.

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For areas that are urbanized rapidly, the practice of Low Impact Development (LID) has gained an important place in stormwater management and urban planning due to its capability and beneficial effects in restoring the original hydrological cycle. The performances of LID alternatives can vary substantially due to different climate conditions. In this study, the SWMM 5 model was applied to simulate the performances on water balance and flood control of these LID alternatives by using 17 years GSMaP rainfall data (from 2000 to 2016) for Tianjin City. A new evaluation method was proposed in this study including the efficiency index for water balance (Iw).It showed that rain harvest system presents comparative advantage in controlling water balance for high imperious urbanized area, then it is porous pavement, and the last is bio retention. This information about the performances of each LID alternative can help decision makers develop a better storm management strategy

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Reconstruction of historical climate is essential for a better understanding of the future climate. However, only a limited number of observations are available before the 19^th century. Historical documents such as personal diary records can be used as an alternative. Even though they have higher temporal resolution respect to other proxies, it is quite challenging to incorporate that information in climate model due to the high uncertainty present in those data. Here we use the Global Spectral Model (GSM) of National Centres for Environmental Prediction (NCEP) as the climate model, along with a local ensemble transformed Kalman filter (LETKF) as a data assimilation technique to investigate the possibility of assimilating different climate variables through idealize experiments. In order to investigate the influence of uncertainties associated with the historical documentations deteriorated JMA data were used. We could show that it is possible to improve the model performance by assimilating various information such as cloud amount, precipitation, and solar radiation.

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In this study, we used MRI-AGCM 3.2 S resolution of 20 km, which is a climate model provided by Program for Risk Information on Climate Change, to input to the land surface model SiBUC, and for multiple future scenarios, assessed the uncertainty of changes in land hydrological quantities due to climate change. We used SiBUC to calculate vertical water balance and used Hydro-BEAM to track spatial and temporal fluctuations. In the future, precipitation and rainfall were uncertainty around Aichi Prefecture and western Japan. At the future flow, in winter, the value changes dramatically, but the difference between models was small, so uncertainty was small. On the other hand, in summer, there were variations between models in any river and uncertainty was large.

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As climate change may increase the risk of flood and drought, research on hydrological prediction becomes more important. This study was performed to evaluate the effect of dynamical downscaling for future flood and drought prediction. We analysed future hydrology in the Yodo river basin using Global Climate Model (GCM) output, meteorological model and hydrological model. The impacts of dynamical downscaling was evaluated by comparing two cases: one with raw GCM output and the other with dynamically downscaled output. In the Yodo river basin, dynamical dowscaling seems to enable to reproduce local climate, but we have to pay attention to the characteristics of models and the validity of results.

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In 2016, Vietnam was hit by the most affected area due to the combination of low flow, rainfall shortage, and saline intrusion. This study calculated standardized drought indices as Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI), and Standardized Precipitation Evapotranspiration Index (SPEI) for different time periods of 1 month, 3 months, 6 months, And 12 months. Afterwards, the results of as historical drought impacts as the influence, The promising results calculated as SDI-6, SPI-6 (January to June) and the number of hours recording salt concentration higher than 1 ppt for the dry season (January to May) were used to carry regression analysis.

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Material circulation such as carbon and nitrogen is important for grasping the dynamics of the earth system, and the material transport process by rivers is under the influence of river water temperature. In order to carry out extrapolation such as future prediction and anthropogenic impact estimation, this study developed an Eulerian deterministic model to calculate river water temperature on a global scale. This model solves one dimensional mass, momentum, heat conservation laws. Heat fluxes is calculated using meteorological forcing data. The formation and melting process of river ice is calculated by mass and heat conservation law. Validation of this model was carried out by global monthly mean river water temperature data. As a result the reproducibility of it is improved by considering the heat balance on floodplain in low latitude area and river ice in high latitude area ice.

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Gia Lai province which is one of the important areas for coffee production in Vietnam has been frequently affected by droughts. However, very few studies on droughts have been conducted for this province. This study studied drought in Gia Lai province by using 2 drought indices. They are Standardized Precipitation Index (SPI) and Crop Drought Index (CDI). Then the relationship between some drought indices and crop yield residuals (spring paddy rice and coffee) of Gia Lai province for the period of 2000 - 2010 was investigated to determine the appropriate index for monitoring agricultural drought. The results show that CDI is better than SPI as it could capture the drought events and had a strong correlation with crop yield residuals. CDI was proved that its values in the mid stage of crop growth season can be used to detect agricultural drought in the study area.

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The long-term effect of flood by typhoon No. 9 2009 in Sayo, Hyogo are investigated. Generally, the long-term influence of flood in mountainous region in Japan has not been studied well. It is important to consider such influence because the impact of flood could be catastrophic for those areas where depopulation is significantly on going. The effects are estimated by statistical analysis of social indices, questionnaire survey, and interviews for local government and communities. The results indicate that the influence of flood was substantially lower than other influence of changes such as depopulation or population aging.

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We investigated the precipitation prediction of local heavy rainfalls from the relationship between the reflection intensity of PHASED-ARRAY-WEATHER-RADER(PAWR, Z) and XRAIN(R). The studied rainfall was the thunderstorm-related heavy rain that continued for approximately three hours and produced 115mm/hr precipitation at the peak in the Ueikeda ground observatory. The results are summarized as follows: (1)Reflection intensity more than 50dBz occured 48 minutes before the heavy rain warning was announced, and the indication of the heavy rainfall can be confirmed. (2)The correlation coefficients between PAWR(Z) and XRAIN(R) were upper than 0.8, and the case of 2,000m~3,000m altitude that equaled precedence time four minutes was the highest. (3)Two equations were made between PAWR(Z) and XRAIN(R) because the change-point happened when PAWR(Z) was 30dbz. The precipitaion which was predicted from PAWR(Z) by using these equations, XRAIN(R), High-resolution Precipitation Nowcasts, and Very Short-range Forecasts of Precipitation were compared. The predicted value and XRAIN(R) were the almost same rain wave pattern. On the other hand, the current predictive methods could not make the relationship with XRAIN(R) exactly.

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We carried out the ground-based direct intensive observation of solid precipitation particles by Ground-based Particle Image and Mass Measurement System at Kanazawa during 2016-2017 winter season. During the intensive observation period, GPM/DPR overpassed and observed the snow event in the early morning of January 25, 2017. G-PIMMS can capture particle images by CCD cameras and measure particle weight by the electronic balance. Two G-PIMMSs were installed at Ishikawa Prefectural University and Kanazawa University, respectively. Major particles observed at Ishikawa Prefectural University were graupel, while they were snowflakes at Kanazawa University. According to the algorithm released on May 2017, the former was classified as “convective”, the latter “stratiform”. It was a reasonable result considering cloud microphysical processes in the cloud.

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The analysis of vortex tube of torrential rainfall is conducted by urban meteorological LES model.Vertical vortex tube is made from horizontal vortex tube, so this analysis focuses on the urban effect to horizontal and vertical vortex tube.

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To fix paralax errors in Himawari - 8 observation, a parallax equation is calibrated by 16 Humawari - 8 and XRAIN data to detect the generation of Guerilla - heavy rainfall by using real observation result. (Rapid Development Cumulus Area) RDCA (Rapid Development Cumulus Area That concepts cumulus cloud development that area 10 km ² and within one hour. That 's all, it' s not exactly the same as that of the concept, Rapid Development Cumulus Area (RDCA) concept, Rapid Development Cumulus Area (RDCA) And Radar echoes, The RDCA concept can detect detect signal of rainfall earlier than radar first echo.

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Young Researchers Association of Japan Society of Hydrology and Water Resources (JSHWR) (hereinafter, YRA) is a research group composed of young researchers in their twenties to thirties. YRA has continued interdisciplinary discussions among several research fields and exchanged opinions on interdisciplinary research collaboration since 2009. As we found these activities are helpful for gaining new perspectives and for making progress in our own research, it is essential to expand interdisciplinary discussions with more new members. At the same time, we wondered how interdisciplinary collaboration in the field of hydrology and water resources is regarded and how much these activities can be expanded. On these backgrounds, YRA 2016 conducted 1) an interdisciplinary seminar among young researchers, 2) a research presentation symposium, and 3) a questionnaire survey on awareness of JSHWR members. As the result, we deepened our understandings on research works of each member and ideas on interdisciplinarity of JSHWR members.

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Interdisciplinary approaches are necessary to solve issues in hilly and mountainous area since the impact of depopulation as well as climate change is important in those areas. A research group which is composed of members from various research filed aims to study those issues with local government and communities. The group conducted three topics; 1) the investigation about long-term impact of flood; 2) the investigation of land-use change in the frequently flooded area; 3) the workshop about small ponds for agriculture. While the discussion is still on going, we found some important keywords which would be the core of our future activities.

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Repeated cycles of water diversion from and return flow to main channels have substantial impacts on the flow regimes of watersheds containing extensive areas of irrigated paddy fields. The stable isotopes of water are the major tracers used to decipher hydrological processes; however, they cannot be used to track the fate of irrigated water because of mixing of precipitation and irrigation water and fractionation during evaporation. The ratio of strontium isotopes (⁸⁷Sr/⁸⁶Sr) can be used to complement the shortcomings of the stable isotopes of water because it has the following characteristics: temporal changes in the Sr ratio can be ignored, and the effects of fractionation are negligible. The applicability of Sr ratio as a hydrological tracer in irrigated watersheds has not yet been examined. Our study shows that the Sr ratio-1/Sr concentration diagram can be used to elucidate the mixing ratio of the water from the surface and subsurface flow paths.

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When the soil is wet enough, only the rainfall in the flood arrival time affect to the peak discharge. In Japan, plan rainfall duration is too long while flood arrival time is generally short.
Firtsly we investigated in the flood arrival time of the upper areas of the discharge observatory in A-class rivers in Japan, and researched the relationship with geographical characteristics; and we revealed that the mean flood arrival time can be represented by the length of river channel. Nextly we compared the flood arrival time and the plan rainfall duration in each basin, and found out that in around 90% basins plan rainfall duration is twice as long as the mean flood arrival time.

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For more accurate real-time flood forecasting by the Chikuma River Flood Forecasting System in operation, we developed a flood forecasting model and reconstructed forecasting of a past big flood event for the Shionada basin with a catchment of 1,179 km². Parameter tuning to be able simulate the timing of peak discharge occurrence reduced relative error of forecasted discharges. Without parameter tuning, remove of feedback contributed to reduction of forecasted discharge.

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This paper describes flood inundation analysis in Sonobe River Basin, Kyoto Prefecture. Flood and inundation often occurs in Sonobe Basin, which is located in the middle of Katsura River Basin, because of a narrow pass at Yokota. Since there was not enough data such as river width in the Sonobe River Basin, we measured in this study. Rainfall-Runoff-Inundation(RRI) Model is used for flood inundation analysis. The event focused in this paper is Typhoon Man-yi flood, September 2013.Regarding water depth and flooding area, we were able to obtain reasonable results.

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This study demonstrated to estimate basin-scale permeability in 126 watersheds of Hokkaido Island, Japan, through a combination of recession analysis and the hydrogeological model. The recession analysis was performed by the log-log plot methods of daily averaged river discharges in each basin. The logarithmic ratio of coefficients of recession was ranged in three order of magnitude and the range was related to the basin-scale permeability. The estimated permeability was higher in the Holocene and the upper Pleistocene basins than in the Neogene and the older basins. The permeability in the Holocene and the upper Pleistocene basins was also variable due to the geologic heterogeneity. The permeability in the basements was relatively high probably because the weathered layers were thick enough as the subsurface aquifer.

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It is required to give appropriate initial soil moisture and water table depth to hydrological simulation because those reduce uncertainly of hydrological simulation. It has been discussed that soil moisture have a connection with groundwater. Essence of initialization is to answer that how equilibrium soil moisture and water table depth is determined by climate conditions. In this study, new definition of equilibrium soil moisture and water table depth determined by climate condition was proposed and accuracy of equilibrium water table depth and runoff on land surface model,MAT-GW were validated. Relative change of climatology is defined as a new criteria of equilibrium condition. In the results, accuracy of water table depth within 20 percent from observation is 9.4 percent of total target grids. Annual Runoff at seven rivers were validated and those match with observation. The area MAT-GW overestimate or underestimate water table depth will be examined by considering elevation of site.

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Pollution assessment was performed by using NO₃^-, NO₂^-, coprostanol (5β(H)-Cholestan-3β-ol), and cholestanol (5α(H)-Cholestan-3β-ol) at the 42 sampling points in the rivers in Shimabara and Unzen. NO₂^- was detected at the 2 sampling points and exceeded 0.04 mg L^-1. NO₃-N + NO₂-N concentrations exceeded 10 mg L^-1 at the 18 sampling points. The highest concentration was 27.5 mg L^-1. High concentrations of NO₃-N were observed in the northern parts of the study area. Coprostanol concentrations at the 8 sampling points exceeded 700 ng L^-1 (Australian drinking water standard). Coprostanol has a potential to distinguish the nitrate pollution sources. The sterols ratio (5β/(5β+5α)) exceeded 0.5 at the 18 sampling points. It revealed that fecal pollution occurred.

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Shimabara city has been experiencing serious nitrate pollution in groundwater. To evaluate nitrate pollution and water chemistry in surface water, water samples were collected at the 42 sampling points in Shimabara including a part of Unzen city. Spatial distribution of water chemistry was assessed by describing hexa and trilinear diagrams using major ions concentrations. Most of the samples showed Ca-HCO₃ or Ca-(NO₃+SO₄). It corresponds to groundwater chemistry. Some samples were classified into characteristic water types such as Na-Cl, (Na+K)-HCO₃, and Ca-Cl. This results represent sea water mixing and anthropogenic pollution. At the upstream of Nishi river, although water chemistry was Ca-HCO₃, ions concentrations were higher than that of the other rivers. It indicates that this site was affected by the peripheral anthropogenic activities.

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To evaluate the environmental fate of radiocesium, it is necessary to predict transport of soil particles in rainfall-runoff process. The behaviors of radiocesium adsorbed to eroded soil particles in the Abukuma river basin, located 30-100 km west of Fukushima Daiichi Nuclear Power Plant, were analyzed by a water quality model. Calculation of lateral inflow load was performed in two cases: one using L-Q equation and the other using Universal Soil Loss Equation (USLE). Results show that 137Cs transported to the ocean in a period from August 10, 2011 to May 11, 2012 was 4070 GBq and 8160 GBq in the cases with L-Q equation and USLE, respectively.

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