[in Japanese]

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The Gifu prefecture spans over a steep central mountainous region of 3000 m in height from the zero meter area of the Nobi Plain, and it has suffered many natural disasters such as flood disasters and sediment-related disasters in conjunction with the high precipitation. In order to secure the quality and safety of the lives of the citizens, it is necessary to properly evaluate the risk of natural disasters, which is basically increasing due to climate change, and to anticipate the trend of decreasing population. Also, it is an urgent task to review social systems such as social infrastructure and land use. In this report, we report on efforts towards adaptation to climate change in Gifu, which is underway with the support of the Social Implementation Program on Climate Change Adaptation Technology (SI-CAT) of MEXT, Japan.

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This study aims to reveal the optimal spatial resolution of rainfall that is necessary for flood analysis using General Circulation Models (GCMs) and Regional Climate Models (RCMs) in climate change impact assessment study in local scale. Therefore, we made an attempt to evaluate the impact of different spatial resolution of rainfall on runoff analysis by using a distributed hydrological model and dynamical downscaling (DDS) experiments on selected past flood events. We are going to make a report these results in this conference.

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[in Japanese]

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In this study, MRI-AGCM 3.2 S (20km resolution) was used to assess the uncertainty of changes in land hydrological quantities due to climate change. 4 different future climate scenarios were generated for RCP8.5 using different SST change patterns (SST ensemble) in the Program for Risk Information on Climate Change (SOUSEI). Land surface model SiBUC was used to calculate surface energy and water balance, then distributed hydrological model Hydro-BEAM was used to calculate river discharge. Evapotranspiration increased almost in all models in Japan, but some of them have been on a downward trend, especially concentrated in the coastal areas of the Chugoku and Shikoku regions.I think that land use and soil differences are affecting, so we will investigate further the change in the amount of evapotranspiration for each land use.

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[in Japanese]

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The flood risk is supposed to increase due to climate change. On the other hand, it is expected that the population exposed to flood will decrease because of population decline. To consider effective flood control measurement over the long term, it is important to estimate flood damage considering both climate change and depopulation. In this research, first, we simulate the flood with current and future climate, and the flood damage is estimated. Then depopulation is reflected to the building area’s damage reduction. Finally, we estimate the impacts of climate change and depopulation on flood damage. Target basins are Omono river and Hiji river basin. The flood damage in Omono river decreases due to depopulation while that in Hiji river does not change because the impacts of climate change and depopulation are nearly the same. This suggests that the financial investment may not fulfill the flood control infrastructure’s expected effect.

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In this research, based on the analysis results, anyone aimed to establish a method to define the type of stone gravel. As a result of classification, it was thought that the Kurobe River and the Joganji River, and each river gravel belonged to granite, rhyolite, andesite and dioritic rock. Looking at the geology of the upstream part of each river based on the seamless geological map, the Kurobe River contains many granitic rocks such as andesite and diorite, the Joganji River is mostly composed of andesite and the upper part is granite or granodiorite It is included.Relatively good results were obtained for the rock type determination of the Kurobe River and the Joganji River in this study, so quantitative rock type determination on site can be performed using the combined analysis proposed in this paper.

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[in Japanese]

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The precipitation could provide a key information to foster understanding the system as it serves as the input in the hydrological modelling. The accurate long tern raingauge precipitation in the Mekong River is very limited; therefore, the main objective of this study is to compare the performances of various gridded precipitation datasets in hydrological simulation. The hydrological model used in this study is Rainfall-Runoff-Inundation (RRI) model. The input information of the RRI model were MERIT DEM, MODIS Land Cover, and JRA-55 evaporation. This study investigated the performance of five gridded precipitation datasets including APHRODITE, GPCC, PERSIANN-CDR, GSMaP Reanalysis Product (RNL), and TRMM (3B42V7). The results indicated that two gridded precipitation datasets (i.e. APHRODITE and GSMaP-RNL) had good quality and were suitable for hydrological modeling in the study area. Moreover, GSMaP dataset has a real-time version which may be suitable for real-time flood modeling as well as flood forecasting.

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[in Japanese]

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In this study, we analyze the spatial deviation of precipitation and precipitation frequency distribution in urban area of Osaka city and its surrounding area.

As a result, the following findings were obtained.

1) In western part of the urban areas, precipitation, frequency of rain , frequency of heavy rain (precipitation(mm/hour)≧5mm) was greater than that in the surrounding area, especially during the time zone during afternoon[Microsof1] .

2) In northwestern part of the urban areas, the tendency that precipitation and frequency of rain was greater than that of the surrounding areas[Microsof2] has been expanded over time

3) In the southwestern part of the urban areas, the tendency of precipitation and frequency of rain was lower than that of the surrounding areas[Microsof3] has been expanded over time.

From the above, we clarified that the impact of cities on weather is different inside the city.

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When X-band MP radar has observed high intensity rainfall area, QPE(Quantitative Precipitation Estimation) of X-band MP radar(X-MP) can't often observe with high accuracy. In fact, QPE of X-MP has underestimated against Rain-gauge data and C-band radar data at JMA Asakura by heavy rain in the Northern-Kyushu region on July 2017. So, this study is to clarify observation characteristics of X-MP using this event such as including high intensity rainfall area. This study has used horizontal polarization (Zh) and specific differential phase shift(Kdp) as polarization parameter of X-MP.

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Although the numerical weather models are effective methods for short-term prediction of rainfall from several hours to one day, it is impossible to avoid errors in thier prediction. It can be effective to apply the deep learning technology, which has made remarkable achievements in big data processing, for the correction of the numerical weather model output.

In this study, we has developed a method to correct the numerical weather model output by using deep learning techniques and output the rainfall amount.
In this research, we used a neural network (all nodes are connected) with a single intermediate layer in the “conventional machine learning” experiment. In the “deep learning” experiment, we used a convolution neural network with the 2 intermediate layers, data expansion, data selection and normalization. The decrease in loss function became smoother in the “deep learning” experiment, compared with “conventional machine learning” experiment.

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[in Japanese]

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Snow melt plays a crucial role in stream flows in cold regions. The melt water is generated when temperature rises in summer. Snow melt depends on various geographic and climatic conditions. Generally, two approaches are applied to quantify it i.e. energy balance and temperature-index. Energy balance method utilizes radiation, vapor pressure, wind speed, air temperature etc. to model the snow accumulation and melt. While temperature-index relies only on air temperature for this purpose. The energy balance approach is more accurate because it involves several climate parameters however, temperature-index has been more common because of less data requirements. Both methods of snow melt modeling have modifications as well like temperature-index has been considering solar radiation and wind speed. This study compares two temperature-index models (SPHY and CemaNeige) to estimate the snow melt in Astore river basin, Pakistan to describe the effects of model features in the estimation results.

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We discussed about the possibility of blowing snow observation using the X-band multi-parameter radar. We estimated the mass flux in the sky from the rain intensity observed by the radar and the Doppler wind speed. Next, the estimated mass flux was compared with mass flux observed on the ground. Here, we considered the advection effect of snowfall particles by the wind. As a result, it was suggested that we could observe blowing snow by using the X-band multi-parameter radar.

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Takayama field station of Gifu university locating Takayama city has continued meteorological observation from 1980. The station locates 1,342m alt. with annual mean temperature 7.2℃(2010-2016), annual precipitation 2,275mm(1980-2002) , and deepest snow depth over 1m condition, but it has electric power supply and its own staffs. The raingauge with heater was compared with the old overflow type raingauge in the winter season from 2016 to 2017. The power of heater was found to be insufficient. The additional heater equipped raingauge show 834mm precipitation from 11 Nov. 2017 to 30 Apr. 2018, while the overflow type showed 867mm. It means only 3.8% difference. And more the bulk method was used to evaluate the evaporation from heater type raingauge. It could explain most of difference.

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[in Japanese]

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This study is for using the IFAS model to apply to Flooding map and water resources of Chikugo River Basin which will be advantaged for every country especially the countries that have a high rate of flooding in rainy season such as Thailand, also for the further study of innovating model, flood analysis and solving plan as well.

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This study investigates the annual water balance for the mountainous Dam basins in Tohoku region and Hokkaido region which are snowy area on the site of Japan sea. The long-term hydrological model based on the hourly time step calculation were used for the data of 14 years. The model include the storage-discharge relations for flood flow and low flow, of which the parameters were optimized. Further more, the prediction of the future runoff was simulated using the GCM data of MIROC5, RCP8.5, for the period from 2080 to 2099. The result showed that the snowfall was conspicuously decreased and it will be affected to the water resources of the snowy region.

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In the tropical regions, demand of oil palm plantations makes a tropical region more vulnerable for floods. However, there is still a lack of research on flood analysis in a humid tropical river basin with deep weathered soil layer. This study examines three simulation conditions using RRI model; default parameter with 1m soil layer (Case 1); Case 1 considering evaporation (Case 2); Case 2 considering 5m soil layer. The model simulates rive discharge from 2012 to 2013 in Batanghari river basin (42,960 km²). Case 1 and Case 3 show good results with Nash Coefficient 0.77 and 0.72 respectively, whereas Case 2 overestimates 2.3 times as much discharge as those. However, Case 1 overestimates the peak discharge and Case 3 underestimated discharge overall with assumption that much more rainfall discharges as a subsurface flow in Case 3.The Case 1 also shows the maximum possible flood map at a basin scale.

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Distributed hydrological models have been developed such that simultaneously analyze rainfall runoff process and inundation process within a whole basin. This study proposes data assimilation method of river water levels based on the optimal interpolation method, aiming at real-time utilization of such models. This study estimates background error covariance matrix from multiple simulations beforehand and correlation decay based on distance, and updates the river water levels of whole basin with observed water levels. The method is applied to the Chikusa River basin in the Hyogo Prefecture for identical twin experiment. The predicted water levels show better agreement with true values both at gauged points and ungauged points.

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In order to detect ground ice melting in an isolated permafrost zone of Mongolia, groundwater age was determined around the Khangai Mountains by the use of transient tracers of tritium and chlorofluorocarbons (CFCs). Spring water samples were collected from August 2015 to April 2018, at several discharge sites including two thermokarst landscapes. Tritium and CFCs concentrations of the spring water discharges at the two thermokarst landscapes were very low. An atmospheric water budget analysis indicated that net precipitation (i.e. net recharge to the groundwater zone) was almost zero at the southern part of the Khangai Mountains. Thus, it was implied that one of the spring water at the thermokarst site contained large amount of ground ice-melt water. Additionally, because the CFCs concentrations at the thermokarst site have been decreasing gradually, the permafrost thawing is now progressive.

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The purpose of this research is to clarify the influence of land use change on the Kurobe River alluvial fan groundwater environment using land use data at seven seasons. In this study, we constructed groundwater model considering land use change, conducted analysis on Kurobe River alluvial fan, and evaluated the influence on groundwater environment. As a result of evaluating the influence of land use change on the groundwater environment by land use change data, the decrease of paddy field area and the increase of building, road, railway area caused the groundwater level to decrease It became clear that there was. In addition, as the area of the paddy field of the Kurobe River alluvial fan decreased by 1 km 2, it became clear that the annual average groundwater level decreased by 0.1 m, suggesting that the role of paddy field's maintenance function of groundwater environment plays a large role.

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This study reports how many items about Lake Biwa can we get from a web application: Climates of Global Lake basins or CGLB (Nakaegawa et al. 2015. Development of a web application for examining climate data of global lake basins: CGLB. Hydrological Research Letters, 9(4), 125-132) as a global lake database. By accessing CGLB, we can get the following hydrogolical properties of Lake Biwa: water area, basin area, coastal line length, mean and maximum depths, climatological surface meteorological variables on ClimatView developed by Japan Meteorological Agency, geographical distribution of the variables in a user-specific area on demand. The rankings of the properties of Lake Biwa are 256th in water area, 1351st in the coastal line length, 133rd in the volume, 9520 in the basin area, and 1439th in mean depth.

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Recently, various schemes related to solving water problems have been adopted. As these are common, there is planned management of basins. Therefore, it is necessary to accurately understand the state of the water area through monitoring and simulation. However, in the simulation of lake water temperature, it is very difficult to always keep the difference between observed value and calculated value within 1 ° C throughout the year, and as far as the authors know, such estimation method does not exist. Water temperature is an important water quality item in order to know the properties of lakes. Therefore, in this article, we aim to improve the estimation accuracy of lake water temperature with optimal interpolation method in heat budget method. And we studied on the annual number of days when the difference between the estimation result of water temperature and the mesuared value is within 1 ° C.

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1. INTRODUCTION
We began researching the Goto Islands from 2012,researching with Tsushima,Iki and Hirado,the features of each island including seasonal change and sea salt influence became clear.This time,we will clarify the water environment of each region from the relation with topography,altitude,land use etc.
2. RESULTS AND DIDCUSSION
On the Goto Islands is Ca-HCO₃ type in Fukue-jima,where the contribution of geology strongly appears,and nitric acid was detected more.In Iki the influence of agriculture appears in EC and TOC,but there is almost no effect of nitric acid.It is thought that there is a factor in paddy fields in Iki,and upland fields in Goto Islands.In addition,Iki has a relatively small change in water quality composition between the upstream and downstream parts,the slope of the riverbed is relatively loose,and the groundwater is used for agricultural water in the upstream part.Tsushima has a steep topography and the flow velocity of river water is fast and short,so EC and dissolved component concentrations are relatively low,the concentration increases with flowing down,and the concentration of calcium and bicarbonate ion also increases in water quality formation.In the Hirado Islands,especially Ca-HCO₃ type in the southern part, there are many points where the influence of the geology is thought to be large,and the concentration tends to rise with the falling,but the influence of sea salt is strong in Losundios island and Tsutayama Oshima It was done.In rainwater,EC tends to rise around March and October,and the pH tends to decline,but in water quality formation,the concentration of sulfate ion etc. is low and the relationship with transboundary contamination is not clear.

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