River Basins In Japan Research Articles

Distributed specific sediment yield estimations in Japan attributed to extreme-rainfall-induced slope failures under a changing climate

Abstract. The objective of this study was to estimate the potential sediment yield distribution in Japan attributed to extreme-rainfall-induced slope failures in the future. For this purpose, a regression relationship between the slope failure probability and the subsequent sediment yield was developed by using sediment yield observations from 59 dams throughout Japan. The slope failure probability accounts for the effects of topography (as relief energy), geology and hydro-climate variations (hydraulic gradient changes due to extreme rainfall variations) and determines the potential slope failure occurrence with a 1-km resolution. The applicability of the developed relationship was then validated by comparing the simulated and observed sediment yields in another 43 dams. To incorporate the effects of a changing climate, extreme rainfall variations were estimated by using two climate change scenarios (the MRI-RCM20 Ver.2 model A2 scenario and the MIROC A1B scenario) for the future and by accounting for the slope failure probability through the effect of extreme rainfall on the hydraulic gradient. Finally, the developed slope failure hazard-sediment yield relationship was employed to estimate the potential sediment yield distribution under a changing climate in Japan. Time series analyses of annual sediment yields covering 15–20 years in 59 dams reveal that extreme sedimentation events have a high probability of occurring on average every 5–7 years. Therefore, the extreme-rainfall-induced slope failure probability with a five-year return period has a statistically robust relationship with specific sediment yield observations (with r2 = 0.65). The verification demonstrated that the model is effective for use in simulating specific sediment yields with r2 = 0.74. The results of the GCM scenarios suggest that the sediment yield issue will be critical in Japan in the future. When the spatially averaged sediment yield for all of Japan is considered, both scenarios produced an approximately 17–18% increase around the first half of the 21st century as compared to the present climate. For the second half of the century, the MIROC and MRI-RCM20 scenarios predict increased sediment yields of 22% and 14%, respectively, as compared to present climate estimations. On a regional scale, both scenarios identified several common areas prone to increased sediment yields in the future. Substantially higher specific sediment yield changes (over 1000 m3/km2/year) were estimated for the Hokuriku, Kinki and Shikoku regions. Out of 105 river basins in Japan, 96 will have an increasing trend of sediment yield under a changing climate, according to the predictions. Among them, five river basins will experience an increase of more than 90% of the present sediment yield in the future. This study is therefore expected to guide decision-makers in identifying the basins that are prone to sedimentation hazard under a changing climate in order to prepare and implement appropriate mitigation measures to cope with the impacts.

DEVELOPMENT OF A STATISTICAL BIAS CORRECTION METHOD FOR DAILY PRECIPITATION DATA OF GCM20

In this study, a simple statistical method is developed to correct bias in the precipitation simulated by GCM20, an atmospheric general circulation model with 20 km spatial resolution developed by the Meteorological Research Institute. The method primarily aims to correct intensity of GCM20 daily precipitation samples to express both seasonal patterns and extreme values appropriately. The basic idea of the bias correction is to adjust the probability distribution of GCM20 daily precipitation to that of its observed counterparts. To examine the correction performance the proposed method is applied to the Yoshino River basin in Japan. The results show that it appropriately corrects the GCM20 bias in both monthly and extreme daily precipitation.

CONSTRUCTION OF FLOOD RUNOFF MODEL UTILIZING RAINFALL FORECASTS FROM JMA

Real-time flood forecasting needs accurate rainfall forecast, because Japanese river basins have a small area and steep topography that cause rapid rainfall-runoff. This paper aims to improve the accuracy of flood forecasting, considering recent advancement of short-term rainfall forecasts provided from the Japan Meteorological Agency (JMA). The method proposed here is to combine predictions by the Meso Scale Model with other predictions such as the Precipitation Nowcast and the Very Short Range Forecast. The results of its application to the Okawa River basin in Miyagi Prefecture indicate improvement in flood forecasting accuracy. Since this method is easy-to-use and effective, it would be useful for the improvement of flood forecasting in other river basins in Japan.

THE CUMULATIVE DISTRIBUTION CURVE FOR DRAINAGE AREAS

In this paper, an equation for describing the cumulative area distribution for river basins is theoretically derived by using a link magnitude law of drainage area and the bifurcation structures of channel networks obtained from Horton’s laws. Analyzed here are 109 large river basins in Japan, which have a wide variety of features in size, geology and climate. The GIS analysis of DEMs for the 109 basins shows that the Shreve’s link magnitude law of drainage areas has a universal scaling property in all of the 109 river basins with the same constant slope. As for the cumulative area distribution, previous researches in GIS analysis and theoretical examination have revealed that it has a power law distribution with a constant slope in lower stream orders. The equation derived here can represent the cumulative area distribution over the whole river basins including the portion of the power law distribution.

Source of N-nitrosodimethylamine in river waters of the upper Tone River basin in Japan

The presence of N-nitrosodimethylamine (NDMA) in the Hirose River and its tributaries, located in the upper Tone River basin, in the Kanto region of Japan, was investigated. NDMA was detected at high levels in the Arato River, one of the tributaries of the Hirose River, at high concentrations (up to 2,100 ng/L). Due to the confluence of the Arato River, NDMA concentration in the Hirose River increased (up to 61 ng/L). The NDMA in the Arato River was due to industrial discharge from a livestock processing plant located near the river. There were three discharges at the plant, with NDMA concentrations of 78, 11, and 33,000 ng/L. The industrial discharges from the livestock processing plant did not contain significant amounts of NDMA precursors on chloramination. On the other hand, sewage effluent was shown to contain NDMA precursors. The amounts of NDMA precursors in the sewage effluent that were rapidly transformed into NDMA were considered to be lower than those slowly transformed into NDMA.

A GIS-based Distributed Parameter Model for Rainfall Runoff Calculation using Arc Hydro Tool and Curve Number Method for Chikugo River Basin in Japan

A GIS-based Distributed Parameter Model for Rainfall Runoff Calculation using Arc Hydro Tool and Curve Number Method for Chikugo River Basin in Japan

Decision support for dam release during floods using a distributed biosphere hydrological model driven by quantitative precipitation forecasts

This study proposes a decision support system for real‐time dam operation during heavy rainfall. It uses an operational mesoscale quantitative precipitation forecast (QPF) to force a hydrological model and considers the forecast error from the previous time step, which is introduced as a perturbation range applied to the most recent QPF. A weighting module accounts for the location, intensity, and extent of the error. Missing precipitation intensities within contributing areas and information from surrounding areas can both be considered. Forecast error is defined as the ratio of QPF to the observed precipitation within an evaluation zone (sub‐basin, basin, buffer, or total domain). An objective function is established to minimize the flood volume at control points downstream and to maximize reservoir storage. The decision variables are the dam releases, which are constrained to the ensemble streamflow's information. A prototype was applied to one of the most important river basins in Japan, the Tone reservoir system. The efficiency of the approach was evident in reduced flood peaks downstream and increased water storage. The results from three events indicate that the developed decision support system is feasible for real‐life dam operation.

Estimating Plecoglossus altivelis altivelis migration using a mass balance model expressed by hydrological distribution parameters in a major limpid river basin in Japan

We examined the influence of several hydrological and meteorological parameters on the migratory movements of ayu Plecoglossus altivelis altivelis in central Japan. When comprehensively evaluating rivers and ayu behaviour on a catchment scale, the subjects of analysis typically include human activities and hydrological and meteorological phenomena. However, limiting analyses to such factors may be too restrictive when human activities are being conducted. Accordingly, we incorporated a biological viewpoint into the evaluation method, analysing hydrological data (river discharge, river water temperature, sea water temperature) to determine watershed characteristics and examining the relationship between these characteristics and the habitat conditions of ayu. Then we constructed a numerical model for ayu migratory runs that incorporated ayu ecology and watershed characteristics. Analyses of ayu movements from a lower estuarine dam demonstrated that downstream displacements were associated with high water flows of more than 200 m 3 s −1 at the beginning of summer. We conclude that it is important to consider the effects of environmental parameters on the movements of different fish species to understand the causes of spatial variation in fish distribution in lowland rivers.

Intense Rainfalls on August 17, 1968 over the Kiso-Hida and Nagara River Basin in Japan Associated with Intrusion of Middle Tropospheric Dry Airs over the Low-level Moist Belt

The synoptic-scale condition related to the intense rainfalls on August 17, 1968, over the Kiso?Hida and Nagara River Basin in the central part of Japan is studied by using European Center for Medium-Range Weather Forecasts 40-year reanalysis data and upper, synoptic-surface, local rain-gauge observation data and satellite cloud images.The intense rainfalls occurred within a long cloud belt formed with a low-level moist belt (LMB), which had formed along the northwestern rim of the North Pacific subtropical anticyclone (NPSA). The LMB was sustained by large-scale moisture transport along the northern rim of the NPSA and mesoscale northward moisture transport along a small anticyclone embedded in the NPSA. In the lower and middle troposphere, dry air spread over the Japan Sea after the passage of a severe tropical storm (STS) over the Japan Sea owing to the prevailing westerlies to the southwest of the STS. The northern edge of the LMB was bounded by the dry air. The northern boundary of the LMB was signified as the dry front because of the strong moisture gradient and very weak thermal gradient.Intense rainfalls occurred in the cloud belt, at a distance of ∼1200 km south of the STS, over the river basin where the large-scale and the mesoscale moist flows converged in association with the orographic convergence. Intense convective rainfalls were accompanied by the increase in the convective instability due to the southeastward intrusion of the middle tropospheric dry air over the LMB. Significant low-level jet stream and mesoscale depression were not found around the intense rainfall area.

多摩川流域における外用医薬品の実態調査と塩素処理性の評価

In recent years, pharmaceuticals and their metabolites have been detected in aquatic environments, and their risk management has become an emergent concern about the environment, water supply and sewerage. In particular, pharmaceuticals for external use may be discharged in large amounts into aquatic environments. In this study, we monitored three pharmaceuticals for external use, namely, crotamiton, lidocaine and diethyltoluamide (DEET), in water samples (i.e., river water, effluent of wastewater treatment plants (WWTPs), and groundwater) from the Tama river basin in Japan. The calculated loads of the target compounds in effluent samples from WWTPs in the Tama river basin were comparable to those in the river water samples, indicating that the major source of the compounds is wastewater effluent. The loads in the WWTP effluent samples varied seasonally depending on their application. The removal efficiency of groundwater recharge varied among the target compounds. Lidocaine and DEET were removed more efficiently than crotamiton. The removal efficiency of chlorination also varied among the target compounds. Although negligible amounts of crotamiton and DEET were removed, lidocaine was almost completely removed within 1 hour.

Diffuse-source particulate nitrogen and phosphorus pollution modeling in Yata River Basin in Japan using process-based WEP model coupled with a sediment erosion-transport model

Diffuse-source particulate nitrogen and phosphorus pollution modeling in Yata River Basin in Japan using process-based WEP model coupled with a sediment erosion-transport model

Using remotely sensed imagery to estimate potential annual pollutant loads in river basins

Land cover changes around river basins have caused serious environmental degradation in global surface water areas, in which the direct monitoring and numerical modeling is inherently difficult. Prediction of pollutant loads is therefore crucial to river environmental management under the impact of climate change and intensified human activities. This research analyzed the relationship between land cover types estimated from NOAA Advanced Very High Resolution Radiometer (AVHRR) imagery and the potential annual pollutant loads of river basins in Japan. Then an empirical approach, which estimates annual pollutant loads directly from satellite imagery and hydrological data, was investigated. Six water quality indicators were examined, including total nitrogen (TN), total phosphorus (TP), suspended sediment (SS), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and Dissolved Oxygen (DO). The pollutant loads of TN, TP, SS, BOD, COD, and DO were then estimated for 30 river basins in Japan. Results show that the proposed simulation technique can be used to predict the pollutant loads of river basins in Japan. These results may be useful in establishing total maximum annual pollutant loads and developing best management strategies for surface water pollution at river basin scale.

Integrated biogeochemical modelling of nitrogen load from anthropogenic and natural sources in Japan

This study proposed an integrated biogeochemical modelling of nitrogen loads from anthropogenic and natural sources in Japan. Firstly, the nitrogen load (NL) from different sources such as crop, livestock, industrial plant, urban and rural resident was calculated by using datasets of fertilizer utilization, population distribution, land use map, and social census. Then, the nitrate leaching from soil layers in farmland, grassland and natural conditions was calculated by using a terrestrial nitrogen cycle model (TNCM). The Total Runoff Integrating Pathways (TRIP) was used to transport nitrogen from natural and anthropogenic sources through river channels, as well as collect and route nitrogen to the river mouths. The forcing meteorological and hydrological data is a 30-year (1976–2005) dataset for Japan which were obtained by the land surface model, Minimal Advanced Treatments of Surface Interaction and Runoff (MATSIRO). For the model validation, we collected total nitrogen (TN) concentration data from 59 rivers in Japan. As a comparison result, calculated TN concentration values were in good agreement with the observed ones, which shows the reliability of the proposed model. Finally, the TN loads from point and nonpoint sources were summarized and evaluated for 59 river basins in Japan. The proposed modelling framework can be used as a tool for quantitative evaluation of nitrogen load in terrestrial ecosystems at a national scale. The connection to land use and climate data provides a possibility to use this model for analysis of climate change and land use change impacts on hydrology and water quality.

Mapping the potential annual total nitrogen load in the river basins of Japan with remotely sensed imagery

The increase of nutrient loads such as nitrogen and phosphorus to a river due to land cover changes in surrounding areas has been one of the major sources of water pollution or eutrophication. Monitoring the influent nutrient load from river basins to rivers is now crucial in the management of river basin environments. The monitoring is not easy, however, because it requires spatial and temporal measurement tools for land cover changes in the river basin and water qualities, and also it requires models relating them. In this study, we first analyzed the relation between the land cover types estimated from monthly maximum Normalized Difference Vegetation Index (NDVI) imagery calculated from NOAA Advanced Very High Resolution Radiometer (AVHRR) imagery and the annual total nitrogen load discharged from river basins. We found that the runoff load factor from urban areas is higher than those of forested areas. We also found that the impacts of land cover such as plantation and field weed communities on the total nitrogen load of each river are higher than the impacts of other land cover types such as Beech and Camellia japonica community type. Finally, we produced two advanced maps of the potential annual total nitrogen load (PTNL) index and the potential annual total nitrogen load for each river basin area (PTNL/area) index by considering the relationship between the land cover types and the annual total nitrogen load discharged from river basins in Japan. The PTNL map will be useful for the risk assessment of total nitrogen load impact on lakes and the sea through rivers from each basin. The PTNL/area index, which considers the effects of river basin areas, will allow evaluation of the state of river basins.

Assessment of global warming impacts on water resources and ecology of a river basin in Japan

Global warming may cause serious problems in the world. However, the influence of water-related factors, such as water resources and basin ecology, due to global warming has not been comprehensively investigated. In this study, a distributed hydrological and environmental model is applied to assess the impacts of global warming on water resources and ecology of the Nagara River in Japan. With GCM outputs for the two periods, 1979 to 2000 and 2079 to 2100, the model simulation mainly reveals four aspects of the influences of global warming: (i) precipitation and streamflow discharge increase in summer; (ii) air temperature and water temperature rise; (iii) fish habitats are improved, except in summer; and (iv) the boundaries of the crop and vegetation move to higher elevations.

Potential Changes in Extreme Events Under Global Climate Change

Climate-related disasters are a serious problem in Asia. Advances in the understanding of meteorology and in the development of monitoring and forecasting systems have enhanced early warning systems, contributing immensely to reducing fatalities resulting from typhoons, cyclones, and floods. The frequency of extreme events causing water-related disasters has increased, however, over the last decade and may grow in the future due to anthropogenic activity. The sections that follow introduce two recent efforts in hydrologic projection in Asia. Time-slice ensemble experiments using a high-resolution (T106) atmospheric general circulation model (AGCM) on the earth simulator revealed changes in the South Asian summer monsoon resulting from climate change. Model results under global warming conditions suggest increases in mean and extreme precipitation during the Asian summer monsoon. increases generally attributed to greater atmospheric moisture content. a thermodynamic change. Dynamic changes limit the intensification of mean precipitation. Enhanced extreme precipitation over land in South Asia arises from dynamic rather than thermodynamic changes. The impact of global warming on heavy precipitation features and flood risks in the Tama River basin in Japan is addressed using 12 atmosphere-ocean coupled general circulation models (AOGCMs). Multi-model ensemble average 200-year quantiles in Tokyo from 2050 to 2300 under Intergovernmental Panel on Climate Changes (IPCC) Special Reports on Emissions Scenarios (SRES) A1B scenario climate conditions were 1.07-1.20 times greater than that under present climate conditions. A 200-year quantile extreme event in the present occurs in much shorter return periods in the A1B scenario. High-water discharge in the basin rose by 10%-26% and flood volume increased by 46%-131% for precipitation in a 200-year return period. The risk of flooding in the basin is thus, even though the increase of extreme precipitation is not substantial, projected to be much higher than that presently estimated.

Occurrence of 70 pharmaceutical and personal care products in Tone River basin in Japan

The occurrence of 70 pharmaceutical and personal care products (PPCPs) was investigated in the Tone River. The river has the largest basin in Japan, and the water is utilized not only for farming, but also as a source of water supply. One day in both January and October 2006, surface waters in the river and its tributaries and effluents from sewage treatment plants (STPs) directly discharging into the Tone River were collected, the location of which ranged over 150 km along the river. The 70 PPCPs in the samples were concentrated by solid phase cartridge and were measured by LC-MS/MS using three analytical methods. Fifty-seven PPCPs were detected in one or more samples. Bezafibrate, caffeine, carbamazepine, clarithromycin, crotamiton and sulpiride were frequently detected. Mass flow profiles of some PPCPs (e.g., crotamiton) were comparable to cumulative inhabitants in the basin, suggesting that these PPCPs could be markers of population. Total load of each PPCP into the basin from upstream, the tributaries, and the STPs were calculated. The contribution of selected PPCPs from the tributaries with lower sewerage system coverage was dominant compared to those from upstream and the STPs, suggesting the installation of sewerage systems is necessary to reduce the load of PPCPs in the Tone River basin.

CHARACTERISTICS OF SEDIMENT TRANSPORT AND RIVER BASINS DISCUSSED ON HYPSOMETRIC CURVES

Characteristics of sediment transport in a drainage basin are discussed from a concept of sediment transport potential estimated by a hypsometric integral of landform weighted with annual precipitation, as a measure of potential energy. A hypsometric curve indicates altitude distribution of the drainage basin topography, and characterizes landform, which resulted from geological and meteorological actions. The sediment transport potentials show high correlation with sedimentation volumes in dam reservoirs in the Kiso river basin, and those of 33 major river basins in Japan prove to be able to explain a generally accepted tendency of sediment yields theory well, and clarify that sediment transport is related with a development of alluvial plain.

Causes of death and renal tubular dysfunction in residents exposed to cadmium in the environment

Objectives: To clarify the causes of death of residents with renal tubular dysfunction induced by cadmium (Cd) in the environment. Methods: A 15 year follow up study was performed with...

A physically based distributed subsurface–surface flow dynamics model for forested mountainous catchments

AbstractThis study was designed to develop a physically based hydrological model to describe the hydrological processes within forested mountainous river basins. The model describes the relationships between hydrological fluxes and catchment characteristics that are influenced by topography and land cover. Hydrological processes representative of temperate basins in steep terrain that are incorporated in the model include intercepted rainfall, evaporation, transpiration, infiltration into macropores, partitioning between preferential flow and soil matrix flow, percolation, capillary rise, surface flow (saturation‐excess and return flow), subsurface flow (preferential subsurface flow and baseflow) and spatial water‐table dynamics. The soil–vegetation–atmosphere transfer scheme used was the single‐layer Penman–Monteith model, although a two‐layer model was also provided. The catchment characteristics include topography (elevation, topographic indices), slope and contributing area, where a digital elevation model provided flow direction on the steepest gradient flow path. The hydrological fluxes and catchment characteristics are modelled based on the variable source‐area concept, which defines the dynamics of the watershed response. Flow generated on land for each sub‐basin is routed to the river channel by a kinematic wave model. In the river channel, the combined flows from sub‐basins are routed by the Muskingum–Cunge model to the river outlet; these comprise inputs to the river downstream. The model was applied to the Hikimi river basin in Japan. Spatial decadal values of the normalized difference vegetation index and leaf area index were used for the yearly simulations. Results were satisfactory, as indicated by model efficiency criteria, and analysis showed that the rainfall input is not representative of the orographic lifting induced rainfall in the mountainous Hikimi river basin. Also, a simple representation of the effects of preferential flow within the soil matrix flow has a slight significance for soil moisture status, but is insignificant for river flow estimations. Copyright © 2005 John Wiley & Sons, Ltd.