The aim of this contribution is to investigate the scaling exponent properties of a mountainous river flow fluctuations analyzed by means of detrended fluctuation analysis (DFA). Streamflow data were collected using Fluvial Acoustic Tomography System (FATS) which is a novel approach for continuous streamflow measurements at a high frequency. The crossover times evaluated from discharge data collected by FATS showed a relative delay estimated by 36±6% approximately in contrast to the times detected by the conventional streamflow measurement approaches. Moreover, the detected crossover time seems to be mainly a function of the watershed area and the higher number of intense precipitation events.
Due to global warming, it is concerned that cooling water for thermoelectric generation would be run short more frequently in many places of the world. We used a Computable General Equilibrium (CGE) model to quantify the socio-economic impact of a hypothetical shock of capital productivity, which represents shortage of cooling water on thermal power generation plants. The result showed that the magnitude of electricity generation change and subsequent economic indicators change due to 1% capital productivity reduction were varied by region. The mean electricity generation loss was largest in Southeast Asia and smallest in North Africa when an identical shock was given to all regions throughout the simulation period. Considerable regional differences in GDP and electricity price were attributed to not only the capital productivity, but also the amount of capital in thermoelectric sector and its contribution for GDP. Additionally, thermoelectric sector shock propagates into the global economy. These finding demonstrate the significance in quantifying the economic consequence of cooling water shortage.
Mangla reservoir is reducing its storage capacity due to sedimentation. The sedimentation rate may increase in future due to climate change. This study will provide the changes in sediment yield in Mangla watershed caused by climate and land use changes in future. The areas of watershed under high annual soil loss have identified using Universal Soil Loss Equation (USLE). Adapting proper land use types, it will be possible to reduce the soil loss and hence reduce the sediment load into the reservoir. Estimations with CMIP5 rcp 4.5 climate scenario gave 12% increase in average annual sediment yield in late 21st century. Similarly, the increase in sediment yield due to future land use change arisen by expansion in urban and agricultural lands is 5% of that in present. Future sediment yield can be effectively reduced by 21% by transforming mosaic vegetation above 2000m and bare areas above 3000m elevation to forests. Contour cropping conservation practice for agricultural lands has found effective in reducing 4 to 5 percent of sediment yield in near future. These adaptation measures will help in enhancing the useful life of the reservoir by 31 years.
Climate change alters the hydrological cycle in river basins and threaten the future surface water resources under the stress of the rapid urbanization and population growth in many cities. Haji Dam, located upstream of the Gono River in Chugoku region in Japan, is a very important green energy resource for urban water supply, hydropower generation, irrigation and flood controls. Therefore, the assessment of the projected inflow and capacity under present operating rule is very important for the multi-purpose reservoir. As a result, the estimated maximum 100-year probable rainfall will surplus at least 5 % in the whole river basin as well as the approximately 35 -60 mm surcharge in July and +5 to +20 mm extra in September will fall east, west and middle of the basin in near future. Finally, the increasing trend is significant with 50 m3/sec/year in the annual basic and around 100 to 150 m3/sec/month during the wet season. It requires to change the release ratio before and during the flood if the current flood control allocation wants to keep constant and reservoir water level continuously retains under the flood alarm level for reservoir safety. Moreover, the present operating rule assures the enough capacity after flood season or from September for multi-purposes.
The tropical cyclones that make landfall in the coastal areas of Vietnam cause increasing economic losses, with an average of six landfalls per year leading to approximately VND 12,500 billion in damages. It is assumed that the losses are mainly due to socio-economic developments, i.e. growing wealth and greater settlement of exposed areas. However, it is also thought that the rise in damages is caused by increasing frequency of severe cyclones resulting from climate change. In this paper, we estimate the impact of socioeconomic and global warming on the tropical cyclones losses. We investigate the historical impact functions of storm damage by using the Ordinary Least Squares estimator and regress damages on tropical cyclone characteristics. Based on simulation results of Typhoon Lekima in 2007 under global warming, socioeconomic development scenarios SSPs (Shared Socioeconomic reference Pathways) and the population density of Vietnam, we estimate the impact of climate and socioeconomic changes on tropical cyclone losses in the end of 21st century. Economic losses caused by typhoon will change under global warming at landfall. Socioeconomic changes will increase losses by approximately three and sixteen times greater than that due to climate-induced changes corresponding to SSP3 and SSP5 scenarios.
Despite increasing utilization and accuracy of models to predict the future climate and hydrology at higher resolutions, urban areas are still underrepresented. A method to determining future distribution of urban parameters in accordance with the global climate and socio-ecoonomic pathways of the future is proposed. An urban growth model was used to project the expansion of urban areas in 2050 of Jakarta. From shared socio-economic pathways (SSP), total population in the future was acquired. Using historical population distribution data, spatial distribution of population was projected until the year 2050. From empirical relationships acquired from population with nighttime lights adjustment, actual urban parameters, and GDP, futuristic urban parameters were calculated. Finally, the calculated future distribution of urban parameters was used in downscaling the future climate of Jakarta using the pseudo-global warming method.
Between 2015 and 2016, Vietnamese Mekong Delta (VMD) has undergone the most severe drought event over the last 90 years, causing damages to agriculture, aquaculture, and fresh water suply. Moreover, upstream Mekong River development by constructing hydropower dams will magnify the severity to the region. This research therefore aims at summarizing some damaged information caused by drought event 2015-2016 and analyzing the impacts of eleven proposed mainstream dams in Thailand, Lao PDR, and Cambodia on hydrology of Vietnamese Mekong Delta under the effect of sea level rise. Results show that the flow discharge is reduced by maximum 14.9% whereas the maximum increase in water level exceeds 220%. This leads to more intrusion of saltwater into the delta and reduction of fine sediment and natural nutrients settling in floodplains.
Time of concentration Tc is defined as the wave travel time from the most hydraulically remote point to the point of study. Tc is an important element in hydrological studies, especially in drainage system designs and the estimations of flood arrival time. The common approach in the estimation of Tc is based on Kinematic Wave (KW) approximation for both overland flow and river routing. This approximation, however, may not be appropriate on a flood plain with inundations. The main objective of this study is to propose the estimation of Tc with Diffusive Wave (DW) approximation considering the effect of flood inundation. The proposed method is demonstrated in the Kelantan River basin, Malaysia, focusing on a severe flood event in December 2014. This study compares the estimated Tc with other estimations based a Rainfall-Runoff-Inundation simulation and with a simple correlation method between rainfall amount in different durations and peak river discharges. In consequence, the proposed method with DW approximation with flood inundation showed closer estimations of Tc by the other two methods.
Since hydrologic drought is a slowly developing phenomenon, it may be possible to forecast low flow conditions, especially in areas with long dry seasons. This study proposes hydrological drought forecasting methods based on two stream flow recession analyses. The first one is based on a recursive digital filters for baseflow separation and recession characterization for the baseflow forecasting. The second one is based on the theory of “simple dynamical systems of catchments”. The applications of the two methods were demonstrated in Lombok Island in Indonesia and showed that the latter method, which reflects more flexible recession characteristics showed better accuracy in the estimations of the low flows. Nevertheless, both of the presented applications showed underestimations in low flow forecastings compared to the observed ones. The underestimations were mainly associated with the ignorance of the rainfall, especially for long lead time cases.
Non-point source pollution contribution is one of the major causes of water quality degradation in Chinese rivers and lakes. This research proposes a non-point source pollution modelling based on hydrograph separation by a distributed hydrological model and Time-Space Accounting Scheme. This method simulates spatially exported non-point source pollution nutrient loads by estimating flow discharge contribution rates from different spatial zones and source runoff concentrations of nutrients for each spatial zone. The source runoff concentrations can be estimated by field measurement or an inverse approach based on multiple stream flow samples. The proposed method was applied at the Pingqiao River Basin for a storm event. The inversely estimated source runoff concentrations showed satisfactory agreement with field measurement in the upstream area. The analysis suggested that this area (22.3 km2) exported about 2,630 kg of total nitrogen during an investigated storm event, and the urban area (5.3% of total area) contributed 18.5% of total nitrogen and 80.1% of ammonia nitrogen. The estimated source runoff concentrations were further applied for one-year simulation (2014/12/1 ～ 2015/11/30), which estimated 102,600 kg of total nitrogen export. The result was compared with the estimation based on measured source runoff concentrations (79,000 kg of total nitrogen) and revealed that the inverse method showed about 30% overestimation.
When tropical cyclone (TC) 201610, namely Lionrock, was moving over the western North Pacific from southeast of Honshu to cut across the Tohoku region during 29-30 August 2016, continuous and intense rainfall occurred in mid- to southeastern Hokkaido, far from the TC center. The Weather Research and Forecast (WRF) model is used to investigate the possible remote effect of TC Lionrock on this heavy rain in Hokkaido. The National Center for Environmental Prediction (NCEP) global final (FNL) analysis is used to provide both the initial and lateral boundary conditions for the model. Three numerical experiments are performed. In the control experiment (CTL), the original FNL is used. In the no-TC experiment (NoTC), the vortex associated with TC Lionrock in the FNL is removed such that the TC signal does not appear at the initial time. In the no-topography experiment (noTopo), the terrain height over Hokkaido set to 1 m if it is higher than 1 m. As verified against observations, the CTL and noTopo experiments capture reasonably well the TC track. The CTL experiment also reproduces relatively well the spatial distribution and temporal evolution of rainfall, whereas the remote rainfall in Hokkaido is largely suppressed in the noTC experiment, suggesting a significant far-reaching effect of TC Lionrock. The combined effect of Lionrock and the stationary low-pressure system located over the Sea of Japan enhances the moisture transport towards Hokkaido through their outer circulation. Particularly, only very small amount of rainfall is observed in Hokkaido in the noTopo experiment, indicating that the orographic forcing of the southeastern mountains in Hokkaido plays the most critical role in this extreme rainfall event.