Binaya Kumar Mishra

Assessment of Future Floods in the Bagmati River Basin of Nepal Using Bias-Corrected Daily GCM Precipitation Data

AbstractIn this paper, climate change impact on flood frequency has been investigated in Bagmati River Basin of Nepal using bias-corrected global climate model (GCM) precipitation output. The research reported in this paper employed a high-resolution (approximately 20-km) daily GCM precipitation and temperature output of Meteorological Research Institute (MRI), Japan. Comparison of observation and GCM data pointed out that the MRI-GCM precipitation consists of significant biases in frequency and intensity values. Quantile-quantile mapping method of GCM bias correction was applied for minimizing the biases in precipitation frequencies and intensities. Concept of homogeneous precipitation regions was introduced to link the uneven observation data stations and GCM grid cells. Analyses of return period curves, shape, and scale factors at different observation stations enabled delineation of three homogeneous precipitation regions. Accordingly, regional quantile-quantile bias-correction technique was developed...

Assessment of future flood inundations under climate and land use change scenarios in the Ciliwung River Basin, Jakarta

This study assessed flood inundation of the Ciliwung River Basin, Greater Jakarta to improve the urban water environment under climate change and unplanned urbanization. The 1-day maximum precipitation data for 50- and 100-year return period under current and future climate conditions were used to assess the impact of climate change. Precipitation output of the MRI-CGCM3, MIROC5 and HadGEM2-ES General Circulation Models (GCM) with RCP 4.5 and 8.5 emission scenario over periods 1985–2004 and 2020–2039 representing current and future climate conditions respectively were used. Similarly, land use data of 2009 and 2030 were used to represent the current and future conditions, respectively. The HEC-HMS model was used to simulate the river discharge at Katulampa, which represents the outlet location for the hydrologic modelling and the inlet location for the flood inundation modelling. FLO-2D, a two-dimensional hydrodynamic model, was used to simulate current and future flood inundation simulations. Increasing flood inundation areas and depths (6% to 31% for different GCMs) in the future reveal the need to improve flood management tools for the sustainable development of urban water environments.

Integrated urban water management scenario modeling for sustainable water governance in Kathmandu Valley, Nepal

The goal of ensuring water availability and sustainable management of water for all by 2030 is one of the top priorities of the UN-SDGs. The fragile institutional capabilities induce the transitioning towards the sustainable urban water paradigm to accommodate the complexities and uncertainties. This research methodically draws sustainable water management strategies to achieve water security after a critical literature review, trends and policy analysis, and scenario modeling of the study area. First, research systematically illustrated the analysis of unmet water demand and coverage during the study period (2015–2030) and evaluated the impact of external factors such as population growth, living standard, and climate change on the current water system of the Kathmandu Valley. The results showed that future water demand is likely to reach 765 MLD by the year 2030 from the estimated current demand of 388.1 MLD. Also, external factors will increase the pressure on the current water supply–demand systems, and hence exacerbate the water stress but result showed the negligible impact of climate change during the study period. The research explored the significance of “Melamchi Water Supply Project (MWSP)” and found that the effective implementation of MWSP will decrease the unmet water demand by 56–66% in the valley. In the second part, comparative analysis of different management strategies under four future scenarios (optimistic, moderate I and II and business-as-usual) were carried out. The comparative analysis revealed that the proposed optimal management strategy (under optimistic scenario) would lead to achieving 100% of water demand coverage by year 2027.

Applying a water quality index model to assess the water quality of the major rivers in the Kathmandu Valley, Nepal

Human activities during recent decades have led to increased degradation of the river water environment in South Asia. This degradation has led to concerns for the populations of the major cities of Nepal, including those of the Kathmandu Valley. The deterioration of the rivers in the valley is directly linked to the prevalence of poor sanitary conditions, as well as the presence of industries that discharge their effluents into the river. This study aims to investigate the water quality aspect for the aquatic ecosystems and recreation of the major rivers in the Kathmandu Valley using the Canadian Council of Ministers of the Environment water quality index (CCME WQI). Ten physicochemical parameters were used to determine the CCME WQI at 20 different sampling locations. Analysis of the data indicated that the water quality in rural areas ranges from excellent to good, whereas in denser settlements and core urban areas, the water quality is poor. The study results are expected to provide policy-makers with valuable information related to the use of river water by local people in the study area.

Assessment of Climate Change Impacts on Urban Rainfall Extremes for Achieving Sustainable Urban Water Development in Hanoi, Vietnam

In recent decades, the increased frequency of disaster events, particularly hydro-meteorological disasters, have threatened human lives and infrastructure. In the context of climate change, urban water management became more complicated because of erratic or heavy rain events or prolonged droughts. Now, sustainable water management and planning requires to visualize the potential impact of climate change on extreme rainfall pattern in order to reduce the climatic vulnerability. This chapter evaluates the impact of climate change on extreme rainfall intensities under different greenhouse gases emission RCP (Representative Concentration Paths) considering future period of 2070–2099 over a baseline period of 1976–2005. The impacts were assessed using rainfall output of 5 General Circulation Models (GCM) under RCP 8.5 (high) and RCP 4.5 (medium) emission scenarios. Bilinear interpolation and quantile mapping technique were applied to extract rainfall data from grid points onto station points and to correct bias of GCM simulations in comparison with the observational data respectively. To derive the rainfall IDF (Intensity-Duration-Frequency) curves, daily rainfall output was temporally downscaled using scaling method. In the study, IDF curves were developed and the performances of the downscaling method were evaluated. The results indicate that the mean of corrected monthly rainfall and the frequency of wet days are considerably closer to observation than the raw rainfall estimates. In addition, the bias correction method accurately captured extreme rainfall values for all 5 GCM and indicated that by the end of the century, under different scenarios the rainfall intensity is increasing for all the durations and the return periods. The results will assist the water manager and urban planner to design the sustainable and robust water infrastructure.

Assessment of Tangible Direct Flood Damage Using a Spatial Analysis Approach under the Effects of Climate Change: Case Study in an Urban Watershed in Hanoi, Vietnam

Due to climate change, the frequency and intensity of Hydro-Meteorological disasters, such as floods, are increasing. Therefore, the main purpose of this work is to assess tangible future flood damage in the urban watershed of the To Lich River in Hanoi, Vietnam. An approach based on spatial analysis, which requires the integration of several types of data related to flood characteristics that include depth, in particular, land-use classes, property values, and damage rates, is applied for the analysis. To simulate the future scenarios of flooding, the effects of climate change and land-use changes are estimated for 2030. Additionally, two scenarios based on the implementation of flood control measures are analyzed to demonstrate the effect of adaptation strategies. The findings show that climate change combined with the expansion of built-up areas increases the vulnerability of urban areas to flooding and economic damage. The results also reveal that the impacts of climate change will increase the total damage from floods by 26%. However, appropriate flood mitigation will be helpful in reducing the impacts of losses from floods by approximately 8% with the restoration of lakes and by approximately 29% with the implementation of water-sensitive urban design (WSUD). This study will be useful in helping to identify and map flood-prone areas at local and regional scales, which can lead to the detection and prioritization of exposed areas for appropriate countermeasures in a timely manner. In addition, the quantification of flood damage can be an important indicator to enhance the awareness of local decision-makers on improving the efficiency of regional flood risk reduction strategies.

Evaluation of aqueous geochemistry of fluoride enriched groundwater: A case study of the Patan district, Gujarat, Western India

Abstract High fluoride (F−) groundwater causes fluorosis which might at severe stages lead to deformation of bones, bilateral lameness. The concentration of F− ranged from 0.4 to 4.8 mg/L. This study suggests that high HCO3− and Na+ in alkaline medium along with water–rock interaction plays important role in enrichment of F− in groundwater. Na-HCO3 is the dominant water type followed by Ca-HCO3 suggesting dominance of Na+, Ca2+ and HCO3− ions in groundwater. Factor analysis of water quality parameters suggests that four principal components account for 74.66% of total variance in the dataset. Factor 1 shows higher positive loading for pH, HCO3− negative loading for F−, Ca2+, SO42− depicting ion-exchange and HCO3 dominant water type responsible for F enrichment in groundwater. Saturation index for selected minerals suggests that most of the samples are oversaturated with calcite and undersaturated with fluorite. Calcite precipitation leads to the removal of Ca2+ from solution thus allowing more fluorite to dissolve. These released Ca2+ ions combine with CO32− ions to further enhance the precipitation of CaCO3.

Modeling water allocation options in Deduru Oya reservoir system, Sri Lanka

Water balance under different management scenarios was tested in Deduru Oya reservoir project system, Sri Lanka with focus on Left Bank canal system to address agricultural, energy, and environmental water deficits in all seasons. A conceptual rainfall-runoff model, SimHyd, was employed for modeling discharge into ancient tanks. CropWat model enabled estimation of irrigation water requirement for rice crops, the main agricultural water demand. Water Evaluation And Planning (WEAP) model was applied for testing deficits between water supply and demand systems. Graphs of coverage and unmet water demands pointed out that most of the tanks are not able to meet two-season irrigation water requirements. Water shortages occurred in the months of March, May, June, and September. In dry climatic year, tanks and reservoir storages together may not be well enough to meet September water demands if operated conventionally (i.e., farmers are free to use tank water as they want). Results of water allocation modeling pointed out that there will be no water shortages if farmers are convinced to retain water of about 40% of tank inflows for the use in September.