Current practice using probabilistic methods applied for designing hydraulic structures generally assume that extreme events are stationary. However, many studies in the past decades have shown that hydrological records exhibit some type of nonstationarity such as trends and shifts. Human intervention in river basins (e.g., urbanization), the effect of low-frequency climatic variability (e.g., Pacific Decadal Oscillation), and climate change due to increased greenhouse gasses in the atmosphere have been suggested to be the leading causes of changes in the hydrologic cycle of river basins in addition to changes in the magnitude and frequency of extreme floods and extreme sea levels. To tackle nonstationarity in hydrologic extremes, several approaches have been proposed in the literature such as frequency analysis, in which the parameters of a given model vary in accordance with time. The aim of this paper is to show that some basic concepts and methods used in designing flood-related hydraulic structures assuming a stationary world can be extended into a nonstationary frame- work. In particular, the concepts of return period and risk are formulated by extending the geometric distribution to allow for changing exceeding probabilities over time. Building on previous developments suggested in the statistical and climate change literature, the writers present a simple and unified framework to estimate the return period and risk for nonstationary hydrologic events along with examples and applications so that it can be accessible to a broad audience in the field. The applications demonstrate that the return period and risk estimates for nonstationary situations can be quite different than those corresponding to stationary conditions. They also suggest that the nonstationary analysis can be helpful in making an appropriate assessment of the risk of a hydraulic structure during the planned project-life. DOI: 10.1061/ (ASCE)HE.1943-5584.0000820. © 2014 American Society of Civil Engineers.

/pdf/revisiting-the-concepts-of-return-period-and-risk-for-1srcjb70l3.pdf

Revisiting the Concepts of Return Period and Risk for Nonstationary Hydrologic Extreme Events

Hydrology deals with the occurrence, movement, and storage of water in the earth system. Hydrologic science comprises understanding the underlying physical and stochastic processes involved and estimating the quantity and quality of water in the various phases and stores. The study of hydrology also includes quantifying the effects of such human interventions on the natural system at watershed, river basin, regional, country, continental, and global scales. The process of water circulating from precipitation in the atmosphere falling to the ground, traveling through a river basin (or through the entire earth system), and then evaporating back to the atmosphere is known as the hydrologic cycle. This introductory chapter includes seven subjects, namely, hydroclimatology, surface water hydrology, soil hydrology, glacier hydrology, watershed and river basin modeling, risk and uncertainty analysis, and data acquisition and information systems. The emphasis is on recent developments particularly on the role that atmospheric and climatic processes play in hydrology, the advances in hydrologic modeling of watersheds, the experiences in applying statistical concepts and laws for dealing with risk and uncertainty and the challenges encountered in dealing with nonstationarity, and the use of newer technology (particularly spaceborne sensors) for detecting and estimating the various components of the hydrologic cycle such as precipitation, soil moisture, and evapotranspiration.

Introduction to Hydrology

Statistical and physically-based methods have been used for designing and assessing water infrastructure such as spillways and stormwater drainage systems. Traditional approaches assume that hydrol...

https://www.tandfonline.com/doi/pdf/10.1080/02626667.2018.1426858

Techniques for assessing water infrastructure for nonstationary extreme events: a review

Although rainwater harvesting system (RHS) is an effective alternative to water supply, its efficiency is often heavily influenced by temporal distribution of rainfall and water demand. Since natural precipitation is a random process and has probabilistic characteristics, it will be more appropriate to describe these probabilistic features of rainfall and its relationship with design storage capacity as well as supply deficit of RHS. This paper aims at developing a methodology for establishing the probabilistic relationship between storage capacities and deficit rates of RHS. A simulation model was built to simulate the input rainfall and water release in RHS. Historical rainfall records were then used as input for simulation and the results were used in probabilistic analysis for establishing the relationships between storage capacities and water supply deficits. The city of Taipei was used as study area for demonstration of this methodology and probabilistic distribution curves for storage capacity and deficit rate relationships were presented. As a result, a set of curves describing the continuous relationships between storage capacities and deficit rates under different exceedance probabilities were generated as references to RHS storage design. At a chose exceedance probability of failure, the engineer can decide from the curve on the storage size under a preset deficit rate.

/pdf/a-probabilistic-approach-to-rainwater-harvesting-systems-1s8mr0k6h3.pdf

A probabilistic approach to rainwater harvesting systems design and evaluation

Rainwater harvesting is now increasingly used to manage urban flood and alleviate water scarcity crisis. In this study, a computational tool based on water balance equation is developed to assess stormwater capture and water saving efficiency and economic viability of rainwater harvesting systems (RHS) in eight cities across four climatic zones of China. It requires daily rainfall, contributing area, runoff losses, first flush volume, storage capacity, daily water demand and economic parameters as inputs. Three non-potable water demand scenarios (i.e., toilet flushing, lawn irrigation, and combination of them) are considered. The water demand for lawn irrigation is estimated using the Cropwat 8.0 and Climwat 2.0. Results indicate that higher water saving efficiency and water supply time reliability can be achieved for RHS with larger storage capacities, for lower water demand scenarios and located in more humid regions, while higher stormwater capture efficiency is associated with larger storage capacity, higher water demand scenarios and less rainfall. For instance, a 40 m3 RHS in Shanghai (humid climate) for lawn irrigation can capture 17% of stormwater, while its water saving efficiency and time reliability can reach 96% and 98%, respectively. The water saving efficiency and time reliability of a 20 m3 RHS in Xining (semi-arid climate) for toilet flushing are 19% and 16%, respectively, but it can capture 63% of stormwater. With the current values of economic parameters, economic viability of RHS can be achieved in humid and semi-humid regions for reasonably designed RHS; however, it is not financially viable to install RHS in arid regions as the benefit-cost ratio is much smaller than 1.0.

Assessing efficiency and economic viability of rainwater harvesting systems for meeting non-potable water demands in four climatic zones of China

A situational analysis of future drought and flood impacts in Zimbabwe is outlined in this present study. The assessment under different scenarios is carried out using Aqueduct Global Flood Analyzer in which all the analyses are based on the gross domestic product (GDP), population, and the  present and future (2030) urban damage. In this study, to effectively estimate future changes, three scenarios were employed, namely, IPCC Scenario A2, the Representative Concentration Pathways (RCP) scenario which represents climate change, and the Shared Socio-economic Pathways (SSP) scenario which represents socio-economic change. All these scenarios were employed from the Intergovernmental Panel on Climate Change 5th Assessment Report. To determine current mean monthly precipitation, 1981–2010 data were used and Meteonorm V7 software was employed for the generation of the mean monthly precipitation from 2011 to 2100. The level of flood protection employed is a 10-year one which is used to identify the population at risk, the effects of this event on the GDP and to determine the rate at which urban damage is happening. Utilizing Meteonorm V7 software, average monthly precipitation is predicted. This study determined that, in any year, the majority of Zimbabwe has a low to medium (2–3% probability) flood occurrence in which a 10-year flood has a 10% occurrence probability in any given year. If there is no flood  protection employed, this 10-year flood could cause around 74.9 million USD affected GDP, 119 thousand affected population and 49.5 million USD  urban damage. As much as it is impossible to eliminate drought and flood events, a diminution approach and proper planning and preparation before their occurrence reduce the economic and social losses. 
Keywords: Aqueduct Global Flood Analyzer drought flood flood protection level Meteonorm V7 software Zimbabwe

/pdf/pre-disaster-planning-and-preparedness-drought-and-flood-3b8i35n1k6.pdf

Pre-disaster planning and preparedness: drought and flood forecasting and analysis in Zimbabwe

Coal-fired power plants are water intensive sources of energy generation. Waste water dumped by these coal-fired power plants is significant threat to our environment and human health. The electric power sector is the major source of toxic wastes in Pakistan, due to coal ash and coal waste, which contain toxic heavy metals such as Cr, Co, Cu, Pb, Mn, Ni, Zn, Hg, Ag, and As. Different Environmental report shows nearly all power plants in Pakistan discharge toxic coal ash or wastewater into public water. This paper provides a brief overview about how badly Coal Industry is poisoning water and later on the characteristics of wastewater discharge from coal based thermal plants are discussed. The study presented in this paper quantitavely evaluates the heavy metals like Cr, Ni, Hg, As, Cd, Pb, Mn and Co emissions in coal ash or waste water of a coal power plant. 1 MW capacity plant was selected for the study and the results showed such a plant will produce Cr 33.7g/kWh, Pb 44.9g/kWh, As 44.9g/kWh and Hg 0.6g/kWh respectively. At the end, some plausible recommendations are suggested for government of Pakistan to mitigate the effects of these power plants. Article DOI:  https://dx.doi.org/10.20319/mijst.2016.s21.135149 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Quantitative assessment of heavy metals in coal-fired power plant’s waste water

A regional frequency analysis using L-moments was performed with time series clustering approaches to identify homogeneous regions using dynamic data sets in Northern Cyprus. In this contex...

Regional Frequency Analysis of Precipitation Using Time Series Clustering Approaches

Cyprus, as the third largest island in the Mediterranean Sea, is located at the South of Turkey and the West of Syria and Lebanon. With a semiarid climate, rainfall is the only source of water in the island. Therefore, changes in rainfall regime directly affect the water resource management and ecosystem in the island. In order to improve water management strategies, it is vital to investigate the changes in the rainfall pattern. In this study, a nonparametric Mann–Kendall rank correlation method is employed to identify the existence of a linear trend in annual and monthly rainfall series. After application of homogeneity test and filling in missing data, this method is applied to the observed rainfall data from 20 rain-gauge stations that are located in the northern part of the island for the period of 1978–2009. The results show that there is no significant trend in the annual rainfall; however, upward trends in September rainfall and downward trends in March rainfall have been observed in most of the stations. This indicates that there are no significant changes in annual total rainfall; however, there is a shift in monthly rainfall regime.

Trend Analysis of Rainfall in North Cyprus

https://iopscience.iop.org/article/10.1088/1755-1315/297/1/012026/pdf

Optimum tank size for a rainwater harvesting system: Case study for Northern Cyprus

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