Water Supply Risk Research Articles

Coincidence probability of streamflow in water resources area, water receiving area and impacted area: implications for water supply risk and potential impact of water transfer

Abstract Under changing environment, the feasibility and potential impact of an inter-basin water transfer project can be evaluated by employing the coincidence probability of runoff in water sources area (WSA), water receiving area (WRA), and the downstream impacted area (DIA). Using the Han River to Wei River Water Transfer Project (HWWTP) in China as an example, this paper computed the coincidence probability and conditional probability of runoff in WSA, WRA and DIA with the copula-based multivariate joint distribution and quantified their acceptable and unfavorable encounter probabilities for evaluating the water supply risk of the water transfer project and exploring its potential impact on DIA. Results demonstrated that the most adverse encounter probability (dry–dry–dry) was 26.09%, illustrating that this adverse situation could appear about every 4 years. The acceptable and unfavorable probabilities in all encounters were 44.83 and 55.17%, respectively, that is the unfavorable situation would be dominant, implying flood and drought risk management should be paid greater attention in project operation. The conditional coincidence probability (dry WRA & dry DIA if dry WSA) was close to 70%, indicating a requirement for an emergency plan and management to deal with potential drought risk.

Bootstrap Aggregation and Cross‐Validation Methods to Reduce Overfitting in Reservoir Control Policy Search

AbstractPolicy search methods provide a heuristic mapping between observations and decisions and have been widely used in reservoir control studies. However, recent studies have observed a tendency for policy search methods to overfit to the hydrologic data used in training, particularly the sequence of flood and drought events. This technical note develops an extension of bootstrap aggregation (bagging) and cross‐validation techniques, inspired by the machine learning literature, to improve reservoir control policy performance on out‐of‐sample hydrological sequences. We explore these methods using a case study of Folsom Reservoir, California, using control policies structured as binary trees, and streamflow resampling based on the paleo‐inflow record. Results show that calibration‐validation strategies for policy selection coupled with certain ensemble aggregation methods can improve out‐of‐sample performance in water supply and flood risk objectives over baseline performance given fixed computational costs. Our findings highlight the potential to improve policy search methodologies by leveraging these well‐established model training strategies from machine learning.

Risk associated with the water infrastructure in rural water suppliers in Turrialba Cartago, Costa Rica

Having enough and good quality drinking water is essential for a country’s socioeconomic development. Drinking water supply indicators in urban areas of Costa Rica are acceptable; in fact, health has not yet been compromised. The management of water supply in rural areas has been delegated to community associations, which have neither the technical preparation nor the financial resources to deal with proper management to sustainability water supply. In a short term, the deficiencies mentioned before, will increase the risk of water supply. This article presents the risk associated with water infrastructure of some rural water suppliers. Also provides some recommendations for improving their performance. To determine the possible contamination of water, the components of the water supply systems were evaluated in four rural water suppliers in Turrialba canton Cartago (6070 inhabitants) Costa Rica. The risk was determined using the “official risk control surveillance instrument of the Ministry of Health”. It was determined that 45% of the storage tanks have a high risk of contamination. Only one of the four water suppliers had a chlorination system, and this was classified as high risk. All the infrastructure studied was more than 30 years old. There is an urgent to improve the infrastructure and management of these water suppliers, to avoid a crisis of water scarcity or pollution in rural areas. The main improvements opportunities for water suppliers are promoting a system of preventive maintenance of the reservoirs, installing chlorination systems, implementing a control of water demand, training technical and administrative staff.

Assessment of Urban Water Supply Options by Using Fuzzy Possibilistic Theory

A comprehensible framework for assessing water supply risk based on existing and under-construction projects is provided. In the proposed framework, the risk factors of current and future water supply options were first investigated using the Fuzzy Delphi method. Then, according to a survey of experts, the probability of the risk for each water supply option was assessed. Markowitz’s theory was used, in the form of an opportunity from the optimistic to the most pessimistic possible case of the risk pool. The results showed that the framework based on the Fuzzy Delphi and possibility theory is befitting to information gathered from experts. Such a framework can provide a simple method to apply the proposed methodology to other water management projects, where, despite the high level of investment, there is no clear idea of the risks and their consequences.

Multiple-risk assessment of water supply, hydropower and environment nexus in the water resources system

Hydropower has been one of the effective and reliable renewable sources utilized for electricity generation globally, which forms over 70% of all the renewable energy measures since 2016. However, this effective energy source can be greatly affected by the uneven spatiotemporal distributions of water resources in the catchment, leading to the potential risks of insufficient water supply, hydropower and ecological water uses. In this study, the multi-dimensional models by coupling water supply, hydropower generation and environment effects were developed to improve the efficiency and sustainability of water resources utilization. To this end, the joint distributions and conditional expectation models were established to analyze the nexus of water supply, hydropower and environment variables, thereby to evaluate multiple risks in the water resources system. For the validation and demonstration of the proposed method, the upper Yangtze River Basin was selected for a case study through multivariate analysis under different conditions. The application results of bivariate analysis indicated that the probability of water supply exceeding a threshold value decreases gradually with the increase of hydropower generation, which means that the risk of insufficient water supply increases with the increasing of the hydropower generation. Specifically, when the frequency of hydropower generation exceeds 90%, both the expected values of water supply sufficiency and water use sustainability will decrease sharply, causing potential risks of water supply insufficiency and environment damage at upstream of the dam. Furthermore, the application results of trivariate analysis evidenced that different combinations of hydropower generation and ecological water use may be achievable for optimally compromising the water resources supply and utilization. The results and findings of this study may provide useful implications for effective multiple function-based development of water resources, with aims to reduce the water supply risks as well as to improve the water utilization efficiency and environmental sustainability.

Adaptation of Water Supply to Changing Climate and Land-Use Activities, Case of Ljubljana Water Supply, Slovenia

A risk management methodology is presented for the adaptation of water supply to changing climate and land-use activities, considering socio-economic aspects. Several management options were selected for the case of the public water supply of Ljubljana, the capital of Slovenia. The major management actions for improving drinking water safety are (1) land-use limitations within the drinking water protection areas and (2) drinking water treatment. Trends in groundwater level are decreasing, above all in the area of well fields; therefore, artificial recharge and setting up a new independent well field were also considered. The management actions were evaluated according to several criteria, such as water supply risk reduction for the various users (drinking, agricultural, and industrial) and realization of the actions (cost, flexibility, and leg time). For management options, the ranking “Fuzzy Decimaker” tool was applied, which is based on a Multiple Criterion Decision Making (MCDM) technique. Ranking of management actions has shown that all management actions are good as they are clustering in the corner close to the ideal value. For a particular well field, farming limitations in the drinking water protection areas are the best and water treatment is the worst management action, which is due to high costs, low flexibility, and longer lag time.

Risk Management of Drinking Water Supply in Critical Conditions Using Fuzzy PROMETHEE V Technique

Water crisis management in drinking water supply systems is a crucial issue. Many different natural and unnatural disasters cause great damages to these systems. Prioritizing effective strategies by expert decision-makers before any incidence can greatly reduce this damage. Moreover, cost minimization in the provision of these strategies is very essential as the urban crisis management organizations are financially limited. Therefore, this study provided a model for the selection of the most appropriate drinking water supply strategies in crisis conditions, considering possible limitations. Fuzzy PROMTHEE V, a multi-criteria decision-making method, is a new approach developed in this research to help the decision-makers in selecting a set of possible alternatives for drinking water supply management, which are ranked based on five criteria determined by decision-makers (water supply reliability, implementation speed and simplicity, implementation cost, social satisfaction, water quality) and budget limitation as the constraint for the optimization problem. This model was applied in a case study of Tehran city in Iran. Due to the uncertainties in expert opinions and parameters needed for drinking water supply risk management, this model was solved with three fuzzy methods and one non-fuzzy method, and the results were compared. Findings showed that strengthening passive defense in water supply, transportation, and distribution systems; providing water consumption management; encouraging people to save water for emergency conditions and planning to exploit popular forces and performing maneuvers are top-ranked alternatives.

Risk Perceptions and Adaptation to Climate Change and Sea-Level Rise: Insights from General Public Opinion Survey in Florida

The Everglades is a unique ecosystem in Florida that offers a variety of ecosystem services (ES), including water supply and flood risk reduction, water purification, habitats for several endemic species, and recreational opportunities. Therefore, the ramifications of climate change, an imminent threat to the Everglades ecosystem, are going to affect these ecosystem services drastically. The climate-induced changes to the ecosystem services are going to affect people’s lives and livelihoods in the region. Thus, understanding public perception and preferences is an important step in addressing the impending risk. In this study, we used an online survey to assess residents’ perceptions about the risk of climate change and their views on mitigating potential consequences. We find that people’s perceptions and preferences are shaped by their level of education, age, participation in outdoor recreational activities, and elevation and distance from the shoreline of their residential location from the mean sea-level. In general, people who are concerned about the flooding risk and people who tend to prioritize environmental conservation are more likely to agree with the potential impacts of climate change and sea-level rise and more likely to support proposed measures for adaptation. We discuss the policy implications for developing socially acceptable plans based on the findings regarding people’s perception and preferences for adaptation in this region.

Water Supply Risk in the United States 2015-2050 Considering Projected Changes in Population and Thermoelectric Power Demand.

Examination of water supply risk is important to identify areas of potential insecurity and prioritize allocation of resources. This work builds on and advances a previous U.S. water supply risk analysis developed at county-scale resolution, which did not account for water flow between counties and identified some counties on major rivers as being at high risk. This limitation is addressed in the present study. The analysis utilized data from U.S. Geological Survey water use reports to assess current water supply risk and also projected water supply risk in 2050. Flow volumes were calculated using the Water Supply Sustainability Index (WaSSI) tool developed by the USDA Forest Service, enabling the analysis to account for changes in climate and hydrology and changes in water demand. A modified Water Risk Index (WRI) was formulated, including five factors to which scaled values were assigned. Results indicate that accounting for natural transfers of water in counties in addition to local precipitation reduced the risk profile of many counties, with a maximum of 36 classified as high or very high risk, compared to over 400 identified in the highest risk category in the previous analysis.

A coupled agent-based risk-based optimization model for integrated urban water management

Integrated urban water management (IUWM) is a comprehensive mitigation strategy to control water deficit due to simultaneous effects of reduction in water resources capacity and increase in water demand. Here we develop a coupled agent-based risk-based optimization model, which is able to account for water resources capacity and water demand uncertainties to determine the optimum annual water allocation. An optimization model based on conditional value at risk (CVaR) is employed to minimize the water supply risk in a long-term horizon and obtain the annual probabilities of complete supply of water demand. According to the generated synthetic weather data by LARS-WG for different climate scenarios, surface water and groundwater resources are modeled using HMETS and MODFLOW, respectively. Then, the developed agent-based model considers agents’ attributes, action roles and interactions by applying Borda scoring approach, and determines the most compatible IUWM strategies to increase water supply or modify water demand. The proposed framework is implemented for the Shiraz city in Iran, revealing a strong need to IUWM strategies to alleviate the water deficit over the period of 2018 to 2050. The proposed approach provides an efficient framework to achieve sustainable management strategies for cities with stressed water resources and rapid urban development.

Impacts of climate change on the hydrology of northern midlatitude cold regions

Cold region hydrology is conditioned by distinct cryospheric and hydrological processes. While snowmelt is the main contributor to both surface and subsurface flows, seasonally frozen soil also influences the partition of meltwater and rain between these flows. Cold regions of the Northern Hemisphere midlatitudes have been shown to be sensitive to climate change. Assessing the impacts of climate change on the hydrology of this region is therefore crucial, as it supports a significant amount of population relying on hydrological services and subjected to changing hydrological risks. We present an exhaustive review of the literature on historical and projected future changes on cold region hydrology in response to climate change. Changes in snow, soil, and streamflow key metrics were investigated and summarized at the hemispheric scale, down to the basin scale. We found substantial evidence of both historical and projected changes in the reviewed hydrological metrics. These metrics were shown to display different sensitivities to climate change, depending on the cold season temperature regime of a given region. Given the historical and projected future warming during the 21st century, the most drastic changes were found to be occurring over regions with near-freezing air temperatures. Colder regions, on the other hand, were found to be comparatively less sensitive to climate change. The complex interactions between the snow and soil metrics resulted in either colder or warmer soils, which led to increasing or decreasing frost depths, influencing the partitioning rates between the surface and subsurface flows. The most consistent and salient hydrological responses to both historical and projected climate change were an earlier occurrence of snowmelt floods, an overall increase in water availability and streamflow during winter, and a decrease in water availability and streamflow during the warm season, which calls for renewed assessments of existing water supply and flood risk management strategies.

Integrated large‐scale circulation impact on rainy season precipitation in the source region of the Yangtze River

AbstractMonthly precipitation data at regular grids of 0.5° × 0.5° derived from observations during June–August 1961–2016 were used to reveal characteristics of large‐scale circulations associated with rainy season precipitation over the source region of the Yangtze River (SRYR). The integrated impact of major influencing circulation patterns was examined by principal component analysis and composites. Results showed that the first rainy season precipitation mode associates with the Southern Oscillation Index (SOI) and the Pacific Decadal Oscillation (PDO), explaining 64% of spatial and temporal rainy season precipitation variance in the region. Composites of precipitation pattern under different phases of SOI and PDO revealed that the effect of PDO on precipitation varies with the SOI phase. When in phase with the SOI, PDO‐induced precipitation anomalies are magnified. When out‐of‐phase, anomalies weaken or even disappear. Composites of moisture flux patterns show that large‐scale atmospheric circulation affects the strength of westerlies that transport moisture to the study area and formation of convergence. In coming decades, the PDO is likely to continue in a negative phase with La Niña (positive SOI) events, implying more precipitation during the rainy season. Consequently, this knowledge can be used to improve decision making regarding water supply and flood risk management in the SRYR.

Implementation of water safety plans in China: 2004-2018.

The application of Water Safety Plans (WSPs) in China varies throughout the country. Although pilot WSP projects in China were initiated shortly after WSP was introduced by the World Health Organization (WHO) in 2004, they have yet to be used for water supply facilities at a large scale. To better understand the evolution of WSP application in China, a systematic review was conducted to identify all published WSP related studies in China. Eighteen studies, which included 311 water systems, were included in the final analysis. Risk matrix, water supply risk factors, and other data were extracted and analyzed. Text mining methods were also used to better understand risks that can be addressed by WSPs (both potential and actual risks). This study revealed a number of noteworthy differences between and among urban and rural water systems in China. The primary risks associated with most urban water supply systems tended to be related to mechanical failure/s in the water treatment process. Rural water supply systems appear to suffer from similar problems, but insufficient overall management capacity was more prevalent in rural systems. Overall, the evidence suggests that, to date, the use of WSPs in China has been primarily limited to pilot studies, and full implementation of WSPs in China appears to still be in the early stages. The paper closes with a summary of the key obstacles identified as well as a discussion of policies and technical options which could increase the use of WSPs in both urban and rural China. Among other recommendations, the data indicate that there is strong need for the development and implementation of a simplified WSP approach designed specifically for small rural systems in China.

Preferences for Intrinsically Risky Attributes

Incentivized experiments and stated preference methods are commonly viewed as substitutes in preference elicitation. We leverage the distinct strengths of each approach by combining a fully incentivized risk experiment with a stated preference survey to model utility for intrinsically risky attributes. A door-to-door survey of 981 participants in a drought-prone region elicits preferences for alternative sources of municipal water, conditional on water price and quality. Participants’ observed and imputed risk attitudes are incorporated into preference estimation. Our results are consistent with the hypothesis that participants are concerned about water supply risk, but not about new technology risk.

Empirical Application of Rubinstein Bargaining Model in Western U.S. Water Transactions

Water transactions are proposed as a policy tool for increasing regional drought resilience and improving allocative efficiency. However, water trading deviates considerably from classical competitive markets and alternative theoretical approaches are useful for understanding water market structure and performance. In this paper, we model a bilateral water transaction using a non-cooperative bargaining model. Then we empirically test predictions regarding time preference, outside options, and water supply risk. The econometric analysis encompasses two transaction regions: Colorado’s Front Range and New Mexico’s Middle Rio Grande Basin. We find evidence suggesting that larger cities pay lower prices in water transactions, faster growing and higher income cities pay higher prices and that prices are higher when snowpack variability is higher. Findings suggest that a stronger time preference results in a less favorable price for urban buyers and that buyer risk-aversion is a greater disadvantage in bargaining in locations with greater water supply variability.

Assessment of the Irrigation Water Requirement and Water Supply Risk in the Tarim River Basin, Northwest China

Studying the relationship between agricultural irrigation water requirements (IWR) and water supply is significant for optimizing the sustainable management of water resources in Tarim River Basin (TRB). However, the related studies have not quantified the total IWR and the imbalance of irrigation water supply and requirements in the TRB. The study analyzed the spatial-temporal variations of IWR by a modified Penman–Monteith (PM) method during 1990–2015. Five major crops—rice, wheat, maize, cotton, and fruit trees—are chosen for calculating the IWR. It was found that the IWR increased significantly, from 193.14 × 108 m3 in 1990 to 471.89 × 108 m3 in 2015, for a total increase of 278.74 × 108 m3. For the first period (1990–2002), the total IWR remained stable at 200 × 108 m3 but started to increase from 2003 onwards. Significantly more irrigation water was consumed in the oasis regions of the Tienshan Mountains (southern slope) and the Yarkand River (plains). Furthermore, there was an intensified conflict between IWR and water supply in the major sub-basins. The ratios of IWR to river discharge (IWR/Q) for the Weigan-Kuqa River Basin (WKRB), Aksu River Basin (ARB), Kaxgar River Basin (KGRB), and Yarkand River Basin (YRB) were 0.93, 0.68, 1.05, and 0.79, respectively. The IWR/Q experienced serious annual imbalances, as high flows occurred in July and August, whereas critical high IWR occurred in May and June. Seasonal water shortages further aggravate the water stress in the arid region.

Water Supply Risk Analysis Based on Runoff Sequence Simulation with Change Point under Changing Environment

This study investigates the water supply risk of Panjiakou reservoir in the Luanhe River basin of China during 1956–2016 under environmental change. Since the monthly runoff series during 1956–2016 is a time series with change points, it is necessary to find a new stochastic streamflow series generation approach to preserve the statistical characteristics of the original series and to refine the reliability of water supply risk analysis. This paper improves a known stochastic streamflow simulation method of previous research to better reflect the characteristics of series with change points. And this paper simulates the monthly runoff series with change point of Panjiakou reservoir during 1956–2016 by three different methods, including Thomas–Fiering model, copula function stochastic simulation method, and copula function stochastic simulation method with the mixed distribution model. Among the three methods, the copula function stochastic simulation method with the mixed distribution model which is improved on the basis of copula function stochastic simulation method in this study performs best in simulating the observed monthly runoff series during 1956–2016, and the water supply risk indices including reliability (time-based and volume-based), resilience, vulnerability, drought risk index (DRI), and sustainability index (SUI) are evaluated for Panjiakou reservoir and analyzed by using the stochastic simulation results. By comparing with the previous studies, all indicators are between the corresponding results of 1956–1979 and 1980–2016 with stationary inflows; it can be seen that change point seriously affects the water supply risk of Panjiakou reservoir. These results make it easy to formulate water supply strategies and schemes in changing environment for water resources managers.

Effect of Frequency of Multi-Source Water Supply on Regional Guarantee Rate of Water Use

Multi-source, combined water supply models play an increasingly important role in solving regional water supply problems. At present, in the area of regional water supply, models are mainly used to study the problem of overall water guarantee rate, and do not take into account the impact of the uncertainty of multi-source water supplies on water supply risk. There is also a lack of research on how changes in multi-source water supplies affect sub-region and sub-user water guarantee rates. To address this knowledge gap, the encounter probability of different frequencies and a refined water resources allocation model of multi-source supplies were used. Using Tianjin as an example, this paper studies the quantitative relationship between the uncertainty of multi-source water inflows and the regional guarantee rate of water use. The objectives of the study are to analyze the changing trend of the water shortage rate and the main body of water supply in each region, and to quantitatively describe the influence of the variation of multi-source water supply on the main body of water supply for users. The results show that under the same requirement of guarantee rate for water use, as the number of water diversion sources increase, the probability of water supply meeting the water use rate increases significantly, and the risk to water supplies decreases. At the same time, suburban areas have a low dependence on external water supplies, while the change in the quantity of external water sources has a great impact on the water supply of the Zhongxinchengqu and Binhaixiqnu areas. The distribution and main body of water supply will change for different water users. Therefore, it is important to ensure a stable supply of external water for maintaining the guarantee rate of regional water use.

Impacts of Inter-Basin Water Transfer Projects on Optimal Water Resources Allocation in the Hanjiang River Basin, China

Inter-basin water transfer project is an effective engineering countermeasure to alleviate the pressure of water supply in water-deficient areas and balance the uneven distribution of water resources. To assess the impacts of inter-basin water transfer projects on optimal water resources allocation, an integrated water resources management framework is proposed, and is applied to the middle and lower reaches of the Hanjiang River Basin in China. Firstly, future water demands are analyzed as inputs. Then, a multi-objective water resources allocation model is formulated mitigating the negative impacts of water transfer projects on downstream water quantity and quality by using the non-dominated sorting genetic algorithm-II (NSGA-II). Finally, the indicators of water supply reliability, vulnerability and resilience are evaluated under different scenarios of inter-basin water transfer projects. The results indicate that: (1) the reliability and resilience of the water donor system will be gradually reduced while the vulnerability will be increased with the expansion of water transfer projects and the increase of water demand, (2) water supply risk is likely to increase in all zones (because zones at the boundary cannot obtain sufficient water due to limitations of local inflow and reservoir operation, while the amount of water available in the zones along the mainstream river is directly decreased by the water transfer projects), (3) more water supply measures and compensation measures will need to be implemented in the water donor areas. The framework proposed in this study to evaluate the comprehensive impact of inter-basin water transfer projects is conducive to water resources management.

Water supply risk analysis of Panjiakou reservoir in Luanhe River basin of China and drought impacts under environmental change

This study investigates the impacts of drought on water supply risk of Panjiakou reservoir in Luanhe River basin of China under environmental change by using a copula-based streamflow series generation approach. To understand how nonstationarity of runoff sequence influences water supply risk, reservoir performance metrics including reliability (time-based and volume-based), resilience, vulnerability, drought risk index (DRI), and sustainability index (SUI) are evaluated with 1956–1979 and 1980–2016 inflows of Panjiakou reservoir, respectively. The results indicated that the prolonged and severe drought may seriously affect the safety of water supply. From two results of generated streamflow time series, the reliability reduction rate reached 58.3% (0.773 to 0.322) when water supply assurance rate was 75% and ecological water level was minimum. Perturbing the copula parameter will make it possible to increase the drought durations and deficits for Panjiakou reservoir to analyze drought impacts on water supply. Based on the reservoir performance metrics, the analysis for Panjiakou reservoir showed that the trend of drought in the future made water supply reliability (time-based and volume-based), resilience, and SUI decrease, but vulnerability and DRI increase, which means the water supply system security became more vulnerable in the future. These results make it easy for decision makers to understand how drought influences future planning and management of Panjiakou reservoir.