Conjunctive use of Inter-Basin Transferred and Desalinated Water in a Multi-Source Water Supply System Based on Cost-Benefit Analysis

Water shortage has forced coastal cities to seek multi-source water supply with a focus on inter-basin water and desalinated seawater. The differences of water supply costs pose a challenge in the optimal use of multiple water resources. This paper aims to understand the impact of desalinated seawater’s variable costs on multi-source water supply through a cost-benefit analysis method based on a multi-objective optimization model, considering different combination scenarios of desalination yield, streamflow condition, seawater desalting plant (SDP) scheme, water shortage index and utilization ratio of the SDP. The application in the coastal city Tianjin, China shows that the desalination yield has an impact on the tradeoff between the water shortage index and the total water supply cost and an optimal desalination yield can be determined at a turning point. And where the turning point appears is influenced by the utilization ratio of the SDP and streamflow conditions of inter-basin water. Moreover, a single centralized SDP is found to have an overall lower water supply cost than several decentralized small-sized SDPs. Lower water shortage index leads to higher cost, and the unit decrease of shortage index will need more added cost when the shortage index is very low. This method is proven to be effective in identifying the best conjunctive use of inter-basin water and desalinated seawater, which can contribute to relieve urban water shortage.     

Integrated Management of Non-conventional Water Resources in Anhydrous Islands

Anhydrous islands are dependent either on non-conventional water resources, such as desalinated seawater or reclaimed water from wastewater, or on water importation from the mainland. The latter option is often expensive and non-sustainable. Desalinated water can be used for potable and non-potable water applications, while reclaimed water can be used for non-potable water applications. Thus all water needs can be satisfied by an optimal blend of desalinated and reclaimed water. It is important to calculate the optimal capacities and locations of seawater desalination plants, wastewater treatment plants and water reclamation plants, and to estimate the water/wastewater conveyance system, in order to minimise water production and distribution costs. Mathematical modelling and optimisation techniques can be employed for calculating the optimum scenario: the satisfaction of all water needs at minimum cost. In this article, we have estimated the water demands taking into account water quality for the anhydrous Greek island of Syros, in the Aegean Sea. Syros has been subdivided into 6 regions, taking into account geographical and population distribution criteria. All water needs are to be satisfied by desalinated seawater and reclaimed water. A mixed-integer linear programming algorithm is used here to calculate the optimal scenario (location and capacities of desalination plants and wastewater treatment and water reclamation plants, as well as the desalinated water, reclaimed water and wastewater conveyance infrastructure needed) by minimising the annualised total cost including capital and operating costs.     

滨海城市非常规水源供水规模优选

滨海地区河流源短流急、地表水资源开发难度大,将再生水、淡化海水等非常规水纳入滨海城市水资源统一配置是缓解水资源短缺矛盾的有效途径。考虑地表水等常规水资源丰枯不确定性,科学确定非常规水源工程建设规模,是实现常规与非常规水资源统一配置的关键。以威海市区为例,建立了考虑水库来水不确定性的海水淡化与再生水厂建设规模优选模型,采用多目标遗传算法进行求解,以可靠性、弹性和脆弱性为指标,评价整个供水系统的性能,并进行多方案比较。结果表明:2030规划水平年威海市区适宜的再生水和海水淡化规模分别为23和15万m3/d;在此规模下,威海市区的供水保证率可由63.8%提高到95.2%,多年平均供水成本为6.6亿元。研究结果可为区域供水规划提供决策参考。     

The Use of System Dynamics Model to Enhance Integrated Resources Planning Implementation

Elsinore Valley Municipal Water District (EVMWD), like many other water agencies in southern California, relies heavily on imported water supply. The uncertainty associated with reliable imported water supplies due to drought conditions and climate change, and the increasing cost of imported water are areas of concern for EVMWD. Considering these conditions, EVMWD, which serves one of the fastest growing regions within Riverside County, embarked upon the development of its first Integrated Resources Plan (IRP) – a long term strategy for providing reliable water supplies to its growing customer base. The IRP’s evaluation methodology consists of three steps: Identification of potential water supply projects, project evaluation, and recommendation of a water supply portfolio comprised of the specific projects. A System Dynamics (SD) Water Resources Decision Support System (WRDSS) was used to evaluate different scenarios and examine EVMWD’s vulnerability to risks such as water supply shortage, and changes to water quality and/or water demand projections. Even though SD has been extensively applied to many water resources planning modeling efforts, based on our literature review, there is not a documented case of SD modeling applied to an IRP project. The recommended water supply portfolio represents the most cost effective option. It meets the forecasted long term deficit and provides the best reliability while providing good quality water supplies to EVMWD’s customers. The recommended water supply portfolio will be implemented using an adaptive management approach to adjust to changing conditions, coupled with long-range resource management policies that optimize water supply and storage assets in times of both drought and surplus.     

Comparing Public Perceptions of Alternative Water Sources for Potable Use: The Case of Rainwater,Stormwater, Desalinated Water,and Recycled Water

This research investigated how people’s perceptions of alternative water sources compare with their perceptions of other technologies, and identified significant predictors of comfort with different alternative water sources. We drew on data from four questionnaire survey studies with a total sample of more than 1200 Australian participants. Relative levels of comfort with the alternative water sources was consistent across the four studies: comfort was always highest for drinking rainwater and lowest for drinking recycled water, with comfort with drinking treated stormwater and desalinated water sitting between these two. Although comfort with drinking recycled water was always lowest of the four alternative water sources, participants were significantly more comfortable with drinking recycled water than they were with nuclear energy, or with using genetically modified plants and animals for food. In general, demographic variables were less important predictors of comfort with alternative water sources than were psychological variables; only age and gender emerged as relatively consistent predictors for recycled water, stormwater, and desalinated water, with older participants and males more comfortable with drinking these water sources. Of the psychological variables, participants’ comfort with technology in general, trust in science and trust in government emerged consistently as significant positive predictors of comfort with drinking recycled water, stormwater, and desalinated water.

     

沧州渤海新区核心功能区需水量预测及水资源利用

针对沧州渤海新区核心功能区用水以工业用水为主,而其所在地——沧州地区淡水资源匮乏的特点,通过调研国内类似区域用水量情况,采用单位面积用水量法对核心功能区需水量进行预测,并对核心功能区水资源的分配利用进行论述。为满足沧州渤海新区用水需求,建议规划时综合考虑利用地表水、外调水、再生水及海水淡化水。     

Forests and water--closing the gap between public and science perceptions.

The public perception that forests are, in all circumstances, necessarily good for the water environment, that they increase rainfall, increase runoff, regulate flows, reduce erosion, reduce floods, "sterilize" water supplies and improve water quality, has long been questioned by the scientific community. The evolving "modern" science perception suggests a more complex and generally less advantageous view of forests. It is suggested that the disparity between the two perceptions needs to be addressed before we are in a position to devise and develop land and water policies which are aimed at either improving the water environment, and by doing so improving the livelihoods of poor people by greater access to water, or conserving and protecting forests. Examples are given of "interactive" research projects in different parts of the world including the UK, South Africa, Panama and India where, through the involvement of stakeholder groups, often with representatives comprising both the science and public perceptions, research programmes have been designed and are being implemented, not only to derive new research findings with regard to the biophysical processes, but also to achieve better "ownership" and acceptance of these research findings by the stakeholder groups.     

引海水冲刷黄河口的试验研究

基于模型试验 ,作者研究和探讨了海水注入点上、下游河道溯源和沿程冲刷过程及平衡比降、冲刷的效果和冲刷后水位的变化。结果表明 ,引海水冲刷黄河口 ,配合小浪底水库运用 ,能够延长河口流路的使用寿命 ,在一定程度上缓解黄河山东河道的防洪压力 ,对减缓黄河下游河床抬高是有利的     

Comparative Evaluation Of Surface Water Availability,Wastewater Reuse And Desalination In Saudi Arabia

ABSRTACT

There is a growing concern in the Kingdom of Saudi Arabia to exploit water resources of acceptable quality to meet demands in domestic, industrial, and agricultural sectors. The agricultural water need, which constitutes approximately 84% of the total demand, was estimated to be 7430 million cubic meters in 1985. The annual domestic and other demands amounted to 1400 million cubic meters for 1985. Various alternative supplies to meet these demands are surface water, renewable groundwater resources, reclaimed wastewater, desalinated water, and non-renewable groundwater. Due to excessive withdrawal of water from deep aquifers, considerable drawdown has recently been noticed.

This paper reviews the existing and future trends in developing surface water resources, reclamation of waste-water from various towns and cities and its use, and the role of desalination plants in the coastal regions of the Arabian Gulf and Red Sea. These alternatives are evaluated and compared in economic terms. Cost-capacity relationships are developed for various alternatives which will be used in developing long-term plans for optimum allocation of available resources in different parts of the Kingdom.     

What does Integrated Water Resources Management from Local to Global Perspective Mean? Qatar as a Case Study,the Very Rich Country with No Water

Management of water resources is a very challenging issue, particularly in regions of the world where water is almost absent. In the Gulf Region, this issue is especially complex due to harsh-arid environments and increasing anthropogenic input of pollutants from the energy industry. The emergence of nations rich in oil and gas, such as Qatar, but poor in water resources requires new and dynamic systems and plans for managing limited water resources in times of extreme growth, such plans are discussed in this paper. The State of Qatar’s average annual evaporation rate is 30 times more than precipitation and the country depends on desalinated water to meet 99 % of its municipal water needs. Additionally, increasing population growth coupled with tremendous urbanization and industrialization add more stress to the existing renewable water resources, and newly produced water, namely desalted seawater and treated wastewater. Absence of water tariff and a water pricing system along with a lack of conservation awareness places Qatar as one of the highest water consuming countries in the world. Municipal water consumption per capita per day reached 500 L/ca.d for the year 2013. Dumping of sea to build new cities and construct towers makes the area very susceptible to salt water instruction, a phenomenon that does not only affect the groundwater aquifer system but also the construction materials and building deformations. Currently, Qatar uses the most advanced technologies for treating wastewater; however, the pure treated wastewater is not considered a viable water resource and is not used in areas of critical water demand such as agriculture and landscaping. Social, religious, and local marketing views limit the current use of treated wastewater. Integrated water and wastewater management strategies are absent and the national players of the two sectors -water and wastewater-are different. Current plans for integrated water resources management (IWRM) cannot answer the basic questions, what to manage and in which scale; is it the brackish and unused groundwater or the desalinated water from the existing technologies, the supply or the demand or all? This paper tries to highlight some facts related to Qatar’s water situation as an arid Gulf State and introduces potential ideas for IWRM. The critical aspects of IWRM discussed herein are relevant to a number of nations in the global community dealing with issues of extreme water insecurity.     

Estimating willingness to pay for desalinated seawater: the case of Djerba Island,Tunisia

Water scarcity can be a growth-limiting factor. Non-conventional water resources, such as desalinated water, represent an alternative means of guaranteeing access to water while reducing water stress. In this study, a contingent valuation survey carried out in Djerba Island, Tunisia, allows the joint modelling of two decisions: societal support for the construction of a desalination plant and households’ willingness to pay for desalinated water. To the best of the authors’ knowledge, no study to date has addressed this relationship. We find that although a clear majority of households are in favour of using desalinated water, far fewer are willing to pay for it. The article concludes that it is worth studying willingness to pay for desalinated water in developing countries in order to avoid investing in projects where it is doubtful that costs will be recouped.     

Chlorinous flavor perception in drinking water.

Chlorinous flavors at the tap are the leading cause of customers' complaints and dissatisfaction with drinking water. To characterize consumer perception and acceptance to chlorinous tastes, extensive taste testing was performed with both trained panelists and average consumers. Taste testing with trained panelists showed that chlorine perception is underestimated by disinfectant flavor thresholds reported in the literature. However, trained panelists significantly overestimate the average consumer's ability to perceive chlorine. In addition, consumer perception seems to be influenced by the chlorination practices of the country they live in. Among water quality characteristics that may influence chlorine perception, temperature was not found to induce any significant change. The influence of total dissolved solids (TDS) on chlorine perception remains unclear and, as reported elsewhere, background tastes such as musty, may significantly impact chlorine threshold.     

Storm Water Harvesting in Saudi Arabia: a Multipurpose Water Management Alternative

This work evaluates the potential for rainwater harvesting at the household level in the dry climate of Saudi Arabia. The amounts of rainwater that can be harvested in several cities in Saudi Arabia were estimated and it was found that a significant volume, exceeding 7.5 m³/100 m² per year, can be harvested. The per cubic meter cost of harvesting rainwater was compared to that of producing desalinated water. It was found that harvested rainwater is cheaper to capture than desalinated water produced from renewable energy-driven desalination plants, but that is not the case for fossil fuel-powered desalination. The study also considered the effects of rainwater harvesting on mitigating floods and reducing greenhouse gas emissions. A cost-benefit analysis of installing rooftop rainwater harvesting systems in Saudi Arabia was performed. It revealed that it is economically feasible to harvest rain in cities including Hail, Jeddah, Taif, and Riyadh, while it is not recommended in the holy cities of Makkah, Medina, and Buraidah.     

The African Development Bank: President's Statement

ABSTRACT

External support agencies and national governments are advocating community management of rural drinking water supplies and sanitation facilities as an appropriate and realistic way ofguaranteeing the long-term sustainability of systems in developing countries. Experience with community managed rural water supplies in the developed world can provide useful insights and guidance for the conceptualization, planning, and implementation of community managed water projects. Lessons from a successful water supply program in Western Canada suggest that a sustainable community managed water supply project must be demand driven, that the implementing agency provide an enabling environment, and that beneficiaries be legally empowered to assume ownership and responsibility for the completed systems.     

The Perception of Residential Water Tariff,Consumption, and Cost: Evidence of its Determinants Using Survey Data

In a survey of 1,500 households in Zaragoza (Spain), we found that respondents did not accurately know what the price of water was, and what the characteristics of the water tariff were, how much water they consumed, or how much it cost them; they thought they consumed less water than they actually did, and thought that their consumption level was normal; they believed they paid more than they really did, and considered the payments to be appropriate or expensive. Based on this sample of households, this paper analyses what determines the level of accuracy in the perception of consumers about their water tariff, their water consumption, and their total water cost, or, in other words, what determines the closeness between their perception and reality. The methodology applied is based on maximum likelihood estimates using various probit/logit models. The results obtained allow to identify the collectives to whom an information policy should be directed in order to approximate their perceptions closer to the real tariff, consumption and cost of water in households, and to point out the kind of information that should be transmitted in order to contribute to the preservation of water resources.

     

Urban Water Management in Developing Arid Countries

Urbanization, industrialization and rapid population growth in developing countries of the Arabian Peninsula are putting increasing pressure on local water authorities and water planners to satisfy the growing urban water and sanitation demands. In the Arabian Peninsula, water resources are limited, average rainfall is low and the seawater and brackish water desalination in addition to limited groundwater resources are the major water supply sources. The population increased from about 17.688 million in 1970 to 38.52 million in 1995 and is expected to reach 81.25 million in 2025. The urban population is expected to rise from 60% in 1995 to more than 80% in 2025. The domestic water demand is expected to rise from 2863 million cubic metres (MCM) in 1990 to about 4264 MCM in 2000 and 10580 MCM in 2025. In Saudi Arabia, the population increased by 143.6% between 1970 and 1995; and it is expected to reach about 40.426 million in 2025, with about 80% urban population. The domestic water demand in the Kingdom is expected to be about 2350 MCM in 2000 and 6450 MCM in 2025. Specialized agencies have been established for water production and distribution, and for wastewater collection, treatment and reuse. Special legislation has been introduced to manage water demands and to protect the interests of the community and its natural resources. Fifty-seven costly desalination plants have been constructed in the Peninsula on the Gulf and Red Sea coasts, as well as water transmission lines to transport the desalinated water to coastal and inland major cities. The seawater desalination unit cost is about US$0.70/m 3 for a large desalination plant with energy priced at world prices. More than $30 billion has been invested on water and sanitation projects. Present desalination production is about 46% of the total domestic demand, and the rest is pumped from deep and shallow aquifers. In general, fragmented legislation and institutional arrangements and low water charges have indirectly resulted in over-usage of domestic water, production of excessive quantities of wastewater, significant leakage, and enhancement of shallow water-table formation and rise in some cities. Facing the challenges of satisfying the growing urban water demands requires several essential measures such as: (a) introduction of new technologies to reduce water demands, and losses, and to enhance wastewater recycling and water conservation; (b) the updating of legislation to coordinate both responsibilities and actions among different water agencies; (c) the introduction of a strong and transparent regulatory framework to adopt different forms of water supply privatization, to reduce the costs of building, operation and maintenance of water and sanitation facilities, and to improve the level of services and billing, leakage and wastewater collection and treatment; (d) an increase in water tariffs to reflect the actual value of the water, and to enhance the awareness of public as to the value of water; and (e) development of short-term and long-term national water plans based on realistic water demand forecasting.     

Comparative stability and growth requirements of S. aureus and faecal indicator bacteria in seawater.

The fate (stability, multiplication) of S. aureus, E. coli and E. faecalis was determined in three classes of recreational waters (seawater, estuarine, stream) supplemented with nutrients in the form of sewage and peptone. In the absence of sunlight (24 +/- 2 degrees C), all bacteria in all water samples did not multiply and were slowly (days) inactivated. When 50% sewage was added to all water samples, E. coli and E. faecalis multiplied but S. aureus did not. When peptone (0.05%, 0.5%) was the added nutrient, the three bacteria multiplied. In the presence of sunlight (15-27 degrees C), S. aureus was inactivated rapidly (hours) in all water samples. These results show that when their nutritional requirements are met, S. aureus, E. coli and E. faecalis can multiply in the high salinity conditions of seawater. However, under environmental conditions, sunlight is an effective natural bactericidal agent.     

Current and future water issues in the Oldman River Basin of Alberta, Canada.

Long-term trends in alpine and prairie snow pack accumulation and melt are affecting streamflow within the Oldman River Basin in southern Alberta, Canada. Unchecked rural and urban development also has contributed to changes in water quality, including enhanced microbial populations and increased waterborne pathogen occurrence. In this study we look at changing environment within the Oldman River Basin and its impact on water quality and quantity. The cumulative effects include a decline in net water supplies, and declining quality resulting in increased risk of disease. Our data indicates that decreases in the rate of flow of water can result in sedimentation of bacterial contaminants within the water column. Water for ecosystems, urban consumption, recreation and distribution through irrigation is often drawn from waterholding facilities such as dams and weirs, and concern must be expressed over the potential for contaminate build-up and disproportionate potential of these structures to pose a risk to human and animal health. With disruption of natural flow rates for water resulting from environmental change such as global warming and/or human intervention, increased attention needs to be paid to use of best management practices to protect source water supplies.     

Optimal Water Resource Allocation in Arid and Semi-Arid Areas

Areas of water shortage comprise many smaller sub-areas into which water is transported from external sources. Fairness and efficiency of distribution are overriding principles. Each local area requires adequate water for community and ecological purposes as well as a supply sufficient to maximise economic growth. Within arid and semi-arid areas, there are conflicts between the sub-areas and between these three types of water use, which can erupt into violent confrontations between different user groups. This study has developed a dynamic model for equitable distribution of water in water-shortage areas and aims to optimally satisfy the requirements of each locality, given limited supplies, and to maximise the total economic benefit of the entire area. The Heihe River Basin in northwest China was chosen as the area for the pilot study.     

Taste and odour testing: how valuable is training?

Correct identification of specific tastes and odours in a water supply can be a powerful tool in identifying the cause of the problem and facilitating rapid remediation. While taste and odour identification can be achieved by laboratory testing, consumer involvement is not only worthwhile as a public education exercise but can also indicate tastes and odours to which the public do not object. Interpretation of taste and odour results is a complex process. The Australian Water Quality Centre (AWQC), based in Adelaide, South Australia, has established a flavour profile panel, trained in Flavour Profile Analysis (FPA). This group was chosen to carry out a survey of tastes and odours present in selected Australian water supplies and laboratory treated water and bottled water. The waters were also assessed by a group of untrained volunteers to simulate the responses of consumers. In two series of tests there were significant differences in responses between the groups with respect to the intensity of the tastes and odours detected. In both instances the responses by the trained group were more consistent, making interpretation of results more straightforward. In the second series of tests the panellists were also asked their personal preferences. The results showed in general the preferred waters were those with minimal taste and odour and this was generally irrespective of the type of taste and odour present.