Daniela Fuchs-Hanusch

A framework for water loss management in developing countries under fuzzy environment

A multi-criteria decision analysis method for water loss management is proposed.The method integrates AHP and TOPSIS methods under fuzzy environment.It is applied to a real water distribution system in a developing country.The prevalent strategies were highly connected to the local conditions. Facing water scarcity conditions water utilities cannot longer tolerate inefficiencies in their water systems. To guarantee sustainable water management one central task is reducing water losses from the supply systems. There are numerous challenges in managing water losses, manifested in a variety of options, their complexities, multiple evaluation criteria, inherent uncertainties and the conflicting objectives and interests of different stakeholders. This study demonstrates the effectiveness of multi criteria decision analysis (MCDA) approaches for decision support in this complex topic. The study covers identifying the key options among a set of options that have been proposed within a framework of strategies to reduce water losses in water distribution systems of developing countries. The proposed methodology was initiated by developing a hierarchical structure of the decision problem that consists of four levels: Overall objective, main criteria, evaluation criteria and options. Different stakeholders were engaged in the process of structuring and evaluating the decision problem. An integrated methodology that combines fuzzy set theory with Analytic Hierarchy Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) methods was then employed. This methodology has the potential to transform qualitative data into equivalent quantitative measures. Fuzzy AHP was used to create weights for main and evaluation criteria, while Fuzzy TOPSIS was used to aid the ranking of options in terms of their potential to meet the overall objective based on the evaluations and preferences of decision makers. The results showed that pressure management and control strategy was the most prevalent one, followed by employing advanced techniques and establishment of district metered areas. Their dominance was highly connected to the local and boundary conditions of the case study. The sensitivity analysis results showed that strongest and weakest options were less sensitive to changes in weights of evaluation criteria, which could be attributed to the strong consensus in strengthening the best option and neglecting the worst option. This study emphasized the successful application of MCDA in dealing with complicated issues in the context of water loss management. It is anticipated that, the integration of this developed framework in the planning policies of water utilities in developing countries can help in conducting better control over water losses.

A bibliometric-based survey on AHP and TOPSIS techniques

A bibliometric based survey on AHP and TOPSIS methods has been conducted.Scopus database was employed to retrieve the required data for this analysis.Assessment of quantitative and qualitative bibliometric indicators was obtainable.Efficacy of these methods promotes the development of related research.More scientific research interests will be devoted to these methods in the future. In recent years, the employment of multiple criteria decision analysis (MCDA) techniques in solving complex real-world problems has increased exponentially. The willingness to build advanced decision models, with higher capabilities to support decision making in a wide range of applications, promotes the integration of MCDA techniques with efficient systems such as intelligence and expert systems, geographic information systems, etc. Amongst the most applied MCDA techniques are Analytic Hierarchy Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The development of a comprehensive perspective on research activities associated with the applications of these methods provides insights into the contributions of countries, institutes, authors and journals towards the advancements of these methods. Furthermore, it helps in identifying the status and trends of research. This in turn will help researchers in shaping up and improving future research activities and investments. To meet these aims, a bibliometric analysis based on data harvested from Scopus database was carried out to identify a set of bibliometric performance indicators (i.e. quantitative indicators such as productivity, and qualitative indicators such as citations and Hirsch index (h-index)). Additionally, bibliometric visualization maps were employed to identify the hot spots of research. The total research output was 10,188 documents for AHP and 2412 documents for TOPSIS. China took a leading position in AHP research (3513 documents; 34.5%). It was also the leading country in TOPSIS research (846 documents; 35.1%). The most collaborated country in AHP research was the United States, while in case of TOPSIS it was China. The United States had gained the highest h-index (78) in AHP research, while in TOPSIS it was Taiwan with h-index of 46. Expert Systems with Applications journal was the most productive journal in AHP (204; 2.0%) and TOPSIS research (125; 5.2%), simultaneously. University of Tehran, Iran and Islamic Azad University, Iran were the most productive institutions in AHP (173; 1.7%) and TOPSIS (115; 4.8%) research, simultaneously. The major hot topics that utilized AHP and will continue to be active include different applications of geographic information systems, risk modeling and supply chain management. While for TOPSIS, they are supply chain management and sustainability research. Overall, this analysis has shown increasing recognition of powerful of MCDA techniques to support strategic decisions. The efficacy of these methods in the previous context promotes their progress and advancements.

Failure Propagation for Large-Diameter Transmission Water Mains Using Dynamic Failure Risk Index

Large-diameter transmission water mains (LDTWM) are lifelines of water supply systems and normally have low failure rates. In Austria the state of the art in condition assessment of LDTWM is to document after a failure and subsequent repair, a routine maintenance or a replacement of valves and accessories. Costs and impacts generated by LDTWM-failures require the necessity to understand the occurrence-probability of failure modes and the associated consequences. Additionally little work has been done on making desirable decisions prior to water main failures. The amount of water losses is one influencing parameter on LDTWM failure costs. Therefore global sensitivity analyses for specific failure modes were executed to define the most sensitive input-parameters on the amount of water losses per break. For 5 Austrian water utilities failure mode statistics have been analyzed on availability, reliability and completeness. A risk assessment methodology, a definition of relevant factors causing specific failure modes responsible for water losses and the use of bivariate logistic regression analyses to derive the main influencing factors on the occurrence of these failure modes are presented in this paper. Furthermore a vulnerability analysis which is used to quantify hydraulic driven consequences of specific failure modes is described. This paper aims to define high risk LDTWM to be prioritized for inspection, repair or rehabilitation. The methods were applied to one Austrian water utility and for 5 different failure modes.

Systematic material and crack type specific pipe burst outflow simulations by means of EPANET2

The calculation of outflow from pipe bursts is of interest for water utilities, as the discharged water may cause large amounts of damage to the adjacent infrastructure. Therefore, the crack type specific relationship between leakage outflow and pressure is of interest. Recent findings offer new opportunities for burst outflow calculations with hydraulic models. In this paper, we compare two calculation approaches according to uncertainties caused by input parameters and give recommendations for the applicability of the methods. Simulations in a case study area have shown large leakage outflow differences between the two approaches for longitudinal cracks. For circumferential cracks, the differences are smaller. Further, due to the uncertain leak size and form of probable bursts we involved Monte Carlo simulations in the model approach. These allow the derivation of mean values and standard deviations of leakage outflow per pipe section to make the uncertainty of the results more transparent.

Efficient Sensor Placement for Leak Localization Considering Uncertainties

Losses in water distribution systems can be between several percent in well maintained systems up to more than 50 percent in developing countries. Most of the losses originate from leaks. Therefore, a fast detection and localization of leaks is crucial for effectively reducing this losses in water distribution networks. Model-based leak localization has become increasingly popular in recent years. Certainly, the performance of these methods is linked to 1) the measurement locations in the system and 2) uncertainties at these locations. This paper provides a methodology that incorporates uncertainties of different types and sources in the optimal sensor placement problem for leak localization shown by the example of the effect of demand uncertainties on potential pressure measurement points. The problem is solved for different numbers of sensors and different strengths of uncertainties are taken into account. Additionally, to describe the relation between the number of sensors and the leak localization quality, a cost-benefit function is derived based on the different sensor placement results and GoF statistics. It was found that the function follows a power law. Results show that incorporating uncertainties leads to other optimal positions than without uncertainties, but the power law behavior still stays true. Additionally, more sensors are needed than without uncertainties.

Cause and effect oriented sewer degradation evaluation to support scheduled inspection planning.

Managing the subsurface urban infrastructure, while facing limited budgets, is one of the main challenges wastewater utilities currently face. In this context targeted planning of inspection and maintenance measures plays a crucial role. This paper introduces a cause and effect oriented sewer degradation evaluation approach to support decisions on inspection frequencies and priorities. Therefore, the application of logistic regression models, to predict the probability of failure categories as an alternative to the prediction of sewer condition classes, was introduced. We assume that analysing the negative effects resulting from different failure categories in extension to a condition class-based planning approach offers new possibilities for targeted inspection planning. In addition, a cross validation process was described to allow for a more accurate prediction of sewer degradation. The described approach was applied to an Austrian sewer system. The results show that the failure category-based regression models perform better than the conventional condition class-oriented models. The results of the failure category predictions are presented with respect to negative effects the failure may have on the hydraulic performance of the system. Finally, suggestions are given for how this performance-oriented sewer section evaluation can support scheduled inspection planning.

Estimates of Arab world research productivity associated with groundwater: a bibliometric analysis

The sustainable management of groundwater resources is a pressing necessity for most countries. As most of the Arab world is facing severe water scarcity, threats of depletion of non-renewable groundwater, and problems of pollution and salt-water intrusions into groundwater aquifers, much effort should be devoted to eliminate these dangers in advance. This work was devoted to bring up insights into Arab world research activities in groundwater, which is a crucial task to identify their status and can help in shaping up and improving future research activities. A bibliometric analysis has been conducted to track these activities. The study identified 1417 documents which represent 3.3% of global research productivity. Egypt was the most productive country (313; 22.1%), followed by Saudi Arabia (254; 17.9%). Total citations were 9720 with an average of 6.9. The h-index of the retrieved documents was 39, and the highest one was 22 for Egypt. The most common subject category was Environmental Science, and the most productive journal was Arabian Journal of Geosciences (99; 7.0%). In international research collaboration, France was the most collaborated country with Arab world (125; 8.8%), followed by the United States (113; 8.0%). The most productive institution was King Abdul-Aziz University, Saudi Arabia (66; 4.7%). The outcomes shows remarkable improvements in groundwater research activities originated from the Arab world. Even though, constructive efforts should be pursued vigorously to bridge the gaps in groundwater-based research. Moreover, promotion of better evaluation tools to assess the risks arising from the mismanagement of groundwater resources is required urgently.

Impact of Failure Mode, Crack Area, and Pressure on Leakage Outflow

The calculation of leakage outflow is of interest for several tasks in water distribution system analysis, e.g., investigation of pipe burst consequences, efficiency estimations of pressure management, or model-based leakage localization. Several studies on pressure-leakage dependencies have shown that this dependency can be much higher than defined with the orifice equation of Torricelli. The findings of these studies differ significantly, even for the same pipe material, failure modes, and sizes. In this paper, we describe the influence of uncertainties on assumptions of emitter exponents and crack areas on discharge rates for different failure modes. An approach for modeling elastically deforming leaks in water distribution pipes was implemented into systematic discharge rate calculations with EPANET2 by the means of an iterative estimation of the emitter exponent. For a partial pipe network of the city of Vienna, the results of the original EPANET2 and the extended emitter approach were compared. The largest differences in leakage outflow and hence in the amount of pipes with potential high failure consequences were found for longitudinal cracks. For this failure mode material, crack size and dimensions have a significant influence on the emitter exponent. Consequently, it is recommended for systematic discharge rate calculations to gather historic data about typical failure modes and failure dimensions of the investigated system. Further, if failure modes with a high sensitivity on the emitter exponent (like longitudinal crack or spiral crack) are relevant for the investigated system, a detailed calculation of the discharge rate is suggested.

Adige: an efficient smart water network based on long-range wireless technology

Outworn water distribution infrastructures require real-time monitoring and management of water pressure and flow, together with accurate leak detection and localization techniques. Smart water networks based on wireless sensors offer a huge potential in this domain, but their deployment and maintenance is often costly and labor-intensive. In this paper, we present Adige: an efficient smart water network architecture based on long-range wireless technology that improves the scalability and robustness of water distribution systems. We developed a sensor node prototype using a LoRa radio transceiver and used it to carry out a set of experiments showing the benefits of Adiges approach. Our evaluation shows that, in contrast to previous approaches, the use of long-range wireless technology allows to significantly reduce energy consumption while covering large areas indoors, outdoors, and underground.

Fitness landscapes and distance metrics for model-based leakage localization

This paper aims to investigate the effect of distance metrics on the fitness landscape for model-based leakage localization and its impact on the performance of the differential evolution optimization algorithm applied to a theoretical water distribution network from literature.