A Realistic Basis for an International Comparison of Real Losses from Public Water-Supply Systems

The paper considers the subject of physical (real) losses from pressurised systems which are used for public water supply. To date, attempted comparisons of leakage management performance between water undertakings world-wide have been severely compromised because there have been no standard methods of defining and calculating real losses. Performance indicators, which have been traditionally used for comparisons, have been too simplistic. Limitations of existing performance indicators are identified in the paper by reference to key factors which should be incorporated in objective comparisons of real losses.
The paper describes an improved methodology which was developed by an International Water Association Task Force, based upon logical concepts using local key parameters, calibrated using auditable assumptions, and tested against twenty-seven diverse sets of data from twenty countries.     

Accounting for Losses: The Bursts and Background Concept

Losses of treated water occur through leakage and overflows from the pressurized pipes and fittings in water undertakers'distribution systems and customers'private supply pipes. The UK National Leakage Control Initiative was formed in 1991 to update previous published work on leakage control policy and practice in the UK.
Although some published technical relationships exist, there has been no overall methodology which attempts to provide a component-based estimate of annual losses in different parts of the distribution system for any particular combination of local circumstances, i.e. pressure, burst frequency, burst flow rate, number of properties, length of mains, method of leakage control, standards of service, and waste notice service/enforcement policy.
The 'bursts and background estimate'spreadsheet-based methodology is designed to provide such estimates. It links 'night-flow'and 'annual losses'concepts, and can be used for a variety of purposes. These include (a) assessment of the likely incidence of losses for different leakage control and waste notice policies, (b) identification (from night flows) of districts in which there are unreported bursts, and (c) assessment of economic target levels for leakage control. The substantial element of annual losses from service pipes, and the considerable influence of pressure on annual losses, are also discussed.     

Water losses investigation and evaluation in water distribution system – the case of SA city in China

Faced with the severe leakage and chaotic water management situation in developing countries, this research is committed to provide an appropriate and practical water audit calculation method for most water companies so as to guide their leakage control management. It prepares a recommended basic standard terminology for calculation of real and apparent losses, which can be consistent with practice in China. Due to more detailed subdivision of unmetered water along with water component analysis, the water consumption of SA city can be calculated more accurately. The proportion of water loss in SA is 18.02%, while unbilled authorized consumption contributes no more than 1% to the total water consumption. Meanwhile, the “Neighbourhood Metering Area (NMA)” project in SA city also suggests that metering inaccuracies and leakage on service connections up to the point of customer metering can be prioritized for active leakage control in China.     

Development of an interoperability model for different construction drawing standards based on ISO 10303 STEP

The purpose of this study is to develop an exchange model for the interoperability of various national standards based on the international standard ISO 10303 in construction. Several countries like Germany, Japan, and Korea have developed the drawing standards STEP-CDS, SCADEC, and KOSDIC, respectively, for the neutral drawing data exchange mechanisms among various applications. However, these standards are not naturally exchangeable due to the differences resulting from the national flavors representing the drawing elements defined in their standards. These problems can be solved using the exchange methodology, EXPRESS-X, defined in ISO 10303. In this study, an exchange model applying the standard exchange methodology has been developed by analyzing the three different drawing standards. The developed exchange model demonstrates that the interoperability among the drawing standards is feasible. In addition, the model shows that the use of the standard exchange methodology based on international standards is beneficial in many ways for the data exchange between schemata.     

Integrated tool for risk assessment in agricultural management of soil erosion and losses of phosphorus and nitrogen

In recent years, increased attention has been focused on models for risk assessment of source areas in agricultural landscapes. Among the simplest of such models are index tools, which have been developed particularly for phosphorus (P) and to some extent nitrogen (N). However, only a few studies have considered the development of an integrated management strategy that includes erosion and losses of both P and N. Accordingly, the major objective of this study was to initiate the development of an integrated risk assessment tool, consisting of indices for erosion, P and N. The strategy used to create the integrated tool was based on the assumption that all input data at field scale should be readily available either from ordinary agricultural statistics or from the farmer. The results from using the indices in a pilot case study catchment illustrated that losses of P and N had often different critical source areas. The P index was highest for fields with manure application and/or high soil P status or with autumn ploughing, and the N index was highest for fields with excessive N application. The integrated risk was greatest for areas with manure application and some areas with a high erosion risk in combination with high nutrient application rate. Additionally, four different management options were assessed: (1) reduced fertilisation, (2) catch crops, (3) autumn ploughing, and (4) no autumn ploughing. The results verified that reduced nutrient application and stubble during autumn and winter led to the largest decrease in index values, and it was also apparent that management changes in high-risk areas had the greatest impact on the indices. Overall, our findings indicate that the present integrated risk assessment tool with readily available input data can be used to rank farm fields according to risk of soil erosion and losses of P and N.     

Performance assessment model development and parameter acquisition for analysis of the transport of natural radionuclides in a Mediterranean watershed

This paper describes the methodology developed to construct a model for predicting the behaviour of the natural radioisotopes of U, Th and Ra in a Mediterranean watershed. The methodology includes the development of the performance assessment model, obtaining water flow and radiological parameters based on experimental data and analysis of results. The model, which accounts for both water flows and mass balances of the radionuclides in a semi-natural environment, provides assessments of radionuclide behaviour in grassland and agricultural soils, rivers and reservoirs, including the processes of radionuclide migration through land and water and interactions between both. From field and laboratory data, it has been possible to obtain parameters for the driving processes considered in the model, water fluxes, source term definition, soil to plant transfer factors and distribution coefficient values. Ranges of parameter values obtained have shown good agreement with published literature data. This general methodological approach was developed to be extended to other radionuclides for the modelling of a biosphere watershed in the context of performance assessment of a High Level Waste (HLW) repository under Mediterranean climate conditions, as well as for forecasting radionuclide transport under similar Mediterranean conditions that will occur in the future in other areas. The application of sensitivity and uncertainty analysis was intended to identify key uncertainties with the aim of setting priorities for future research. The model results for the activity concentration in the reservoir indicate that for (238)U and (230)Th the most relevant parameter is the initial concentrations of the radionuclides in the reservoir sediments. However, for (226)Ra the most important parameter is the precipitation rate over the whole watershed.     

Using the bimonthly water balance of a non-fully monitored water distribution network with seasonal water demand peaks to define its actual NRW level: the case of Kos town,Greece

Water losses in pipe networks are usually the biggest ‘water use’ due to the high leakage occurring. The need for conservative water use is today more pressing than ever due to the stressful climate change conditions, forcing water utilities to consider applying effective Non Revenue Water reduction strategies. The assessment of a network's current operating status based on the IWA water balance (WB) is a good start. Although IWA suggests the WB to be annually assessed, this is not ideal for networks experiencing seasonal demand peaks, like in Kos town, capital of Kos Island in Greece. The WB for Kos town network was assessed on a bimonthly basis, following the water billing period used by the local water utility. The results revealed that higher real loss rates occur during the lower water demand periods due to the higher operating pressures. The annual WB can not reveal water loss peak timing.     

Underground water resources in Kazakhstan

The assessment of natural resources and the ecological demand for underground water in Kazakhstan is based on a water-balance equation which considers underground lateral flow, hydrogeoecological regions and river basins. We propose a methodology to estimate the underground water resource for this region. The flow of water in all the rivers of Kazakhstan is estimated at 102.3 km³/year, of which 57.6 km³/year originates in the territory of the country, and 44.7 km³/year in the adjacent countries. With potential increase of the underground water usage up to 15.5 km³/year, the surface water volume could be decreased to 5 km³/year. Optimization of water resource use should be based on the introduction of the water-efficient process of reinjecting and recycling the water supply in all branches of industry, and a reduction in losses during distribution.     

Efficiency assessment of household water use

This paper presents a novel methodology for assessing the overall efficiency of indoor water uses in the household. The methodology comprises three main components of assessment: the evaluation based on efficient patterns, the comparison with peers grouped by clustering techniques and the performance of water use devices based on penalty functions. A water use index is calculated for individual households for each component; this index can be used to compare and to rank the performance of different households. The most representative results from a real life case study composed of 43 households are presented herein. The proposed methodology can support urban demand managers to identify low efficiencies, to set viable water efficiency targets, to calculate potential water savings and, subsequently, to implement water demand management strategies customized to less-efficient water use devices and to groups of consumers with specific socio-demographic characteristics.     

Water leakage detection using remote sensing,field spectroscopy and GIS in semiarid areas of Cyprus

Water pipelines need to be systematically monitored in order to minimize losses from possible leakages. In this paper, remote sensing techniques have been exploited in semiarid areas of Cyprus. In addition, ground spectroradiometer has been used to define the leakage's threshold values. The data were analysed in a GIS environment. Two known leakage problems have been examined. In the first case study, a high resolution QuickBird image was used for the detection of the exact point of leakage. In the second case study a multi-temporal analysis was performed using SPOT images. This methodology was able to record 10 possible leakage points along the pipeline. Throughout the 25 km length of the pipeline, the in-situ observations were minimized to only 0.4%. In both studies the Normalised Difference Vegetation Index (NDVI) was applied. The final outcomes highlight the contribution of remote sensing to the early detection of leakages especially in difficult and near inaccessible areas.     

A composite indicator for water meter replacement in an urban distribution network

In water supply management, volumetric water meter are typically used to measure users' consumption. With water meters, utilities can collect useful data for billing, assess the water balance of the system, and identify failures in the network, water theft and anomalous user behaviour. Despite their importance, these instruments are characterised by intrinsic errors that cause so-called apparent losses. The complexity of the physical phenomena associated with metering errors in aging water meters does not allow meter replacement to be guided by single parameters, such as the meter age or the total volume passed through the meter. This paper presents a meter replacement strategy based on a composite ‘Replacement Indicator’ (RI) that aims to reduce apparent losses. The performance of a meter during its operating life was analysed by means of this indicator, which signals when the meter needs to be replaced. To test the reliability and robustness of the proposed indicator, a Monte Carlo uncertainty analysis was performed. The methodology was applied to a real case study: a district metered area (DMA) in the Palermo city water distribution network (Italy). The analysis showed that ranking based on the composite indicator is better than common ranking procedures based on typical variables (e.g., the meter error curve or the meter age): the proposed indicator can better select the meters to be replaced and favourably affect the associated costs.     

Seismic Fragility of Steel Piping System Based on Pipe Size,Coupling Type,and Wall Thickness

In this study, a probabilistic framework of the damage assessment of pipelines subjected to extreme hazard scenario was developed to mitigate the risk and enhance design reliability. Nonlinear 3D finite element models of T-joint systems were developed based on experimental tests with respect to leakage detection of black iron piping systems, and a damage assessment analysis of the vulnerability of their components according to nominal pipe size, coupling type, and wall thickness under seismic wave propagations was performed. The analysis results showed the 2-inch schedule 40 threaded T-joint system to be more fragile than the others with respect to the nominal pipe sizes. As for the coupling types, the data indicated that the probability of failure of the threaded T-joint coupling was significantly higher than that of the grooved type. Finally, the seismic capacity of the schedule 40 wall thickness was weaker than that of schedule 10 in the 4-inch grooved coupling, due to the difference in the prohibition of energy dissipation. Therefore, this assessment can contribute to the damage detection and financial losses due to failure of the joint piping system in a liquid pipeline, prior to the decision-making.     

Leakage Targets and Socio-Economic Efficiency

During the last few years, the introduction of mandatory leakage targets for UK water companies has had the positive effect of reducing levels of leakage, while requiring the companies to operate at an economic level of leakage. Unfortunately, the determination of company-specific economic levels of leakage have been a source of disagreement between the water companies and the Government, with the Government view that water companies are not using the true long-term marginal costs of water abstraction, and therefore are not safeguarding the environment.
This paper (a) reviews the model which was used to define the economic level of leakage, (b) argues the case for resource management based on the impact of water abstractions on the socio-environmental quality of a resource rather than the myopic focus on leakage reductions, (c) presents the concepts of effectiveness and efficiency in relation to socio-environmental quality, and (d) proposes a new methodology which allows the determination of water abstraction rates while maintaining a desired level of socio-environmental quality.     

Estimation of the benefits yielded by pressure management in water distribution systems

The occurrence of water losses in Water Distribution Systems is inevitable. Knowing that most of the real losses take place in distribution mains and in service connections, the methodology proposed in this paper is based on several leakage-assessment approaches from literature and on water distribution network modeling. This allows assessment of the benefits that can be achieved by pressure management in Water Distribution Systems, particularly in terms of water production reduction. Moreover, this approach can be useful for cost benefit analysis to help establish the level after which there is no more economic interest in reducing water losses (Economic Level of Leakage). Finally, the results from hypothetical case studies are presented and discussed, assuming the installation of Pressure Reducing Valves at District Metered Areas entry points.     

Vulnerability of buildings to windstorms and insurance loss estimation

Windstorms cause enormous loss to life and property worldwide. Insurance companies use risk assessment models to assess the financial risk to their insurance exposure due to windstorms. The estimation of the intensity of hazard and the vulnerability of buildings to windstorms are important parts of a windstorm risk assessment model. The vulnerability functions (or curves) are, in general, based on analyses of loss data from insurance companies. The loss data available from insurance companies following a natural disaster is generally comprised of losses representative of a wide variety of buildings, often lacking information on building-specific characteristics such as height and material. Analysis of such data may not go beyond the development of an aggregate (or generic) vulnerability curve for a combined portfolio giving no idea of the vulnerability of individual building types represented by this curve. The paper discusses the vulnerability of buildings to windstorms and the development of vulnerability functions for windstorm loss estimation. A methodology is presented for the disaggregation of a generic vulnerability curve into several curves representing individual building types. The methodology provides a convenient way of translating known vulnerabilities for a region to those for another region by combining them with actuarial data and building inventory information of the region. The methodology is applied for the disaggregation of generic vulnerability curves for the Caribbean Island of Puerto Rico. The hurricane hazards and the consequent property losses in the region are also discussed.     

Estimating Pipe Reticulation Losses in a Municipal Water-Supply System

Domestic water consumption in the city of Dunedin, New Zealand, is unmetered. Recently, the Council's Water Department adopted sampling methods to estimate domestic water consumption and system losses, consistent with the recent reports on managing leakage produced by the UK water industry. This paper describes the exercise (which is ongoing), including the treatment of practical issues which arise in applying the methodology. System losses were estimated to increase substantially over the initial two years of the study, leading to the investigation of an assignable cause. The data reflect the effects of the corrective action, lending considerable support to the validity of the method.     

Leakage detection and location in water distribution systems using a fuzzy-based methodology

Loss of water due to leakage is a common phenomenon observed practically in all water distribution systems (WDS). However, the leakage volume can be reduced significantly if the occurrence of leakage is detected within minimal time after its occurrence. This paper proposes a novel methodology to detect and diagnose leakage in WDS. In the proposed methodology, a fuzzy-based algorithm has been employed that incorporates various uncertainties into different WDS parameters such as roughness, nodal demands, and water reservoir levels. Monitored pressure in different nodes and flow in different pipes have been used to estimate the degree of membership of leakage and its severity in terms of index of leakage propensity (ILP). Based on the degrees of leakage memberships and the ILPs, the location of the nearest leaky node or leaky pipe has been identified. To demonstrate the effectiveness of the proposed methodology, a small distribution network was investigated which showed very encouraging results. The proposed methodology has a significant potential to help water utility managers to detect and locate leakage in WDS within a minimal time after its occurrence and can help to prioritise leakage management strategies.     

Modeling the thermal distribution efficiency of ducts: comparisons to measured results

This paper presents a comparison of predictions from a duct efficiency model developed by the authors with measured real-time heating system efficiency measurements from six site-built residential homes with natural gas furnaces in the Puget Sound region. The model takes into account the interaction between supply and return side losses, the interaction between conduction and air leakage losses, the interaction between unbalanced leakage and natural infiltration, and the recovery of heat through the building envelope from ducts in various locations within the home. It does not take into account losses due to cycling. Field testing was done using a short-term coheating methodology. Both the modeling and tests were done before and after aggressive duct air leakage sealing and insulation retrofits.     

European case studies supporting the derivation of natural background levels and groundwater threshold values for the protection of dependent ecosystems and human health

The EU Water Framework and Groundwater directives stipulate that EU member states have to assess groundwater chemical status by the use of groundwater threshold values derived for the protection of dependent ecosystems and human health. This paper presents a synthesis of main results of 14 European case studies evaluating a methodology for derivation of natural background levels (NBLs) and groundwater threshold values (TVs) proposed by the EU research project "BRIDGE". The 14 investigated groundwater bodies were selected to represent as many aquifer types, climate settings and European ecoregions as possible within the project group that included partners from 17 EU countries. The selected case study sites include transboundary groundwater bodies, EU Pilot River Basins and other important groundwater systems. Some are known to interact with associated ecosystems, while others do not. The proposed method derives groundwater threshold values based on environmental objectives for dependent ecosystems or groundwater "itself" using relevant reference criteria such as natural background levels, environmental quality standards and drinking water standards. Derived groundwater threshold values for dissolved Cl and As applying drinking water standards as examples of reference values, are compared for all 14 case studies. Additionally, more detailed analyses are conducted for the Odense Pilot River Basin and the Vouga River Basin, where groundwater threshold values for N and P and Cl, As, Cd, Ni, Pb, and Zn, respectively, are derived based on environmental objectives and quality standards for groundwater dependent ecosystems. Results demonstrate that the proposed methodology is operational and may be used to protect human health and the environment. Further they show that groundwater threshold values derived from environmental objectives and environmental quality standards for dependent ecosystems in some cases may be significantly lower than drinking water standards, e.g. for nitrate.     

Comparison of remote sensing data, model results and in situ data for total suspended matter (TSM) in the southern Frisian lakes

Suspended matter plays an important role in water quality management since it is related to total primary production and fluxes of heavy metals and micropollutants such as PCBs. Synoptic information on suspended matter at a regular frequency is difficult to obtain from the routine in situ monitoring network since suspended matter is (like chlorophyll) a spatially inhomogeneous parameter. This can be solved by the integrated use of remote sensing data, in situ data and water quality models. A methodology previously developed for integrating information from remote sensing, and models (Vos and Schuttelaar, Neth Remote Sensing Board (1995) report 95-19), was applied for the assessment of suspended matter concentrations in the southern Frisian lakes in the Netherlands. The model is a one-dimensional network model. Remote sensing data (Landsat-TM5 and SPOT-HRV) were atmospherically corrected and converted to total suspended matter maps. The algorithms are based on analytical optical modelling, using the in situ inherent optical properties. This methodology enables the development of multi-temporal algorithms for estimating seston dry weight concentration in lakes from remotely sensed data; thus satellite data can now become an independent measurement tool for water management authorities.