Angela Marchi

Battle of the Water Networks II

The Battle of the Water Networks II (BWN-II) is the latest of a series of competitions related to the design and operation of water distribution systems (WDSs) undertaken within the Water Distribution Systems Analysis (WDSA) Symposium series. The BWN-II problem specification involved a broadly defined design and operation problem for an existing network that has to be upgraded for increased future demands, and the addition of a new development area. The design decisions involved addition of new and parallel pipes, storage, operational controls for pumps and valves, and sizing of backup power supply. Design criteria involved hydraulic, water quality, reliability, and environmental performance measures. Fourteen teams participated in the Battle and presented their results at the 14th Water Distribution Systems Analysis conference in Adelaide, Australia, September 2012. This paper summarizes the approaches used by the participants and the results they obtained. Given the complexity of the BWN-II problem and the innovative methods required to deal with the multiobjective, high dimensional and computationally demanding nature of the problem, this paper represents a snap-shot of state of the art methods for the design and operation of water distribution systems. A general finding of this paper is that there is benefit in using a combination of heuristic engineering experience and sophisticated optimization algorithms when tackling complex real-world water distribution system design problems

Incorporation of variable-speed pumping in multiobjective genetic algorithm optimization of the design of water transmission systems

AbstractGlobal warming caused by human activities presents serious global risks. Individuals, governments, and industries need to be more energy efficient and contribute to the mitigation of global warming by reducing their greenhouse gas (GHG) emissions. In previous research, GHG emission reduction has been identified as one important criterion in improving the sustainability of urban infrastructure and urban water systems. Within the water industry, opportunities exist for reducing GHG emissions by improving pumping efficiency via the use of variable-speed pumps (VSPs). Previously, VSPs have been used in the optimization of the operation of existing water distribution systems (WDSs). However, in WDS design optimization problems, fixed-speed pumps (FSPs) are commonly used. In this study, a pump power estimation method, developed using a false position method based optimization approach, is proposed to incorporate VSPs in the conceptual design or planning of water transmission systems (WTSs), using optimi...

Evaluating the Approximation of the Affinity Laws and Improving the Efficiency Estimate for Variable Speed Pumps

Affinity laws relate to the characteristics of pumps operating at different speeds, and in a water distribution context, are usually used to predict the pump curve of variable speed pumps (VSPs). VSPs can adjust the pump curve to meet the network requirements more efficiently with resultant savings of energy. The estimation of the effectiveness of a VSP is based on hydraulic simulations, in which the behavior of VSPs is described using the affinity laws. The affinity laws, however, contain approximations because they do not take into account factors that do not scale with velocity. In particular, the approximation inherent in the affinity law that computes power and efficiency can produce a misleading result, especially for small-size pumps. The research reported in this paper estimates the error in efficiency for a wide range of pump sizes and tests the use of a previously proposed formula as an alternative to the affinity law. Results show that a better estimation can be achieved for the efficiency of small- and medium-size pumps. Moreover the formula can be easily implemented in hydraulic solvers.

Correction of the EPANET Inaccuracy in Computing the Efficiency of Variable Speed Pumps

AbstractOne attractive possibility for saving energy in water distribution systems is the introduction of variable speed pumps (VSPs). However, to assess the cost effectiveness of using VSPs, a correct estimate of VSP energy consumption, and therefore efficiency, is essential. This task involves estimating the efficiency of various components: pump, motor, and variable speed drive. Hydraulic solvers, which are used to check the hydraulics of the system, usually use the affinity laws to describe the pump behavior in a VSP pumping system. This paper demonstrates the inaccuracy of the popular hydraulic solver EPANET 2, which does not properly take into account the affinity laws in the efficiency computation when the speed changes for VSP operations. The correction of the code is presented and an additional improvement of the toolkit to directly retrieve the efficiency is introduced.

Integrated Approach for Optimizing the Design of Aquifer Storage and Recovery Stormwater Harvesting Schemes Accounting for Externalities and Climate Change

AbstractHarvested stormwater is now being considered as an alternative water source in a number of cities because of concerns over water scarcity and population growth. However, the availability of this source varies as a result seasonality and climate change. This paper introduces an approach for optimizing the design of a stormwater harvesting scheme including aquifer storage and recovery that explicitly takes into account future climate change and its impact on the optimal design of the scheme. The proposed approach also accounts for the externalities associated with the use of harvested stormwater. The approach is applied to a specific case study in South Australia, considering four possible climate scenarios for planning horizons of 2030 and 2050 and the additional benefits of reducing withdrawals from the river source and the salinity of the water supplied. Results show that climate change will reduce the yield and the net present value (NPV) of the optimal stormwater scheme. They also indicate that...

Comparison of pumping regimes for water distribution systems to minimize cost and greenhouse gases

AbstractA single-objective optimization model has been developed for water distribution system (WDS) pumping operations, considering five different types of pump operating regimes. These regimes use tank trigger levels, scheduling, and a combination of both to control pumps. A new toolkit development to alter rule-based controls in hydraulic simulation software has allowed more complex pump operating regimes than have previously been considered to be optimized. The performance of each of the regimes is compared with respect to two different objectives: cost and greenhouse gas (GHG) emissions, which were optimized separately to allow the comparison of regimes to be made more clearly. Two case study networks, including one that represents a segment of the South Australian WDS, illustrate the effectiveness of the model. Time-based scheduling operating strategies were found to perform better than the other types of pump operating regimes. Significant cost savings were achieved for the South Australian case st...

Identification of Optimal Water Supply Portfolios for a Major City

AbstractIntegrated urban water management (IUWM) considering alternative water supply options is attracting increasing attention from water resources managers due to its efficiency and flexibility ...

Multiobjective Design of Water Distribution Networks through the Generation of Pseudofronts in the Hydraulically Feasible Region

AbstractThe design of a water distribution network (WDN) is conceptually a multiobjective problem characterized by stringent constraints. Even in its most simple formulation, which requires only the maintenance of minimum pressures, it is difficult to solve, and the simplifications introduced often impair the practicality of the solutions. The paper aims at integrating an engineering approach to the optimization problem by generating pseudofronts in the hydraulically feasible region of the search space. The optimization algorithms provide an entirely feasible trade-off between cost and considered constraints, which may be directly used by a hypothetical decision maker. This engineering approach requires a fast tool to search for feasible solutions: the recently developed genetic heritage by stochastic evolution transmission (GHEST) algorithm, used herein, has proved to be effective and efficient in solving the optimal design problem of WDNs. Tests are carried out on two large-size water distribution netwo...

Ecosystem Service Impacts of Urban Water Supply and Demand Management

Utilities face the challenge of enhancing long-term water security while minimising undesirable economic, social and environmental impacts of supply and demand management options. This paper provides an example of how the ecosystem services concept can be used to enumerate and organise broad impacts of water supply options. A case study of Adelaide, South Australia, is used to examine costs and benefits associated with different sources of water and source-water mix scenarios. Ecosystem service impacts are estimated using estimates from the literature. Seven water supply and demand management options are considered for Adelaide: 1) the River Murray, 2) Mt. Lofty Ranges catchments, 3) wastewater reuse, 4) desalination, 5) stormwater harvesting, 6) groundwater and 7) water conservation. The largest costs are associated with sourcing water from conservation measures such as water restrictions on outdoor watering estimated at

Evolutionary algorithms and other metaheuristics in water resources

1.87/kL. Salinity damage costs associated with residential uses are estimated at up to