Journal of Water Resources Planning and Management

A major challenge for society in the 21st century will be replacement, design, and optimal management of urban infrastructure. It is estimated that the current worldwide demand for infrastructure investment is approximately three trillion dollars annually. A Drinking Water Infrastructure Needs Survey conducted by the U.S. Environmental Protection Agency estimated that community water systems nationwide have an immediate need of $12.1 billion in infrastructure investment, primarily to protect against microbiological contamination. This paper presents equations that can be used to estimate the cost of system construction, expansion, and rehabilitation and repair for distribution system components. Equations have been developed for installation of new pipe, trenching, embedment, and the other unit operations that are required to replace or construct new distribution system components. Equations have also been developed to estimate the cost of cement mortar lining, sliplining, and corrosion control. These equations can be used in an additive manner to estimate the cost of all of the unit operations required for replacing or laying new distribution system piping, and for a limited set of rehabilitation and repair options.

Secondary or postdisinfection is widely used to maintain protective levels of disinfectant within water distribution systems. In contrast to conventional methods that apply disinfectant only at the treatment works, booster disinfection reapplies disinfectant at strategic locations within the distribution system to compensate for the losses that occur as it decays over time. Building on the writers’ previous work, this paper addresses the problem of locating disinfectant booster stations that minimize the dosage required to maintain residuals throughout the supply network, and introduces a useful parameterization for disinfectant source types. The model is related to the general fixed-charge facility location problem and is formulated as a mixed integer linear programming problem. Results for an example network show that disinfectant dosage savings are achievable with the adoption of booster disinfection, and that the rate of savings decreases as the number of booster stations utilized increases. Furthermore, booster disinfection may provide a more even distribution of disinfectant concentrations throughout the network, and has the potential to reduce aggregate exposure of the population to chlorine (and its by-products) while simultaneously improving residual coverage in the periphery of the distribution system.

An Eulerian-Lagrangian numerical solution for the advection-dispersion equation in water supply networks is presented. Because of the dispersion term, the numerical scheme produces a large linear system of equations. A technique that uses numerically computed Green’s functions is proposed to decompose this large system into three tridiagonal systems for each pipe and one (much smaller) system for the concentration at the pipe junctions. The resulting system is thus efficiently solved and the model can be applied to large networks at a reasonable computer cost. The proposed model is applied to simulate fluoride and chlorine propagation in a real network for which published data of field measurements and simulation with the EPANET advection-reaction model are available. Comparisons are presented which show that, while for high and medium pipe-flow velocities the two models give similar results, for low pipe velocities the new advection-dispersion model predicts more closely the concentration evolution, provided an appropriate value for the dispersion coefficient is used.

While the extent of human-induced global warming is inconclusive, the vulnerability of natural systems to rapid changes in climate patterns is regarded as one of the most challenging issues in recent years. Water resources are a main component of natural systems that might be affected by climate change. This paper characterizes water resources in several Middle Eastern countries and evaluates regional climate predictions for various scenarios using general circulation models. The country of Lebanon is selected as a case study for an in-depth investigation with potential impacts on the water budget and soil moisture as indicators. Adaptation measures are assessed, with a focus on no-regret actions in the context of local socioeconomic and environmental frameworks.

An integral part of groundwater management in Las Vegas Valley, Nev., is artificial recharge. Artificial groundwater recharge started in the late 1980s and as of the year 2000, the Southern Nevada Water Authority entities have recharged over 246,000,000 $m^3$ (200,000 acre-ft) of water, which is in storage in the valley’s aquifer system. Benefits from artificial recharge accrue to all valley residents, but in particular to municipal-industrial, domestic, public supply, and commercial well owners. The benefits are lower energy costs for pumping, decreased need to deepen wells, lower maintenance for wells that could potentially be damaged by subsidence, and additional water for the aquifer system. Although artificial recharge is currently a “free” benefit to all nonmunicipal groundwater pumpers, active management of the aquifer system would be enhanced by participation of all users in the artificial recharge program. In an effort to include all groundwater pumpers in the management of the aquifer system, a groundwater management program (GMP) was established. The costs and benefits for participation by nonmunicipal groundwater pumpers are presented, indicating a savings of about $700 annually for nonmunicipal members of the GMP.

Winter and summer water demand of apartments in Tucson, Ariz., is analyzed for 308 apartment complexes in the Tucson Water and Flowing Wells water districts. A general regression model revealed that water price, value per bedroom, number of bedrooms, apartment age, indoor water-saving devices, and swimming pools were significant determinants of winter water use per apartment. Water price, value per bedroom, number of bedrooms, apartment age, vacancy rates, and indoor water-saving devices were significant determinants of summer water use per apartment.

The presence of chlorination by-products such as trihalomethanes (THMs) in drinking water has become an issue of particular concern for utility managers. Modeling THM occurrence in water may be a valuable tool for decision makers in dealing with these potentially hazardous by-products. This paper presents the application of artificial neural networks (ANNs) to model THM occurrence in drinking water. ANNs are compared with other modeling approaches, logistic regression and multivariate regression, to classify water utilities according to their susceptibility to generate high levels of THMs and to predict concentrations of formed THMs with variable water quality and chlorination conditions, respectively. In general, for both applications, ANN models gave similar or better results than other modeling techniques.