This paper reviews the evolution of bioretention systems, a promising at-source storm-water best management practice. The introduction of bioretention systems in the 1990s by Prince George’s County, Md. is examined along with the motivations behind the development of the systems. A summary of the research findings on the performance of bioretention systems is provided including proposed design modifications to improve the field performance. Also included is an overview of past and current bioretention design guidelines in North America, as well as a discussion of issues surrounding the public adoption and implementation of bioretention systems. Potential alternative uses for the systems are highlighted and a review of bioretention modeling work is provided. Finally, the paper outlines research needs and anticipated future work necessary to bring about the widespread use of bioretention systems.

Climate change has made environmental impact a factor of growing importance in decision making for municipalities. Increasingly, the environmental impacts of expanding and operating a water distribution system (WDS) are considered alongside the cost and hydraulic design. This paper presents a nondominated sorting genetic algorithm (NSGA-II) that minimizes capital costs, annual pumping energy use, and environmental impacts in WDS design that adheres to hydraulic constraints. A previously developed environmental impact (EI) index is included in the environmental objective function of the optimization program. The EI index normalizes and aggregates multiple environmental measures evaluated with an economic input-output life-cycle assessment (EIO-LCA) model. The EIO-LCA-based NSGA-II was applied to the Anytown network. Annual pumping energy use was found to dominate the EI index while capital cost and the EI index were inversely related, and the annual pumping energy use and the EI index followed a near linea...

The paper explores the connection between the urban form of water distribution networks and their energy use. Urban form corresponds to the network pipe configuration and the spatial distribution of water users. An analytical model is developed to quantify the energy use to fabricate pipes, to repair pipes, to pump water, and to dispose of pipes in a trunk line. Results show that only a 10% reduction in annual per capita energy is achieved in the trunk line by increasing population density from 10 ca∕ha to 275 ca∕ha . The analysis is extended by computing energy use in networks with gridiron, radial, and satellite pipe configurations and uniform, monocentric, and polycentric population distributions. On average, the radial/monocentric combination exhibits the lowest annual per capita energy use. The paper is concluded by discussing changes to the form of cities and water main infrastructure to reduce environmental impact.

An index-based method for the evaluation of the environmental impact of water distribution systems is introduced. The method is developed according to a set of methodological criteria to assess the environmental effect of water networks. A number of environmental measures are incorporated into the index-based method to account for nonrenewable resource consumption, greenhouse gas emissions, and emissions to air, land, and water. The index-based method can be included into a multiobjective optimization program to find design solutions that minimize cost and environmental impact. The index-based method was applied to the design of a water transmission system over a 20-year design horizon. Design alternatives were compared on the basis of the environmental impact index and cost. For the system analyzed, results indicated that of the hydraulically feasible alternatives, the five most environmentally acceptable alternatives were the five most cost-effective alternatives. Results also showed that the environmen...

This paper presents a stochastic design approach that quantifies the expected annual damages sustained by residential, commercial, and industrial users during low- and high-pressure hydraulic failures in a water network. The approach, which couples stochastic models of water demand, fire flow, and pipe breaks with Monte Carlo simulation, was used to solve part of the Anytown design problem. Results indicated that a significant proportion of low-pressure failures occurred during low-demand months in the last $10\text{years}$ of the planning period. The timing and spatial distribution of demands observed during failure differed significantly from the demands assumed in conventional design (maximum hour and maximum day $\text{demand}+\text{fire})$ . The results also indicated that including damages in design makes it possible to produce cost effective systems that yield a low level of expected annual damages. This gives force to framing the network design problem as a stochastic, multiobjective one to balance cost efficiency with system capacity/redundancy and provide a hedge against hard-to-anticipate temporal and spatial patterns of demand in networks.

The aim of water distribution design is to size and configure a system so that it meets existing and future demands while providing pressures above a minimum level for service and fire protection. Extended period simulation (EPS) is used in design to determine network pressures under varied diurnal demand patterns. In EPS, diurnal demands are almost invariably assumed to change in unison, or in statistical terms, to be strongly correlated in space. This paper first tests this common assumption by investigating the extent to which cross correlation in demand affects the mean and standard deviation of pressure heads in water networks, and then investigates how cross correlated demands can influence capital costs in network design. Preliminary findings from two examples indicate that the standard deviation of pressure head and capital costs can be sensitive to the level of cross correlation between nodal demands. Thus a realistic assessment of cross correlation in demand can lead to a more economical design.