Yves Filion

Review of Bioretention System Research and Design: Past, Present, and Future

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.

Evaluating the Environmental Impacts of Water Distribution Systems by Using EIO-LCA-Based Multiobjective Optimization

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...

Evaluating the Impact of Climate Change Mitigation Strategies on the Optimal Design and Expansion of the Amherstview, Ontario, Water Network: Canadian Case Study

The objective of this paper is to assess the impact of proposed Canadian climate change mitigation policies (discounting and carbon pricing) on cost, energy use, and greenhouse gas (GHG) emissions in the single-objective design/expansion optimization of the Amherstview water distribution system in Amherstview, Ontario, Canada. The single-objective optimization problem is solved with the elitist genetic algorithm (EGA). The optimization approach is used in a parametric analysis to examine the impact of discounting and carbon pricing on GHG reductions for cement-mortar ductile iron and polyvinyl chloride pipe materials. Preliminary results indicate that the discount rate and carbon prices investigated had no significant influence on energy use and GHG mass in the Amherstview system and did not meet the emission-reduction targets set by the Canadian government. This result was attributed to a number of factors, including adequately installed hydraulic capacity in the Amherstview system, the use of a time-dec...

EFFECT OF TIME STEP AND DATA AGGREGATION ON CROSS CORRELATION OF RESIDENTIAL DEMANDS

End-use water demands are one of the most important and vexing inputs to a network hydraulic model. Accurate water demands are essential for meaningful network calibration, validation and simulation exercises as well as for design, analysis and performance assessment. However, assigning water use to network nodes is fraught with many difficulties, including questions about the demand magnitude, the temporal pattern and the cross (i.e., spatial) correlation. It is not unusual in practice to assume that, during extended period simulations, all demand nodes follow the same synchronized hourly demand pattern. In essence, the demands across the distribution system are often taken to be perfectly cross correlated in space. Clearly, the degree of cross correlation between nodal demands (if any exists) could have a profound effect on the results of subsequent hydraulic and water quality simulations. Despite the importance of the water use cross correlation issue, there has been relatively little work on this problem – perhaps due to a lack of field data. This paper seeks to quantify the degree of cross correlation that exists in 365,000 residential water demands collected from 21 single family homes in Milford, Ohio, during a seven month period. This collection of field data represents one of the most extensive high resolution records (one-second interval) of continuous residential water use ever assembled. In particular, the paper investigates two important research questions: (i) How does cross correlation between indoor water demands change with the level of spatial aggregation (e.g., two groups of five or ten homes)? (ii) How does cross correlation between water demands change with the averaging time step (i.e., one second, one minute, one hour, or longer)? This investigation offers empirical insights into the degree of cross correlation between water demands that exists in a small residential neighborhood, including a picture of how the cross correlation between demands is affected by changes in temporal averaging (time step) and spatial aggregation. Principal findings show that cross correlation tends to increase with an increase in spatial and temporal aggregation.

Least-Cost Design of Water Distribution Networks Including Fire Damages

The implicit goal of water network design is to provide acceptable service during normal and peak demands and to limit damages to property and people during fires. Despite this, fire damages are seldom explicitly included in network design. This paper presents a single-objective particle swarm optimization program that incorporates a new measure of expected conditional fire damages to size local water distribution mains for fire flow protection in residential service areas. The optimization approach generates trade-off information to help utilities determine the cost effectiveness of adding new pipe capacity to reduce the risk of fire damages in water networks. The optimization program was applied to an 8-pipe network and a 34-pipe network to generate trade-off curves for pipe cost and fire damages. A sensitivity analysis indicated that the level of uncertainty in fire flow had a little impact on pipe sizing and cost in the eight-pipe network. Optimization results in the 34-pipe network supported the indu...

Climate Change: Implications for Canadian Water Resources and Hydropower Production

In this paper the possible effects of climate change on Canada’s water resources, and the attendant implications for hydropower production are discussed. A change in climatic conditions could spawn drastic changes in the way that the Canadian hydroelectric sub-sector manages the operations of its hydropower stations. Supporting arguments draw largely on four modelling studies in which general circulation models (GCMs) and hydrological models have been used to predict significant climatic and hydrological changes in Canada’s major watersheds. The areas investigated include the interior of British Columbia and southern Yukon (Coulson, 1997), the basins surrounding James Bay in Quebec (Singh, 1988), the Great Lakes Basin in Ontario (Cohen, 1986), and the Saskatchewan sub-basin which transects the provincial borders of Alberta, Saskatchewan and Manitoba (Cohen, 1991). A synthesis of the results of these studies is used to decipher the multitude of annual and seasonal changes in runoff, precipitation and evaporation that may occur in the future. There are indications that the annual volume of runoff and hydropower capacity may increase in northern regions, and decrease in southern regions. As for seasonal changes, northern areas may see a more intense spring runoff due to an increase in snowpack, while southern areas may experience heavier winter runoff due to larger winter rainfalls. A greater number of spring or winter floods could force hydropower installations to divert flood water to their spillways more frequently, amounting to missed opportunities to produce energy. The frequent occurrence of extreme events such as large storms and flash floods could also jeopardize the integrity of certain hydropower stations. Other problems such as melting glaciers, ice jams, sediment loading and hydraulic surging could adversely affect the operations of hydropower stations. These problems may be exacerbated by increases in demand for domestic and irrigation water, as well as energy for interior cooling. The paper concludes by enumerating mitigatory and managerial strategies to alleviate the possible difficulties faced by the hydropower sub-sector.

Issues and Implications of Carbon-Abatement Discounting and Pricing for Drinking Water System Design in Canada

Water utilities generate greenhouse gas (GHG) emissions when they construct, retrofit, and operate their water distribution systems. The prospect of introducing carbon-abatement strategies such as carbon pricing and using low discount rates for project planning could potentially change the manner in which water utilities plan and design their drinking water systems. The objectives of this paper are to: (i) Review the current issues and controversies surrounding the choice of discounting rate and carbon prices in Canada to reduce the GHG emissions linked to operating water systems in Canada; (ii) Review previous research that has examined the impact of discounting and carbon pricing on design decisions in water supply and distribution systems, and; (iii) Illustrate the possible implications of carbon-abatement strategies (discounting and carbon pricing) on the design of Canadian water systems by way of a real-world case study. The implications of discount rate and carbon price uncertainty on water distribution system design are illustrated with the Amherstview-Odessa water transmission system in Ontario, Canada. The results of the Amherstview study indicated that lowering discount rate led to significant increases in electricity costs. The study results also suggested that for a sufficiently low discount rate of 1.4%, increasing carbon price led to a larger pipe size and pipe cost to offset carbon costs levied on fossil-fuel based electricity to operated the pumps for the life of the system. Additional studies are needed on large-scale water systems to inform decisions on system upgrades taken by water utility managers.

Energy Dissipation Mechanisms in Water Distribution Systems

An important issue in the context of design and analysis of a water distribution system is the rate of energy dissipation of a transient disturbance. In this paper, a preliminary numerical investigation is undertaken to establish the role and significance of primary energy dissipation mechanisms commonly found in water transmission and distribution systems. The role of steady friction, unwanted leaks, topological complexity and surge control devices in the decay of transient energy is preliminarily investigated. An energy approach previously derived is reviewed and used to track the progress of dissipation in a system. Transient simulations are run on a hypothetical series pipeline and distribution network with a waterhammer simulator to explore the dissipative effectiveness of some of the primary mechanisms.Copyright

CROSS CORRELATION ANALYSIS OF RESIDENTIAL DEMAND IN THE CITY OF MILFORD, OHIO

Estimating future demands with a high degree of accuracy in water distribution network design remains an elusive goal. The desired outcome is to match the design demands to the demands that are eventually “realized” in the built system. To this end, this paper explores the cross correlation between demands in an existing system in order to gain a better picture of the representative spatial and temporal patterns of design demands. The aim of the paper is to analyze the cross correlation in the residential demand data collected in the city of Milford, Ohio. More specifically, the paper begins to answer five important questions concerning the cross correlation of the Milford demand data: how strongly cross correlated are indoor, residential demands? How strongly correlated is the deterministic, diurnal component of residential demand? How strongly correlated is the random noise component of residential demand? To what extent does the choice of time step influence the strength of correlation between these 3 demand components? Does the correlation between these 3 demand components differ significantly between weekdays and weekends? To answer these questions, a periodic regression model was used to isolate the deterministic and the random noise components from the residential demand data collected in Milford. Correlation indices were formulated to measure the cross correlation of residential demand, its deterministic, diurnal component, and its random noise component. The Milford results pointed to a number of preliminary findings: (1) both residential demand and its deterministic, diurnal component had a positive and moderate to high correlation, while the random noise component of demand had a low level of correlation for the cases investigated; (2) increasing the time step length (from 600 s to 3,600 s) did increase the strength of the correlation in residential demand and its deterministic, diurnal component. This suggests that a longer time step increases both the coherence in diurnal demand patterns and their synchronicity. It is unclear whether time step length had any influence on the correlation of the random noise component of demand; (3) both residential demand and its deterministic, diurnal component were more strongly correlated during weekend periods than during weekday periods. This finding suggests that weekend periods may be characterized by less erratic water use patterns between customers leading to more coherent and synchronous diurnal patterns. It is unclear whether the random noise component was influenced by day-of-week effects. The implications of these preliminary results are discussed in the context of extended period simulation (EPS) and water quality modeling as they pertain to cost-effective design.

Stochasticity of Demand and Probabilistic Performance of Water Networks

Accurate prediction and modeling of water demand is crucial to understanding the long-term performance of systems, as it is to mounting an effective design and operational planning effort. The paper investigates the influence of cross correlation and autocorrelation in demand on the probabilistic, hydraulic performance of water networks, as measured with the mean and variance of nodal pressures. A stochastic demand model that accounts for lag-1 autocorrelation and lag-0 cross correlation between demands is applied to generate synthetic series of correlated demands. A Monte Carlo Simulation is coupled with EPANET2 to generate time series of pressures and update the mean and variance of nodal pressures. Preliminary results indicate that enforcing a strong lag-0 cross correlation in demand decreases the mean of pressures and increases the variance of pressures. This indicates that the frequency of low-pressure, hydraulic failures is contingent on the level of correlation measured or assumed in a reliability study. Enforcing a strong lag-1 autocorrelation memory at system nodes produces little or no changes in the mean and variance of nodal pressures, but it is found to govern the period of time a pressure signal can persist below a minimum-pressure constraints and remain in a hydraulic failure state.