Journal of Water Resources Planning and Management

Accurate modeling of water distribution systems is fundamental for planning and operating decisions in any water network. One important component that directly affects model accuracy is knowledge of nodal demands. Conventional models simulate flows and pressures of a water distribution network either assuming constant demand at nodes or using a short-term sample of demand data. Given the stochastic behavior of water demand, this assumption usually leads to an inadequate understanding of the full range of operational states in the water system. Installation of sensor devices in a network can provide information about some components in the system. However, the requirement for a reliable water distribution model that can assist with understanding of real-time events over the entire water distribution system is still an objective for hydraulic engineers. This paper proposes a methodology for the estimation of online (near-real-time) demand multipliers. A predictor-corrector approach is developed that (1) predicts the hydraulic behaviors of the water network based on a nonlinear demand prediction model; and (2) corrects the prediction by integrating online observation data. The standard particle filter and an improved particle-filter method that incorporates the evolutionary scheme from genetic algorithms into the resampling process to prevent particle degeneracy, impoverishment, and convergence problems, are investigated to implement the predictor-corrector approach. Uncertainties of model outputs are also quantified and evaluated in terms of confidence intervals. Two case studies are presented to demonstrate the effectiveness of the proposed particle-filter model. Results show that the model can provide a reliable estimate of demand multipliers in near-real-time contexts.

Pump scheduling in water distribution networks is important, especially with current high energy prices. A good pump schedule is one that reduces pump energy and maintenance costs without worsening the overall system performance. Because of the nonlinearity of the hydraulic energy balance equations and the complexity of water distribution networks, pump scheduling problems cannot be easily solved by hand, especially in the general case of a network with multiple tanks and pumps/pumping stations. A number of approaches exist in the literature addressing the trade-off between effectiveness (i.e., optimality of schedules generated) and computational efficiency, but there seems to be no ideal solution. In this paper, an effective and efficient optimization method, the iterative extended lexicographic goal programming (iELGP), is developed to solve a least-cost pump scheduling problem. The method is tested on two multitank networks. The results obtained demonstrate that by using the iELGP method, an optimal pump schedule can be obtained with high computational efficiency which makes the method suitable for real-time application.

This paper considers the sectorization of a large water distribution network into district metered areas (DMAs) and simultaneously optimizes rehabilitation of the network with new pipes, control valves, and storage tanks. Because available water resources are much lower in the dry season, both the design and operational settings are optimized to satisfy water-demand, water-quality, and pressure constraints, as well as efficiency indices under stringent conditions. Because of the heterogeneity of the multiple decision variables and the complicated way they interact through the multiple objectives (some complimentary and some conflicting), it is not possible to fully automate the simultaneous sectorization, rehabilitation, and operational optimization. Therefore, a multistage approach is used where engineering judgment and network graph simplification and visualization tools are used to find a good feasible solution that serves as a first guess for further optimization of sectors and operational settings, to achieve feasible solutions with better cost of implementation, demand similarity among DMAs, and better pressure uniformity in operations. A multiobjective agent swarm optimization framework is used to iteratively change the sectors at the boundaries. For the final configuration, sequential linear programming is used to find optimal valve and pump settings.

Assessing freshwater availability under changing climate and land-use conditions is critical for tropical islands, where small watershed sizes and unique hydrological features mean that freshwater resources are very sensitive to these changes. The objective of this study is to assess the impact of climate change on the water budgets of the Nuuanu area watersheds (NAW), Oahu, Hawaii, and most importantly, on the potential of water harvesting from Nuuanu Reservoir 4 (NR4). The harvest approach concerns water diversion from the reservoir for artificially supplementing groundwater recharge through injection into the subsurface. Following calibration and validation at multiple streamflow gauging stations across the watershed, the soil and water assessment tool (SWAT) model was applied to assess current and future water availability in the NR4. Multiple statistical evaluation criteria were used to demonstrate that SWAT adequately reproduced the observed daily streamflow hydrographs at all stations. Climate change analyses used the representative concentration pathways (RCP) 4.5 and 8.5 scenarios. The reported analysis suggests that the water-budget components of the NAW will generally be adversely affected by climate change. Compared to the baseline of 35 years, the amount of water available from the NR4 for harvesting will decrease by as much as 27%, and the corresponding outflow values will decrease by as much as 37%. Despite future temperature increases, the actual monthly watershed-scale evapotranspiration will decrease because of the overall decrease in rainfall and soil-moisture availability. Rainfall has the dominant control over the magnitude of water-budget components and harvesting compared with temperature and solar radiation. This study presents a blueprint for surface-water-harvesting scenarios, which may become a necessity across the Pacific and other islands in the future.

Water management for oil and natural gas extraction in the United States has become a topic of public interest and concern. This societal relevance simultaneously heightens the need for rigorous performance and dissemination of scientific work and invites caution from experts who are communicating within what is likely a politicized public conversation. This paper uses interviews to investigate experts’ current practices and comfort with communicating about water use for oil and natural gas. Participants cite face-to-face interactions and trust-based relationships as important in their interactions, which is consistent with research about effective communication. However, few participants highlight techniques specific to communicating about water as it relates to oil and gas or about controversial issues generally. Participants also rarely use communication science related to objective setting, framing, and measuring success for improvement, likely in part because of a lack of evidence-based training. In many cases, interviewees expressed attitudes consistent with the deficit model of scientific communication, which holds that presentation of scientific facts will change public opinion. This model has been shown to be relatively ineffective. This paper highlights the need for careful communication and evidence-based opportunities for improvement, including a suggestion that professional societies host communication training and coaching sessions.