Journal of Water Resources Planning and Management

A new content-based, box-constrained, active-set projected Newton method is presented that solves for the heads, the pipe flows, and the nodal outflows of a water distribution system in which nodal outflows are pressure dependent. The new method is attractive because, by comparison with the previously published weighted least-squares energy and mass residuals (EMR) damped Newton method, (1) it typically takes fewer iterations, (2) it does not require damping, (3) it takes less wall-clock time, (4) it does not require the addition of any virtual elements, and (5) it is algorithmically easier to deal with. Various pressure-outflow relationships (PORs), which model nodal outflows, were considered and two new PORs are presented. The new method is shown, by application to eight previously published case study networks with up to about 20,000 pipes and 18,000 nodes, to be up to five times faster than the EMR method and to take between 34% and 70% fewer iterations than the EMR method.

This paper presents a simple tool for the assessment of maximum overtopping probabilities of dams. The tool is based on empirical relations between the overtopping probability and the basic hydrological and hydraulic characteristics of the dam-reservoir system: the unit storage capacity, $V_F^{*}$, and the unit spillway capacity, $Q_{\mathrm{Cap}}^{*}$, both weighted with the relative importance of the 1,000-year flood. The surface issued from the tool represents the limit above which no $V_F^{*}-Q_{\mathrm{Cap}}^{*}$ combination is statistically expected to offer a higher probability. The tool was calibrated using the detailed overtopping models of 342,233 synthetic cases generated from 30 existing dams and then validated against a set of 21 independent cases. The tool is useful when analyzing a portfolio of dams in previous screening phases of dam risk analysis. It aims at identifying overtopping as a relevant failure mode and easily classifying each dam in terms of its overtopping probability. The tool is also a support for the definition and prioritization of corrective measures since it assesses their impact in the overtopping probability reduction.

Sampling of drinking water distribution systems is performed to ensure good water quality and protect public health. Sampling also satisfies regulatory requirements and is done to respond to customer complaints or emergency situations. Water distribution system modeling techniques can be used to plan and inform sampling strategies. However, a high degree of accuracy and confidence in the hydraulic and water quality models is required to support real-time response. One source of error in these models is related to uncertainty in model input parameters. Effective characterization of these uncertainties and their effect on contaminant transport during a contamination incident is critical for providing confidence estimates in model-based design and evaluation of different sampling strategies. In this paper, the effects of uncertainty in customer demand, isolation valve status, bulk reaction rate coefficient, contaminant injection location, start time, duration, and rate on the size and location of the contaminant plume are quantified for two example water distribution systems. Results show that the most important parameter was the injection location. The size of the plume was also affected by the reaction rate coefficient, injection rate, and injection duration, whereas the exact location of the plume was additionally affected by the isolation valve status. Uncertainty quantification provides a more complete picture of how contaminants move within a water distribution system and more information when using modeling results to select sampling locations.

The regulation of rivers has always been a controversial issue, with potential benefits but also environmental impacts. In western Canada, the construction of W.A.C. Bennett Dam in the headwaters of the Peace River has raised concerns over the ecological health of the Peace-Athabasca Delta (PAD), a socioeconomically and ecologically important delta with national and international significance. The major concern is the reduced frequency of ice-jam floods, which are particularly effective in replenishing the high-elevation basins of the PAD. Previous studies have suggested that releasing water at opportune times from the dam could promote ice-jam flooding of the delta; however, ice-jam flood events can also be severe and devastating to riverside communities and economies. Thus, a critical and challenging question is how to promote flooding in the downstream deltaic ecosystem where it is essential without necessarily increasing the flood risk in upstream communities of the Peace River. This study reviews previous approaches and explores possible reservoir operation schemes with an integrated hydrologic and hydraulic river ice modeling framework to minimize flood risk and maximize flood potential at desired locations. It is demonstrated that by increasing reservoir release in the breakup period, it is possible to increase the likelihood of ice-jam flooding in the PAD without necessarily causing ice-jam floods in the upstream communities. However, the timing of the flow release, taking into account the receding ice front and local hydrometeorological conditions, is critical.

The results of a sensitivity analysis performed to examine the impact of uncertain parameters in an agent-based model (ABM) on the prediction of water use and energy use for pumping and water treatment in a distribution system are presented. The ABM was coupled with a water end-use model and the EPANET2 network solver to simulate word-of-mouth communication between water users and the adoption of water-efficient fixtures that lead to water use and energy savings in distribution systems. Three key ABM parameters (adoption probability, initial penetration rates, and connections per agent) were found to have an important impact on the adoption rate of low-flow fixtures. The parameter values were chosen from relevant literature and the sensitivity analyses determined that the adoption of four specific low-flow fixtures—toilets, showers, washing machines and dishwashers—were estimated to have the potential to reduce water use (9%) and energy use (9%) for pumping and treatment within a mid-sized Canadian water distribution system. The work provides an innovative framework that simulates human interactions and evaluates how these interactions can affect water and, subsequently, energy use in distribution systems.

State estimation of hydraulics (i.e., pressure and flows) in water distribution networks is an important tool for efficient and resilient operation. However, hydraulic state estimation is a challenging task in practice due to the scarcity of measurements and the presence of several modeling uncertainties. Standard state estimation techniques may produce unreliable estimates with no information of the estimation error magnitude, especially when historical data are used in place of missing measurements. This paper proposes a comprehensive methodology for generating hydraulic state bounding estimates by considering both measurement and parametric uncertainties. The methodology is based on solving the nonlinear interval hydraulic equations using bounding linearization, a technique that restricts the nonlinearities within a convex set, thus converting the problem to a form which is solvable using linear optimization. An iterative procedure improves the bounding linearization, converging to the tightest possible bounds. Simulation results demonstrate that the proposed methodology produces tight state bounds that can replace Monte Carlo simulations.

To achieve maximum efficiency in water pressurized transport, it is necessary to perform a global analysis, whenever possible starting from the system’s conception. The first stage of the process is the network layout, the main topic of this paper. The optimum topology from an energy point of view (or eco-layout) is the one that, insofar as is feasible, allows equalizing the network’s pressure to the set pressure standards. Eco-layouts can be easily designed in new systems but are difficult to implement, mainly in the short term, in operating networks. Nevertheless, because no system is eternal, the required actions can be gradually implemented. Therefore, the main goal of this paper is to identify and discuss these guidelines and actions, some of which are apparently contradictory to current design criteria, whereas others endorse modern management trends. These strategies can be summarized in two points: (1) providing lower pressure to consumers saves energy, and (2) setting up smaller pressure zones in terms of the elevation steps between zones will enable water companies to supply water at lower pressure in hilly areas. In the end, networks with more-efficient layouts can achieve important energy savings.

Smart water infrastructures are prone to cyber-physical attacks that can disrupt their operations or damage their assets. An algorithm was developed to identify suspicious behaviors in the different cyber-physical components of a smart water distribution system. The algorithm incorporated multiple modules of anomaly-detection techniques to recognize different types of anomalies in the real-time monitoring and control data. Trained artificial neural networks were used to detect unusual patterns that do not conform to normal operational behavior. Principal component analysis was conducted to decompose the high-dimensional space occupied by the sensory data to uncover global anomalies. The algorithm was trained using a historical data set of trusted observations and tested against a validation and a test data set, both featuring a group of simulated attack scenarios. The proposed approach successfully identified all the attacks featured in the Battle of the Attack Detection Algorithms (BATADAL) data sets with high sensitivity and specificity. Nevertheless, the performance was sensitive to high background noise in the sensory data.

Accelerated economic development in arid areas results in harmful stress on limited surface and groundwater resources. Flash flood and rainfall harvesting is a promising renewable resource. Using a theoretical water budget approach, this paper investigates groundwater recharge after a flash flood in three small dam reservoirs and one moderate-capacity dam reservoir in the Al-Alb basin, central Saudi Arabia. This approach is validated against water level measurements at five recharge wells. Watershed modeling of this basin was conducted using an analysis of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital elevation models, in which the morphometric variables were calculated. Landsat-8 and Spot-5 images from April 2015 were classified to identify different land-use and land-cover categories. The soil conservation service curve number (SCS CN) method was used to estimate the effective rainfall, where the estimated CN values of different land uses and the spatially distributed time-area zones of the catchment were identified. The rainfall-runoff relationship was assessed using the Hydrologic Engineering Center–Hydrologic Modeling System (HEC-HMS) model, and the results were validated using the actual reservoir storages of these dams. The lag time, time of concentration, time to peak, and maximum of discharge storage reservoir sizes and volumes were estimated for the main and subbasins of the Al-Alb basin. This research shows that considerable amounts of water can be harvested using these small dams ($0.21\times {10}^6{\mathrm{m}}^3$ to $6.95\times {10}^6{\mathrm{m}}^3$). The hydrographs show that the construction of smaller dams upstream of the main dam at the Al-Alb location decreases the main peak magnitude by 14%, and the main runoff volume by 3%. Because of the high evaporation rate and low natural groundwater recharge as a result of siltation process in the dam lakes, recharge wells were drilled in the dam reservoir, increasing groundwater recharge by 44% and decreasing evaporation loss by 86%. With time, well recharge efficiency decreases, owing to clogging by the siltation process. Consequently, it is recommended to periodically clean and maintain the recharge wells.