Journal of Water Resources Planning and Management

Authorities of municipal separate storm-sewer systems (MS4s) are required to address illicit discharges as part of the United States’ National Pollutant Discharge Elimination System’s (NPDES) stormwater program. Field reconnaissance is an effective measure to detect and identify illicit discharges, but requires substantial staff and financial resources to conduct. While risk-analysis techniques and guidelines have been developed to facilitate MS4 prioritization of field operations, neither a standard set of indicators nor a standard operating procedure has been adopted. This study investigates the relationships among indicators of illicit-discharge potential (IDP) and the locations of illicit discharges in two Virginia MS4s. Results of the study indicate that certain risk factors are statistically more effective at predicting IDP, suggesting that a core set of factors can be used to map illicit-discharge risk. The results also show that risk-mapping tools are significantly impacted by uncertainty in model inputs. Recommendations are provided for MS4s interested in pursuing IDP risk mapping as a tool to improve cost-effectiveness and guide illicit-discharge program implementation.

Although many recent studies have quantified the potential effects of climate change on water resource systems, the scientific community faces now the challenge of developing methods for assessing and selecting climate change adaptation options. This paper presents a method for assessing impacts and adaptation strategies to global change in a river basin system at different temporal horizons using a hydro-economic model. First, a multiobjective analysis selects climate change projections based on the fitting of the climate models to the historical conditions for the historical period. Inflows for climate change scenarios are generated using calibrated rainfall-runoff models, perturbing observed meteorological time series according to the projected anomalies in mean and standard deviation. Demands are projected for the different scenarios and characterized using economic demand curves. With the new water resource and demand scenarios, the impact of global change on system performance is assessed using a hydro-economic model with reliability and economic indices. A new economic loss index is defined to assess the economic equity of the system. Selected adaptation strategies are simulated to compare performance with the business-as-usual scenario. The approach is applied to the Jucar River water resource system, in eastern Spain, using climate projections from the European Union (EU) ENSEMBLES project. Results show that the system is vulnerable to global change, especially over the long term, and that adaptation actions can save $€3–65\mathrm{million}/\mathrm{year}$.

Clear Creek watershed, located in the Ozark Mountain Region of Northwest Arkansas, has experienced ecosystem degradation as a result of increased urbanization. Riparian zones are known to play an integral role in maintaining ecosystem integrity and are often used as management tools for protecting watershed ecosystem services, especially in urbanizing areas. To determine whether residents of the Clear Creek watershed would be in favor of the establishment and maintenance of riparian zones in their region, a mail survey was conducted using contingent valuation methods (CVMs) to elicit local willingness to pay (WTP) for riparian zones. The study found that residents were willing to pay an average of $80.07 in increased state income taxes for the ecological services provided by riparian zones. Bid amount, income, and attitude toward willingness to pay were shown to have the most significant influence on the residents’ overall WTP. Survey results were also used to assess residents’ abilities to perceive ecosystem quality as a factor of WTP but analysis found this perception to be insignificant in affecting respondent WTP.

To estimate pipe roughness in water distribution networks, a parameter estimation method based on head loss adjustment is proposed. In order to minimize the sum of the squares of the corrections of pipe head losses, pipe head losses simulated by EPANET are adjusted by using weighted least squares (WLS) constrained by head measurements. Pipe roughness (the Hazen-Williams C-factor) is computed by using the ratio of simulated to adjusted head losses, while the outliers are detected and removed by using boundary-fence and gross-error-detection techniques. The iterative loops of model simulation and head loss adjustment under multiple operating conditions support that pipe roughness can be realistically estimated even when nodal demands and head measurements are noisy. The method was verified on a hypothetical network and part of a real network from the literature. The results show that the method is effective for pipe roughness estimation.

The dilemma of managing the trade-off between immediate human needs and maintaining the ability of the Earth to provide ecosystem services is considered to be one of the greatest challenges of this century. Many management strategies have applied the ecosystem service concept to address this challenge, which incorporates land management, policy, and economic decisions to achieve overall ecosystem health. The intent of this research was to improve such decisions through an increased understanding of the relationship between urban stormwater control measures (SCMs) and freshwater provision, erosion regulation, and flood regulation ecosystem services. Fifty-six land management scenarios with varying densities of targeted SCM application were simulated using the software PCSWMM. The ecosystem services resulting from these land management scenarios were quantified using a set of mathematical indices. Results demonstrate that the application of bioretention cells improved both freshwater provision and erosion regulation services immediately downstream from the implementation site and at the same time increased erosion regulation services at the greater watershed scale.

This work contributes a modeling framework to characterize the effect of cyber-physical attacks (CPAs) on the hydraulic behavior of water distribution systems. The framework consists of an attack model and a MATLAB toolbox named epanetCPA. The former identifies the components of the cyber infrastructure (e.g., sensors or programmable logic controllers) that are potentially vulnerable to attacks, whereas the latter allows determining the exact specifications of an attack (e.g., timing or duration) and simulating it with EPANET. The framework is applied to C-Town network for a broad range of illustrative attack scenarios. Results show that the hydraulic response of the network to a cyber-physical attack depends not only on the attack specifications, but also on the system initial conditions and demand at the junctions. It is also found that the same hydraulic response can be obtained by implementing completely different attacks. This has some important implications on the design of attack detection mechanisms, which should identify anomalous behaviors in a water network as well as the cyber components being hacked. Finally, the manuscript presents some ideas regarding the next steps needed to thoroughly assess the risk of cyber attacks on water distribution systems.

Local high points widely exist in wastewater pressure pipe system. In reality, wastewater pumps are cyclically switched on and off so that the force mains may not be always pressurized as usually assumed. Understanding the hydraulics of those gravity driven pipes is very important to the reliable operation of wastewater pumping. In this study, a differentiation-based method was developed to determine the temporal and spatial dynamics of wastewater in force main by solving the equations involving pump curves and system curves for both gravity-driven and pressurized flows. The solutions to the equations determine the operation points of pumps. The method was applied to a wastewater pumping system of the City of Lakeland, Florida, with multiple local high and low points in the force main. Field investigations and theoretical analyses are incorporated to calibrate pump head characteristic curve and pipe friction coefficient, enabling more accurate simulation of force main hydraulics. With its simplicity and affordability, this method would be of interest to water utility engineers.

A critical issue faced by the water industry is to efficiently manage limited water supplies to satisfy water demand from different sections (e.g., industrial, agricultural, energy and residential) and provide fresh and reliable sources of water for people’s everyday life. Most existing research focuses on either water consumption planning (e.g., supply–demand balance) or water postconsumption planning (e.g., wastewater planning). It is expected to be more cost-effective to integrate the water consumption and postconsumption planning into a holistic model since they are highly interdependent. In this research, a closed-loop integrated water system including sources, water plants, end users, and wastewater systems is modeled using the network theory, and a robust planning decision model is developed to minimize the total system costs including operation costs (e.g., water production and distribution costs, and wastewater treatment costs) and penalty costs associated with directly emitting untreated wastewater to the environment. Various levels of uncertainties from both water demand and pipeline efficiencies are considered. Three sets of experiments are developed to test the effectiveness of the proposed decision model. The experimental results conclude that (1) the integrated decision approach can achieve more cost savings compared to separated decision processes for both the deterministic and stochastic scenarios; (2) the authors’ proposed robust model can provide good balance between system robustness and cost; and (3) the integrated water system is more cost-effective when the water processing cost is dynamic, which highlights the benefits of the inventory and on-site third-party water plants. Analogous to the smart power-grid innovation, which employs on-site generation and storage systems to improve energy efficiency and environmental sustainability, the authors’ proposed model demonstrates the benefits of using on-site inventory and third-party water plants to renovate the existing water infrastructure for more cost savings and reduced environmental impacts.

The aim of observability analysis (OA) is to determine if a given measurement setting is sufficient to compute the current status of a water distribution network. There are several approaches in the technical literature for making such an analysis. With all of them, there is an assumption that the lie of the land of the network in terms of the status of its pumps and/or valves is known. This paper omits this assumption and introduces the concept of topological observability analysis (TOA), which aims to determine not only if it would be possible to compute the hydraulic state of a network from the available measurement set (ordinary OA), but also if the status of pumps and valves would be observable as well. Additionally, a method is proposed that modifies the standard measurement Jacobian matrix by incorporating either equations and/or unknowns depending on the available information for each specific pump or valve. The rest of the analysis can be undertaken using any of the existing methods for OA in the literature. An illustrative example is presented by way of illustration to show the potential of TOA, which would certainly enhance online monitoring systems.

The optimization of a water distribution system (WDS) is challenging because of its nonconvex head loss constraint. To address this issue, this paper proposes a modeling technique to represent the nonconvex head loss equation by convex constraints. In the convexification, the head loss equation is first rewritten into nonlinear inequalities, then disjunctive programming is used to represent the flow direction and pipe selection. The technique is applied to formulate a convex mixed-integer nonlinear programming (MINLP) model for WDS design. Effectiveness of the convexification is demonstrated by several benchmark examples.