Journal of Water Resources Planning and Management

Ecosystem restoration calls for reservoir reoperation. Traditionally, a minimum water release is set as a constraint for downstream ecosystem flow requirement. Recently, research has been conducted for the purpose of recovering natural flow regimes to a practical degree. This paper examines the practicality of adding an ecological objective to the operation of Lake Shelbyville, a reservoir situated on the Kaskaskia River in east central Illinois, which has been used primarily for flood control. A multiobjective optimization model that minimizes flood damage (the dominating priority in the historical operation) and maximizes fish diversity for the downstream ecosystem is developed for daily operation of the reservoir. The challenges addressed in this paper include handling daily reservoir release for the ecological assessment and evaluating the practicality of changing the existing operation rules for the purpose of including an ecological objective. The model results in the reduction of the maximum allowable water release to avoid extreme flooding events and an increase of the minimum water release. Thus, adding an ecological objective to Lake Shelbyville’s operation can improve downstream fish habitat without jeopardizing its original flood control objective. Furthermore, the effect of hydrologic variability on the results is explored with Monte Carlo simulations of reservoir inflows. The robustness analysis shows that the modified operation rules are sensitive to water levels; the biased representation of the role of water level in the reservoir release function can cause the bias of water release from its optimal value. Despite the limited data for the case study, this paper presents a method to improve conventional reservoir operation rules with consideration of both ecological and economic objectives.

This paper presents an analysis of a newly developed draft agreement on the allocation of water and energy resources of the Syr Darya basin considering transboundary cooperation and benefits sharing. The method uses a river basin model and game theoretic concepts to assess the potential benefits to the four riparian countries, under various arrangements of cooperation, ranging from independent action to full cooperation as envisioned in the draft agreement. The analysis shows increased benefits to all countries in the basin if they follow the four-country cooperative arrangements outlined in the draft agreement. Different methods for allocating the benefits of cooperation are considered. The Shapely allocation provides each country with increased economic benefits and is stable in relation to each country’s likelihood of treaty compliance. Other methods to allocate of the gains are considered, such as proportional shares, equal shares, the Nucleolus, and Nash-Harsayni, which all result in allocations that are more likely to be violated and are less stable than the Shapley allocation. The analysis indicates the upstream country of Kyrgyzstan can be encouraged to participate in and comply with the agreement through additional compensatory payments; however, if their conditions are not right, they may be prone to noncompliance and disruption of the treaty. The concepts illustrated in this paper can be used as the basis for analyzing benefits sharing and cooperation in other transboundary basins.

In coastal areas with shallow aquifers, the minimum elevation of newly developed land is typically required to exceed the water-table elevation corresponding to a given return period. Determination of this regulatory water-table elevation usually requires a nonstationary frequency analysis of measured water-table elevations. In this paper, a simple and effective power-transform frequency-analysis procedure for extracting the requisite regulatory water-table elevation is presented and demonstrated. This procedure identifies the critical period yielding the maximum water-table elevation for a given return period, which is a robust regulatory elevation that might not need frequent updates. The assumptions underlying the proposed power-transform frequency-analysis procedure are shown to be valid at 23 of the 24 wells investigated in this study.

Pressure-driven analysis of water distribution networks (WDNs) can realistically reproduce the actual behavior of the hydraulic system, especially with reference to leakages, which are not under human control, and, sometimes to demands in pressure-deficient conditions. Classical WDN models represent the demand and leakage outflows in terms of either prior fixed nodal discharges, in classical demand-driven analysis, or dependent on actual nodal pressures, in pressure-driven analysis. This work presents a WDN pressure-driven algorithm that allows accounting for actual leakage and demand patterns along pipes or, as a complementary feature, for network topological simplification. It is on the basis of the enhanced global gradient algorithm (EGGA) and has been introduced and discussed in comparison to classical pressure-driven GGA. Three test networks have been used to study the convergence issue of the newly proposed algorithm, and the largest network has been used to discuss its computational efficiency.

The end-use model SIMDEUM for residential water demand has been extended to incorporate nonresidential water demand. The model was developed to predict water-demand patterns with a small timescale (1 s) and small spatial scale (at the water meter connection). The end-use model is based on statistical information about users and end uses: data on occupancy; the frequency of use; duration and flow per water-use event; and the occurrence over the day of different end uses, such as flushing the toilet, doing the laundry, and washing hands. The model follows a modular approach, in that each type of building is composed of functional rooms, such as lodgings, restaurants, and conference rooms. A functional room is characterized by its typical users and water-using appliances. With this approach, nonresidential buildings’ water-demand patterns over the day can be simulated. The simulation results for an office building, a hotel, and a nursing home were compared to measured water-demand patterns with regard to attributes such as peak flow and daily total water use, as well as the shape of the pattern. The simulation results show a good correspondence to measured water demands. The end-use model is based on independent statistical information and not on flow measurements. The input parameters are available before any information on annual or daily water use is available; the parameters are not fitted on flow measurements. Therefore, the model is transferable to a diverse range of nonresidential water-demand types. The model can be applied in the design stage (prebuild), in scenario studies, and in distribution network models.

Remote Field Eddy Current (RFEC) technology allows the in situ inspection of metallic water distribution pipes. RFEC tools provide the location and magnitude of corrosion defects on the inspected pipes. The capacity of an RFEC tool to detect corrosion defects is evaluated in this paper by comparing its results with those obtained from the analysis of computed tomography (CT) scan images of the inspected pipes. Localization and characteristics of defects identified with the RFEC tool and from the CT scan images were compared for six cast iron pipes. An original method is proposed for the analysis of the CT scan images from which wall thickness losses were estimated by using the basic principle that the attenuation coefficient of X-rays in a homogenous material is a linear function of its density. The results show that the RFEC tool is able to localize most of the defects identified from the analysis of CT scan images. These findings reveal that the tested RFEC probe provided reliable information on the main corrosion defects, and thus on the general structural integrity of the inspected pipes.

This work presents a model for the inclusion of chemical water stability in optimizing the operation of water distribution systems. When desalinated water is mixed with surface water and/or groundwater, the blend can become chemically unstable. Such a state can cause the phenomena of “red water,” an increase in corrosion rates, and a reduction in disinfection efficiency. In this study, a methodology is developed that links a genetic algorithm, a hydraulic and water quality extended period simulator, a numerical scheme for computing the calcium carbonate precipitation potential (CCPP) [the quantitative measure of the precise thermodynamic potential of a solution to precipitate (or dissolve) ${\mathrm{CaCO}}_{3(\mathrm{s})}$], and the pH of the water. The model minimizes the cost of pumping and treatment subject to quantities, pressures, CCPP, and pH constraints. Two example applications are utilized for demonstrating the methodology capabilities. Although the model provides a new tool for the explicit inclusion of chemical water stability in optimal operation of water distribution systems, it overlooks variations in pump efficiency at operational points, does not constrain the number of pump switches, the minimum pump operation and off times, the durations between pump start and shutoff, and the plant or source capacity. Those limitations should be considered in possible extensions of this study.

The hydraulic reliability of a water distribution system (WDS) can be improved by increasing the resilience to failure conditions. In previous research, numerous measures have been developed to quantify network resilience, which has been consequently linked to the hydraulic reliability of WDSs. Often, the difference between the output pressure head and the minimum required pressure head is required in the calculation of these network resilience measures. Difficulties arise when these measures are applied to water transmission systems (WTSs). The reason for this is that in a WTS, water is often pumped into a storage tank or reservoir, in which case the difference between the output pressure head and the minimum required pressure head is always zero. To overcome this shortcoming, it is suggested that the surplus power factor can be used as a network resilience measure because calculation of this measure does not require the pressure value at the outlet of a WDS. In the research presented here, three case studies are used to assess the suitability of the surplus power factor as a network resilience measure for WDSs. A fourth case study is used to demonstrate the application of surplus power factor as a network resilience measure for WTSs, to which the other measures cannot be applied. The results show that the surplus power factor can be used as a network resilience measure to incorporate hydraulic reliability considerations into the optimization of WDSs and particularly WTSs.

This paper proposes a modified genetic algorithm (GA) for optimization of water distribution systems. A method of dynamically expanding the pipe-choice-table selections and reducing the number of decision variables is introduced, which occurs during a GA run. On the basis of the progressive selection, an initially reduced choice table for each decision variable is allowed to dynamically expand, and then the number of decision variables is gradually reduced. This process enables the GA search to concentrate on promising regions of the search space. The dynamically expanding choice-table genetic algorithm (${\mathrm{GA}}_{\mathrm{DECT}}$) has been applied to a benchmark case study, the New York Tunnels Problem. The results obtained show that the ${\mathrm{GA}}_{\mathrm{DECT}}$ yields a superior performance in terms of solution quality and computational efficiency.