Journal of Water Resources Planning and Management

Numerical models of ground-water flow within the regional aquifer underlying Lambton County, Ontario, Canada, are constructed by the conjunctive application of methods of regression and inverse analyses. Regression analysis of physiographic and hydraulic head data reveals a distinct relation between ground-water levels and ground-surface topography that is used to condition the aquifer models that are subjected to inverse analysis. Inverse analysis determines the variation of hydraulic head along the perimeter of the region and the distribution of ground-water recharge and discharge within the region that optimally replicate the observed hydraulic head data. The use of physiographic data as a substitute for geologic data in the construction of the aquifer models is defended on the basis of the constraints that apply to the investigation and the opportunity to invoke hydrogeologic judgment in the evaluation of the results. Interpretation of the results of the analyses reveals important characteristics of the hydrogeology of Lambton County, including an area of elevated ground-water recharge and the partitioning of ground-water discharge to the Saint Clair River.

Water demands at four single-family residences were monitored for a 1-yr period. About 8,000 demands per capita were recorded and converted to single equivalent rectangular pulses. Each pulse was classified by type (deterministic or random), location (indoor or outdoor) and day (weekday or weekend). Basic exploratory data analyses were performed to estimate sample statistics, cumulative distributions, and hourly occurrences of the intensity, duration, and volumes of the rectangular pulses according to type, location, and day. In addition, the hypothesis that residential water demands occur as a nonhomogeneous Poisson rectangular pulse process was examined. Results show that the simple rectangular pulse provided a very reasonable approximation of indoor water demands. However, the variance of the daily pulse count appears to be too high for a Poisson process. Potential causes of the high variances in the daily pulse count are discussed. Findings and data from this study can be used to develop and verify fine-resolution network models designed to predict the fate and travel time distribution of substances moving to remote points of consumption in the water distribution system.

The relationship between water price and the installation of low-flow faucets, low-flow toilets, low-flow showerheads, and drip irrigation of plantings was analyzed for apartments and individual households in Tucson, Ariz. The difference between individually metered household motivations and apartment-owner motivations to install these devices is discussed. Logit regression analysis of household data found water price to be a significant factor at the 0.05 confidence level in the installation of low-flow faucets, low-flow toilets, and drip irrigation for plantings. Other household variables examined included moral obligation to save water, household size, and family income. For households, moral obligation to save water significantly motivated the installation of low-flow toilets, showerheads, and faucets. Analysis of apartment data found water price to be a significant factor at the 0.05 confidence level in the installation of low-flow showerheads and low-flow faucets. Other apartment variables included the average assessed value per bedroom and the number of apartments in the complex. Larger size apartment complexes were found significantly associated with low-flow showerheads, low-flow faucets, and drip irrigation.

Sediment and nutrient loads from a 73 km ² mixed pasture/forested watershed that drains to eutrophic Lake Rotorua (New Zealand) were measured before and after diffuse-source controls were implemented. In the pastoral areas, these controls were exclusion of grazing (“retirement”) from the banks of most perennial streams, erosion-prone hillslopes, and remnant pockets of native forest. After implementation, the loads changed by −85% for sediment, −27% for particulate P, −26% for soluble P, −40% for particulate N, and +26% for dissolved N. Calculated total phosphorus specific yields for the pasture portion of the watershed were 89 kg km ⁻² yr ⁻¹ (preimplementation) and 41 kg km ⁻² yr ⁻¹ (postimplementation). When these findings were applied to the whole Lake Rotorua watershed, we predicted that control measures had reduced TP loads by 20%. This reduction in phosphorus loads was predicted to reduce the chlorophyll a concentration by about 5 mg m ⁻³ , and help shift the lake's trophic state from eutrophic to mesotrophic.

The percentage of storm-water runoff volume, or of the number of runoff events captured is a key factor when designing storm-water quality control facilities. Design criteria originally developed for sizing flood control detention are not appropriate for sizing detention for storm-water quality control. This paper presents a simple technique that can be used to estimate the needed storm-water detention volume of structural water quality best-management facilities. This volume is based on the point where diminishing returns begin to occur in either the long-term runoff volume capture and treatment or in the number of runoff events captured and treated. This volume is defined as the “maximized” volume. The procedure presented is intended for preliminary planning or design when detailed local investigations have not been performed. It is not intended to replace detailed, site-specific investigations. Its accuracy, however, was verified by comparing its results against similar findings that emerged from several detailed local investigations.

A Chebyshev criterion is used to develop robust direct regulation water-quality management models. The reserve capacity of the stream, in terms of the excess capacities above the water-quality goal at the most critical water-quality checkpoints, is used as a measure of robustness of the management solutions to uncertainties in the water-quality input information. The models maximize the minimum reserve capacity along the river. They are applied to the control of biochemical oxygen–demanding waste in an example river basin based on the Willamette River in Oregon. The addition of a robustness measure in the model formulation gives additional insight into the management system. Although the mathematical formulation of the application is simple, the results provide important information for decision makers, such as identifying polluters with high waste-treatment cost per unit dissolved oxygen improvement at the critical stream locations. Such information is often useful for screening alternative options and making sophisticated water-quality policy and management decisions, based on detailed dynamic water-quality simulation.

Urban storm-water utilities are an important funding method for storm-water programs. The rate structure is the basis on which the utility forms its fees and other secondary funding methods and rate modifiers. One rate modifier is the use of crediting mechanisms. Credits are often granted to provide incentives to implement or carry out an overall community storm-water management plan or to advance some other social or environmental objective. Bases for credits range from a classification of ratepayers, the class of property, location within the watershed or service area, certain activities that improve the system beyond normal expectations, certain ongoing activities on the property that reduce impact, and certain ongoing activities on the property reduce the city's cost of service. This paper explores the use of these different bases discussing the pros and cons for each, and details an approach that accounts for the expected impacts of development in terms of flow peak, flow volume and pollution discharge.

This paper proposes a method called the adaptive search algorithm to optimize a water supply system. The adaptive search algorithm is a discrete optimization search model that selects which pumps to switch on or off using a combination of influence coefficients and pipe network pressure readings. Pressure readings at strategic points in the pipe network are monitored. When the pressure increases or drops beyond the allowable values, the pump that has the greatest influence and delivers water at least cost is selected to correct the pressure by either turning it on or off as required. This is an initial feasible solution. The algorithm iterates between the optimization model and the simulation model (KYPIPE) until an optimal solution is found. One of the advantages of the adaptive research algorithm is its speed. It reaches a solution after two or three iterations, which qualifies it for real-time control of the water delivery system. The adaptive research algorithm is applied to the water distribution system of Memphis, Tenn., and shows a promise of significant savings in water delivery costs.

A laboratory experiment was conducted to investigate the effects of various kinds of access to a simulation model on water-resources negotiation outcomes and processes. The (mock) negotiation involved determining a release schedule from two reservoirs through a negotiation between subjects representing hydroelectric, agricultural, and flood-control interests. Results revealed the following: (1) The model was of only limited value in helping negotiators understand the behavior of the environmental system; (2) the model did provide assistance in finding policies that satisfied specific task constraints; (3) the availability of the model encouraged negotiators to consider more policies; and (4) the benefits of using the model directly, rather than getting access to model results produced by an assistant, were offset by the burden of direct use. The findings are evaluated in light of a growing trend in many governmental organizations to make water-resources simulation models available to stakeholders and the public at large.

Yields from a proposed ground-water storage facility are evaluated using a nonlinear optimization model of the California State Water Project (SWP) and the Central Valley Project (CVP). Model constraints account for the major hydrologic, regulatory, and operational features of both projects, including mass continuity, facility capacities, regulatory standards, and delivery contracts. The model maximizes long-term SWP yields over a 70-year period, using a quarterly time step and assuming current facilities are in place. Maximum yields are recomputed for a second scenario that includes new ground-water storage in the North Las Posas Basin, located in Ventura County. Delivery increases associated with the new facility are computed as the difference in optimized project yields between the two model runs. Results indicate that the ground-water storage facility may increase the average annual yield of SWP by 6%.