Journal of Water Resources Planning and Management

The concept of consumer surplus is used to estimate the benefits from a new water source for urban water customers. This benefits model is estimated for the projected arrival of Central Arizona Project (CAP) water in Tucson, Ariz., using the parameters of a regression‐based demand model. The estimated benefits to water users of the anticipated CAP water are $91 million compared to costs of $175 million at the 8.625% discount rate currently required for federal projects. Thus direct costs exceed direct benefits by $84 million over the 100 year life of the project. To keep current water customers from suffering net losses, a payment of $2,514 in 1985 dollars would be required from each new housing unit over the 100 year life of the project. The internal rate of return for the project is 4.86%, which exceeds the 3.25% rate used in the original analysis of the project. This research demonstrates the practical application of the frequently advocated but less frequently used consumer‐surplus model in estimating the benefits of increasing the supply of urban water.

Most mathematical modeling efforts in water resources fall far short of adequately including social and environmental objectives. Although many modelers have good intentions at the start of their analyses, the objective functions and constraint sets do not provide a good mechanism for addressing these resource issues. Results from a three‐reservoir network simulation model are numerically rated for impact upon 22 natural resource attributes associated with seven resource objectives. Priority weighting of individual resource objectives is included, as well as the ranking of importance for each attribute to its respective resource objective. The technique described provides a quantitative and objective approach to evaluate flow regulation alternatives. Input from special interest groups, the general public, and concerned individuals, as well as professionals in each resource area, are a part of the overall analysis. The simple technique provides a screening tool to identify good and bad flow alternatives. An example is provided for a three‐reservoir system at Voyageurs National Park on the Minnesota and Canadian border.

Water‐resource managers are often faced with rife task of balancing recreational activities in an attempt to maximize the overall recreational benefits from a river system. Available recreation‐use functions for white‐water rafting, boating, and fishing as a function of river flow are used to estimate benefits. This paper focuses on the use of optimization models to generate alternatives (MGA) that maximize total recreational activities. Monthly river‐flow scenarios that produce different mixes of the three recreational activities, yet have essentially the same value of total recreational benefits, were sought. Four MGA methods were evaluated with data for the New River Gorge National River in West Virginia. Two of the MGA methods were based on linear programming, and two were based on dynamic programming. For this study, the MGA methods based on dynamic programming were easier to use and modify. Examples of the types of alternative flow strategies generated for the New River Gorge are presented.

Among the various factors that reduce the rate of recharge in an artificial recharge basin with time, the settling of the suspended sediments in the recharge water is usually the most important. An equation is developed to represent the change of infiltration rate of a turbid water with time and with the concentration of suspended sediments. This equation is further generalized to consider the effect of the basin size on the recharge rate. Optimal scheduling of consecutive recharge and dry periods is determined to result in the maximum recharge rate in the long run. A computer model is developed to provide the optimal design of an intermittent multibasin recharge (IMBR) system. The model is run using a set of real field data, and the results show that when a constant flow rate is available during the recharge season, IMBR would be a more efficient system of artificial recharge than either continuous or intermittent recharge on a single basin.

Making wise investments is the goal of every investor. This is certainly true for public utilities as they invest in infrastructure to fulfill their mission of providing safe, reliable, cost‐efficient service to their customers. Starting from a capacity deficit condition, the city of Austin, Texas, faced a boom‐and‐bust development cycle in the 1980s that made sizing and timing decisions for new water and wastewater facilities extremely difficult. In this case‐study paper, infrastructure investment decisions are examined for a decade in which Austin experienced a 30% increase in demand, followed by five years of almost no growth. The paper first addresses basic demand‐versus‐capacity relationships, then gives a perspective of the investment climate by describing the unusual rates of development activity. The making of investment decisions is addressed in terms of the effects on decision making of service policies, rate impacts, environmental considerations, and political considerations, including revenue bond voting and the formation of municipal utility districts. Austin's experience calls attention to the importance of certain basic infrastructure planning guidelines, and these are presented as lessons learned.

An optimization model is presented for determining the optimal design capacities of a water delivery system integrating small hydropower plants. A discrete distance model of the transmission pipeline is solved by employing dynamic programming. The model determines the proper allocation of available pressure head to various potential hydropower sites along the supply main and determines the optimal pipe diameter. The practical value of the model is demonstrated in an example for a supply system to serve four towns. The solution of the model gives the set of turbine capacities, pipe diameters, head allocation resulting in maximum net benefit for a given quantity of available water and demand, and the expected net benefits.

This study develops regionally optimal ground‐water extraction strategies. Alternative explicit planning objectives are: (1) Maximize total pumping from the underlying aquifer while causing the evolution of a steady potentiometric surface; and (2) maintain a prespecified target potentiometric surface. Implicit objectives involve controlling stream/aquifer interflow and water flow across a state boundary, and attempting to avoid gross disruption of current cropping patterns. Models, bounds, constraints, and data are formulated. Alternative optimal strategies and the rationale for preferring one strategy are presented for a region in Arkansas. The objective of maintaining the relatively unstressed target potentiometric surface yields politically and socially unacceptable water‐use strategies. The most acceptable strategy maximizes sustainable ground‐water extraction, maintains recent ground‐water flow to Louisiana, maintains current potentiometric surface heads at the Louisiana‐Arkansas border, maintains more than minimally acceptable surface water flow to Louisiana, and approximately maintains current cropping distributions. Developed planning models utilize the embedding approach, over 300 pumping variables, and 700 total variables, indicating the utility of the embedding method for regional sustained yield (steady‐state) planning.

A methodology was developed to rank the relative vulnerability of ground‐water areas to contamination by agriculturally applied pesticides. The method uses the advection‐dispersion equation for chemical transport in soils to develop the leaching potential index (LPI), which is an indicator of the relative susceptibility of each area. The index incorporates the effects of depth to ground water, natural and irrigation recharge rates, absorption, and chemical decay. The importance (weighting) of the hydrological factors is physically based, not subjective as it is in a number of approaches reviewed. The weights are not required to have constant values, as is typical of other methodologies; instead dependent on the specific chemical properties of the pesticide under consideration. The methodology is verified by comparing the calculated rank of 381 1‐sq‐mi $(2.51‐{\mathrm{km}}^2)$ areas with available analyses for 1,2‐dibromochloropropane (DBCP) in ground water in the same area. The method will be a useful planning tool for early identification of agricultural areas susceptible to ground‐water contamination and efficient management of sampling resources.

The provision of on‐line computer‐based control schemes for water‐supply and distribution systems has for many years eluded the water industry because of the unavailability of reliable applications modules, as well as the limitations on computing power. Recent technological advances, however, have enabled the development and implementation of one such scheme for a major city (Severn‐Trenk Water) network in the United Kingdom. Specific objectives for such an on‐line control implementation include demand prediction based on historical records, least‐cost pump scheduling based upon predicted demand consumption, management of all the on‐line data, coordination of the real‐time activities, monitoring of all major system data, generation of appropriate alarm messages and signals, and advice on regulatory decisions during the control period. The paper describes in some detail the various aspects of such a control scheme, which has been implemented with encouraging results.