Journal of Water Resources Planning and Management

Forecasting of seasonal snowmelt runoff is an important exception to the otherwise limited accuracy of long‐term runoff forecasts. Conceptual models of the snow accumulation and ablation and precipitation‐runoff processes have been advocated as a means of introducing physical understanding of the dominant hydrologic processes into seasonal snowmelt runoff processes. However, the paucity of information and extreme spatial variability of meteorological processes and watershed characteristics in mountainous watersheds often result in large simulation errors. The analysis reported here relates monthly simulation error statistics to maximum achievable seasonal runoff forecast accuracy, presuming perfect knowledge of future (gage) precipitation and temperature, but without updating of model parameters or states. In some cases, this accuracy limit is less than that actually achievable using simpler models. The results suggest a preference for simple models if the coefficient of variation of monthly simulation error cannot be reduced below about 10–15%.

Projects for disposal of wastes by application to land must be implemented within a complex framework of institutional constraints, with landuse controls a significant component. Controls imposed by local government are the most direct form of constraint and include zoning ordinances and local environmental controls. Local governmental controls are especially significant where publicly owned land application projects are proposed outside the political boundaries of the owner since such location is likely to generate controversy. The applicability of local controls to extraterritorial projects varies under existing state enabling legislation and judical determinations. A second relevant land‐use constraint is the private lawsuit based on property rights. Landowners have the legal right to be free from unreasonable interference with the use and enjoyment of property. The rights of landowners adjacent to a land application facility therefore act as a constraint on offsite impacts and have some potential to provide a basis for legal prohibition of such facilities. Therefore land use controls, both publicly and privately enforced, are a determinant of the feasibility of land application proposals.

A method for long‐range reservoir operation planning to meet an outflow temperature goal is described. The outflow temperature of TVA's Norris Reservoir is characteristic of the seasonally modified temperature regime produced by deep and large storage reservoirs. Outflow temperatures stay around 10° C from the beginning of the year until about mid‐July. Then they rise to their annual peak of about 18° to 22° C by the end of October and decline to about 10° C by the end of the year. For downstream water uses it may be beneficial to keep the maximum outflow temperature in fall at or below a target temperature. This goal can be accomplished by limiting the total amount of discharge after the spring filling of the reservoir. The limit on discharge is expressed by the cold water index, which is the ratio of total discharge during the planning period to the reservoir volume at the start of the period. The practical use of the concept is illustrated by modifying historic operations which did not meet a prescribed outflow temperature goal. The effect of such operational modifications on other reservoir uses, especially on power generation, is also described.

Preemptive goal programming is applied to the real‐time, daily operation of multiple‐purpose, multiple‐reservoir systems. A significant advantage of the goal programming approach is that it may be based on physical operating criteria. It does not require the penalty‐benefit functions that may be difficult to define but are essential to other real‐time operating models. Therefore, it is easier to implement. The goal programming model is applied to the Green River Basin (GRB) system comprising four multipurpose reservoirs. The GRB system operations resulting from use of the goal programming model are compared to operations resulting from another optimization model which is more data intensive and which was designed specifically for the GRB system. Both sets of operations are comparable in their effectiveness, although in some cases the goal programming operations are better.

Interactive simulators utilizing current microprocessor technology have been developed and applied to several categories of contemporary water planning and management problems. Specific issues addressed include realtime system operation, training programs for system managers and technicians, demonstration of system management alternatives, and public education programs and workshops. Both generalized and site‐specific water management systems have been modeled by simulators which allow the user to interact directly with the computational stream of the system model. Simulator units have been constructed using various combinations of visual displays, monitors, and printed output devices to monitor system performance. Results of this 4‐yr investigation indicate that interactive simulator technology offers an effective and flexible alternative to traditional digital computer simulation.

A finite difference computer modeling system has been developed to predict future subsidence as a function of ground‐water pumpage in Harris and Galveston Counties, Texas. Two previously developed models, one for ground water, the other for subsidence, were specifically calibrated for the area and linked through the common parameter of potentiometric surface elevation. The two pumped aquifers, Chicot and Evangeline, are modeled using a modified Trescott, three‐dimensional flow model, while subsidence is calculated at 21 specific subsectors within the Harris‐Galveston Coastal Subsidence District using a modification of Helm's one‐dimensional Terzaghi‐consolidation model. Both models have been calibrated against historical data. The predictions run to date indicate changing trends in the location of future subsidence‐prone areas. The modeling system will allow the District to make rapid, reproducible, documented predictions of land subsidence resulting from anticipated future pumpage of ground water.

A planning model is presented for the optimal management of groundwater systems. The model, which is formulated as a bi‐objective optimization problem, allocates over a series of planning periods, groundwater to competing water (irrigation) demands in a river basin. The model is predicated on the response equations of the ground‐water system. The equations are developed for an inhomogeneous, isotropic aquifer system with the Galerkin finite element method. The matrix calculus is used to obtain a continuous solution in time relating the hydraulic head and the initial state of the system, the system's time dependent boundary conditions, and the planning or management policies. The planning model is applied to the Yun Lin groundwater basin in southwestern Taiwan. Parametric linear programming is used to generate optimal planning policies, the set of non‐inferior solutions, and the relationship between the total water deficit and: (1) The maximum pumping rate; and (2) the minimum permissible head values in the aquifer system.

The value of existing federal water resources projects is estimated from historical construction costs. The value of improved operation of existing facilities is then estimated and shown to be at least as large as the value of new construction for the next 20 years. It is suggested that these improvements in operation of existing facilities can be obtained at about one percent of the cost of constructing new facilities to produce the same amount of benefits. Finally, recommendations are presented for reviewing and improving the operation of existing projects.

To estimate the operation and maintenance (O&M) cost of facilities, such as pumping stations, wellfields, water and wastewater treatment plants, using some type of O&M cost function, it is necessary to know the actual flow rate handled by the facility. If the flow rate varies over the life of the project, it is difficult to determine which rate to use as the average flow for the life of the project. This paper presents some easy to use graphs to assist in determining the flow rate to enter into the cost function.