Journal of Water Resources Planning and Management

Existing methods for determining the perennial safe yield of ground-water basins are examined in this paper. The inherent problems of these methods are described. A new method of estimating the safe yield is developed, which includes approximate representations of basin dimensions, hydraulic characteristics, and estimated duration of the worst drought. The application of the method uses a simple graph. The suitability of the method for application to real aquifers is tested using a distributed parameter surface water/ground-water model of an aquifer in the English Midlands. For this particular example the method is shown to work well. Therefore, it can be tentatively concluded that a new way of estimating the perennial safe yield of an aquifer has been developed.

An optimization model is developed for selecting between candidate surface-water reservoirs and ground-water development. The model may be used to perform a preliminary screening of alternatives for water-supply development, and to identify storage capacities at reservoir sites, as well as aquifer pumping at candidate locations. A hybrid simulation-optimization strategy is used to consider monthly operation of the reservoir and aquifer system using historical or synthetic hydrologic data. A modified sequent peak algorithm is used for reservoir sizing, and a unit response matrix approach is used to model the ground-water subsystem. A target aggregate firm yield from the surface water–ground water system may be specified. Decisions on the failure of firm yield at each reservoir site during a critical period for streamflow, with a corresponding increase in ground-water pumping such that the system firm yield is maintained are considered. Example applications with data from the Jordan River basin in Utah demonstrate the utility of the model relative to a disjunctive analysis of surface water–ground water development.

This paper discusses the need for the reporting of a variety of physical, chemical, climatic, geological, biological, and meteorological parameters along with the data required by various investigators on the performance of structural stormwater best management practices (BMPs) used to enhance stormwater quality. A standard list of minimum parameters is suggested. Such a list is needed if we want to exchange and transfer data between various studies being conducted throughout the world, or even within the United States. Transferability of performance results and consistency, or lack of it, in the performance of various BMPs, has been an ongoing problem. A mutually agreed upon minimum list of reporting parameters that can be used to relate the performance to some, or all, BMPs could begin to address this problem. Over time such standardization will conserve the resources being expended, not only by individual BMP investigations, but also in the selection and appropriate design of various BMPs.

The Federal Water Pollution Control Act, which later became the Clean Water Act, handles pollution from industrial and commercial discharges differently from dredge and fill pollution associated with waterway maintenance and navigation. Congress divided responsibility for the latter between the Environmental Protection Agency and the Corps of Engineers. Some ambiguity has arisen as to which agency has primary responsibility for the 404 permit program. Although the Corps is presumed to have major administrative responsibility, the Environmental Protection Agency through its veto power to the permit system has become the dominant agency since 1980. A Virginia project that involves a permit to destroy wetlands for an urgently needed water supply illustrates the problems associated with shared responsibility. The validity of a permit for this project is currently in the courts. There is the possibility that the policy guiding the current 404 permit program may change, at least with respect to permits involving water supply. The ultimate decision in this case could make significant changes in the operation of the 404 permit program in the future.

A number of water supply agencies in the western United States have begun to integrate water transfers into their overall water supply planning, including the use of transferred water as an additional water source with particular cost and availability characteristics. This paper presents applications of two-stage and multistage linear programming for preliminary estimation of the least-cost integration of several water marketing opportunities with water conservation and traditional water supplies. Water marketing opportunities here can include dry-year options and spot-market water transfers.

An efficient system simulation methodology that solves the contaminant-transport problem in drinking-water-distribution systems is developed. The method can be effectively used for modeling the time-varying interaction of water quality and hydraulic behavior within the distribution-system environment. The solution of the time-varying water-quality problem is obtained in an event-oriented system-simulation framework. This allows for dynamic water-quality modeling that is less sensitive to the structure of the network and to the length of the simulation process itself than previously proposed methods. In addition, numerical dispersion of concentration front profile resolution is nearly eliminated. The resulting method can be applied to every type of water-distribution system while requiring the least number of calculations necessary to carry out the simulation process. The performance of the method is demonstated by application to an example water-distribution network. The method should prove to be a valuable tool for managing water quality in drinking-water-distribution systems.

A study of the possible impacts of climate change due to the equivalent of doubling the atmospheric CO ₂ on the water-supply system of metropolitan Boston showed serious decreases in reservoir-system safe yield due to the climate-change scenarios of some general circulation models (GCMs). Temperature increases alone and a longer growing season also resulted in severe impacts. Impacts may be mitigated if there are increases in vegetation canopy evapotranspiration resistance due to enriched CO ₂ or in precipitation. The decreases in reservoir yield occur because there is less streamflow and downstream-flow maintenance requirements require more water be released. The scenarios of other GCMs result in an increase in safe yield; in those scenarios, evaporation and evapotranspiration increases are offset by large increases in precipitation. The contradictory results of the GCMs are not surprising and again indicate the present uncertainty in climate-change impacts.

A sampling design methodology for monitoring contaminant distribution in lake sediments is presented in this paper. Two optimization approaches are employed: a minimization of the variance of estimation approach and a sampling cost minimization approach, allowing an economically efficient sampling design and a decision-making tool given the multiobjective nature of the problem. The geostatistical method of cokriging is used as a tool on which the proposed sampling design is based. The adopted technique incorporates spatial as well as intervariable correlations, to improve the prediction and estimation of sampled quantities. The methodology is applied to Clear Lake, California, to design a network for sampling mercury concentrations in lake sediments. The network design takes advantage of the cross correlation between the mercury concentrations and sediment grain size index. A sensitivity analysis is carried out to assess the sensitivity of the solution to the optimization model inputs.

In April 1991, the ASCE's Board of Direction adopted the Water Conservation Policy Statement developed by the ASCE's National Water Policy Committee. The Board officially supports the conservation of water as an essential aspect of water-resources management and recognizes that water conservation should include activities that promote the efficient use and management of water. This paper summarizes the results of survey data received from 47 Association of Metropolitan Water Agencies member agencies as an indication of the efforts being made by water utilities throughout the nation to implement the activities encouraged in the ASCE Water Conservation Policy Statement. The paper also contains a brief summary of the Seattle Water Department's current and planned water-conservation programs, and the department's experience with water-use-curtailment measures that successfully augmented the ongoing water-conservation programs during the 1987 and 1992 droughts in the state of Washington.

This paper develops an estimation method for discontinuous distributions used for fitting hydrologic series with several zero events. Such series are observed in arid and semiarid regions, and may include monthly precipitation in dry seasons, annual low flow, etc. The study consists of a derivation of the basic equation of the frequency distribution, derivation of distribution moments and parameters, plotting positions for positive values that form a part of the series instead of the full sample as conditional distribution, and transformation of the conditional distribution parameters into those of the marginal distribution. Using monthly precipitation and annual low-flow data from China, and annual maximum peak discharge data from the United States, the suitability of the distribution and the estimation method is assessed.

The seasonal distribution of extreme rainfall is important in hydrology and agriculture, especially in problems related to water control. The amounts at selected return periods vary by season and geographic location, as do the surface conditions of soil moisture and vegetation. Therefore, a particular size storm may have a different impact if it occurs during summer as opposed to winter (over frozen ground). In terms of total precipitation and the top-ranked storms, summer is the dominant season for extreme rainfall in the northern states, while the other seasons increasingly contribute more in the central and southern portions of the Midwest. This effect is maximized in Kentucky, as well as in southern Illinois and Indiana, where winter precipitation approaches that of summer in magnitude. This has important consequences, since soil moisture is generally quite high in the Midwest at this time of year. The combination of large winter rainfall events and near-saturated soil conditions can lead to high runoff. An examination of seasonal rainfall frequencies, along with seasonal soil conditions, may lead to the optimal solution to a water control design problem.