Journal of Water Resources Planning and Management

Water shortage is a major socioeconomic problem facing society today. From the viewpoint of water-resources planning, an effective water-shortage index should capture such basic characteristics as its frequency, intensity, and duration. Moreover, a shortage index should serve as an indicator of the social tolerance limits to water shortage. A well-designed water-shortage index plays an important role in water-resources planning and management, particularly in conducting feasibility studies associated with system-capacity expansion. The main purpose of this study is to develop a generalized shortage index (GSI) by modifying other water-shortage indices that are currently utilized in Japan and the United States. The proposed GSI not only incorporates the basic shortage characteristics, but also emphasizes the consequential socioeconomic impacts of water shortage. By using historical streamflow records, projected future water demands, and a river-basin simulation model, a methodology is developed to analyze the various capacity-expansion alternatives in connection with water-resources planning for the Kaoping river basin in Taiwan. The simulation results indicate that the proposed GSI is more precise and effective than other indices for resources-planning purposes.

Daily reservoir operations rely increasingly on accurate streamflow forecasts, which today are derived from computer modeling. This paper documents development of a hydrologic-process-based daily streamflow-forecasting model with a built-in parameter-estimation routine. The model [called the National Taiwan University (NTU) Daily Model] closely captures the physical reality while maintaining the robustness of the statistical model, both of which must be considered in the day-to-day operations of a reservoir. Several equations are used to describe various simplified hydrologic processes, such as direct runoff, baseflow, infiltration, evapotranspiration, and change in ground-water storage. It is assumed that these equations can generate total daily streamflow from precipitation forecasts and initial conditions. The model parameters are automatically determined by a built-in Gauss-Newton algorithm. Model performance was analyzed by five statistical error measurements, including correlation coefficient, coefficient of efficiency, relative error, standard error, and volume error. The proposed model was calibrated and verified using historical streamflow data from three gauging stations in Taiwan. The results obtained indicate that the NTU Daily Model for streamflow forecasting is satisfactory for use in daily operation of the reservoir.

A nonstationary Markov chain approach to designing seasonal risk-equivalent water-quality management strategies is presented in this paper. Unlike many existing models for determining seasonal waste load allocations, this approach considers a wider range of possible low-flow conditions than those in the observed historical record. It explicitly incorporates the probabilistic relationships between low-flow data at adjacent gauging stations. The approach is demonstrated for the management of biochemical oxygen demanding (BOD) waste on the Willamette River in Oregon. The results of this application are compared with those of an existing model for seasonal risk-equivalent waste management. The treatment strategies derived for the Markov chain approach are similar, but slightly more conservative than those for the alternative program. Moreover, the ability of these treatment strategies to achieve an acceptable probability of water-quality violation is potentially less sensitive to the length of the historical record.

In contrast to annual peak river flows, annual maximum lake levels often possess significant autocorrelation. The presence of autocorrelation in the time series of annual lake floods can be exploited to generate conditional estimates of near-term flood risk that are more accurate than estimates from traditional frequency analysis. Lake flooding is visualized as the joint occurrence of a time-dependent lakewide static water level and an independent local storm surge. Data from three gauges on Lake Erie show that the static water level behaves as a normal AR(1) process and the storm surge is normally distributed. Conditional trajectories of annual maximum water levels, obtained from the convolution of the static level and storm surge, are computed along 20-year time horizons for various initial conditions. Results show that traditional frequency analysis overestimates the risk of near-term flooding when static levels are low, and it underestimates the risk of near-term flooding when static levels are high. Knowledge of the near-term conditional distribution of annual maximum lake levels can be helpful in developing more-effective shoreline management plans.

This paper presents alternative formulations of optimal pumping design for contaminated ground-water cleanup. Remediation-efficiency indicators are proposed for evaluating well performances in terms of contaminant removal. For a selected remediation period, the alternative objective functions are: (1) Total volume of the extracted and/or injected water; (2) total contaminant removal; (3) total residual contaminant; and (4) any weighted combination of the first and second or first and third items. With the introduction of a field variable, referred to as the temporal accumulative contaminant concentration, the contaminant removal by any remediation well is computed directly by solving a temporal-integrated contaminant transport equation. Ground-water-quality constraints can be placed on the residual average and/or maximum concentrations in selected aquifer zones and the concentrations at specified locations. The state sensitivities to the injection and extraction components of the pumping rates are computed using formulations derived analytically from the state simulators.

Two standard test problems that are nonconvex with multiple local minima are considered. An outer flow search–inner optimization procedure is proposed for choosing better local minima. Each pipe network is judiciously subjected to the outer-search scheme that chooses alternative flow configurations to find an optimal flow division among pipes. An inner linear program is used for the design of least-cost diameters. The algorithm can also be used for the optimal design of parallel expansion of existing networks. Because the problem is nonconvex, two global-search schemes, MULTISTART and ANNEALING, are used to permit a local-optimum-seeking method to migrate among various local minima. MULTISTART selectively saturates portions of the feasible region to identify the local minima. ANNEALING iteratively improves the objective function by finding successive better points, and, to escape out of a local minimum, it exercises the metropolis step, which requires an occasional acceptance of a worse point. The optimal solutions thus found have significantly smaller costs than the ones reported previously by other researchers.

Water transfers are a common component of many regional water systems, and are increasingly being considered for meeting growing water demands and for managing the impacts of drought. Water transfers can take many forms and can serve a number of different purposes in the planning and operation of water resource systems. However, to be successful, water transfers must be carefully integrated with traditional water supply augmentation and demand management measures. This integration requires increased cooperation among different water-use sectors and resolution of numerous technical and institutional issues, including impacts to third parties. This paper identifies the many forms that water transfers can take, some of the benefits they can generate, and the difficulties and constraints that must be overcome in their implementation.

Saudi Arabia faces severe water problems and needs new water policies to achieve sustainable development in its harsh environment. Problems include balancing supply and demand while facing aridity and water scarcity, nonrenewable supplies, poor quality of ground water, maldistribution of supplies, salt water intrusion, and overdrafting and contamination of aquifers. Although a great deal is known about its water resources and problems, developing effective planning and regulatory systems and other institutions is Saudi Arabia's principal water policy challenge. Building on previous reports on water issues, this paper compares the kingdom's water-management tasks with state government programs in the United States, including water law; planning, management, and coordination processes; organizational structure; infrastructure development; water-quality management; conservation programs; regulation, standards, and enforcement; and support functions. Water law and regulations are needed in Saudi Arabia, especially for conservation, ground-water management, and water-quality management. Defining roles and responsibilities is a challenge in both the United States and Saudi Arabia, but in Saudi Arabia intergovernmental issues are less daunting than in the United States. However, water security is a bigger challenge in Saudi Arabia. As the kingdom moves into the next decade, a water-management system should clearly be high priority during policy making.

Impacts of global warming on streamflows were estimated for four large watersheds in New York State using a daily streamflow model. Three different 100-yr daily weather sequences were input to the model. The first was produced using statistics of current (1961–90) weather records. The second and third sequences were based on modifications of these historic statistics according to the monthly mean temperature and precipitation changes associated with a doubling of atmospheric CO ₂ as predicted by two different general circulation models. For 2 × CO ₂ conditions, mean annual water balances for all four watersheds indicated modest (1–9%) decreases in precipitation, but much larger (16–42%) decreases in streamflow due to increases in evapotranspiration. Winter flows generally increased, but flows in the remaining seasons often decreased. Monthly streamflow changes varied considerably among watersheds, and we could not attribute these changes to specific differences in land uses or soils.