Showing papers in "Journal of Water Resources Planning and Management in 1989"

Water Distribution System Design Under Uncertainties

Abstract: A chance constrained model is presented for the minimum cost design of water distribution networks. This methodology attempts to account for the uncertainties in required demands, required pressure heads, and pipe roughness coefficients. The optimization problem is formulated as a nonlinear programming model which is solved using a generalized reduced gradient method. Details of the mathematical model formulation are presented along with example applications. Results illustrate that uncertainties in future demands, pressure head requirements, and pipe roughness can have significant effects on the optimal network design and cost.

Implicit Network Calibration

Abstract: An implicit mathematical model is developed for use in calibrating hydraulic network models. The calibration model uses a nonlinear optimization algorithm along with a general network solver to adjust selected model parameters for either steady state or dynamic operating conditions. Adjustable model parameters include: pipe roughness, source grades, and nodal demands. Both a steady state and an extended period calibration example are presented.

Optimal Operation of Water Distribution Systems

Abstract: Optimal operation of a water supply system is solved by progressive optimality (PO), an iterative dynamic programming (DP) method. Given the forecasted demands for the coming 24 hr, the initial and final conditions in the reservoirs, the hydraulic properties of all system components, and the variable energy cost over the day, an optimal schedule of pump operation is found. The algorithm cycles iteratively over the time steps (hours of the day) and network subsystems, and converges to the optimum from any (feasible or infeasible) initial solution. The global optimum is guaranteed only under certain conditions; otherwise a local optimum may be reached. The method is developed and demonstrated on a regional water supply system with eight reservoirs and seven pumping stations.

Low-Flow Frequency Analysis Using Probability-Plot Correlation Coefficients

Abstract: Although a vast amount of literature exists on the selection of an appropriate probability distribution for annual maximum floodflows, few studies have examined which probability distributions are most suitable to fit sequences of annual minimum streamflows. Probability plots have been used widely in hydrology as a graphical aid to assess the goodness of fit of alternative distributions. Recently, probability-plot correlation-coefficient (PPCC) tests were introduced to test the normal, two-parameter lognormal and Gumbel hypotheses. Those procedures are extended here to include both regional and at-site tests for the two-parameter Weibull and lognormal distributional hypotheses. In theory, PPCC-hypothesis tests can only be developed for two-parameter distributions that exhibit a fixed shape. Nevertheless, the PPCC is a useful goodness-of-fit statistic for comparing three-parameter distributions. The PPCC derived from fitting the two- and three-parameter lognormal, two- and three-parameter Weibull, and log-Pearson type III distributions to sequences of annual minimum seven-day low flows at 23 sites in Massachusetts are compared. How the PPCC can be used to discriminate among both competing distributional hypotheses for the distributions of fixed shape and competing parameter-estimation procedures for the distributions with variable shape is described. An approximate regional PPCC test is developed and used to show that there is almost no evidence to contradict the hypothesis that annual minimum seven-day low flows in Massachusetts are two-parameter lognormal.

Cluster Analysis as Applied to Regional Flood Frequency

Abstract: A statistical tecnhique for delineating groups of stations to be considered a region for regional flood frequency analysis is presented. The technique, which utilizes cluster analysis, allows the inclusion of a diversity of factors which might be considered to be of relevance when seeking stations in differing basins having similar extreme flow characteristics. The method incorporates both a basin similarity measure, imbedded in the clustering algorithm, and a regional homogeneity measure used to evaluate station partitionings obtained from the clustering algorithm. The result is that groups of stations are identified that can be considered sufficiently homogeneous to effect an efficient spatial data transfer. An application of the methodology to rivers in southern Manitoba, Canada, is presented to illustrate pertinent aspects of the procedure.

Pressure and Flow Uncertainty in Water Systems

Abstract: In the monitoring of water distribution systems, the inaccuracy of input data contributes greatly to the inaccuracy of system state estimates calculated from them. It is important, therefore, that the system operators are given not only the values of flows and pressures in the network at any instant of time but also that they have some indication of how reliable these values are. The quantification of the inaccuracy of calculated flows and pressures caused by the input data uncertainty is called here confidence limit analysis. Several confidence limit analysis algorithms are presented. These include a Monte Carlo simulation method, an optimization method, and a sensitivity matrix technique. The performance of these algorithms is assessed in terms of their suitability for real‐time control or design stage applications. Results are presented for a realistic test network.

Methodology for Improving Pump Operation Efficiency

Abstract: A methodology to optimize the operation of water supply pumps is developed for use in minimizing pump operation costs. The developed methodology is directly applicable to complete water distributio...

Expected Annual Damages and Uncertainties in Flood Frequency Estimation

Abstract: The expected annual damages is the most frequently used index of the impact of flooding at a site. However, estimates of expected annual damages are very uncertain as a result of uncertainties in both the estimation of the flood frequency relationship from limited data and the relationships between magnitude and damage. Computer simulation experiments using synthetic flood peak data and fixed magnitude-damage functions have shown that the sampling distribution of estimates of expected annual damages is highly skewed to a degree depending on the form of the damage function, and most importantly, that bias in the estimates is most closely related to error in the estimated probability at which damage begins. The use of expected probability leads to a very significant increase in bias in the estimation of expected annual damages.

Network Flow Algorithm Applied to California Aqueduct Simulation

Abstract: The California Department of Water Resources has developed a water resources planning model (DWRSIM) to simulate the combined operation of the California State Water Project (SWP) and the Federal Central Valley Project (CVP) as discussed by Barnes and Chung (1986). A least-cost network flow programming procedure, the Out-of-kilter Algorithm (OKA), has been incorporated into DWRSIM to perform the operation of the CVP-SWP facilities south of the Sacramento-San Joaquin Delta. The OKA is an improvement over the traditional mass balance accounting approach of reservoir and streamflow routing in that it increases the flexibility of the model. This flexibility is essential in the management and planning of complex water systems such as the CVP-SWP system. An added benefit of the OKA over the mass balance approach is that the OKA is a computationally more efficient algorithm, resulting in a substantial savings in computer execution time. Since a typical operation study using DWRSIM involves a study period of approximately 60 years, and since a typical study may involve numerous model runs, the resulting time savings can be significant.

Expert System for Calibrating Swmm

Abstract: EPA'S Storm Water Management Model (SWMM) simulates all aspects of the hydrologic and quality cycles. Using expert system technology, an interactive user‐support framework has been developed to automate the calibration of the runoff block. It acts as a front end to assist the user in the initial estimation of the parameter values and in building the SWMM input files. It interprets the simulation results and suggests some useful adjustments in the value of significant parameters thus reducing the user's time and effort. For the interpretation of simulation results, production rules are employed to help the user decide what parameters need to be adjusted. Some heuristics have been developed to evaluate the new parameter values. The combination of simulation techniques and expert system methodologies facilitates the use of sophisticated models such as SWMM.

Comparison of Method of Residuals and Cluster Analysis for Flood Regionalization

Abstract: The method of residuals was recently used by the US Geological Survey (USGS) to delineate seven flood regions for the state of Kentucky An alternative approach is to use cluster analysis in conjunctin with important statistical properties of the maximum annual flood-peak series Applying the FASTCLUS clustering procedure of the Statistical Analysis System, five cluster regions are identified using a similar data base as the USGS study Flood regions delineated under these two methods of flood regionalization are then compared by examining trends in important hydrological characteristics within each of the regions, and through a discriminant analysis based upon watershed physical attributes Results show that, although cluster regions are in no way similar to those defined by the method of residuals nor coincident with geographical boundaries, they are more distinguishable and better discriminated in terms of the hydrological characteristics controlling flood response than the USGS regions Furthermore, standard errors associated with the regression equations relating the log-Pearson, Type-III 50-year flood estimate to watershed physical attributes are comparable under the two methods of regionalization

Remote Sensing and Fully Distributed Modeling for Flood Forecasting

Abstract: The advantage of introducing Landsat‐derived land‐cover information into a flood‐flow forecasting model is examined. Two modeling alternatives, with and without Landsat data, were applied to 10 km by 10 km grid sizes. The landcover information is primarily derived from Landsat imagery and used directly for rainfall‐excess estimation and runoff routing. Runoff is calculated separately for each of six land‐use/land‐cover classifications for each watershed element. Without Landsat data the model is a lumped‐parameter mpdel, while with Landsat data it is a fully distributed model. The advantage of calculating runoff for each landuse/land‐cover class separately is that a watershed element can be substantially larger than a typical homogeneous hydrologic unit. The paper reports that the improvement of predicting flood peaks and total runoff gained by using Landsat data is at the 10% level of significance.

Minimization of Raw Water Pumping Costs Using MILP

Abstract: With increasing demands for water, increasing costs for electrical energy, and often stagnant budgets, water utilities must begin to investigate alternative pumping policies that achieve cost savings while not sacrificing system performance. A study was performed for the city of Raleigh, North Carolina, to determine efficient raw water pumping policies to take advantage of existing storage and newly available time‐of‐use power rates. The problem was formulated as a mixed‐integer linear‐programming (MILP) model. Binary integer variables are used to model commercial demand charges, which are once‐per‐billing period assessments on the maximum on‐ and off‐peak electrical demands. Other costs to be minimized include commercial energy charges, as well as standby generator costs to avoid on‐peak commercial power use. Constraints include satisfaction of water demands, minimum and maximum reservoir levels, minimum and maximum pump run times, and other constraints necessary to ensure feasibility. The model is now b...

Hydraulic Geometry of Streams and Stream Habitat Assessment

Abstract: Quantification of the relationship between stream discharge and the availability of suitable aquatic habitat requires detailed information on the values of local depths and velocities as they vary through riffles and pools. Conventional flow models are inadequate to supply the needed information. A basin model is presented which provides a new approach to basinwide flow modeling for stream habitat evaluation. Streams within a basin exhibit similar patterns of development, varying in scale with the drainage area. Average width, depth, and velocity increase in a predictable way with drainage area and discharge. Hydraulic geometry relations define the average values of width, depth, and velocity for any stream in the basin. Local variations of depth and velocity about the average are evaluated from probability distribution models developed from field measurements made throughout riffle and pool sequences. The basin flow model provides the needed hydraulic data to apply the Instream Flow Incremental Methodology (a state-of-the-art methodology for stream habitat evaluation) of the U.S. Fish and Wildlife Service.

Public Involvement, Conflict Management: Means to EQ and Social Objectives

Abstract: Engineers, scientists, and even some social scientists prefer to look at water resources planning and management as primarily analytical. However, more and more of the water professionals' analytical work depends on peopleoriented techniques either to relate their activities to outside interests or to build better internal team relationships. Frequently, the major problems that engineers and scientists face are not technical. They are problems of reaching agreement on facts, alternatives, or solutions. Public involvement and conflict management techniques are keys to servicing such needs. After briefly describing public involvement and conflict management techniques, seven observations on why incorporating social and environmental objectives into water resources planning and management require these process, techniques are presented.

Chance-Constrained Model for Management of Stream-Aquifer System

Abstract: A chance-constrained optimization model for a stream-aquifer system is developed using an approximate solution for the transient drawdown of the water table of an aquifer by a well operating near a river. The model explicitly considers the random nature of the hydraulic conductivity and specific yield of an unconfined aquifer. This enables the determination of the optimal groundwater pumping pattern and induced recharge from the stream to the aquifer (i.e., stream depletion rate) under specified system performance probability requirements. An application of the model is demonstrated using a hypothetical problem, and the sensitivity of the results is examined by varying probability requirements and the statistical properties of the aquifer parameters, which are: the coefficient of variation of the log-hydraulic conductivity; the coefficient of variation of the log-specific yield; and the correlation between the log-hydraulic conductivity and log-specific yield. The results obtained by the model indicate that the optimal pattern of pumping rates obtained by the management policy are highly sensitive to the probability levels and coefficient of variation of the log-hydraulic conductivity. The induced rate of stream depletion is insensitive to the coefficient of variation of the log-specific yield and is slightly sensitive to the probability levels.

Management of Phosphorus and Nitrogen Inputs to Lake Rotorua, New Zealand

Abstract: The water quality of Lake Rotorua has deteriorated since the 1960s because of excessive phytoplankton growths caused by increased inputs of phosphorus and nitrogen from the Rotorua city sewage treatment plant. Removal of phosphorus alone may produce no measurable improvement in lake condition unless it can be made the limiting nutrient. Even then, this may take a number of years, because of recycling of phosphorus already in the lake system. Removal of nitrogen alone may reduce phytoplankton growth, in the short term (say 5–10 yr) but is not recommended because the algal community may become dominated by heterocystous blue‐green algae, which can meet their nitrogen requirements by fixing dissolved molecular nitrogen and form dense unsightly assemblages. Thus, removal of both nitrogen and phosphorus is recommended. A suggested aim is to restore the lake condition to that which prevailed prior to the 1960s, before widespread public concern about phytoplankton growths developed. The scientific view is that t...

Water Resources Management in North China Plain

Abstract: A conjunctive groundwater-surface water planning model is presented. The optimization model maximizes the net revenue generated from the production of wheat, corn, and cotton over a one-year planning horizon. The costs of production include distribution costs for Yellow River water, fertilizer, and nonlinear groundwater pumping costs. The decision variables of the model are the groundwater pumping schedules and the allocation of surface water, fertilizer, and land to the four drainage basins of the study area. Agricultural production functions are developed for the Yucheng County region of the North China Plain. The production functions relate the yield per hectare of wheat, corn, and cotton and the applied water and fertilizer. The groundwater hydraulic response equations are developed using the finite element method and the matrix exponential. The groundwater equations are imbedded as constraints in the planning model. Optimization results are presented for a range of hydrologic conditions. The results are compared with present allocation patterns in Yucheng County.

Network Models of Water Rights and System Operations

Abstract: A raw water supply Master Plan has been prepared for the City of Boulder, Colorado. The city's portfolio of water rights includes decrees for native water from Boulder Creek and shares in two large transbasin diversion projects. The supply system is operated to meet municipal and industrial demands, provide minimum streamflows for Boulder Creek, and generate revenues from hydroelectric turbines installed in raw‐ and treated‐water transmission lines. The Master Plan was developed with the use of three applications of the Central Resource Allocation Model, a microcomputer‐based network‐optimization tool, which uses the Out‐of‐ Kilter Algorithm. The three applications addressed the yield of the city's native water rights, the yield of its transbasin diversion project holdings, and the economic operation of its water delivery system to meet future demands. The Master Plan recommends modifications to certain operating policies, enlargement of some delivery and treatment facilities, and sale or lease of one of ...

Water Rights Modeling and Analysis

Abstract: A generalized model for simulation of surface water management under a prior appropriation water rights system was recently developed and applied to a major river basin in Texas. The water rights analysis model provides capabilities for evaluating institutional as well as hydrologic water availability. The case study provides a perspective on key considerations in water rights modeling and analysis. A river basin should be viewed as an integrated system. Water available to a particular water management entity depends upon the impacts of other water users in the basin. Increases in reservoir yield achieved by system operations should be properly reflected in water rights. Assigning priorities by appropriation date versus type of use and assigning priorities to refilling storage capacity are two other issues which are illustrative of the complexities of administering and modeling water rights.

Decision Support for Estuarine Water Quality Management

Abstract: Management of water quality in estuarine systems is a multistepped process, ranging from characterization of the hydrological and hydromechanical properties that govern water quality changes through identification of waste loads, regulatory constraints, and water quality attributes to identification of alternative candidate plans and selection by so-called decision makers of the best plan to be implemented. The ultimate step in this complex process is to operate the physical system within the stipulated performance goals. Recently, with the advent of ever-increasing computer power, geographic information systems (GIS) and interactive graphics, supporting integrated user-friendly data management and processing have been added to the body of tools intended to support the decision process through its many steps. This paper focuses on implementation of a new generation microcomputer as the sole host of the decision support system, and seeks to demonstrate how it may be used at each step of the decision process. Special attention is given to features like: (1) Object-oriented data and control handling; (2) the integration of simulation models into the decision support system; and (3) the water quality management process. The case of a small estuary in Southern California is presented as a demonstration of the approach.

Hydropower Optimization Via Sequential Quadratic Programming

Abstract: Optimal allocation of powerplant releases during peak demand periods carries an economic advantage in the operation of hydropower systems interconnected to large electrical networks. This paper presents an alternative formulation for determining release strategies when the objective is not maximizing total hydroelectric generation per se, but rather the economic benefit stemming from it. The proposed hydropower problem is formulated within the realm of concave programming without sacrificing realism in the formulation, thus yielding a nonlinear‐concave objective function. A nonlinear mathematical programming technique, sequential quadratic programming (SQP), is used to solve the problem by successive solution of quadratic programming problems. The concave characteristic of the nonlinear objective function is fully exploited by SQP, which exhibits a rapid convergence to the global optimum. An expeditious procedure to formulate the hydropower problem under the SQP framework is also presented. The methodolog...

Risk Assessment of Extreme Events: Application

Abstract: The safety of many existing dams could be improved by modifying hem structurally in accordance with recent advances in statistical hydrology and mproved availability of meteorological and hydrological data. Any increase insafety that might be gained by structural changes must be balanced against their costs. The risk analysis methodology known as the partitioned multiobjective risk method (PMRM) is explored in this paper through a dam‐safety problem. The PMRM is well suited to the task of solving the probabilistic optimization problem posed by such risk‐versus‐cost considerations. With the PMRM, a number of conditional expected‐damage functions are generated. Of these, one that represents events of a more extreme and catastrophic character is of particular interest here. The close relationship that exists between the expectation of damage and the statistics of extremes is shown to simplify the implementation of the PMRM, and the relationship also permits the derivation of closed‐form equations that determ...

Rainfall Intervention Analysis for On‐Line Applications

Abstract: Rainfalls during summer season are a major cause of sporadic nonlinear transient drops in daily municipal water consumption. The nonhomogeneous, nonlinear effects induced by rainfall interventions on water use complicate time series model identification and estimation. An iterative computer algorithm, that employs a model‐switching transfer function, is proposed for sequential estimation of the transient drops in the water consumption, so that they can be removed from the time‐series data. Existing time series analysis techniques, which are based on homogeneous, covariance stationary assumptions are not directly applicable, since the water‐use time series never reaches statistical equilibrium. The practical data transformation procedure introduced in this paper is useful for achieving approximately homogeneous and stationary time series prior to model identification and estimation of rainfall intervention effects. The resulting empirical model is a transfer function of intervention time, number of uninter...

CCGP Model for Multiobjective Reservoir Systems

Abstract: This paper presents an application of chance-constrained goal programming methodology to a system of multipurpose reservoirs Several objectives which may be conflicting and noncommensurate such as flood protection, municipal and industrial (M&I) water supply, hydroelectric power generation, recreation, etc are considered in the model The system goals and constraints are expressed either deterministically or probabilistically depending on whether the random variable term for inflow into a reservoir is present or not For a constraint, the requirement must be strictly satisfied For a goal, it is desired to achieve the solution which is as close as possible to the specified target Stochastic inflows with one period correlation in successive periods are explicitly considered with conditional distribution functions based on normal and lognormal distributions of inflows provided The application of the methodology to a three-reservoir system in Oklahoma is reported The proposed model uses a time period of a month and may be employed for planning rather than real-time applications

Impact Evaluation Procedures: Theory, Practice, and Needs

Abstract: Over the past 50 years, planning procedures and analytical methods for evaluating social and environmental effects have played an increasingly important role in federal water planning Yet the impact of these procedures on decision making has been less than what their proponents hoped for Among the reasons for this are the inability of many methods to provide the information most needed by decision makers and insufficient education of potential users A recent Engineering Foundation conference addressed social and environmental goals in water management This paper summarizes conclusions reached there regarding the theory, practice, and needs of evaluation procedures One conclusion is that recent changes in federal water planning guidelines are but a pragmatic adaptation to the way planning actually takes place and that multiobjective methods will continue to play a role A recommendation is that these planning procedures be adapted to the new federal cost-sharing rules and for use in conflict management

Water Requirements versus Water Availability in Saudi Arabia

Abstract: Water demand in the Kingdom of Saudi Arabia has increased from 1750 million cubic meters (Mm3) in 1975to more than 9,600 Mm3 in 1985, a five-fold increase in ten years. At the same time increase on the supply side through water recycling and seawater desalination has been from around 18 Mm3 to 605 Mm3 during the same period. The development of these additional water supplies have been, however, far short of the increase in water demand, with groundwater making up the difference. This paper examines the above problem from the viewpoint of supply-demand balance. First, the paper assesses the surface and groundwater resources of the Kingdom, and the present as well as the future conditions of sea water desalination and water cycling. The water demands of the various use sectors are given followed by projections of future water demands. The third phase compares the water supply-demand situation under present and future conditions. From this comparison it was evident that unless there is a change in the current water use practices, groundwater, the major water resource of the Kingdom, will be mined in few decades and the extent that its usefulness may be severely diminished as a resource. When this develops, a severe water crisis will occur. The crisis can be reduced in severity, or averted, by taking the needed steps to bring into balance the annual water use with annual water supply.

Pollutant Washoff Under Noise-Corrupted Runoff Conditions

Abstract: The first‐order surface pollutant washoff model is examined under noise‐corrupted runoff conditions. Statistics of the pollutant load are derived using the derived probability distribution concept and verified using Monte Carlo simulations. The investigation demonstrates that under noise‐corrupted runoff conditions a bias is introduced in the estimate of the pollutant load. The bias is sensitive to: (1) The time step of the simulation; (2) the variance of the noise in runoff; and (3) the time from the start of the simulation (duration of the simulation). Statistics are derived for both the incremental pollutant washoff load (ΔP) and the mass of pollutant remaining on the street surface (P), The results of this study can be incorporated in any rainfall‐runoff model (e.g., SWMM, STORM, etc.) that makes use of the first‐order pollutant washoff model.

Water Resources of GCC: International Aspects

Abstract: Rapid economic development in the member states of the Gulf Cooperation Council has led to major hydrologic stresses being laid on the aquifers underlying most of the Arabian Peninsula. These aquifers presently constitute the major local resource and, to a significant degree, they are shared across international boundaries. The “Basic Law” of the GCC provides necessary and sufficient rules for the creation of an international framework to manage these shared groundwater resources.

Estimating Terminal Lake Level Frequencies

Abstract: A reliable method of predicting long‐term future lake levels with associate exceedance frequencies is essential to establish planning elevations in the lakeshore environment. A methodology is proposed here to develop level‐frequency relationships for terminal lakes. The methodology is applied to Devils Lake, North Dakota. An autoregressive moving average (ARMA) model with a deterministic trend component for the annual storage changes is used as the basis. The storage changes are derived from the historical annual average level time series, and the level‐storage relationship. Using the validated ARMA model and simulation techniques, many sequences of annual incremental storage time series are generated. The concepts of mass curve and range analysis are applied to each synthetic sequence for deriving maximum and minimum lake volumes in each sequence. The resulting set of maximum and minimum lake volumes are then analyzed for their underlying frequency distributions. Utilizing the elevation‐storage function,...