Showing papers in "Water Resources Planning and Management and Urban Water Resources in 1991"

Water Supply Impact Analysis of Proposed Water Quality Control Plan for Salinity for San Francisco Bay and Sacramento-San Joaquin Delta Estuary

Abstract: This paper presents the procedures and techniques employed as part of the Bay-Delta proceedings to evaluate the water supply impacts of various proposed flow and water quality objectives for the Delta. The primary tool selected for analyzing the impacts was DWR's Planning Simulation Model. A number of alternative objectives to protect various beneficial water uses were proposed by the Board in their plan. Simulation studies were formulated and conducted to analyze the proposed objectives individually and in combination. Impacts were examined by comparing study results with a base study using current Delta flow and salinity requirements. The CVP-SWP system was used as a surrogate to the whole system to evaluate overall water supply impacts. These impacts could then be used to evaluate the relative benefits or trade-offs of proposed changes in Delta flow or water quality objectives. This process brought various water interests together so that agreement on technical methodology could be used as a basis for reaching a clearer understanding of statewide impacts of proposed Delta water quality plans.

An Alternate Formulation of Time as a Decision Variable to Facilitate Real-Time Operation of Water Supply Systems

Abstract: With the advent of a new focus on energy conservation and the availability of cost efficient computer technology, many water utilities are investigating new ways to improve the efficiency of their water distribution system operations. Of particular concern is improved operation of the pumping facilities since pumping generally accounts for a large fraction of the total operating costs. One way to improve such operations is through the use of optimally generated pump schedules. Optimal pump schedules may be generated using some type of optimization approach coupled with a physical description of the water distribution network. Where the distribution system can be characterized as a serial configuration, dynamic programming can be efficiently applied to generate an optimal control policy. When the system is nonserial, an optimal control policy may be obtained through the use of dynamic programming coupled with a spatial decomposition scheme or through the application of nonlinear programming.

The Hydrology of Urban Runoff Quality Management

Abstract: Recent regulatory requirements to reduce pollutant discharges from municipal storm sewer systems have intensified the need for approaches to developing design parameters, such as the selection of a design storm, which can be applied to urban stormwater quality management facilities. Examination of six U.S. cities in areas with widely varying climatic conditions reveals that most rainfall occurs during small storms. Hydrologic simulations using long-term rainfall records of these areas indicate that a reasonable design storm is on the order of the 1-month to 4-month storm, and a unit storage volume of roughly 0.2 to 0.9 inches will provide effective pollutant capture. Detention basins which capture these smaller storms can be provided to control urban stormwater pollutants. It may be possible to retrofit existing flood control basins for this purpose; however, water quality control basins employ a significantly different storage strategy and should serve relatively large (typically over 50 acres) areas.

Water Supply and Sanitation Policies in Mexico

Abstract: The National Water Commission (CNA), is the responsible Department for the Governmental Water Division in Mexico. Within the National Potable Water Supply and Sanitation Program, the Commission gives technical and administrative assistance to decentralized operating systems. This paper focuses on the water supply and sanitation policies that have been established within the country, by the Commission.

Uncertainties in Planning Inter-Agency Water Supply Transfers

Abstract: San Francisco Water Department, facing a possible fifth year of drought, purchased surplus water from the Placer County Water Agency and arranged for wheeling of the water through State Water Project facilities to an emergency turnout on the State's South Bay Aqueduct. Planning for construction of the emergency turnout and the inter-agency transfer of water included many operational pitfalls and environmental uncertainties.

Stormwater/Wastewater Management: How an Application Can Drive a GIS

Abstract: Decision makers are finding that a much-needed application may be the key that drives the creation of a city- or county-wide Geographic Information System (GIS). A start-up GIS developed in Cincinnati and Hamilton County, Ohio, was driven by the demand for a 100-year master plan for stormwater/wastewater management.

Totally RAD Urban Drought Management from California

Abstract: The paper discusses some novel drought management measures which have arisen during the recent 4-year California drought. Many of these options are new ideas on the part of California water utilities while others represent implementation of ideas substantially researched in academia. All of these measures are new and different compared to traditional drought management for urban water supply.

Unique Water Quality Aspects of Lake Pontchartrain

Abstract: Natural factors causing changes in Lake Pontchartrain, can be grouped into the following: subsidence and wetland loss due to the deterioration of the St. Bernard Delta, natural variations and long term cycles cause year to year and decade to decade changes, and hurricanes and other major storms produce short term and long term environmental change. The most significant factor affecting the water quality of Lake Pontchartrain is the activities of the over one million people who reside on the wetlands that in the past nourished it. During rains, the south shore becomes a mixing zone for urban runoff which is pumped from outfall canals into the lake. The city's drainage network is composed of a subsurface collection system that discharges into either open (102 miles) or covered (89 miles) canals. These canals convey the water to the pumping stations located throughout the city. To be able to reduce the environmental effects on Lake Pontchartrain of the urban runoff from New Orleans, it will be necessary to estimate the quantity and quality of the stormwater entering the lake. The quantity of urban runoff can be obtained by a flood frequency analysis for the outfall canals from the drainage system. This unique drainage system produces a unique flood frequency analysis.

Low Stream Flow Frequency Analysis with Ordinary and Tobit Regression

Abstract: In order to estimate the low-flow quantiles at ungaged sites, it is necessary to estimate low-flow quantiles at gaged sites Two linear regression methods, denoted NR and NE, are compared for estimating the mean, standard deviation and low-flow quantiles when some annual low-flow values are zero or indistinguishable from zero Results of a Monte Carlo simulation show that the NE method is better than the NR method Methods for estimating the parameters of low-flow logarithmic regression models are needed for the situations where some of low-flow quantiles (the dependent variable in the regression model) are zero Two methods which have been used to estimate the parameters of low-flow regression model are examined in this paper One, denoted OLSC, adds a positive constant to all the low-flow quantiles before estimating the logarithmic regression model's parameters The other, denoted OLSD, ignores all observations having zero low-flow quantiles then estimating the parameters of the regression model using ordinary least squares (OLS) The maximum likelihood estimation method for Weighted Tobit (WT) and Ordinary Tobit (OT) models are also used for estimating the parameters of the regional regression model since these methods include all observations without distortion A Monte Carlo study shows that OLSC and OLSD on average provide poor parameter estimates The WT and OT methods provide efficient parameter estimates of low-flow regression model based on the sampling mean square error (MSE)

Summary of Stormwater Quality Management Practices

Abstract: The control of water quality in urban runoff is in its technical infancy. Never-the-less Water Quality Act of 1987 states that stormwater pollution must be reduced to the maximum extent practicable (MEP). There are methods and techniques that can insure that the levels of reduction achieved are indeed the maximum practicable. The purpose of this paper is to provide general guidelines for runoff quality controls intended to meet this goal.

A Comparison of Two Large Scale NLP Strategies for Determining Optimal Pump Station Controls

Abstract: To solve the general nonlinear problem which is not simplified using the uniform spatial demand patterns, a two-level hierarchial scheme has been identified. The purpose of this decomposition is to reduce space of possible pump combinations at each time period. Thus, a DP technique may be then easily applied to find out an optimal combinations. The first stage of the algorithm is to solve a nonlinear programming problem (NLP) for the optimal tank trajectories. The decision variables in this problem are each pump station's discharge and pumped head for each period. The second level, a DP method is applied to find the best combination for each operation time period based on the optimal tank trajectories. Within the scope of this paper, the authors only focus on the first level, e.g., the NLP module. The real-time pump station operation problem has been posed as a large scale NLP which can be efficiently considered using a problem reduction technique. This formulation is discussed in detail. A discussion of two methods to solve the resulting NLP is presented and conclusions regarding their advantages are discussed.

Management of a Groundwater Basin Using an Integrated Numerical Model and a Geographic Information System

Abstract: This paper describes the development and application of an integrated three-dimensional groundwater model and geographic information system (GIS) to the management of the San Fernando Valley Groundwater Basin (SFVGB). The SFVGB, and important source of water supply to Southern California, provides a significant portion of the water to Los Angeles, San Fernando, Burbank, Glendale and La Crescenta. Water rights agreements for the SFVGB strictly limit allowable extraction, recharge and storage for each of the water users in the basin. With the recent discovery of widespread groundwater contamination from volatile organic compounds (VOCs), the scope and importance of efficient management of the water supply in the basin has expanded greatly. Conjunctive use of the basin's water supply now includes evaluations of potential groundwater production areas on the basis of hydrogeologic conditions, water quality, and contaminant plume management.

A Comprehensive Algorithm for Network Calibration

Abstract: An explicit calibration algorithm is proposed which provides the direct and rapid adjustment of the pipe roughness coefficients and junction node demands that exactly meet a specified set of field observations of pressure or grade at designated test nodes throughout the distribution network under multiple demand loadings and corresponding network operating conditions. Both the individual pipe roughness coefficients and the junction demands are adjusted using a set of global parameter adjustment factors. The resulting algorithm is both fast and efficient and guaranteed to yield a mathematically consistent solution.

Methods for Designing Hydraulic Aquifer Remediation Techniques

Abstract: This paper reports on recent research to develop methods for accommodating uncertainty in designing hydraulic remediation systems for contaminated aquifers. The methods rely respectively on a new chance-constraint linear programming formulation and a neural network application. Results as application to a hypothetical polluted aquifer are presented.

Integration of an ARC/INFO GIS with HEC-1

Abstract: A hypothetical watershed was constructed to test the efficacy of using an ARC/INFO Geographic Information System to provide input for the U.S. Army Corps of Engineers HEC-1 hydrologic model. Difficulties were encountered in using the TIN module to accurately assess average rainfall intensities and in using the label command to find watershed subbasin centroids. In addition, the control of output format was rather cumbersome. The use of this type of expensive system (capital cost for software and equipment, and operating cost for personnel training and digitization) may not generally be warranted for projects which are limited in scope (hydrologic analysis only with a limited number of future alternatives).

New Jersey Department of Transportation Bridge Scour Evaluation Program

Abstract: The New Jersey Department of Transportation's (NJDOT's) newly initiated bridge scour investigation program will assess the vulnerability to failure by scour of all existing bridges over scourable waterways. It offers a model to other states as one of the first to apply to the real world, the FHWA's recent technical advisory for scour evaluation. This paper describes preliminary suggestions for useful procedures, specialty software, and weighting methods for quickly identifying priority bridges and bridges that are scour critical.

Statistical Analysis of Ground Water Quality Data

Abstract: The Resource Conservation and Recovery Act (RCRA) requires owners and operators of hazardous waste facilities to utilize design features and control measures that prevent the release of hazardous waste into ground water. These regulations require that a statistical method and sampling procedure approved by the EPA be used to determine whether there are releases from regulated units into ground water. The guidelines currently approved by the EPA (1989) prescribe statistical methods to test hypothesis regarding the presence of ground water contamination based on chemical data. The hypothesis that can be tested encompass the following situations: (1) comparisons of chemical concentrations between background and compliance wells; (2) comparisons of chemical concentrations at wells with fixed standards; (3) intrawell comparisons of chemical concentration variability over time with background well data; and (4) comparisons as in (2) and (3) when the chemical data has many 'nondetects' (i.e., data are reported as 'below detection level'). The current methods for ground water quality analysis are summarized and their assumptions highlighted according to their applicability to field conditions. Our review of the EPA (1989) guidelines indicates a need for extending these statistical methods to include: (i) geo-statistical methods, and (ii) space-time methods, to account for the spatial and temporal dependence of ground water quality data.

Adaptive Control of Groundwater Hydraulics

Abstract: Adaptive control has been extensively applied in industrial settings for the control of unknowns systems, systems with uncertainty in the parameters The approach is recursive, the response of the system to control is used to update the parameter estimates in order to improve future control Adaptive control is applied to the control of groundwater hydraulics in order to meet target heads at well locations in the presence of uncertainty in the transmissivity and hydraulic conductivity

Uncertainty in urban hydrologic modeling

Abstract: Uncertainty is pervasive in hydrologic modeling. Uncertainty is present in the formulation of the physical situation to be modeled, in the form of the model to be used, in the boundary conditions stipulated, in the parameters required by the model, in the procedures used to estimate model parameters, in the input functions required to drive the model (rainfall, etc.), and in the data used to verify the model. This paper addresses these various sources of uncertainty. An example is given based on the estimation of flood peaks.

Optimum Dredging Procedures for Artificial Nourishment of Beaches

Abstract: This brief article discusses conventional and new procedures for nourishment of beaches taking advantage of recent years' development of more effective equipment of smaller capacities operating more frequently. An optimization procedure comparing old and new practices is described comparing it to similar procedures for maintenance dredging of navigation channels.

Use of Models in Water Resource Systems: CRSS Experience

Abstract: The Colorado River Simulation System (CRSS) is an in-house governmental computer-based model designed to be used as a decision support tool in performing long and mid range planning and operational studies of the Colorado River Basin The primary objectives of this paper are to provide information on the actual use of the CRSS and identify the key factors which have contributed to the extensive and effective use of the CRSS in supporting the planning and operational decision making process It is concluded that among many other factors, the 'institutional setting' in which the CRSS was developed, used, and maintained has greatly influenced the success of the model

Urban Water Issues/Strategies in the Humid Tropics

Abstract: Annual rainfall volumes in the Humid Tropics are large, and the events can be quite intense, but they can also be highly variable, with periods in which little or no rainfall occurs. Streams and canals can have high ratios of high to low flows, and low flows can occur over extended periods, resulting in low capacities for natural purification. The predominating high temperatures can further reduce the capability. The capacities of countries of the humid tropics to respond to the challenges are also hampered by a number of inadequacies in knowledge of the natural systems existing in the region and in the attitudes to the preparation and implementation of management policies. The institutional arrangements for the control of urban water-related problems are often unmanageable and result in greater negative impacts on the environment through a lack of integrated water management strategies.

Reliability Consideration in Capital Improvement Programs

Abstract: This paper shows an application of network reliability modeling in water supply capital improvement programs. The proposed approach consists of combining geometrical and structural properties of pipelines in a Pipe Importance Factor defined as the rate at which water supply reliability improves as the reliability of the pipeline improves. A case study demonstrates the application.

The Danby Pipe Renovation System

Abstract: This paper describes a pipe renovation system and its structural characteristics which is cost effective and technically suitable in all sizes of pipe from 8 inches (200 mm) to the largest man-entry drains (and sewers).

Field Data-Gathering: Critical First Step for a GIS

Abstract: Gathering data in the field is one of the first major tasks required for developing a geographic information system (GIS) or automated mapping/facilities management (AM/FM) system. This process, which is labor-intensive and often underestimated in terms of time and money, is a critical step in the development of a reliable GIS. Recently, great strides have been made in the technology and accuracies that can be achieved when obtaining structure locations and attributes in the field. Choosing the best data-gathering option depends on several factors. These include: the applications for the GIS, the accuracies required, the type of terrain, the amount of development, the time allowed, the type of data needed, the budget, and the equipment used. Based on these criteria, the features and benefits of several options for obtaining facility and structure locations and attributes are compared and contrasted.

Optimizing Urban Ground Water Supply Systems

Abstract: The cost of Pumping comprises a major part of total water operation and maintenance expenses. Most utilities attempt to keep these costs down. However, there are areas of study that may help to additionally reduce water delivery costs. For example, the optimal time to clean water mains, the optimal system pressure over time, etc. This particular investigation emphasizes determining the optimal pumping schedule for a well field. The objective is to produce a unit volume of water at minimum cost.

Environmental Assessment of Lake Maggiore, St. Petersburg, Florida

Abstract: Lake Maggiore is a shallow 385 acre (156 ha) hypereutrophic lake located in St Petersburg, Florida The lake's watershed contains a variety of urban land use types that have discharged untreated stormwater runoff directly to the lake for many years Lake water quality had declined due to the accumulated effect of stormwater discharges, and other factors such as past dredging and filling activities An environmental assessment project was completed that included quality and quantity monitoring of stormwater discharges within the watershed; an inventory of hydrologic characteristics; and an assessment of long term hydrologic and pollutant loadings to the lake (CH2M HILL, 1991) A calibrated SWMM model was used to evaluate long term land surface runoff volumes to the lake Flow averaged pollutant concentrations were used to estimate pollutant loads The water quality sampling and modeling analysis allowed investigators to evaluate and summarize the origin of non-point source pollutants in the watershed; and to recommend management activities that would contribute to their control

Projecting Climate Change to Small Basins: Potential Impact of Global Warming on Hurricane-Induced Flooding in South Florida

Abstract: An important difficulty in evaluating potential hydrologic impacts of climate variability is that predictions of climate change require global simulation models that do not resolve phenomena typically needed for hydrologic impact analysis (regions a few tens of kilometers across or less). This difficulty can be overcome by using a physical model for smaller-scale phenomena to transfer the climate change in a coarse resolution, global model to a watershed model having the resolution needed for impact analysis. Specifically, the authors use Emanuel's model of hurricanes to derive changes in severe rainfall characteristics for watersheds that are subject to hurricane-induced flooding. As an example, the method is used to examine the potential impact of CO 2 doubling on a flood-control drainage system in South Florida.

Model Mania in Urban Hydrology: Present Dilemmas

Abstract: A recent ASCE Task Committee on microcomputer software in urban hydrology has just completed its inventory of 40 software packages available at modest cost to the urban drainage engineer The TC was formed in response to the explosion in software development for the urban drainage field, seen here as a kind of model mania in which fundamental assumptions and basic hydraulic principles are either lost or at best poorly understood by the average software user For example, the kinematic wave equations are firmly entrenched as the physical basis for urban subarea runoff modelling Yet, there are numerous examples where the use of these equations by themselves does not guarantee a useful result The success of the modelling effort depends on the numerical solution scheme, the rainfall excess determination, the friction relationship, and, in the case of long-term hourly simulation, the rainfall disaggregation procedure This paper examines fundamental assumptions in the context of kinematic wave modelling of overland flows This is done in an effort to circumscribe present difficulties and identify future directions in urban hydrology modelling

Flood Hazard Scenarios in a Pleistocene-Holocene Basin

Abstract: Technical scenarios are used to characterize the flood hazard in the Bayou Fountain Basin, an area of complex geomorphology and urbanization. Floods from three sources, 1) local precipitation, 2) backwater from the Amite River, and 3) the Mississippi River, are described and areas of especial hazard are identified. Technical scenarios such as these are useful in land planning and as an adjunct to conventional hydrologic studies.