DYNAMIC PROGRAMMING FOR OPTIMAL CAPACITY EXPANSION OF WASTEWATER TREATMENT PLANTS1

ABSTRACT: A dynamic programming procedure for the planning and operation of a wastewater treatment plant over a long period of time is presented. In order to meet increased demands for wastewater treatment in the future, the expansion of existing plants must be considered. Dynamic programming is employed to determine the optimal schedule of expansion at each plant, simultaneously determining an optimal operating policy (treatment level). The optimal schedule of expansion at each plant depends on the following: (1) the shape of the projected wastewater demand function; (2) the interest rate used; (3) the locations and capacities of the facilities available; and (4) the rates of increase of the costs of construction, labor, chemicals, and electric power. An example illustrating the use of the procedure is presented.     

A MULTI-BASIN PLANNING STRATEGY1

ABSTRACT. The purpose of this paper is to present and discuss a procedure for finding an optimal staging plan for implementing a multi-basin water resource system-a system that must meet, with tolerable shortages, pre-specified but highly variable demands for water that increase over time-a system such as the proposed Texas Water System. The paper stresses that, in the past, planners have paid little attention to quantifying explicitly the impact that uncertainty has on the decision process, and in that context, presents a means for explicitly evaluating the impact that uncertainty has on finding and evaluating the performance of the optimal and several alternate staging plans. The procedure presented evaluates the impact that uncertainty, in both the hydrologic and the economic variables, has on the decisions that need to be made. The decisions requiring resolution are (1) which of an over-specified set of facilities should be constructed, (2) how large each of the facilities should be at various points in time, and (3) how should the system be operated so as to minimize the capital plus operational costs over the planning period.     

THE EFFECTS OF RISK AND RELIABILITY ON OPTIMAL RESERVOIR DESIGN1

A chance-constrained linear programming model, which utilizes multiple linear decision rules and is useful for river basin planning, is used to evaluate the effects of risk and reliability on optimal reservoir design. Streamflow forecasts or predictions can be explicitly included in the linear program. The risk associated with the predictions is included in the model through the use of cumulative distribution functions (CDF) of streamflows which are conditioned on the predictions. A multiple-purpose reservoir on the Gunpowder River in Maryland is used to illustrate the effectiveness of the model. In order to provide the decision makers with complete and useful information, trade-off curves relating minimum reservoir capacity (a surrogate for dam costs), water supply and flood control targets, and the reliability of achieving the targets are developed. The trade-off curves may enhance the decision maker's ability to select the best dam capacity, considering technological and financial constraints as well as the trade-offs between targets, risks, and costs.     

IMPROVED RIVER BASIN UTILIZATION THROUGH SYSTEMS ANALYSIS1

ABSTRACT. Theoretical and practical results are summarized for a study to determine optimal water resource allocation in a proposed water conservancy district. The area of this district, which covers several river basins, contains a large number of existing and proposed facilities such as reservoirs and diversions. The operation of all of these facilities was to be determined along with the sizing of the proposed facilities in order to optimize given objective functions. Related efforts in optimal river basin utilization were surveyed, and linear programming was selected as an expedient optimization technique. The problem is formulated by identifying time stages which together constitute a repetitive cycle such as a year. With these stages, it is possible to associate operational and capacity variables with network components, which are branches and nodes. Objective functions are assembled for the component variables. Constraint equations are written in terms of the variables to reflect network nodal continuity, capacity restrictions, and adjudications such as water rights. A numerical example is considered in which the existing and proposed facilities are aggregated to produce a small, tractable number of facilities. This paper examines the example results and suggests future improvements for models of this type.     

Tools for Groundwater Protection Planning: An Example from McHenry County, Illinois, USA

/ This paper presents an approach for producing aquifer sensitivity maps from three-dimensional geologic maps, called stack-unit maps. Stack-unit maps depict the succession of geologic materials to a given depth, and aquifer sensitivity maps interpret the successions according totheir ability to transmit potential contaminants. Using McHenry County, Illinois, as a case study, stack-unit maps and an aquifer sensitivity assessment were made to help land-use planners, public health officials, consultants, developers, and the public make informed decisions regarding land use. A map of aquifer sensitivity is important for planning because the county is one of the fastest growing counties in the nation, and highly vulnerable sand and gravel aquifers occur within 6 m of ground surface over 75% of its area. The aquifer sensitivity map can provide guidance to regulators seeking optimal protection of groundwater resources where these resources are particularly vulnerable. In addition, the map can be used to help officials direct waste-disposal and industrial facilities and other sensitive land-use practices to areas where the least damage is likely to occur, thereby reducing potential future liabilities. KEY WORDS: Geologic mapping; Groundwater; Aquifers; Aquifer sensitivity; Land-use planning     

ASSESSING ENVIRONMENTAL EFFECTS OF SEVERE SUSTAINED DROUGHT1

ABSTRACT: Evaluation criteria for reservoir and stream resources were developed to provide decision makers with feedback on environmental consequences of water allocation decisions under conditions of severe sustained drought within the Colorado River Basin by using the AZCOL gaming simulation model. Seven categories of flow dependent resources were identified which highlight resource states associated with reservoirs or river reaches within the AZCOL model. AZCOL directly simulates impact of water management decisions on five resource categories: threatened, endangered or sensitive fish; native nonlisted fish; wetland and riparian elements; national or state wildlife refuges; and hatcheries or other flow dependent facilities. Two additional categories - cold and warm water sport fish - are not modeled explicitly but are incorporated in the evaluation of monetary benefits from recreation on Colorado River waters. Each resource category was characterized at each time step in the simulation according to one of four environmental states: stable, threatened, endangered, or extirpated. Changes in resource states were modeled by time and flow-dependent decision criteria tied to either reservoir level or stream flows within the AZCOL model structure. Gaming results using the AZCOL model indicate environmental impacts would be substantial and that water allocation decisions directly impacted environmental resource states.     

A mixed integer linear programming model for optimisation of organics management in an integrated solid waste system

In this paper, the authors propose a mixed integer linear programming model for designing an Integrated Solid Waste Management System (ISWMS) to meet specific economic goals. The model refers to a set of municipalities, known as ‘local basin’, which have to share a common waste management system. At the municipal level the model allows for an identification of the optimal collection service option; at the local basin level, the model provides the optimal waste flow appropriate to the collection service option of each municipality. The model has been applied to a full-scale case study of an area located in southeast Italy. A scenario analysis was carried out to investigate alternative municipal solid waste management options, which fundamentally differ in the organic flow mass rate to be either collected and composted or landfilled. Findings show that an increase in the cost of landfilling determines the optimal collection scenario and the configuration plants tend to recover higher rates of organics in separate collection and thus higher refuse derived fuel productions. The results obtained validate the application of the model in both the strategic planning and operational phases, by supporting public administrators at both municipality and local basin level in decision making and evaluation of technical and economic performances of ISWMSs.     

RECREATIONAL ENHANCEMENT OF HIGH COUNTRY WATER SUPPLY RESERVOIRS1

ABSTRACT: There is considerable misconception about the dangers of opening to a recreating public in great need of additional open areas. A systematic procedure for identifying the factors essential to the selectio, planning, and management of reservoirs for recreation is described. A detailed case study conducted by an interdisciplinary project team is presented to demonstrate the feasibility fo maintaining storage levels in recreation-conductive high country reseroirs without unduly injuring downstram water users. The idea is to trade water with reservoirs having less recreation potential. The optimal means of doing this is found via a river basin simulation model with quasi-optimizing capability. Results of the case study show that this strategy is indeed feasible. Applicable to other areas may require analysis of tradeoffs if at least some damage to downstream users is unavoidable.     

REGIONAL PLANNING FOR LAND DISPOSAL OF WASTEWATER1

ABSTRACT This paper describes the development and use of a mixed integer programming model for the planning of land disposal wastewater treatment facilities. Consideration is given to relevant construction and operating costs for land sites, transmission arteries, land acquisition costs, tangible benefits from land use, controls on aquifers, and various other engineering and technical constraints The model is used to determine which land disposal sites should serve which treatment plants, when initial construction should be initiated and completed, and when capacity expansion should occur. The model's application to the St. Louis Standard Metropolitan Statistical Area is illustrated and discussed.     

The Decision-Identification Tree: A New NEPA Scoping Tool

decision-based scoping —provides an effective methodology for improving the EIS scoping process. Decision-based scoping, in conjunction with a new tool, the decision-identification tree (DIT), places emphasis on first identifying the potential decisions that may eventually need to be made. The DIT provides a methodology for mapping alternative courses of action as a function of fundamental decision points. Once these decision points have been correctly identified, the range of actions, alternatives, and impacts can be more accurately assessed; this approach can improve the effectiveness of EIS planning, while reducing the risk of future disconnects between the EIS analysis and reaching a final decision. This approach also has applications in other planning disciplines beyond that of the EIS.     

Siting and Routing Assessment for Solid Waste Management Under Uncertainty Using the Grey Mini-Max Regret Criterion

Solid waste management (SWM) is at the forefront of environmental concerns in the Lower Rio Grande Valley (LRGV), South Texas. The complexity in SWM drives area decision makers to look for innovative and forward-looking solutions to address various waste management options. In decision analysis, it is not uncommon for decision makers to go by an option that may minimize the maximum regret when some determinant factors are vague, ambiguous, or unclear. This article presents an innovative optimization model using the grey mini-max regret (GMMR) integer programming algorithm to outline an optimal regional coordination of solid waste routing and possible landfill/incinerator construction under an uncertain environment. The LRGV is an ideal location to apply the GMMR model for SWM planning because of its constant urban expansion, dwindling landfill space, and insufficient data availability signifying the planning uncertainty combined with vagueness in decision-making. The results give local decision makers hedged sets of options that consider various forms of systematic and event-based uncertainty. By extending the dimension of decision-making, this may lead to identifying a variety of beneficial solutions with efficient waste routing and facility siting for the time frame of 2005 through 2010 in LRGV. The results show the ability of the GMMR model to open insightful scenario planning that can handle situational and data-driven uncertainty in a way that was previously unavailable. Research findings also indicate that the large capital investment of incineration facilities makes such an option less competitive among municipal options for landfills. It is evident that the investment from a municipal standpoint is out of the question, but possible public–private partnerships may alleviate this obstacle.     

BASIN SCALE WATER MANAGEMENT AND FORECASTING USING ARTIFICIAL NEURAL NETWORKS1

ABSTRACT: Water scarcity in the Sevier River Basin in south‐central Utah has led water managers to seek advanced techniques for identifying optimal forecasting and management measures. To more efficiently use the limited quantity of water in the basin, better methods for control and forecasting are imperative. Basin scale management requires advanced forecasts of the availability of water. Information about long term water availability is important for decision making in terms of how much land to plant and what crops to grow; advanced daily predictions of streamflows and hydraulic characteristics of irrigation canals are of importance for managing water delivery and reservoir releases; and hourly forecasts of flows in tributary streams to account for diurnal fluctuations are vital to more precisely meet the day‐to‐day expectations of downstream farmers. A priori streamflow information and exogenous climate data have been used to predict future streamflows and required reservoir releases at different timescales. Data on snow water equivalent, sea surface temperatures, temperature, total solar radiation, and precipitation are fused by applying artificial neural networks to enhance long term and real time basin scale water management information. This approach has not previously been used in water resources management at the basin‐scale and could be valuable to water users in semi‐arid areas to more efficiently utilize and manage scarce water resources.     

A DECISION SUPPORT TOOL FOR THE MANAGEMENT OF MULTI‐RESERVOIR SYSTEMS1

ABSTRACT: A decision support tool is developed for the management of water resources, focusing on multipurpose reservoir systems. This software tool has been designed in such a way that it can be suitable to hydrosystems with multiple water uses and operating goals, calculating complex multi‐reservoir systems as a whole. The mathematical framework is based on the parameterization‐simulation‐optimization scheme. The main idea consists of a parametric formulation of the operating rules for reservoirs and other projects (i.e., hydropower plants). This methodology enables the radical decrease of the number of decision variables, making feasible the location of the optimal management policy, which maximizes the system yield and the overall operational benefit and minimizes the risk for the management decisions. The program was developed using advanced software engineering techniques. It is adaptable in a wide range of water resources systems, and its purpose is to support water and power supply companies and related authorities. It already has been applied to two of the most complicated hydrosystems of Greece, the first time as a planning tool and the second time as a management tool.     

OPTIMAL CAPITAL INVESTMENT IN THE EXPANSION OF AN EXISTING WATER RESOURCES SYSTEMS1

The study of the optimal expansion of existing water resources systems is of continuing importance because of the rising demand and limited supply of water in many areas of the world, particularly in the southwestern part of the United States of America. This study is concerned with the investigation of the optimal expansion of a realistic water resources system to meet an increasing demand for municipal and industrial use, irrigation, energy, and recreation over a planning horizon of T years. A number of possible dam sites are available for the further regulation of river (canal) flows in the basin and/or the regulation of imported waters into the basin. To maximize, over the set of alternative projects, the sum of discounted present value of net earnings subject to the demands and various institutional, physical and budgetary limits, an optimization problem (Problem I) was formed as a 0-1 mixed integer programming problem and was decomposed into the set of all feasible combinations (Problem II). The economic return was determined for each combination (Problem III). Problem II was solved by a branch and bound procedure which selected each feasible combination of dams while the optimal return for each such combination (Problem III) was found by a network analysis code.     

A multi-objective optimisation approach to water management

The management of river basins is complex especially when decisions about environmental flows are considered in addition to those concerning urban and agricultural water demand. The solution to these complex decision problems requires the use of mathematical techniques that are formulated to take into account conflicting objectives. Many optimization models exist for water management systems but there is a knowledge gap in linking bio-economic objectives with the optimum use of all water resources under conflicting demands. The efficient operation and management of a network of nodes comprising storages, canals, river reaches and irrigation districts under environmental flow constraints is challenging. Minimization of risks associated with agricultural production requires accounting for uncertainty involved with climate, environmental policy and markets. Markets and economic criteria determine what crops farmers would like to grow with subsequent effect on water resources and the environment. Due to conflicts between multiple goal requirements and the competing water demands of different sectors, a multi-criteria decision-making (MCDM) framework was developed to analyze production targets under physical, biological, economic and environmental constraints. This approach is described by analyzing the conflicts that may arise between profitability, variable costs of production and pumping of groundwater for a hypothetical irrigation area.     

Hydrologic Sensitivity to Climate and Land Use Changes in the Santiam River Basin,Oregon

Future changes in water supply are likely to vary across catchments due to a river basin's sensitivity to climate and land use changes. In the Santiam River Basin (SRB), Oregon, we examined the role elevation, intensity of water demands, and apparent intensity of groundwater interactions, as characteristics that influence sensitivity to climate and land use changes, on the future availability of water resources. In the context of water scarcity, we compared the relative impacts of changes in water supply resulting from climate and land use changes to the impacts of spatially distributed but steady water demand. Results highlight how seasonal runoff responses to climate and land use changes vary across subbasins with differences in hydrogeology, land use, and elevation. Across the entire SRB, water demand exerts the strongest influence on basin sensitivity to water scarcity, regardless of hydrogeology, with the highest demand located in the lower reaches dominated by agricultural and urban land uses. Results also indicate that our catchment with mixed rain‐snow hydrology and with mixed surface‐groundwater may be more sensitive to climate and land use changes, relative to the catchment with snowmelt‐dominated runoff and substantial groundwater interactions. Results highlight the importance of evaluating basin sensitivity to change in planning for planning water resources storage and allocation across basins in variable hydrogeologic settings.     

Criteria for the Assessment of Sustainable Water Management

Pressure on the world’s water resources is increasing, restraining social and economic development in many countries, and threatening ecological values in others. In order to manage water resources in a more sustainable manner, new planning methodologies/processes for river basin management need to be developed. This study attempts to construct a set of useable normative criteria for the analysis and evaluation of such processes. The criteria were designed as a response to the lack of deductive approaches in the evaluation of methodologies and working procedures used in the context of river basin management, making it possible to highlight their potential for sustainable development. The criteria are based on the twin concepts of participation and integration. These concepts function as well-established dimensions of both sustainable development and sustainable river basin management, and they are of significant methodological relevance. A synthesis of the key aspects connected to the two concepts is undertaken, based on a broad literature review. Focus is laid on how in methodological terms, and in relation to regional water management, to achieve participation and integration in a decision-making or planning process. The criteria are concerned with how knowledge and values are integrated into the planning process and how commitment, legitimacy, or acceptance for the resulting plan is generated.     

Nonstationary Water Planning: An Overview of Several Promising Planning Methods1

Waage, Marc D. and Laurna Kaatz, 2011. Nonstationary Water Planning: An Overview of Several Promising Planning Methods. Journal of the American Water Resources Association (JAWRA) 47(3):535‐540. DOI: 10.1111/j.1752‐1688.2011.00547.x Abstract: Climate change is challenging the way water utilities plan for the future. Observed warming and climate model projections now call into question the stability of future water quantity and quality. As water utilities cope with preparing for the large range of possible changes in climate and the resulting impacts on their water systems, many are searching for planning techniques to help them consider multiple possible conditions to better prepare for a different, more uncertain, future. Many utilities need these techniques because they cannot afford to delay significant decisions while waiting for scientific improvements to narrow the range of potential climate change impacts. Several promising methods are being tested in water utility planning and presented here for other water utilities to consider. The methods include traditional scenario planning, classic decision making, robust decision making, real options, and portfolio planning. Unfortunately, for utilities vulnerable to climate change impacts, there is no one‐size‐fits‐all planning solution. Every planning process must be tailored to the needs and capabilities of the individual utility.     

Solid waste management in urban areas: Development and application of a decision support system

A decision support system (DSS) developed to assist the planner in decisions concerning the overall management of solid waste at a municipal scale is described. The DSS allows to plan the optimal number of landfills and treatment plants, and to determine the optimal quantities and the characteristics of the refuse that has to be sent to treatment plants, to landfills and to recycling. The application of the DSS is based on the solution of a constrained non-linear optimization problem. Various classes of constraints have been introduced in the problem formulation, taking into account the regulations about the minimum requirements for recycling, incineration process requirements, sanitary landfill conservation, and mass balance. The cost function to be minimized includes recycling, transportation and maintenance costs. The DSS has been tested on the municipality of Genova, Italy, and the results obtained are presented.     

LINEAR PROGRAMMING USE FOR EVALUATING WATER RESOURCES AND COST AND BENEFIT ALLOCATION1

ABSTRACT A linear programming model for a river basin was developed to include almost all water-related economic activity both for consumers and producers. The model was so designated that the entire basin or basin sub-division could be analyzed. The model included seven sectors, nine objective function criteria, and three river-flow levels. Economic basis for conflicts among sectors over incidence of cost allocation and level of economic activity can be traced to some chosen objective. The disposal of untreated household waste water, particularly from the rural household, directly into the river was consistent with maximizing net benefits and minimizing costs. The optimum resource allocation, water-treatment plants, farms and industry activities would change with flow level. For each of the three industries analyzed separately, paper, wool and tanning, public treatment of industrial waste water was the optimal treatment process in one or more of the solutions. Lake shoreline was the dominant feature determining lake-resource valuation. Implied capital value varied from $126 per shoreline foot to over $250 depending on discount rate. Implied prices on lake surface ranged from $42 to $147 per acre. Strong economic forces encouraged small lot sizes for vacation cottages.