Blog 10

THE USE OF OPTIMIZATION MODELS IN PUBLIC-SECTOR PLANNING

By E. Downey Brill, Jr.
Management Science Vol. 25, No. 5, May 1979

Summary

This paper had many similarities to the paper about “wicked” problems that we read at the beginning of the semester. The overall jest of the paper was that optimization models are useful for public-sector planning but should not be viewed as a way of obtaining “the answer.” After outlining the shortcomings and limitations of optimization models, the author presents different uses of optimization models as a means of aiding in the planning process. He proposes that optimization models be used in conjunction with other tools such as simulation models and analytical methods as well as other models. The use of various models and methods helps create numerous different alternative solutions that can be evaluated by the decision makers. The author endorses this outlook on the use of optimization models because he believes that models cannot truly capture the nature of a complex problem and inventive and creative solutions are needed to meet all quantitative and qualitative constraints and priorities. Optimization models cannot truly create inventive solutions since this is creative human process, although they can promote creativity by proposing possible alternatives when the complexity of the problem overwhelms the planner.

Discussion

In the thirty years since this paper was published, computational speed has increased dramatically and optimization methods have evolved; however, this paper is still relevant and probably will be for at least another thirty years if not longer. The reason for its relevancy is that computers cannot be depended on to give “the answer” when solutions deal with non-quantitative variables that are often political and social in nature. That is why high-level human decision makers are needed to choose the best solution from a range of choices. Hopefully it stays this way until I’m not replace by a computer.






GA-QP MODEL TO OPTIMIZE SEWER SYSTEM DESIGN

By Tze-Chin Pan and Jehng-Jung Kao
Journal of Environmental Engineering ASCE, January 2009


Summary

The author uses a combination of genetic algorithm (GA) and quadratic programming (QP) optimization models to find alternative solutions for the design of sewer systems. The decision variables associated with the GA model were coded as chromosomes. Pipe diameters and the location of the pumping stations are decision variables which are expressed as genes within each chromosome. The QP model decision variables are the slopes and buried depths at the downstream ends of the pipes.

Alternatives were also created by using MGA. The author says, “To facilitate the analysis for the selection of an appropriate alternative, various near-optimum design alternatives were generated by applying the MGA method. The purpose of the MGA is to identify maximally different solutions which can still be regarded as good alternatives when compared to the mathematically optimal solution.”

The optimization strategy outlined above was applied to a sewer system for a residential area with a total drainage area of 260 ha, 56 nodes, and 79 links. The models gave numerous design alternatives with various costs for the planner to choose from. In situations where essential factors are excluded, the author finds that the GA-QP and DPPP alternatives may be inappropriate or infeasible and MGA alternatives provide the best solutions.

Discussion

This paper was interesting and its principles may very well be applied to a multitude of systems; however, it seems that the authors ignore many of the things that constrain real-life sewer systems. Most city sewer systems are old and often buried in unfavorable locations. Certain sites or pipe depths proposed by the model may be extremely expensive because they require special equipment to place the pipe or the land use above the pipe makes it difficult to place the pipe. For instance, if the pipe is placed in extremely rocky soil or underneath a major roadway. These addition cost are not factored into the model. In the authors defense, if these expenses were modeled as constraints it would take a lot of addition work and make the model a lot more complex.

Blog 9 billion and 63

Compromise Programming Methodology for Determining Instream Flow under Multiobjective Water Allocation Criteria
By Jenq-Tzong Shiau and Fu-Chun Wu

Journal of the American Water Resources Association
October 2006

Summary

The purpose of this paper is to quantitatively address “the problem of compromises between human water demand and instream flow requirements.” To illustrate this problem, the authors choose to model the Kaoping diversion weir in southwestern Taiwan. The diversion weir was designed to “simultaneously assure the water supply reliability and sustain the natural flow variability.” However the second objective was not meet (at least not at an acceptable standard), since the weir flow often varied significantly from the naturally flow. There are three primary demands placed on the flows of Kaoping Creek: 1) Instream flow releases; 2) Agriculture water withdraws; 3) Municipal uses. The water allocation priorities are in the same order as listed.

In an effort to optimize this multiobjective system, the authors utilize the Range of Variability Approach (RVA) to evaluate the hydrologic alterations. The RVA resulted in 32 Indicators of Hydrologic Alterations, which are integrated into a single index that allows for the optimization of the multiple conflicting objectives. The optimal operation scheme was “then determined using the compromise programming among multiple conflicting objectives.” The objective function was to minimize both hydrologic impacts and water supply shortages.

The model determined “that the current minimum flow release of 9.5 m3/s does not effectively serve to restore the natural flow variations.” It was found that if the water releases were increased the overall stream flow variations would be reduced; however, the increase in flow releases would simultaneously increase the water supply shortage ratios. If equally weighting was given to the natural flow variability and water supply reliability, the optimal instream flow is 26 m3/s.


Discussion

Did anyone else find it a little peculiar that the registered agricultural water withdraws remained nearly constant for the entire year but the diversions for municipal use was extremely variable? Typically it is the opposite. Do these people find it beneficial to irrigate all year around but consider bathing and drinking only important from May to December? I’m assuming they have some other water source, but still.

Blog 8

Neural Network-Based Simulation-Optimization Model for Reservoir Operation
By T.R. Neelakantan and N.V. Pundarikanthan

Summary

In many reservoir operations studies - such as that of Chennai, India, which is the case used for this article – complex simulation models combined with optimization models are computationally infeasible when trying to model the problem. In an effort to circumvent this problem, the authors propose a way to develop a “planning model for reservoir operation that uses a simulation-optimization approach.” To do this they use a neural network-based simulation model, which was developed for reservoir system operation, as a submodel in a Hooke and Jeeves unconstrained nonlinear programming model. The optimization model minimized the operation policies.
That’s it in a nutshell… if you want more you’ll have to wait until Wednesday when Michelle and I present. The suspense is killing you I’m sure.

Discussion

I thought this article was a little more difficult to follow than the previous few articles. Or it could be that I’m already creating excuses for why I might be clueless come Wednesday.  Either way, I still don’t feel I have a great grasp on all the terms and concepts explained in the paper. In particular, I don’t really understand how the exemplars are selected or how a neural network simulation model is formed.

Blog 7

Optimal Location of Infiltration-Based Best Management Practices for Storm Water Management
By Cristina Perez-Pedini, James F. Limbrunner, and Richard M. Vogel

Summary

The purpose of this study was to introduce a methodology to determine the optimal number and location of infiltration-based BMPs on a watershed to reduce peak flow flood flows at the watershed outlet (Perez-Pedini 441). Although the research can be applied to numerous watersheds, the Aberjona River watershed northwest of Boston, Massachusetts was the focus of this study. This small highly urban catchment was modeled in a spreadsheet and optimized using a genetic algorithm (GA) to determine areas within the watershed where the application of infiltration-based BMPs would be most effective in decreasing flood flows at the catchment outlet (Perez-Pedini 442). A distributed, event-based hydrologic model, along with the SCS curve number method, was employed to determine the runoff and infiltration for each of the 4,533 hydrologic response units (HRUs)

During the optimization process, the overall goal was to locate the HRUs which, if BMPs were applied, would lead to a maximum reduction in peak stream flow at the watershed outlet (Perez-Pedini 444). The end result revealed that the optimal location of the BMPs was a complex function of HRU characteristics and locations. The authors summarize the results by creating a Pareto frontier depicting the number of BMPs, which is synonymous to the project cost, and peak flow reduction.


Discussion

The research conducted by Perez-Pedini has great applicability because (1) it can be applied to nearly any watershed; (2) the analysis could be used to inform policy decisions regarding future storm water management investments; (3) the optimal number of BMPs can be constructed in stages as funds become available, while still achieving optimal reduction during each stage (i.e. When only a few BMPs are located, their optimal locations are subsets of the optimal locations of a much larger set of optimal BMPs.).

Blog 6

OPTIMIZATION OF REGIONAL STORM-WATER MANAGEMENT SYSTEMS
By Pradeep Kumar Behera, Fabian Papa, and Barry J. Adams

Summary

This paper presents dynamic programming optimization methodologies which seek to minimize the cost associated with detention storage. The objective function that is minimized is constrained by two environmental constraints that the regional outlet must satisfy: 1) environmental regulations for runoff quantity and 2) environmental regulations for runoff quality. The primary cost associated with storm-water detention ponds – and the cost which are used in the objective function - is the land which the detention pond occupies and the initial construction, operation, and maintenance costs. It should be noted that an optimizing methodology is presented for determining the design parameters of a single storm-water management pond and is then expanded (using dynamic programming as mentioned earlier) to a multiple parallel catchment system (Behera 107).
Numerous inputs are entered into the model (you’ll have to read the paper if you want to know what they all are because I’m sure not going to list them all) but there is only one thing minimized and that is the cost of all detention ponds for the desired levels of runoff and pollution control.


Discussion

I really enjoyed this paper because the basic methodologies and techniques used to solve the optimization problem can be easily applied to any other real-world system with any number of catchments (although the paper only used three). In addition, the decision variables and constraints of this model can be easily adjusted to meet different requirements of either the developer, the engineer or various government regulations – something that adds even more flexibility and applicability to the model. My understanding of DP is still incomplete but I hope by the end of the semester we will all have enough expertise in the subject to be able to implement research such as this.

Another one...

SENSOR PLACEMENT IN MUNICIPAL WATER NETWORKS
By Jonathan W. Berry; Lisa Fleischer; William E. Hart; Cynthia A. Phillips; and Jean-Paul Watson

Summary

The findings presented in this paper were to address the concerns of the U.S. Environmental Protection Agency that most of the U.S. water supply is highly susceptible to contamination (either accidental or intentional) and that any contamination would go largely undetected, which would place a high risk on public health. The authors present a model that optimizes the placement of sensors in municipal networks to detect maliciously injected contaminants (Berry 237). The LP method utilized is a mixed-integer program that seeks to minimize the fraction of the population at risk. Three separate networks were tested (two fictional networks taken from EPANET and one real-life network). The result of the research is an MIP model that effectively solves large-scale sensor-placement problems (so claims the authors, although the effectiveness and validity of the findings can always be disputed). It was also demonstrated that noise or uncertainty in the data had very little impact on the results of the analysis.

Discussion

Although several assumptions made in the paper were a little unrealistic (constant flow path and velocity, no variance over time and space of contaminant concentration, etc.), I would deem the overall work both viable and reasonable considering the purpose of the research. I found the paper to be a good follow-up to the previous discussion paper.
The authors speak on how this knowledge will be easily transferable to real-world large-scale sensor-placement problems. I wonder how many public water supply companies 1) are aware of this research; and 2) would know how to go about implementing this work if they did… maybe they could hire us!

Clean Water Monitoring Stuff

OPTIMAL LOCATIONS OF MONITORING STATIONS IN WATER DISTRIBUTION SYSTEM
By Byoung Ho Lee and Rolf A. Deininger


Summary

The passing of the Safe Drinking Water Act in 1974 required monitoring to be instituted in water distribution systems around the country; however, no guidance was given on how the sampling was to be executed. The authors address the best methods to locate monitoring stations in a water distribution network. The paper presents these methods by 1) defining new or relevant concepts 2) providing two examples that demonstrate the methods and concepts in real-world practice. The authors claim that the best set of stations is one that maximizes the coverage (as defined in the paper).

Discussion

This paper seems like it has lots of real-world applicability – after all, nearly every water distribution system in the US is required to monitor and I would bet that most of them are not optimizing their coverage. It has been nearly 17 years since this article was written and I would be interested if any more work has been done optimizing monitoring stations – not just research but have communities actually used this knowledge to expand their system’s coverage. If this information has merely lain on the shelf unused, I would be curious as to why. Is it too costly to implement? Are communities unaware that their systems are relatively ineffective?

Keep it in your pants - an article concerning restricted baby-making

The Tragedy of the Commons
by Garrett Hardin
Science, 1968

Summary
The Tragedy of the Commons uses the illustration of a common parcel of land shared by herders for the grazing of their cattle to allude to a grander commons – the Earth and its finite resources – and its users, all mankind. Following this analogy, Hardin contest that it is in each herder’s best interest to raise as many cattle as possible because the individual herder gains all the benefit while the cost is distributed amongst all the common’s users. Although this action may be justified on an individual level (any rational person will try to maximize their net benefit), it will eventually bring about the demise of the commons (and all the herdsmen) because when everyone seeks to maximize their benefit, the finite resources provide by the commons are diminished. Hardin claims that, in a similar manner, we are all seeking our own ends by over-breeding and the world’s exponentially increasing population will eventually destroy all “commons” that we share today. Hardin suggest that there is no technical solution in solving this quagmire, but that only a moral and social adjustment can manage and possibly avoid the currently inevitable destruction of all resources and mankind.
In conclusion, Hardin notes that there was benefit in different “commons” throughout history but that circumstances and increasing populations has caused us to abandoned using the commons as a means of food gathering and waste disposal in progression to privately owned agricultural land and designated waste disposal areas. In an effort to ensure the longevity and prosperity of all mankind, the author contest that the next common that should be given over to regulation is that of breeding.


Discussion
Although the paper was written over 40 years ago, I believe it is more applicable today than when it was written. Since the Tragedy of the Commons was written the population has more than doubled to nearly 7 billion people. The worldwide population growth shows no signs of regression, which will place an even heavier burden on our finite resources. Hardin’s recommendation is both compelling and controversial because it seeks to restrict something that mankind has tried to maximize since its dawn – the number of offspring they produce. Although I agree that something needs to be done and his argument makes sense (on a logically level), I don’t think it will ever be implemented. Or maybe I should say this… I don’t believe a breeding restriction will be placed on mankind until it has reached a point where considerable, irreversible damage has been done. Government is typically retroactive, not proactive.

How to get crap out of underground water (laymen terms)

Hydraulic Gradient Control for Groundwater Contaminant Removal
Dorothy Fisher Atwood and Steven M. Gorelick
Journal of Hydrology, 76 (1985) 85-106

Summary

As its title implies, the focus of Atwood and Gorelick’s paper is how to control the hydraulic gradient of an unconfined aquifer as a means of containing a contaminant plume for save and effective removal. Although the research is a hypothetical test, the aquifer that is modeled is a real aquifer under the Rocky Mountain Arsenal near Denver, Colorado.

The authors chose to use a two-stage approach in modeling the problem so to avoid nonlinearities that would otherwise prohibit the use of linear optimization technique. The two-stage planning procedure successfully selects the best wells and their optimal pumping/recharge schedules to contain the plume while a well or system of wells within the plume removes the contaminated water (Atwood 85). The first stage of the test involved determining the plume boundary location as a function of time by combining a groundwater flow and solute transport model. The second stage used a linear program to determine the optimal (as defined by minimal pumping and recharge) well selection and pumping/recharge rates.

Two different optimization strategies were used: 1) Sequential optimization, which relies primarily on the previous pumping period for its initial conditions and 2) Global optimization, which optimizes the system over the entire 32 pumping periods. The total pumping/recharge rates are comparable for the two optimization strategies; however, the well selection and pumping schedules are very different (Atwood 102). The research shows that the cumulative pumping/recharge rates of the global solution are approximately 10% better (as deemed by pumping/recharge volumes) than the sequential solution. However, the authors urge that although the global optimization produces a better solution than the sequential strategy, the solutions are similar enough that other factors such as economic or social conditions should be considered.



Discussion

The number of groundwater contaminant incidents will continue to increase over the next several decades as we begin to reap some of the pitfalls of industrialization and ineffective environmental safeguards. This article is not only interesting but also useful because it gives an effective and generalized method for handling groundwater contaminant plumes. With that being said, I would have liked to seen the author extend the scope of the research and model the impacts of having multiple wells that remove the plume. To be quite candid, I know little about groundwater contaminant removal but my intuition tells me that 16 years of pumping to remove the groundwater pollutants is not only an extremely long period but very expensive – something that most communities who would be paying for this would not appreciate. I would like to see further research that would optimize the pumping cost and time with multiple wells removing the contaminate plume.

Assignment #1

Article 1

“Some Simple-Minded Observations on the Role of Optimization in Public Systems Decision-Making”

Jon C. Liebman
August 1976
INTERFACES Vol. 6, No.4

Summary

The private sector has long applied models to problems and, with great success, optimized those models to solve the problems and reach the goals of the decision-maker: whether that goal be related to increasing efficiency, optimizing profits, or reducing costs in military and industrial applications. By and large, these problems were relatively straightforward and simple. Times have changed.

At the time this article was written, models were becoming more complex in the private sector and model optimization was beginning to be applied to public applications. Although the tools and techniques for solving optimization problems had advanced and become more complex –accounting for most of the added complexity in the private sector – the complexity of modeling in the public sector had to do with the nature of the public’s problems.

Dissimilar from the private sector, which typically has well established goals and a unified set of decision-makers, the public sector is often hampered by a number of stakeholders with a diversity of problem perceptions, objections, goals, measures of effectiveness, and constraints. The author suggests that the old way of modeling, optimizing, and then applying will no longer work and that this approach should be abandoned when solving complex public problems (which he coins as being “wicked”). However, the author still believes there is a place for optimization and modeling in the public sector.

The author suggests that the role of models and optimization in the public sector should be to “illuminate conflicts and generate a set of alternatives for further exploration.” The analyst should use their intuition, insight, and understanding - along with the model - to guide the decision-makers through the maze of conflicting resolutions and priorities of the numerous stakeholders.


Discussion

The author was very straightforward at the beginning of his article in saying that “This paper will not provide any earth shaking answers… Further, this paper will not raise any new and highly penetrating questions.” I would deem his assertion accurate. In most cases I would consider a paper that doesn’t pose any new questions or answers as a paper unworthy of journal publication. However, the author was very clear from the beginning that his intention was to merely provide some “simple-minded observations” as opposed to groundbreaking research. Personally, I found the paper very interesting because of my relatively limited knowledge on the optimization of models and the author’s simple and concise writing style - which made it easy to grasp some of the major elements of modeling and optimization.

I would be interested in research documenting the progression of optimization over the 30 years since this paper was written. What advancements have been made in the tools and techniques used by analyst? Has complexity been reduced or increased with the new tools and techniques? What role has advanced computer modeling played in this field since the paper was written?




Article 2

“The Optimal Joint Provision of Water for Irrigation and Hydropower”

Bishu Chatterjee, Richard E. Howitt, and Richard J. Sexton
July 1998
Journal of Environmental Economics and Management
Article No. EE981047

Summary

The main focus of this article is on the trade-off between water used for agriculture versus water used for hydroelectric power, namely in the central California. The central issue arises because there is a timing discrepancy between peak irrigation demands and periods of peak demand for power. It was found that the citizens who were actively involved in decision making (via voting and attending meetings) were primarily farmers who used the water for irrigation. Therefore, the cooperative water supply organization (WSO) set its primary goal to deliver water for irrigation to farmers. However, the authors demonstrate that this is not the optimal way to utilize the water.

The research presented establishes rules for the optimal intraseasonal allocation of surface water for a WSO that produces water for both irrigation and hydropower. The rules prescribe the allocation pattern that maximizes farmer-members’ welfare as users of irrigation and as de facto owners of the scarce water resource. The article outlines the benefits and possible negative side effects of instituting the proposed optimal water allocation.

Discussion

The article was very interesting in that it dealt with the very important issue of optimizing water allocation – an issue that will continue to gain attention as water becomes scarcer around the world. Although interesting, I would liked to have seen the research incorporation other demands on the water resource, such as the water used for municipalities or industry in the area. I realize that the major users in the area are agriculture and hydropower but I don’t think they should simply ignore all other uses in the optimization model.

There will continue to be a lot of research and studies in optimizing water allocation. It will be interesting to see the reallocation of water in certain areas around the country as the economics of water use continue to evolve and be understood more fully.

Assignment #0

There was not one particularly reason, nor was there a singular goal I hope to achieve when I decided to take CVEN 665. The honest and candid reasons I chose to take this class were:
1. It seemed to be one of the more interesting amongst my alternatives.
2. Dr. Zechman seems to be nice enough and I figured she would be a really good teacher (plus she went to UK, which definitely gives her and the class bonus points).
3. I enjoyed CVEN 664 and thought this class might be a good follow up.
4. I’m hoping to learn how to apply system theory to real world problems that I will face upon graduation.

“Critical thinking consists of mental processes of discernment, analysis and evaluation. It includes possible processes of reflecting upon a tangible or intangible item in order to form a solid judgment that reconciles scientific evidence with common sense. Critical thinkers gather information from all senses, verbal and/or written expressions, reflection, observation, experience and reasoning. Critical thinking has its basis in intellectual criteria that go beyond subject-matter divisions.” (Wikipedia)
Michael Scott (The Office): Wikipedia is the best thing ever. Anyone in the world can write anything they want about any subject, so you know you are getting the best possible information.