Assignment #4

1) Article Reference
LEE, B. H. and DEININGER, R. A. (1992) “Optimal Locations of Monitoring Stations in Water Distribution Systems”, Journal of Environmental Engineering, 118(1) pp. 4-16

2) Summary
As a requirement of the Safe Drinking Water Act the water quality in water supply systems has to be monitored. Although the sampling frequency and the water quality parameters are prescribed by law, there are no specifications for representatively sampling within the pipe network. Placing a monitoring point in a demand point represents coverage for that specific demand. However this water might be coming from a series of upstream nodes and going to a series of downstream nodes. The water flow path within the network carries water quality information. The nodes upstream or downstream of a monitored node are likely to be known. The water flow in a pipe network is modeled today with a variety of hydraulic models.
The paper presents a small example to demonstrate its methodology. This network with seven nodes and seven demands is used to illustrate the principles of sampling and coverage nodes. “From this network is derived a matrix called the water fraction matrix. From this matrix several knowledge carrying matrices can be derived based on a decision on which fraction of water is acceptable to call a node covered”. A general form algorithm is presented for generating the coverage matrix. To apply this procedure a demand scenario, the flows and the flow directions for a given water distribution system must be knows. Basically one node is chosen arbitrary and all flows upstream are mapped and if the demand is greater than the threshold value its given value one otherwise zero.
An example of the formulation of an optimization model is provided considering the task of placing two monitoring point in a distribution system. The question is where to places this points to maximize the demand coverage. Two sets of variable are used. They are both 0 and 1 value and one represents the whether there is a sampling station or not and the other represents whether the demand is covered or not. A maximization function and constrains are derived for the simple case example.
A case study is presented at the distribution system for the city of Flint, Michigan. The system had 337 pipes, 211 nodes and 14 monitoring points covering 18% of the demands. An integer programming was formulated with 211 constrains, 422 variables and over 6.000 non zero entries in the tableau. The solution was developed using two different programs, the COVER and the COVTOIP. Respectively they are used to solve the hydraulic flows and determine the coverage matrix. An optimal solution if found with a coverage of 54%, considering only one scenario.
The multiple flow scenarios approach permits the inclusion and consideration of the patterns of variation of the demand, such as daily, monthly or seasonally differences. A general optimization equation is provided and a solution for the small example is also provided using LINDO programming.
A second example is provided, with a case study for the city of Cheshire, Connecticut. To model this system four scenarios were used, where each scenario represents a demand and flow pattern pre established. This problem had 245 variables and 197 constrains and was solved using LINDO integer programming code. There were 4 monitoring stations to be optimally placed. The results showed the best location for the monitoring station according with the number of station to be included.
As a conclusion the author demonstrated the importance of an optimal location of monitoring station within a water distribution system as its location can have a great affect in the coverage of the system.

3) Discussion
I really enjoyed reading this article as it is becoming clearer and easier to read this kind of approach. The authors used simple examples to clarify the methodology and presented two specific case studies to illustrate the point. The optimization functions, constrains and the set up of the matrixes were quite interesting. I think further research in this theme would be to verify different methods of optimization and to also implement water quality decays models between the nodes.

Assignment #3: The Tragedy of the Commons

Review Article

1) Article Reference
HARDIN, G. (1968) “The Tragedy of the Commons” Science, 162, pp. 1243 – 1248.

2) Summary
The tragedy of the commons is a classical paper that presents an important recognition by society that a finite resources world would not be able to supply the demands of an exponential increasing human population. Although it was written 40 years ago, by that time, nature was already charging its price and pollution problems become more and more apparent in highly populated places. This recognition can easily be seen as the author says: “A finite world can only support a finite population; therefore the population growth must eventually be equal to zero”. The author analyses the possibility of trying to maximize population and maximize goods and find this goal impossible, as he concludes: “the optimum population is then, less than the maximum”.
The classical story behind the tragedy of commons is based on the example of the “commons” as the place where all the herdsman of a small society would, in common, raised their herbs. The principle of the commons is that everyone could raise it´s herbs inside the collective space. The point is that any rational individual would soon realized that if he increased his number of animals, he would increase not only increase his profit but also share the costs of the resources needed to develop the animal with all society. When each individual increases his herbs to a point where the total herb demand is greater than the resources that the commons could offer, the system collapsed and nobody could than rise their herbs anymore.
The author than point some specific examples of the tragedy of the commons that were taking place by his time. He mentions the national parks that were been overused and over developed. The oceans, which are treated by the nations as a huge “commons”, where each tried to get as much as possible out of it to guarantee it´s profit. The pollution problem illustrates very well the relation of the commons and its tragedy collapse. Pollution in small scale can easily be treated by nature within the natural cycle. But when it overpasses the limit of auto depuration, pollution very quickly demonstrates all the magnitude of the tragedy of the commons.
The author points out the controversial of the United Nations Universal Declaration of Human Rights that states that every family has the right to choose its size. The author recognizes that is very hard for the individuals to give up a share of the commons, as he says “It is a mistake to think that we can control the breeding of mankind in the long run by an appeal to conscience”.
Several alternatives are pointed by the author considering that “Not prohibition, but carefully biased options are what we offer him”. A very good example that society have learned to avoid the tragedy of the commons are the taxes system. Nobody enjoys taxes, but everyone agree to use a compulsory system knowing that in a voluntary system would favor the conscienceless. The author is very prismatic and urges the necessity to control the human breeding is becoming vital to guarantee other and more precious freedoms.

3) Discussion
This paper was published almost 40 years ago at the end of the sixties in a rather different social context than we face today. By that time cold war was taking place in a nuclear world. In the fastest growing cities it was becoming more evident that society was reaching a point where nature could not adequately supply all that mankind was ready to charge.
I think this paper represents the beginning of the human awareness of the earth limited resources and that the increasing population would soon face shortage of basic resources. After this paper many more recent concepts related to this theme have evolved such as pollution control, the sustainable development and clean energies alternatives. Although today we have evolved in many aspects of trying to increase the availability of resources I feel humanity still believes it is possible to maximize population and resources, although it was wisely recognized by the author decades ago that this is not possible.
I recognize that future research within this theme would be how to apply modern optimization techniques to find limits and the best alternatives to use wisely the resources available to an increasing population.

Assignment #2

Review Article

1) Article Reference
ATWOOD, D., F. and GORELICK, S., M. (1985) “Hydraulic gradient control for groundwater contaminant removal” Journal of Hydrology 76 pp. 85 - 106

2) Summary
This paper presents a methodology for determining an optimal operation schedule for an aquifer restoration plan. The aquifer restoration plan consists of the use of wells for both cleaning up pollutants from the aquifer as well as stopping the flow of the contaminant plume to spread out.
A case study was developed in the Rocky Mountain Arsenal, which is a military facility design to manufacture and process toxic chemicals. This aquifer is located near Denver, Colorado. The study area was chosen due the high quantity of hydrological and geological data available.
The groundwater management plan for pollutant removal basically is consisted of wells for pollutant removal (those wells have to be located inside the pollutant plume) and hydraulic gradient control wells (which have to be located outside the plume area) that are used to control the flow of the groundwater (pumping on high elevations or recharging in low elevations). An optimization model is used to find the best operation plan for this purpose. Note that a pump can be inside the plume at the beginning of the operation, but after some clean up, become outside of the plume and could them be used for hydraulic gradient control.
The equations used to model this process were the finite difference model developed by Trescott et al. (1976) for the ground water movement and the solute transport combined with groundwater flow simulation in the computer code developed by Konikow and Bredehoeft (1978) for pollutant transport. The methodology is dived in two main stages. First the velocity field is assumed based on initial data. Within this stage the plume boundary is estimated. With this information the Contamination distribution is approximated. On Stage 2, the optimization for the best well selection and operation is developed. Based on the known velocity field the solution is checked and some interactive process back in Stage 1 can be developed.
For the optimization model, the objective is to minimize the sum of pumping and recharge rates. One constrain is to guarantee the flow to go inwards in the direction of the center of the plume. For this gradient control constraint detailed information is provided.
The results showed that a best selection of wells and operation schedule could be achieved. The two stage procedure allowed a single global optimization for all 32 pumping periods. A verification of the results is provided by running the model with the chosen conditions.

3) Discussion
I think this paper is very interesting and shows the utility of optimization procedures solving water resources problems. It seems to me that optimizations procedures are intrinsically related to modeling practices in the modern time. The application of models that represent a reality is followed by an optimization procedure that allows the decision makers to choose from a set of alternatives the one that best fits the desiring goals.
Still this paper is a little too advanced for me, as some of the constrains and the matrix operation were not very clear to me. But the good part is I can feel is getting much more easy to understand them and I hoping by the end of the semester we will be pretty close to develop applications such as this one.

Assignment #1

Review Article 1

1) Article Reference
Liebman, Jon (1976) “Some simple-minded observations on the role of optimization in public systems decision making” Interfaces 6 (4) pp. 102-108

2) Summary
This paper was written in 1976 and presents a very good overview on the constrains for the application of optimization (in this case could be: modeling, operations research, system analysis) in the public sector. The author provides some definitions of public sector and two specific examples of applications by the NY fire department and for a watershed water quality plan.
The main point of the paper is to present the crucial difference in applying optimization to solve wicked and unwicked problems. To clarify the understanding of wicked problems, I´m considering the wikipedia definition “Wicked problem is a phrase used in social planning to describe a problem that is difficult or impossible to solve because of incomplete, contradictory, and changing requirements that are often difficult to recognize. Moreover, because of complex interdependencies, the effort to solve one aspect of a wicked problem may reveal or create other problems.”
According to the author, usually in the past, optimization procedures could have been solved using linear programming methods such as the Simplex method. By this time the analyst had the simple task of processing many alternatives to find the best solution. The author consider that the decision makers in the private sector organizations have often the some goals and objectives, which makes the role of optimization a lot easier and direct. But in the case of the public sector, considering the existence of many different stake-holders, and even the difference between individuals, there are many goals which can be completely different from each other, characterizing a conflict, resulting often in two groups, the winners and the losers.
Optimization procedures have evolved a lot since the limitation of non-linear problems but the increasing perception of the complexity evolved in most of public decision making processes have showed that “optimization can only be useful when the goals are clear and explicit”. Considering that, the author states that instead of “The role of optimization and modeling in nonwicked problems is the selection of a solution among alternatives” is switching to “The role of optimization and modeling in wicked problems is the formulation of alternatives rather than the selection of one of them”. Even though a direct use of optimization models is not appropriate to wicked problems, those models can have a great value for illuminating the conflict, for example: expanding the problem understanding, to formulate alternatives or even to evaluate scenarios.

3) Discussion
a) I think the paper represents a very good overview from the 80´s about the constrains of the application of optimization models to complex or wicked problems. Considering the use of optimization trough history, the author points a moment in time where society is finding that optimization models are as good as the goals provided to them. If the decision makers don’t agree with the some goals, optimization procedures can´t be set to solve them.
b) I don’t see many limitations on this work, as I think is hard to tell what was the reality or the understanding of complex problems by that time.
c) If this where my research I would focus in the point of finding benefits and trying to develop specific applications to improve decision making with optimization models in wicked problems. That would include conflict resolution and processes that try to find the best for all, minimizing the existence of the winner/losers distinction. I find this a very interesting research topic.

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Review Article 2

1) Article Reference

Karterakis, S., M.; Karatzas, G., P.; NIKOLOS, I., K. and Papadopolou, M., P. (2007) “ Application of linear programming and differential evolutionary optimization methodologies for the solution of coastal subsurface water management problems subject to environmental criteria” Journal

2) Summary

This paper presents an application of optimization methods to solve groundwater management’s problems including environmental criteria. The authors used linear programming and differential evolutionary methods. This study is applied to the coastal region of Hersonissos, Crete.
A comprehensive literature review about optimization applications for environmental issues is presented. To approach the conceptual model and develop the physical model a characterization of the study area is provided among the theoretical concepts used for the simulation of seawater intrusion phenomenon (Sharp interface approach).
The goal of the optimization is to maximize the total extracted water from five selected pumping locations. The constrains are to ensure no further intrusion of the seawater front at ten selected observation well were the calculated hydraulic head should be greater than 102.5m at the end of the 10 year management period.
A brief overview and literature review of linear programming (the simplex method) and heuristic optimization (differential evolution algorithm) is provided. The solutions of the simulations with both methods are compared. A extensive sensitivity analyses is also provided.
The main conclusion for this case study both methods had very similar results, by the exception of one well. The simplex method had much less computer time demand but needs a constantly interaction worth the user and the heuristic methods although requires much more computer time is completely automated.

3) Discussion
I felt really enthusiastic seeing that the Journal of Hydrology is currently publishing applications of optimization procedures for water resources management problems. This is particularly interesting in the sense to show the importance of the subject for my research. I think maybe more management alternatives could have been analyzed. To improve the research I would try different optimization approach and enlarge the alternative scenarios.

Assigment # 0 : " What is critical thinking ? "

Hello Everyone!!
I´m currently a 1st year PhD student of Water Resources Engineering in the Civil Engineering Department at Texas A & M University. My back ground is Environmental Engineering (M.Sc.), Hydrology (M.E.) and Civil Engineering (B.S.). My research line is GIS applied to Water Resources under the supervision of Dr. Francisco Olivera.
The main reason why I´m taking this class is to learn more about the mathematical models used for water resources analyses and optimization. My goal this semester within this class is to gain confidence in the selection, application and analyses of different models for water resources systems.

Now the difficult question: “What is Critical thinking?”
If we look at several definitions for “critical thinking” we will find that each applies better for the context or purpose we want to use it, e.g.: teaching critical thinking, applying critical thinking or developing critical thinking. For example, from Wikipedia: “when using critical thinking one makes a decision or solves the problem of judging what to believe or what to do, but does so in a reflective way”. I think the key here is reflective way. Do whatever is the right thing to do, but always in a reflective way. This means, always think “why”.
I think another key expression that would bring the same meaning would be: “Think outside the box”. Be creative and always try to come up with something new.
Teaching critical thinking within engineering schools is not a direct task. Usually engineers are tough to solve problems using available knowledge. Questioning the available knowledge is not usually part of the recipe. But if we consider that the basis of the engineering work that is done today was developed hundreds years ago, isn’t it inspiring to think: Isn’t there anything new that we can come up with? The advance of science or the development of new knowledge is only going to be possible with critical thinking and people that thinks outside the box…