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Personal computer as a tool for sustainable development
Vikram Vyas
The Ajit Foundation
396 Vasundhara Colony, Tonk Road
Jaipur 302 018, India
Email: visquar@jp1.dot.net.in
Introduction
In our efforts to evolve towards a global community that lives in harmony with its environment, any tool that can give us some clue as to the impact that our decisions will have on the environment is obviously welcome. Restricting our attention to small rural communities, and to land, water and energy as the resources that we wish to utilize - many questions immediately arise. How should we use these resources so that the future generations too can have access to them? How should we use these, often very limited resources in a manner that the needs of the community are meet reliably? How should these resources be developed without diminishing the richness and the well being of the planet as a whole? In meeting these varied objectives there are many rooms for a conflict, even when the community agrees to the objective and the philosophy of sustainable development.
Consider the case of developing water resources in a small village in a semi-arid region. The community typically has access only to underground water and rainwater stored in open ponds or closed tanks. Our objective would be to meet the water needs of this community adequately and reliably, without exploiting the available resources in a manner that would deny their access to the future generation or cause harm to the environment. This would require answering questions like, to what extent should the community depend on underground water and to what degree should it rely on rainwater harvesting systems? Should it make provisions for recharging ground water? Also, the question of using the water resources in a sustainable manner is related to the use of land and energy sources. Where should we build ponds to store rainwater? What part of the community land be set aside as a catchment area for rainwater harvesting? How to transport water from the sources to the users. Thus, the community is faced with numerous choices and a wrong choice would propagate the error down to the future.
It is here that the ideas of making a mathematical model of the various resources and using the model as a guideline for the future decisions emerge. The idea of using mathematical models for development is of course very old, but its use until now has been restricted to large industrial and developmental projects. So it does not come as a surprise that a modern aircraft is first designed and tested on a computer before even a prototype is build - we would like to know if the aircraft would perform the way we want it to without having to do expensive testing by trial and error. But in the recent decades a new opportunity has emerged which is to use these techniques for small developmental efforts, and this has been possible because the computational power required for modeling, say water resources, is now readily available in form of the ubiquitous personal computers (PCs). My aim in this course is to introduce you to the idea of modeling, and hopefully giving you enough background that you can use the available tools in your own developmental work.
Complementing the modeling is the more familiar use of the PCs, for information storage and retrieval. We will see during the course of this lecture how these two aspects combine together to give a powerful tool for making appropriate decisions for sustainable development.
The outline of the course will be following. In the next section I will introduce the idea of a mathematical model and the related idea of simulation. In the third section I will make these ideas specific by giving an example of model for simulating rainwater-harvesting system. The fourth section will describe how mathematical modeling and information database combine together into an extremely useful tool. The final section will be devoted to an overview of various tools that are available.
Mathematical Models and Computer Simulation
It is an extraordinary fact, which we often take for granted, that all natural phenomenon show a regularity that can be encapsulated into certain "laws" of nature. Further more the natural language in which these laws can be formulated, and their consequences explored, is the language of Mathematics . Perhaps the most familiar example of this is the law of gravitation. It is this law that allows us to predict with incredible accuracy the trajectory of a satellite or a spacecraft. But the processes and phenomenon that will be of interest to us are, in certain sense, more complex. Consider the case of loss of water from a pond due to evaporation, our ability to predict the loss due to evaporation is much more restricted than our ability to predict the trajectory of a spacecraft. It is worthwhile to understand why this is so. It is not that we do not know the laws governing evaporation, our knowledge of these laws is as certain as our knowledge of gravitation, but a law of nature only tells us how things will evolve in the future given the present situation. So to predict the trajectory of a spacecraft we need to know what is its position and velocity to start with, and also the position and velocity of sun, and other planets at that moment. With this information we can predict the future position of the spacecraft. Similarly if we know the temperature of the water, temperature of surrounding air, the atmospheric pressure over the pound, and the wind velocity over the pond, then we can predict the evaporation loss precisely. Taking wind velocity is as an example, what is required is not just the wind velocity at one point but at all points over the pond, since the wind velocity can change rapidly from place to place, therefore a very large amount of initial information is required before we can make an accurate prediction. Obviously such a description and a mathematical model based on its is of no use to the community for determining evaporation losses.
For a mathematical description to be useful for rural development, it has to be based on few parameters that can be easily measured or obtained. Thus, continuing with the example of evaporation loss, what we would like to have is a mathematical model that predicts evaporation loss based only on the average temperature, average pressure, and average wind speed. Such a model in general will be less accurate than the fundamental description of the phenomenon, for we are disregarding the fluctuations in the parameters like wind velocity. Therefore in using the simplified model we would also like to know the validity of the approximations made. To what degree can we trust its predictions? If the accuracy is sufficient then this simplified model becomes a useful tool, allowing us to estimate evaporation losses with known degree of reliability.
Such simplified mathematical descriptions are often called effective or phenomenological models. Their relationship to the fundamental description is many a time incomplete and their validity is based more on comparing their predictions with the actual observations.
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