Evolution of Water Consumption in the USA: A Network Approach
thesisposted on 27.02.2015 by Sk Nasir Ahmad
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
Water is essential to life, and knowing the consumption trends in water is paramount if we aspire to become more sustainable. The traditional statistical tools such as mean and standard deviation, can easily fail to capture these trends. For this work, the limits of these traditional statistical tools are first highlighted and a new network approach then developed and applied to better understand trends in water consumption. Data from the United States Geological Survey (USGS) for the years 1985, 1990, 1995 and 2005 were used in gallons of water per-capita per day for all US counties. Essentially, a network is formed between counties when they have consumption values within a certain range, ± ξ, of one another. A giant cluster rapidly emerges, containing more than 80% of the nodes for a ξ of 1%. The counties with the highest number of connections are associated with the mode of distribution, and multi-modal patterns are observed for earlier years. Moreover, the average shortest-path length can be seen as the spread of a distribution. The diameter and density of the networks are also used. Overall, beyond a possible process of homogenization, water consumption patterns do not seem to have evolved much from 1985 to 2005, and no spatial correlation was detected. While the methodology is yet to be formalized, it manages to give meaningful insights while addressing the limitations of traditional statistical analyses.