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CONFRONTING THE MODIFIABLE AREAL UNIT PROBLEM FOR INFERENCE ON NITRATE IN REGIONAL SHALLOW GROUND WATER
Citation:
Faulkner*, B P. CONFRONTING THE MODIFIABLE AREAL UNIT PROBLEM FOR INFERENCE ON NITRATE IN REGIONAL SHALLOW GROUND WATER. Presented at ASCE Worl Water & Environmental Resources Congress 2003, Philadelphia, PA, June 23 - 26, 2003.
Impact/Purpose:
To inform the public.
Description:
The modifiable areal unit problem results from data aggregation to a level which is so arbitrary that critical information is lost. Yet aggregation is necessary for assessment under the U.S. Environmental Protection Agency's Regional Vulnerability Assessment Program. This work presents an extension of an information statistical method, applied to assessing confidence of compliance with a percentile standard for nitrate in shallow ground water of Maryland, U.S.A. Nitrate poses a risk to future water supplies when observed in shallow ground water because it can be stored for many years following aquifer replenishment and act as a continuing load to surface water at regions of discharge. In such circumstances base flow loading of nitrate is known to be a major contributor to eutrophication.
The current study takes into consideration the informational value of data from wells and maximizes an Akaike Information Criterion. This method has been applied to geographical analysis of mortality rates in Japan. Here an extension is developed by exploiting a Bayesian approach for confidence of compliance with a binomial likelihood and beta distributed prior. A log-likelihood function for the unknown parameters resulting from census block group aggregation is obtained by using De Finetti's theorem for exchangeable events. The resulting map is a parsimonious expression of information at the regional level.