Assessment of Ordinary Kriging for Zonal Management of Arsenic Contamination of Shallow Aquifers in Bangladesh

In this study we investigate the effectiveness of ordinary kriging for making rapid decisions on zonal (~25 km2) management of arsenic contaminated shallow ground water in Northwestern Bangladesh (total area ~ 35,000 km2). The arsenic database for reference comprised the nation-wide survey (of 3534 drinking wells) completed in 1999 by the British Geological Survey (BGS) in collaboration with the Department of Public Health Engineering (DPHE) of Bangladesh. A Monte Carlo (MC) framework was devised for selection of randomly-sampled networks of zones from this reference database, where each zone was assumed equivalent to a local administrative unit. On the average, the kriging method was found to have a 90% probability of successful prediction of safe zones according to the WHO safe limit of 10 ppb while for the Bangladesh safe limit of 50 ppb, the safe zone prediction probability was 97%. Findings from this study exemplify that mainstream geostatistical approaches (e.g., ordinary kriging) can delineate an approximate strategy for zonal management of arsenic contaminated shallow ground water if applied carefully. The kriging methodology is applied to a test case in Northwestern Bangladesh; the approach, however, is general and is expected to have application in rural settings for other developing countries where arsenic contamination of ground water is also widespread (e.g., parts of India, Vietnam, Taiwan and Mexico).