INFORMING MANAGEMENT OF THE WORLD'S LARGEST GROUNDWATER SYSTEMS WITH SIMPLY-STRUCTURED MODEL ANALYSIS

During the 50 years since its development, groundwater flow modeling has become the tool of choice that, when used wisely, provides deep insight into the functioning of aquifer systems that can become a foundation of effective water-resources management. This presentation reviews typical difficulties in characterizing aquifer systems (due to heterogeneity and data scarcity) and argues that simply-structured models are the most-effective means of dealing with inevitable uncertainties. Two examples of simply-structured model analyses of very large aquifer systems with sparse data will be presented. (1) In West Bengal, India, and Bangladesh, dissolved arsenic concentrations exceeding world standards exists in the drinking water of about 50 million people, making this the world's largest groundwater contamination problem. Previous scientific and technological efforts aimed at solving the problem had been largely directed towards understanding the chemistry of arsenic occurrence and release, but this groundwater modeling study is unique in providing a possible region-wide solution to the problem. (2) The Nubian aquifer is the world's largest non-renewable groundwater resource. It is a transboundary aquifer belonging to Chad, Egypt, Libya, and Sudan. International questions regarding resource fate, equitable use of the resource by each country (most current usage is by Egypt and Libya), and adverse impacts of cross-border pumping drawdown on shallow wells and oases were the reason for development of this model as part of a four-country Global Environmental Facility (GEF) project led by the International Atomic Energy Agency (IAEA). Simply-structured model development provided robust answers to these questions, and provided a relatively simple tool that could be adopted and used by water managers in each country.