Stochastic contaminant transport monitoring in heterogeneous sand and gravel aquifers of the United Arab Emirates

Abstract

Stochastic numerical simulations were performed to investigate the evolution of plumes from pulse sources that can result from accidental leaks. The stochastic advection-dispersion equation was solved for hydraulic conductivities typical to the heterogeneous sandy and gravel aquifers encountered in the United Arab Emirates. Dispersivities were similar to those found in field studies at sandy aquifers, such as those conducted at Borden and Cape Cod, and at the Vejen, Denmark tracer tests. Our work showed that the detection probability, P d , of a monitoring network was affected strongly by the medium's dispersivity with a large number of wells (larger than 12) required, even in relatively simple geological environments, in order to detect contaminants with confidence. Monitoring systems following minimum regulatory requirements in terms of the number of wells were able to detect contamination at best in only one out of five cases. The frequency of sampling did not appear to be critical when the dispersivity was low and bi-annual sampling appeared to be satisfactory. In highly dispersive media monthly sampling was needed in order to increase detection. Increase of a medium's dispersivity in relative homogeneous aquifers reduced the performance of large well-systems to less than 50 %. Strongly heterogeneous and dispersive subsurface environments led all monitoring systems to fail in detection, irrespectively of frequency of sampling. Finally, large contaminant quantities did not improve the detection capabilities of low density wellsystems with detection enhancements restricted to high density ones.

High-Resolution Spatiotemporal Trend Analysis of Precipitation Using Satellite-Based Products over the United Arab Emirates

“…However, recent studies reported that the annual rainfall of the country experienced a downward shift in 1999, and the average rainfall has decreased when compared to annual rainfall before the shift [9,12,36]. The country's aquifers are composed of interior heterogeneous sand aquifers, gravel aquifers in the Eastern and Western plains, and coastal and limestone aquifers [37]. The limited UAE agriculture industry is largely dependent on groundwater and the major arable land is located in the northeastern region.…”

Waste-to-energy: An opportunity for a new industrial typology in Abu Dhabi

“…The water table at the coastal areas of UAE is less than 1 m below the surface, and this is where the two major population centers, Abu Dhabi and Dubai, are located. Even in the interior at the city of Al Ain, close to the border with Oman, the water table is a few tens of meters below ground surface [17]. Although heterogeneous the subsurface environment is characterized by high permeability material.…”