Application of Particle Tracking Models to Aquifer Contamination Assessment

Abstract

Particle tracking models are very useful tools in aquifer contamination assessment and management. They help acquiring better insight into the physical, environmental and economical aspects of water quality problems. This paper describes the application of particle tracking models in the assessment and management of contaminant transport in aquifer system. The potential bacteriological contamination of Seiy’un wellfield due to the migration of contamination from the cesspools and sewage disposal pits is assessed using the United States Geological Survey (USGS) particle- tracking code MODPATH in conjuction with the USGS flow model MODFLOW. The developed model is used to assess the potential contamination of the wellfield, by identifying the flow pattern in the wellfield aquifer and the capture zones of individual wellfield boreholes and estimating contaminant travel times from sources to boreholes.

1. INTRODUCTION
Particle tracking models are very useful tools in the assessment of well capture. They can be used to identify potentially responsible parties for contamination of drinking water well as well as to identify regions for well head protections. In many contaminated sites, multiple possible sources or responsible parties could cause the pollution. The need to identify the responsible party or parties results in litigation and assessment of groundwater flow patterns [Harr, 1996]. Models are used to simulate the groundwater flow and to see whether groundwater underneath potential sources is eventually captured by the pumping well. To further assess the feasibility of a potential source, the travel time of contaminants from the source to the well is estimated to see if the timing fits with possible releases from the site. Numerical Particle tracking models in conjunction with numerical flow models can be used to evaluate the capture zone and travel times. In wellhead protection, the headwaters of the well or regions which supply water to the
well are identified. The community councils and the regulatory authorities decide on appropriate land use for these regions which will have minimal impact on the subsurface groundwater.