ModelCARE 2005, IAHS Publication
304, p. 281-287
Complex groundwater whirl
systems
KICK HEMKER
Hydrology
and Geo-Environmental sciences, Vrije Universiteit Amsterdam, De Boelelaan
1085,
1081 HV Amsterdam, the Netherlands
e-mail: info@microfem.com
MARK BAKKER
Dept. of Biological and
Agricultural Engineering,
Abstract By analyzing three-dimensional flow patterns
in models of layered anisotropic aquifers, we found that streamlines often have
the shape of spirals. A bundle of such spiralling streamlines was termed a
'groundwater whirl'. Experiments include aquifers in which all layers have a laterally hetero-geneous anisotropy. In box-shaped
aquifers with horizontal layers and a uniform horizontal gradient along the
boundaries, all whirls have their axes in the same flow direction. In such
cases projected streamlines can be represented by stream function contours. It
allows an easy 2D interpretation of the main characteristics of complex whirls
patterns. Clockwise and counter-clockwise whirl axes occur at the interfaces of
adjacent layers with different anisotropic hydraulic conductivities. One or
more clockwise whirls may occur within one counter-clockwise whirl, and vice
versa. Where contours of different whirls meet, saddle points are found. There
is a fixed relation between the number of whirls and the number of saddle
points. As a consequence of groundwater whirls, the exchange of water between
aquifer layers is intensified, which may have a significant impact on contaminant
spreading.