Abstracts

The aquifer is mostly confined; but is exposed at some places along the Assiniboine River
Valley. Initially, the groundwater quality was poor with high chlorides and total dissolved
solids. With the increased pumping, the quality improved. Heavier and evaporitic isotopes
indicated that water from the Assiniboine River was recharging the aquifer.
Two major pumping centers have developed deep drawdown zones in the potentiometric
surface, where some areas indicate a strong recharge boundary from the Assiniboine River.
This recharge boundary sustains the aquifer’s ability to supply large amounts of water.
However, there are groundwater flows moving towards the pumping wells from other areas
which still contain older glaciogenic water. Groundwater sampling shows that the groundwater
in the dynamic zones is improving in quality, and indicates recharge. Over the last
five years drawdown has developed in the western areas of the aquifer due to the pumping
of the City of Brandon emergency supply wells. This new drawdown has dramatically
altered the potentiometric surface and at some places the geochemistry.
Numerous groundwater level observation wells show annual aquifer recharge with normal
seasonal and climatic conditions. The network also records the effects of changing pumping
rates. During the few years on several occasions, the Assiniboine River has reached
flood stage, and the aquifer rises and falls very rapidly to the river water level changes.
The Brandon Channel Aquifer is an important aquifer that provides substantial water
supply for industrial use in the City of Brandon. The recent municipal use of the aquifer,
shows that proper management is required of this complex buried valley aquifer. Therefore
additional groundwater investigations should be undertaken.
184 - Free convection or variable density flow within groundwater
flow systems?
K. Udo Weyer & James C. Ellis
WDA Consultants Inc., Calgary, Alberta, Canada
There exists a scientific conflict between the postulated but unproven existence of free
convection under hydrodynamic on‐shore conditions and the well‐established existence of
gravitational groundwater flow systems under the same conditions. The extensive literature
on free convection indicates that downward directed fingers of higher density fluid may
develop via free convection under hydrostatic laboratory conditions. Numerical codes have
subsequently been developed which model these fingers in an hydrostatic environment.
So far, there has not been any conclusive proof of the field occurrences of free convection
under hydrodynamic on-shore conditions presented, despite strong claims to the contrary.
The claims were mainly based on 2008 geo-electrical field measurements in the shore near
sabkha (salt flat) areas in Abu Dhabi (van Dam et al., 2009).
Repeat geophysical measurements in 2009 did not find the ‘fingers’ which were claimed
to have existed in 2008. Subsequently a prominent proponent of free convection stated
subsequently: “Hundreds of papers on theory, modelling & laboratory experiments on
finger instabilities associated with free convection…. But a complete lack of conclusive
172 IAH-CNC 2015 WATERLOO CONFERENCE