Permanent removal uses
Long-term, or permanent withdrawal uses remove water from the source, and from the hydrological cycle, for extended periods of time, or degrade the water to such a degree of toxicity that the water cannot be made fit for consumption by humans or nature in the foreseeable future.
Main examples of those uses are:
- Canada’s oil sands producers are major permanent withdrawal water users. Located in northeastern Alberta, the Oil Sands, also referred to as the Athabasca Tar Sands, are large deposits of bitumen, or heavy crude oil, which are encased in a mixture of silica sand, clay minerals and water. Enormous amounts of water and natural gas are required to extract the bitumen from the clay mixture to produce usable crude oil. Between 2 and 4.5 cubic metres of water are required to produce one cubic metre of synthetic crude oil. While some of the water is recirculated, some is discharged and stored in giant pools called tailings ponds. Once in the pond, the sedimentation of solid particles is allowed to happen, leaving those particles to settle on the floor of the pond. Tailings ponds, however, including those of Alberta’s Oil Sands, often contain a mixture of water and solid particles that are highly toxic. In 2008 hundreds of ducks died when they landed in what they mistook for an ordinary pond in the Alberta Oil Sands. While the ponds do prevent the toxic particles from being transported by the wind, the water in those ponds has been rendered useless in terms of the hydrological cycle.
- Deep aquifer injection represents another long-term removal use of water. Researchers are conducting studies whereby natural gas, energy and carbon dioxide would be sequestered into underground reservoirs, such as deep saline aquifers. The injected substances would remain isolated from the atmosphere for long periods of time. The water in those aquifers, however, would no longer be available for use by humans or nature as part of the hydrological cycle.
This piece describes what tailing ponds are, as well as how they work. Both narrated descriptions are supported by full-colour imagery and diagrams.