Types of Reservoirs
The term “reservoir” can refer to a man-made or natural lake, as well as cisterns and subterranean reservoirs. In this section we focus only on man-made reservoirs.
Man
Types of Reservoirs
The term “reservoir” can refer to a man-made or natural lake, as well as cisterns and subterranean reservoirs. In this section we focus only on man-made reservoirs.
Man-made reservoirs are made when dams are constructed across rivers, or by enclosing an area that is filled with water. There are two main types of man-made reservoirs: impoundment and off-stream (also called off-river).
Reservoirs can vary in size and be as small as a pond and as big as a large lake. There is so much variability when it comes to reservoirs – they can differ in size, shape and location. For this reason, it can be misleading to make blanket statements about reservoirs without “significant qualification as to their type”.
Depending on the purpose of a reservoir, operators will fill a completed reservoir with water, let water flow on through the dam and downstream, or leave the reservoir site empty until it is needed (e.g. a dry dam site for flood mitigation).
Click image to enlarge.
An impoundment reservoir is formed when a dam is constructed across a river. Impoundment reservoirs are usually larger than off-river reservoirs and are the most common form of large reservoirs.
Off-stream reservoirs are reservoirs that are not on a river course. Rather, off-stream reservoirs are formed by partially or completely enclosed waterproof banks.
The embankments around an off-stream reservoir are usually made from concrete or clay. The size of an off-river reservoir will depend on how large of an area is excavated and how high the embankment is built.
Off-stream reservoirs are generally simple in shape and “virtually uniform in depth”  compared to impoundment reservoirs, which tend to have shallower shores and varying volumes and shapes.
Environmental Impact Assessment and Stakeholder Engagement
An environmental impact assessment (EIA) must be completed prior to construction beginning on a large or impactful reservoir and dam site. The EIA process is regulated at the federal government level by the Canadian Environmental Assessment Agency.
The Alberta government also has its own process for completing an EIA. Alberta Environment and Sustainable Resource Development is responsible for the laws that are related to EIAs in Alberta (the Environmental Protection and Enhancement Act and the Water Act). At an inter-governmental level, the Ca