Channel - a natural passageway or water course connecting two bodies of water.

Climate - long term (over 30 years) average in temperature, humidity, and wind for example.

Delta - an accumulation of sediment where a river enters a lake or ocean. The shape and size of a delta are controlled by the climate, the water discharge of the river, the amount of sediment supplied by the river, the size of the waves, the current and the tides in the receiving body of water.

Evaporation - the change of state from liquid to water vapor.

Groundwater - the water beneath the surface of the ground. In northern Canada much of the groundwater is frozen as ice within permafrost. However, since the area beneath the channels and lakes in the Mackenzie Delta are not frozen, groundwater movement may occur through these zones.

Hydrology - the scientific study of the portion of the earth that is water, in liquid, frozen, or vapor form, as it moves or is distributed on the earth's surface, under the ground, or in the atmosphere.

Ice Jams - occur in river channels when floating ice is blocked at a constriction in the channel. The resulting partial blockage of the channel can lead to very high water levels upstream of the jam (see text box for further details).

Lake sill elevation - the elevation that a lake is perched above the main channels of the delta.

Mean sea level - the average elevation of the sea surface (see text box for further details).

Negative water balance - water flows out of the lake or evaporates from the lake faster than it is replaced by rainfall or runoff into the lake. As a result, the lake water level declines.

Net radiation - the difference between the incoming and outgoing electromagnetic radiation received by a surface. The incoming radiation includes the visible radiation from the sun as well as the infrared radiation emitted by the atmosphere and clouds. The outgoing radiation includes the visible radiation reflected by the surface and the infrared radiation emitted by the surface.

Permafrost - Ground that has a temperature of below 0°C for more than two years. The ground may or may not contain ice. The Mackenzie Delta is located within the Continuous Permafrost Zone. However, permafrost often does not occur below the channels or lakes in the delta.

Positive water balance - the opposite of negative water balance, where the amount of water added to the lake is larger than that leaving the lake due to evaporation or runoff. As a result, lake level increases.

Radiation - electromagnetic energy that travels as a wave. Radios and TVs receive programs by radiation. Visible light is also a type of electromagnetic radiation. All material emits electromagnetic radiation with the wavelength of the emitted radiation dependent on the temperature of the body. In the case of the sun, the wavelength is in the visible range of humans. In the case of most natural surfaces, the radiation has a longer wavelength and is in what is called the infrared range.

Return period - the average time between extreme events. Bridges and culverts often are designed to resist a so-called 1 in 100 year flood event. Over a long period of time, say 500 years, a 1 in 100 year flood would be expected to occur 5 times. However, it is possible to have a number of these events within a fairly short period of time, followed by a long period of time with no events of this size.

Storm surge - short term rise in sea level due to strong offshore winds (see text box for further details).

Talik - an unfrozen zone through the permafrost.

Tides - the periodic rise and fall of the waters of the ocean and its inlets, produced by the attraction of the moon and sun, and occurring about every 12 hours. In the Beaufort Sea the maximum tidal range is approximately 0.37 m.

Transpiration - the passage of liquid water through a plant from the roots through the vascular system to the atmosphere as water vapor.

Weather - day to day variations in temperature, humidity and wind, for example.