Water Sector Overview

AuthorElaine L. Hughes, Arlene J. Kwasniak, Alastair R. Lucas
Arlene J Kwasniak
Everywhere on eart h, the ultimate water source is precipitation — rain,
snow, sleet, and hail. Precipitation can be adsorbed (inf‌iltrated) into
the soil, which allows water to seep into the ground and to be stored
underground as groundwater. Water can become runoff and f‌low into
rivers, streams, and other water bodies or be stored in areas such as ice
caps, puddles, ditches, or depressions. Water is returned to the atmos-
phere through evaporation or transpiration through plants (together
evapo-transpir ation), and then returns back through precipitation. The
entire process is ca lled the hydrological cycle or water cycle.1
A key concept in water management is watershed or drainage ba sin.
A watershed or drainage basin i s an area where all water and whatever
is carried with water (sediment and dissolved materials) drain from
the land to a common body of water such as a river, lake, or ocean.
The Canadian Atla s identif‌ies f‌ive major drainage basins in Canada.
Such drainage basin s may be huge, for example the Hudson Bay drain-
age basin, which measures 3,861,400 square kilometres, or relatively
1 For information on t he hydrological cycle, see, for example, E nvironment and
Climate Cha nge Canada, “The Hydrologic Cycle,” online: www.ec.gc.ca/eau-water/
default.asp?lang=En& n=23CEC266-1; United States Geological Sur vey Water
Science School, “Sum mary of the Water Cycle,” online: http://water.usgs.gov/
edu/waterc yclesummary.html; and t he Foundation for Water Research, “The
Hydrological Cycle,” online: w ww.euwfd.com/html /hydrological-cycle.ht ml.
small, for example, the Milk R iver Basin in the Canadian Prairies,
which measures 21,600 square kilometres.2 Drainage ba sins may be
divided into smaller ba sins, sub-basins, sub-sub-basins and so on. In
each case, there w ill be a watershed. For example, Alberta water man-
agement identif‌ies eleven major basins in the province.3 With each of
the basins, water f‌lows to a common river, and then, depending on the
basin, water eventually w ill f‌low to the Arctic Ocean, Hudson Bay, or
Gulf of Mexico.
The water cycle and watershed are affected by many factors. One is
the rate of rainfall — t he slower and lighter it rains, generally spe aking,
the more opportunity to inf‌ilt rate soil; the faster and harder it rains, the
more apt it is to become runoff, and the more quickly it will reach r ivers
and water bodies. Natural topology is a lso a factor; grade or slope will
inf‌luence whether water inf‌iltrates or becomes r unoff. Human activities
and development may greatly impact water cycle and watershed. For
example, constructing i mpermeable surfaces (such as roads and pave-
ment) will result in runoff or water gather ing instead of inf‌iltration.
Drainage of water bodies and development on drained areas can block
groundwater replenishment (recharge). Dams, diversions, and storage
projects all affect how water travels th rough a watershed and water
cycle (for example, inf‌luences on rate of evaporation). Water quality in
a watershed is impacted by everyt hing that goes on in it, such as min-
ing, forestry, development, urban and rural pesticide use, other agricul-
tural runoff, ma lfunctioning municipal sewage discharges, and so on.
Generally, water is categorized as surf ace water or groundwater. Sur-
face water is water on the ground surface, including r unoff, that gath-
ers in a stream, la ke, river, wetlands, ocean, or reservoir. Groundwater
is water under the surface of the ground. Groundwater is rech arged
by precipitation that seeps into the ground. It seeps downward until it
reaches a depth where water has f‌illed a ll of the porous areas in the soil
or rock (the saturated zone). The top of the saturated zone is the water
table. The porous area between the water table and the la nd surface is
the unsaturated zone. Some groundwater is hydrologically connected
to surface water and some is not. At common law, groundwater that is
not hydrologically connected with surface water in law is called “per-
colating groundwater.”4 An aquifer is water-bearing rock, sand, gravel,
2 See the Can adian Atlas, “This Water-rich La nd,” online: ww w.canadia ngeo-
graphic.ca /atlas/themes .aspx?id=WATERRICH&sub=WATERRICH _BASICS_
DRAINAGE&lang=En .
3 Water Act, RSA 2000, c W-3, s 1(1)(ff) def‌inition of “major river b asin.”
4 Chasemore v Richards (1859), [1843–60] All E R Rep 77 (HL).

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