Water Cycle

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Water moves continuously through our environment in a cycle. The rain or snow that falls from the sky flows overland to a river, creek or lake or seeps into the ground or into wetlands and lakes where it is stored. Plants absorb this water and animals drink it. Water evaporates from the surface of lakes or is released by plants. The moisture is carried on the air. It rises, condenses to form clouds and then is released to fall to earth once again.

This flow of water through the landscape of the river's drainage area, or watershed, supplies the needs of all life and links all natural features and all communities of the watershed together. Within this watershed area, or ecosystem, everything is connected to everything else, and people are as much a part of this system as are the trees, animals and fish.

Surface Water and Ground Water

The precipitation that reaches earth follows one of three major routes:

• runs off to a lake, wetland or pond

• runs off over the land to a river or creek

• is absorbed into the ground and eventually seeps through into the groundwater (known as infiltration). Surface water is the water that flows on the surface of the earth, as in the first and second point above. But groundwater is different. Groundwater is found underground in the cracks and spaces in rocks, soils and sands. Imagine pouring a glass of water onto a pile of sand. Where does the water go? The water moves into the spaces between the particles of sand. Groundwater is the same.

• Groundwater is stored in, and moves slowly through layers of soil, sand and rocks called aquifers. Heavy rains or melting snow may cause the water table to rise as more water is stored in the aquifer. An extended period of dry weather may cause the water table to fall, as less water is stored in the aquifer.

  The speed at which groundwater flows depends on the size of the spaces in the soil or rock and how well the spaces are connected. It may move several hundred metres a year in fractured limestone rock, or only move several centimetres a year through clay.

  In our area groundwater eventually flows into creek, a river or even into Lake Ontario itself.

  In many communities, groundwater is the sole source of water. In the Credit River watershed our municipalities are the largest consumers of groundwater, providing it to their local communities from underground wells.

  Did you know... two-thirds of the world's freshwater supply is found underground. 65% of the Credit River's flow comes from groundwater The Caledon Creek Wetlands, Silver Creek, and the Credit River all depend on groundwater.

   

Water that flows into the watershed also leaves our watershed by four natural means:

• evaporation from lakes, rivers and soil

• released by plants and trees, called transpiration

• creek and river run off to Lake Ontario

• discharges of groundwater into a river or creek or into Lake Ontario

• Recently, people have become concerned about the removal of water from watersheds by other, human-caused, means. These include diversions (damming or changing the course of a river to increase or decrease water supplies elsewhere) and removal (loosing water by shipping it out as bottled water or in agricultural products high in water).

What is a Watershed?

An example of a Watershed.

The entire area of land that drains, or 'sheds', its rain or snow melt into a particular river is known as the watershed of that river. The area surrounding a smaller river or creek which contributes to a larger river system, is called a subwatershed. For example, since the West Credit River contributes water to the Credit River, the area surrounding the West Credit River is considered to be a subwatershed.

The Credit River Watershed is part of a larger picture - the greater Toronto bioregion. This region is bounded on the west by the Niagara Escarpment, on the north and the east by the Oak Ridges Moraine and on the south by the north shore of Lake Ontario.

How Humans Affect the Water Cycle

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Every time humans interrupt the natural water cycle there will be an effect.

We interrupt water pathways in two ways:

1) Withdrawals:

2) Discharges:

We add substances to the water - intentionally or not. As precipitation falls on the ground and moves into rivers and creeks, it picks up a whole range of pollutants. In rural areas these pollutants may include farm pesticides, herbicides and fertilizers as well as wastes from faulty septic systems and improperly handled manure. In urban areas, the soup may include gas, oil, pet waste, fertilizers, pesticides, salt and treated human waste from sewage treatment plants.

What we do to this system affects everything within it. For example, what happens if rain that falls from the sky or the water that flows through our streams is contaminated? These contaminants may infect plant or animal life including human beings. What happens if large quantities of water are diverted or taken out of the system? The reduced flow will likely affect the local water supply but it may eventually change the local environment and alter the plant and animal species that are found here. As we place different stresses on this system, we run the risk of overloading it and causing serious harm.

The local Credit River is an important part of the watershed and the water cycle in this area. What we do here affects us locally and eventually affects the health of the water and the communities downstream from us, including people living in the cities of Brampton, Mississauga, Toronto and others bordering Lake Ontario.

Water Budget

Like any budget, a water budget looks at balancing needs with the available resources. A water budget is based on a clear understanding of the way that the water cycle works in a specific area. To create a water budget we need to understand:

1. the amount of water stored in the system - as ground water, flowing overland as surface water, recharging back into the river and ground from marshes and other storage areas, and the amount leaving the system through evaporation, run-off or even removal.

2. the amount required - for the health of the watershed including the needs of the plants and animals that make up the ecosystem, and for human needs now and based on projected growth.

The demand for water has escalated considerably in the last three decades as the Province of Ontario has experienced tremendous growth pressure. It is expected that the Credit River watershed will continue to experience extensive development pressures and, with this, ever-increasing demands for water. In addition, forecasts predict that climate change could result in droughts and changes in precipitation patterns. This would result in lower baseflow in the river and its tributaries and in lower groundwater levels.

CVC is working with its partners to develop a Water Budget to begin to address these concerns.