In this demonstration, students will learn what watersheds are and how they impact our local waters.
To understand the importance of water and water conservation, we must first understand how water interacts with the world around us. This activity demonstrates how water moves, and how water collects.
Most of the Earth’s water is found in the ocean. Water evaporates from the ocean, lakes and rivers and condenses into clouds. When these clouds fill with water, the water will eventually fall as precipitation. Precipitation can be rain, snow, hail or sleet. Once the rain hits the ground it will flow downward following the path of least resistance. For some of the water, this is in the form of infiltration, which means that the water flows through the soil to the ground water. For some water this is in the form of surface flow in creeks and rivers. In both cases, the water will continue to flow and pick up minerals, nutrients and pollution, until it reaches a body of water that is at low elevation. For most water, this ends up being the ocean. Then, evaporation continues the cycle.
The direction of flow can therefore be predicted based on the ground’s elevation and soil type. An area where all water drains to the same river or body of water is called a watershed. A simple way to imagine this is using a shower analogy. When water moves from the shower heads (and ‘rains’), the water will hit the shower curtains, the walls and the bottom of the shower. All the areas that the shower head water hits is part of the same ‘watershed’, because it will all flow down into the same ‘river’, the drain pipe.
In Metro Vancouver, there are three separate watersheds that we use to collect water into a storage body or reservoir. Over half of BC’s population uses these three reservoirs as our source of drinking water.
In our modern age, we transport water from one watershed to another in many ways.
- We transport bottled water collecting it from one place and sending it to another.
- We transport food, which is full of water, from country to country.
- We pipe water away from a watershed to be used in irrigation for our agriculture.
If we take water out of one watershed faster than it is replenished (by precipitation, or mountain glaciers melting) then our reservoirs will slowly decrease in size.