Presentation on theme: "PHYSICAL GEOGRAPHY GROUNDWATER UNIT What is groundwater? Why is it important?"— Presentation transcript:
PHYSICAL GEOGRAPHY GROUNDWATER UNIT What is groundwater? Why is it important?
Recall the HYDROLOGICAL CYCLE (studied earlier in the Rivers unit.) Precipitation that lands either runs off, or percolates into the ground. What is groundwater?
Once under the ground, it begins to fill the spaces in the soils and porous rocks. The parts where the spaces are not completely filled with water, are called the UNSATURATED ZONE. Below the unsaturated zone, all the spaces become filled. This is called the... …wait for it... SATURATED ZONE What is groundwater? The top of the saturated zone is called the WATER TABLE. The water table is the water level in a well. (More on this later.)
What is groundwater? A layer of porous rock (such as gravel) within the saturated zone is called an AQUIFER. Since aquifers are rarely level, the groundwater flows within it. When the water table is at or above the ground level, a marsh, swamp, bog, or lake occurs.
Try to guess the percentages of the earth’s water that falls in the following categories: Oceans: Fresh water: 97% 3% Of that 3%, how much falls into each of the following categories: Atmosphere: Rivers: Ice sheets and glaciers: Lakes: Soil moisture (in unsaturated zone): Ground water: 0.035% 0.03% 75% 0.3% 0.06% 24.5% Why is it important?
Some uses of groundwater are: 22% of all freshwater withdrawals 34% of agricultural use (mostly for irrigation) 40% of the public water supply withdrawals 53% of all drinking water for the total population 97% of drinking water for the rural population
Why is it important?
Needless to say, if we deplete or contaminate our ground water, the consequences are serious. This unit will examine depletion of groundwater, particularly through well use, and contamination of groundwater, as happened at Walkerton. Why is it important?