Ground Water
Much of our drinking water comes from groundwater. This videographic explains how it works. VIDEOGRAPHIC
Category
🗞
NewsTranscript
00:00 [Music]
00:06 Much of our drinking water comes from groundwater.
00:11 Groundwater is fed by rain, which seeps into the ground and descends into the earth.
00:16 After passing through the layer of soil, the water trickles down between sediments and rocks.
00:21 When it reaches an impermeable layer, it collects in the empty spaces.
00:25 This water-saturated space is called an aquifer.
00:28 The water table is the boundary between this space and unsaturated ground.
00:33 Below the water table, groundwater fills around the sediments and cracks in the rocks.
00:38 Shallow water tables are known as groundwater, which generally refers to unconfined aquifers,
00:44 as rainwater flows directly down to the impermeable layer.
00:48 But there are also confined aquifers, which are trapped between two impermeable layers.
00:53 These aquifers are deep, sometimes more than a thousand meters.
00:57 The largest aquifers are in sedimentary basins of highly porous rock, such as limestone, sand, and chalk.
01:04 They are less common in crystalline and volcanic rock formations.
01:07 Water in the aquifer flows down the slope of an impermeable layer and becomes saturated with minerals as it goes.
01:14 The pace of the flow can depend on the type of rock.
01:17 The water sometimes flows hundreds of kilometers, which can take centuries.
01:21 The water stream joins other aquifers, rivers, marshes, and even the sea.
01:26 Groundwater feeds nearby rivers in the spring and summer.
01:32 Rivers then resupply the underground aquifers in the autumn and winter.
01:39 To extract groundwater, people drill wells.
01:41 Since the water in a confined aquifer is generally under pressure,
01:45 the well creates pressure so the water can gush out spontaneously.
01:49 This is an artisan well.
01:52 To preserve good water quality, aquifers must remain at a certain level.
01:56 There are also protective parameters encircling catchment areas, as groundwater is sensitive to pollution.
02:02 [BLANK_AUDIO]