WWC - Accumulation of Water Lesson

 

Accumulation of Water

The fate of water that precipitates to Earth depends on several factors, including the type of precipitation and the environmental conditions. In general, water will either soak into the ground, stay at the surface, or evaporate back into the atmosphere (or may undergo a combination of these factors). Water that soaks into the ground is termed groundwater, while water that accumulates at the surface can form freshwater bodies of water (puddles, ponds, and lakes), or moving water, such as streams and rivers.

Water that soaks into the ground works its way down through the spaces between particles of sand and soil, or through cracks and pores in solid rock. Some of the water is retained in these tiny spaces (the same way that a sponge traps water in its spaces), keeping soil moist. If there is enough groundwater, it will percolate downward until it reaches an impermeable layer - solid rock or clay, for example - and then the water begins to build up towards the surface (think of pouring water into a glass filled with sand; at first the water soaks into the sand, but once it reaches the bottom of the glass it starts to fill back up). Permeable rock, such as sandstone, has tiny pores throughout it that can fill up with this water, forming aquifers.

The water table is the surface of the aquifer. As shown in the illustration, the water table may be underground, or above. Water in a lake, for example, must first soak into the ground until it reaches an impermeable surface and then build up from there. A similar example occurs when you dig a hole into the sand at the beach; once you reach sea level, the hole fills with underground seawater.

Complete the aquifers and groundwater activity below:

Water that accumulates at the surface is pulled by gravity, causing it to flow downhill. As it flows, it collects with additional water to form streams and rivers. Since the surface of the Earth is not flat, water tends to run down hills and mountains, and these high points serve as divisions between the runoff areas that feed a river. In other words, water that lands on one side of a mountain flows in one direction, and water that lands on the other side flows in another direction. The area between high elevations is known as a watershed - the land that supplies runoff water that feeds a particular river.

Runoff has several effects on the Earth's surface. As rivers flow along the surface, they move materials from one location to another through the processes of weathering, erosion, and deposition. Other substances are actually dissolved from the rocks into the water and flow with it to the oceans. Since the water that evaporates from the oceans leaves these minerals behind, these dissolved substances have continued to build up in higher and higher concentrations, which is how the oceans became the salty, mineral-rich environments that we know today.

 

IMAGES CREATED BY GAVS OR OPENSOURCE