7 FACTORS INFLUENCING EXISTENCE OF GROUND WATER

7 FACTORS INFLUENCING EXISTENCE OF GROUND WATER

Precipitation

For groundwater to exist precipitation must exceed evaporation. Light rain falling over a long period of time infiltrates more than a heavy short-lived downpour.

Slope

On flat and gently sloping areas rainwater has ample time to infiltrate because it remains in one place for a long time. On steep areas, there is low infiltration since a lot of water turns into a runoff because of getting less time to percolate.




Nature of Rocks

There is a greater possibility of the existence of groundwater where there are permeable surface rocks.

Groundwater exists where impermeable rock overlies an impermeable one so that when water infiltrates and percolates underground it’s trapped by impermeable rock and accumulates above it.

Aquifer – permeable rock which is permanently saturated with water.

Permeable rocks




Rocks that allow water to pass through them.

Types

a) Porous – Those with pores/airspaces between rock grains through which water passes e.g. sandstone, limestone and chalk.

b) Pervious – Ones with cracks fractures and joints through which water enters and passes e.g. granite, limestone and chalk.

Impermeable rocks

Ones that don’t allow water to pass through them.




Types

Aquifuge – Impenetrable impermeable rocks e.g. gabbro, shale and slate.

Aquiclude – Porous rocks which absorb water and expand narrowing air spaces between grains preventing water to percolate downwards e.g. clay.

Vegetation

CoverPlants break the speed of raindrops causing drops to hit the ground gently giving rainwater ample time to percolate. On bare surfaces, most of the precipitation flows away as runoff.




Level of Saturation of Ground

Infiltration is more on dry ground because it has wide open-air spaces while and less on ground whose air spaces are saturated with water.

Water Table

Water that infiltrates and percolates into the ground fills air spaces creating zones of saturation whose upper levels are called water tables.

Zones of Saturation

Zone of Non-saturation




Zone of permeable through which water passes but doesn’t remain in the pores for a long time. Well sunk to this zone doesn’t contain any water.

Zone of Intermittent Saturation

Zone which during the rain season the rocks are saturated with water while during the dry season they are unsaturated.

Temporary water table – Upper level of groundwater in the zone of intermittent saturation.

The zone of non-saturation and that of intermittent saturation are called a vadose zone.

Zone Of Permanent Saturation




Zone where pores spaces are permanently filled with water.
Permanent water table – Upper level of groundwater in the zone of permanent saturation.

The presence of groundwater leads to the formation of springs, wells boreholes, and artesian basins.

RELATED POSTS

1 thought on “7 FACTORS INFLUENCING EXISTENCE OF GROUND WATER”

  1. Pingback: DIFFERENCE BETWEEN MIXED CROPPING AND INTERCROPPING

Comments are closed.

%d bloggers like this: