3a - e: Hyrological Cycle, Aquifers, Groundwater

What percentage of the worlds water is freshwater

1%

What is the water cycle known as

Hydrological Cycle

Why is the hydrological cycle a closed system

• no water is added to or lost from it

• it recycles the worlds water over and over again

How does the water cycle work

1. Sun heats surface of Earth

2. Water is evaporated from oceans, rivers, lakes ect

3. This warm, moist air rises (because it is less dense)

4. This warm air condenses and is converted to water droplets, forming clouds

5. Precipitation occurs as water droplets get bigger and heavier (fall as rain, snow and sleet ect)

What is evaporation

Process where water from a liquid → vapour

What is transpiration

Water vapour is evaporated from vegetation

What is condensation

• Water vapour cools → liquid water

What is precipitation

Fall of water from earths atmosphere to earths race (rain, hail, sleet, snow)

What is surface runoff

Water flows over the land surface into rivers and lakes

What is infiltration

Movement of water in the soil

What is percolation

Movement of water in the rock

What is groundwater

Water stored beneath the Earths surface in aquifers

What are the two kinds of rock in Malta

• Permeable rock: allows water to pass through it

• Impermeable rock: does not allow water to pas through it (only blue clay is impermeable in Malta)

Explain the formation of aquifers

• When it rains, water passes down through the soil and into the rock. Since Upper Coralline Limestone and Greensands are permeable, water passes through. As it reaches the Blue Clay layer, it cannot pass through (impermeable) and is stored above it in an aquifer called the perched aquifer

• As there are cracks in the Blue Clay, water passes through the cracks and continues downward through the Globigerina and Lower Coralline limestone as they are permeable.

• As freshwater percolates downwards, it reaches a layer of seawater, but the freshwater is less dense than the saltwater so it rests on top, forming the mean sea level aquifer (deep in the lower coralline limestone layer)

So what is an aquifer

• a body of rock holding freshwater

What are the two aquifers in Malta

• the perched aquifer (lies over Blue Clay layer)

• the mean sea level aquifer (found deep in Lower Coralline Limestone layer)

In what shape are aquifers

Shape of a lens (thick at centre, thin at sides)

What’s the difference in the size of aquifers during winter and summer

• winter months: water in aquifer increases

• summer months: water in aquifer decreases

Understand

Yes

Where is the perched aquifer mainly found

West of Malta (Rabat and Dingli)

What can perched aquifers create

Natural springs

Why are perched aquifers important

• Biodiversity: Natural springs (formed from perched aquifers) provide water for plants and animals, increasing biodiversity.

• Ecology: Natural springs support endemic and native species, such as the Painted Frog and Freshwater Crab.

• Agriculture: Provides water for irrigation and was once an important source of drinking water. Today, farmers pump water from it through boreholes (used to be done via wind pumps)

Do we still use the perched aquifer for drinking water

• yes, but much less than the last

• most water now comes from desalination systems and mean sea level aquifers

• mostly used for water for irrigation

What happens if there is a lack of rainfall/aquifer is overused and therefore aquifer depletion

• Biodiversity loss: Plants and animals that live in natural springs will be affected and lose their habitat (and even become extinct)

• Agriculture: Farmers have less water from natural springs and rain, so they have to buy more water (increasing cost of crops)

• Saltwater infusion: If too much freshwater is pumped out of an aquifer, seawater can enter and mix with the freshwater. This is called saltwater intrusion. The water becomes salty, making it unsuitable for irrigation and causing the soil to become less fertile.

• More electricity use: More water will need to be taken from the sea and filtered through reverse osmosis, using lots of energy, time and resources

Why is it called the mean sea level aquifer

Aligned with the sea level

How is water brought up from aquifers

Through boreholes which are dug into rocks and galleries (horizontal tunnels in the rock)

What are 2 galleries in Malta

• Ta Kandja

• I/o Siggiewi

What is the water stored in aquifers called

Groundwater (which is freshwater)

What are threats to groundwater/Maltas aquifers

• less rainfall (which is relied on to replenish aquifers) due to climate change

• over-extraction (taking more water from aquifers than is being naturally replenished) causing seawater infiltration (water becomes dirty and unusable)

• p ollution from pesticides and fertilisers can contaminate aquifers. Rainwater carries these chemicals through the soil and permeable rocks into the groundwater.

• sewage can also contaminate aquifers as it gets mixed with rainwater.

• population increase (higher demand for freshwater, hence more is pumped out of aquifers)

• urban/infrastructure development leads to less areas (such as fields) where water can infiltrate into the rocks and fill the aquifers (roads & concrete are impermeable)

• tourism (increased demand for water)