Have you ever wonder how do we get water from a well? When I was a kid, my grandma told me that we would get water if we dug the ground deep enough, that was the way people obtain water back in China years ago. The theory was so fascinating to me at that time that I tried digging around in the backyard but no water came out in the holes that I dug. Another issue that had bothered me was during sand castle building at the beach. A sand castle surrounded by a moat filled with seawater was something really cool that we kids wanted to imitate from the castles we had seen on TV. You guess it right, water seeped right through the sand no matter how much seawater we poured into the pitch. How could a natural pond hold so much water but not the hand-dug one?
It's a common knowledge that 71% of Earth's surface is covered by water where 96.5% of the water belongs to the oceans. Out of all the freshwater, most of them are sealed in glaciers and ice sheets (around 85%) and groundwater takes up a total of 14%, which means only 1% of freshwater resides in the atmosphere or surface waters (lake, river etc.). The ground that we are stepping on is not pure solid, but it is mad of with unconsolidated (soil) and consolidated rocks. There are many tiny pores in the soil and cracks in rocks that can be filled up with water like a sponge or a container. When it rains, water will first infiltrate into the 'unsaturated zone' of the ground which is moist where plants obtain the water they need before percolating into the 'saturated zone' which is always loaded with water. This saturated zone is normally called water table or aquifer, which is the storage of groundwater where we can extract clean drinking water from.
Beneath the groundwater, there is a layer of concrete material called bedrock that prevents the water from seeping away, holding the water in one place. However, the groundwater is not stagnant like an underground lake, it is constantly flowing very very slowly with a rate of meters per year, being recharged regularly by rain water and surface water with the help of rainforests which allows rain water to steadily seep into the ground instead of running off the earth surface quickly. This free flowing groundwater storage can be called 'unconfined aquifer' which can be reached by digging a well as shown in the image above. With the existence of 'unconfined aquifer', we have 'confined aquifer' too where the groundwater is being contained by impermeable layers of soil or rocks which can be reached only if we drill through that tough layer as shown in the image below.
According to a study named An Overview of Groundwater Chemistry Study in Malaysia, even though groundwater accounts for more than 90% of our freshwater resources, less than 10% is being utilised as water supply in this country. Most groundwater extractions are carried out in east coast of Peninsular Malaysia due to the type of soil that makes groundwater extraction productive. Besides, it is carried out commonly on islands too as it is the cheapest source of freshwater compared to having to transport freshwater from mainland. In Kelantan, 41% of freshwater supply comes from groundwater especially in the northern part of the state. Even though groundwater does not play a major role in supplying freshwater in Malaysia, groundwater constantly support our rivers and lakes, preventing them from drying up; it also prevents the intrusion of seawater into aquifers in coastal regions or islands unless over-extraction of groundwater occurs.
Even though we do not see groundwater and it does not directly affect our daily life (unless you obtain water from a well), we must keep in mind that groundwater is part of the whole hydrological cycle. Locating just below our feet, we might accidentally do something that would affect the quality of groundwater without knowing it:
- cementing the ground, it might make the ground easier to be cleaned but it prevents rain water from recharging the groundwater
- dump toxic wastes such as batteries on ground instead of proper disposal, this causes toxic chemicals to leak into the groundwater
- spill soap water onto the ground after car wash etc., same as the point above, the soap water will seep into the groundwater, causing contamination
Of course, on a larger scales, these are the actions that cause major groundwater disruption which can have serious consequences:
- deforestation that clears off a huge piece of water catchment area, causing excessive runoff that can lead to dry spell as the groundwater cannot be properly replenished over a long period of time (instant flash flood can happen too)
- over-extraction of groundwater can cause land subsidence where the land collapses due to the lack of support underground by groundwater besides leading to seawater intrusion which can pollute the rest of the aquifer with salts that the water is not drinkable anymore
- pollution due to improper waste disposal or accidental spillage that can render the whole aquifer not suitable to be used unless remediation is carried out to remove the pollutants
We have experienced several shortages of water and water resource pollution this year which lead to water rationing for some period of time here, groundwater utilisation might be a good solution to temporarily solve the crisis we are facing. However, relying on groundwater solely while continuing polluting rivers and cutting down forests does not seem to be a smart long term idea to be carried out. Groundwater can become one of our main water supply resources, if the careful extraction is done together with other efforts that can ensure clean water supply for the following generations to come.
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