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| Surface water - Lake Wanaka, New Zealand |
Surface water is the water that lies on the surface naturally as streams, rivers, marshes, lagoons, ponds, and lakes. Surface water can also be collected and stored in containers that have been built especially for that purpose. These containers are called reservoirs. Fresh water also collects in areas of soil and rock underground. This is groundwater.
Rain falling from the sky and snow melting in the springtime can flow downhill to gather in stream or riverbeds. From there, the water flows to a lake or ocean. In other locations, the rain or melted snow is soaked up by the soil and makes its way further down into the ground because of gravity (the force of attraction between all masses in the universe).
Uses of surface and groundwater
Surface water tends to be used by humans more often than groundwater. This is because it is much easier to obtain surface water. Inserting a pipe or tube into the water and then pumping out the water is all that is needed. Sometimes, if the surface water source is located on a hillside, the water flows through the pipeline because of gravity.
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Surface water makes up almost 80% of the 410 billion gallons of water that is used in the United States every day. Groundwater makes up the remaining approximate 20% This huge amount of water is enough to fill 400,000 Olympic swimming pools, every day of the year!
Drinking water. The main use of surface and groundwater is for drinking water. Without freshwater to drink, animals such as humans die within days. Much of our drinking water is surface water, which must be treated before drinking.
Soil and plant material can wash into surface water in a rainstorm or as the snow melts into the stream, river, pond, or lake. Microorganisms that live in the feces of animals can also be washed into the water. If the water is not treated to remove the material and the microorganisms, the contaminated water can make humans and animals ill.
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| Drinking water |
This is why campers and hikers filter their drinking water or add chemicals that kill the harmful organisms in the water. This is also why the water that comes out of the tap in towns and cities has usually come from a water treatment plant; a place where the water is put through a series of steps to make it potable (drinkable).
Groundwater may not require treatment before drinking. This is because the ground itself is a filter. As the water moves down into the soil and rocks, big objects like leaves are left on the surface, and smaller objects including bacteria (a million bacteria could fit on the period at the end of this sentence) either stick to the soil or cannot pass through the even tinier holes in the rock.
By the time the water collects in the ground, the harmful microorganisms and chemicals have been removed by the filtering action of the soil and rock layers. This can often mean that potable water can be pumped out of the ground from wells.
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However, it is wise for those who have a private well to have their water tested at regular intervals. Community wells are checked every month to ensure that no contamination of the groundwater has occurred that could be harmful to the community that the well supplies.
Recreation. Diving into the swimming pool, water-skiing, and fishing in a lake are all fun (recreational) uses of water that make use of surface water. Groundwater aquifers are sometimes the source of warm or cool springs that come to the surface and are also popular for recreational use.
Agriculture. Both surface and groundwater help keep crops growing. Depending on the type of crop being grown, water can be pumped or sprayed onto the field.
Additionally, farm owners and their livestock such as cattle, pigs, and poultry all require drinking water to stay healthy, and water is needed to keep the farm clean.
Industry. Industry uses large amounts of water to keep machinery cool, to pump into oil fields to help force the oil up to the surface, to generate electricity, and for other purposes. Much of this water is used and then put back into the ground or onto the surface.
Surface water is used to generate electricity by building a wall (dam) across a river. The dam causes water to collect on one side. When gates in the dam are opened, water rushes through. The rushing water turns turbines, a device that converts the fluid into mechanical motion that in turn generates electricity.
While dams are necessary to supply the electricity that big cities need, they can sometimes change the river in ways that are not healthy for the animals, plants, and microorganisms that live further in the river.
