Wondering what happens to rainwater that falls on land? Water generally goes from the atmosphere to land then to the hydrosphere in an endless cycle.
The water that falls from the sky when it rains forms lakes, rivers, and other bodies of water.
After falling on the land, rainwater flows through various regions before reaching the sea. Water evaporates from the ocean and enters the air as vapor. The vapor condenses into clouds that fall onto the land as rain or snow.
A Break Down of the Cycles of Rainwater
By its very nature, rainwater is always looking for a medium for the various transformations or cycles.
Here are the cycling processes that rainwater goes through:
- Converted to ice in polar regions
- Get to Oceans
- It gets stored as groundwater
- Stored in lakes and ponds
Note: The process could take weeks, even months, but a massive chunk of rainwater often ends up as rain again.
Surface Runoff
Understanding what happens when rain falls on the ground it’s equally essential to comprehend surface runoff.
When rainwater, stormwater, meltwater, or other water sources overflows on the ground’s surface and cannot sufficiently infiltrate into the earth’s soil fast enough, it is called surface runoff.
Surface runoff often forms on uneven land and runs downhill.
In doing so, it moves toward the sea, or in another direction, where there are hollows that hold water or soak into the ground.
Surface runoff is one of the significant components of the natural water cycle.
Effects of Surface Runoff
1. Flooding
Urban flooding results from the combination of surface runoff and poor drainage in urban areas.
These conditions often lead to enormous property damage, mold in basements, and dampness. Surface runoff also causes street floods.
2. Runoff Pollution
Urban and suburban rainwater runoff can damage streams, pollute swimming beaches, kill fish, flood homes, and cause many problems.
However, land development practices can be adapted to reduce or eliminate the damage caused by urban and suburban rainwater runoff.
Such pollution can cause problems for local streams and the aquatic life that lives in them.
Stormwater runoff collects a variety of pollutants, including litter, animal waste, oil, antifreeze, and pesticides.
3. Soil Erosion
Surface runoff causes erosion which often degrades landscapes immensely. The eroded soil is usually deposited downstream or in water bodies such as lakes, rivers, and artificial dams.
It’s worth noting that the strength or energy of a surface runoff significantly impacts the extent of soil erosion and often subsides over time.
Erosion can be reduced by using perennial grasses, such as switchgrass and big bluestem.
Buffers of perennial grasses left ungrazed on the borders between waterways and pastureland can help control runoff, which improves the water quality of rivers and streams.
Fact: Impervious surfaces are generally more prone to surface runoff than previous surfaces.
Rainwater, Plants, and Evapotranspiration
Plants absorb a lot of groundwater to keep themselves alive. Plants are a large medium when considering what happens to rainwater that falls on land.
The importance of water in the nourishment of plants cannot be understated because without sufficient water plants won’t survive.
Evapotranspiration is the sum of evaporation from the land surface plus transpiration from plants (i.e., the water they release through tiny pores in their leaves).
Like all living organisms, plants need water from the soil to carry out life processes.
Note: Plants absorb water through their roots, and about 90% of what is absorbed through roots is transpired back into the atmosphere through transpiration.
Evapotranspiration in Numbers
Unlike arid areas with little or no plants, heavily forested regions generally experience a lot of rain because of evapotranspiration.
Of the world’s annual 4,000 billion cubic kilometers of rainfall, 77 percent falls over water and 23 percent on land.
Because water evaporates more quickly from the seas than from continental areas, 83 percent of global evaporation comes from seas and oceans and only 17 percent from land and continents.
Significance of Rainwater that Falls on Land
Here are some of the importance of rainwater:
Support Aquatic Life
Rainwater supports several ecosystems in streams and lakes. Fish and other aquatic life forms depend on rain’s constant nourishment in their ecosystems.
Crop Irrigation
Rain can be harvested and stored in dams and can provide water for power plants and crop irrigation in places with unpredictable or insufficient rainfall.
Such crops would otherwise not be farmed in such environments.
Produce Hydroelectric Power
Rainwater fills rivers which can be tapped into dams that can be used to produce hydroelectric power.
Much of the world still depends on hydroelectric power as a source of energy which is a massive driver in almost all aspects of modern civilization.
Human Consumption
Rain is a source of fresh water which can be harvested for human consumption. Rainwater stored in tanks and ponds can help alleviate unexpected water shortages.
Rain is a Source of Humidity
Rainfall causes humidity in the atmosphere. Humid conditions have been refreshing and reduce blood pressure in humans and other mammals.
Humidity also helps in science explorations and manufacturing sectors.
Cultural Importance
Most cultures view rain as a source of rejuvenation, refreshment, fulfillment, and happiness.
Culturally, rain signifies optimism and a future filled with opportunities and abundance.
Agricultural Use
Much of the earth’s agricultural sector depends on rain for crop and livestock farming.
Rain nourishes grass which can be used to feed livestock and create sustainable livelihoods for millions of people.
It’s also worth noting the role rainfall plays in modern climate change mitigation strategies.
Warmer oceans increase the amount of water evaporated into the air, forming moisture-laden clouds.
These clouds move over land masses or converge into storm systems, producing more intense precipitation—for example, heavier rain and snowstorms.
The Cycles of Rainwater in Context
1. Rainwater On Land And Sea → Evaporation → Vapor → Clouds → Rain
Water from lakes and ponds evaporates due to the sun’s heat, turning into water vapor.
Water vapor mixes with the air and forms clouds. Clouds can’t hold much more water, so they release it as rain when they get too full.
2. Rainwater On Land And Sea → Condensation → Clouds → Rain → Groundwater
Under the right circumstances, rainwater on land and sea can condense, leading to cloud formation.
Once the clouds are heavy enough, the water falls back on land as rain but doesn’t end up on oceans, lakes, or seas. Instead, the water is stored as groundwater.
Groundwater can be harvested in boreholes, aquifers, and oases in arid and semi-arid areas.
Fact: This explains why even in the driest deserts when you dig deep enough, you'll always reach a water table.
3. Rainwater On Land And Sea → Evaporation → Clouds
Sometimes rainwater hits land or seas and evaporates to form clouds that aren’t heavy enough to create rain.
Such clouds hover around in the atmosphere over large distances. So it might be cloudy in your area, but you may not see any rain anytime soon.
4. Rainwater On Land And Sea → Condensation → Ice
Whenever rainwater loses heat energy, it freezes and becomes ice.
Condensation occurs when water vapor in the atmosphere cools down and changes into liquid water to form clouds.
This is the natural course of the water cycle in polar regions.
Fact: Winter blizzards also form when condensed water doesn't turn to liquid but falls on the ground as snow.
Read Next: How Do Large Bodies of Water Affect Climate?
Final Thought
What happens to rainwater that falls on land is that it goes through cycles of being stored as groundwater, absorbed by plants, forming surface runoff, or condenses into snow or ice.
Rainfall is very crucial for our existence on planet earth.
Many governmental and non-governmental organizations work tirelessly in transforming arid areas to receive more rainfall.
Such efforts include planting more trees through reforestation or preserving existing trees.
As an individual, you can also do your part by maintaining your environment to receive more rain so that it’s sustainable for all life.
