Effects of Uneven Rainfall: Causes, Effects, Examples

Rainfall is a form of precipitation. It is a natural phenomenon by which water droplets come back to the earth and evaporate to form clouds. Rainfall is the major source of freshwater that maintains the water cycle. Effects of Uneven Rainfall can cause many destructions and harm the ecosystem. 

When this rainfall occurs adequately, it seems a blessing to living creatures on the earth. But, if it occurs unevenly, lots of destructions may come. For example, very little or no rainfall for a prolonged period leads to drought, while too much rainfall in a particular area for a long tenure leads to flood. Both droughts and floods are natural calamities that cause huge losses to the country’s life, property, and economy. In this article, let’s learn everything about the effects of uneven rainfall in detail.

Effects of Uneven Rainfall

We know that our country is the global agricultural powerhouse, and Indian agriculture is rain-fed to a great extent, i.e., around \(55\%\) of the gross cropped area comes under rain-fed farming. Thus, it is very necessary to get an adequate amount of rainfall for an uninterrupted food supply worldwide. Various factors affect the distribution of rainfall around the earth’s surface, such as airflow direction, the temperature of the air, moisture-laden winds, ocean currents, distance inland from the coast, and mountain ranges.

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Define Uneven Rainfall

The rate of rainfall is not steady all the time. Sometimes, precipitation falls unevenly. Some days, we have no precipitation; some have steady light drizzle or snowfall, and a few days have copious downpours. This unevenness or asymmetry in rainfall patterns has certain impacts: Areas with little precipitation can lead to drought, while areas with prolonged heavy downpours can lead to floods. This irregularity in rainfall distribution all over the world is known as uneven rainfall.

Causes of Uneven Rainfall

The distribution of rainfall is uneven in different places because of the following reasons:

1. The direction of Winds – The places located on the windward side of the mountains receive more rainfall because when the moisture-laden winds strike the windward side of the mountains, it causes rainfall. On the other hand, the places located on the leeward side of the mountains get scarce rainfall.
2. A monsoon trough is a trough of low pressure that leads to unpredictability of the monsoon in different regions, resulting in uneven rainfall. The monsoon trough is also known as the Intertropical Convergence Zone. The trough and its axis keep on moving, northward or southward, which determines the rainfall distribution over a certain region. The plains receive rainfall when the trough lies over this region. When the axis shifts towards the Himalayas, the plains become dry and widespread rainfall occurs in the mountainous region.
3. Distance from the Sea: Places near the coastal region get more rainfall than the places situated far away from the sea. Cyclonic disturbances caused due to depression: The occurrence of cyclonic depressions, which originate over the sea, generally cross the coastal areas, cause heavy and widespread rain in those areas.
4. Geographical reasons:  Due to latitudinal extent, the coastal areas, tropical regions, and plains receive more rainfall than the plateau and deserts.
5. The rate of evaporation also affects the rainfall to a large extent. More water vapours get evaporated, more will be the precipitation.
6. Movement of Clouds – Clouds affect both weather and climate as they are the key elements of the water cycle. The precipitation conditions over a particular area depend upon the type and amount of clouds because clouds carry moisture from one place to another.
7. Global Warming – Due to global warming, as temperatures rise and the air becomes warmer, more water vapour evaporates from land and water into the atmosphere. More moisture in the air generally means more precipitation in rainfall and snow and more heavy downpours. The melting of Polar ice caps is also a significant result of global warming that increases the sea level. This plays a vital role in bringing floods.

Uneven Rainfall Effects

Due to several reasons for uneven rainfall, as discussed above, we notice many undesirable effects. Though rainfall is a boon to us if it occurs unevenly, it may lead to adverse effects, as discussed below:

1. Drought

A weather condition in which the rainfall is less than normal for a prolonged period of weeks, months, or years is known as drought. Mostly, areas that rely on rainfall and surface water are more likely to experience drought. A lack of water in stores such as rivers, lakes, reservoirs, and underground water can lead to drought. Surface water evaporates rapidly in warm, dry conditions leading to an increased risk of drought.

2. Flood

Due to continuous downpour for a prolonged period, the overflow of water in a huge amount beyond its limit, submerging the entire affected area, is known as the flood. It is one of the most dangerous effects of uneven heavy rainfall that leads to the dam burst, making the situation even worse.

3. Impact on Agriculture

The importance of monsoon cannot be overlooked for a country like India, where 60% of the population is dependent on agriculture for their livelihood. Agriculture in India is mostly dependent on rainfall for irrigation. Adequate rainfall is very important for sowing seeds to growing crop plants, also to maintain soil fertility. But agriculture is adversely affected by both droughts as well as floods. 

4. Effect on Economy

Again, agriculture plays a vital role in maintaining the economy of a country, especially India. Natural calamities such as drought and flood, along with irregular monsoon, reduces food stocks as well as food production for a particular year which eventually affects the GDP (Gross Domestic Product) rate of the country.

5. Effect on Ecosystem

Adequate rainfall is very important for the survival of all living creatures. Due to lack of fresh water, aquatic organisms and other plants and animals, including human beings, will suffer scarcity that may even be fatal. Also, in floods, the entire ecosystem gets disturbed when living organisms lose their habitats.

6. Landslide

The Himalayan range is vulnerable to torrential rainfall in the form of a cloudburst, flash flood, or glacial lake outburst flood. Cloudburst and flash floods occur due to high-intensity rainfall that may cause a landslide that blocks the river channels.

Examples of Effects of Uneven Rainfall

• 1. In India major impact of uneven rainfall is seen in agriculture. For example:
  • a) Floods in West Bengal affect the sowing of rice.
  • b) Poor rains in Maharashtra and Gujarat can affect the production of cereals, pulses, oilseeds, etc.
• 2. Heavy rainfall is relatively common in New Zealand. A huge amount of precipitation occurs in only a few hours, leading to severe flooding and landslide risk.
• 3. Flash floods in Teesta valley in \(1968\), in Sutlej valley in \(1993\) and \(2000\), and in Alaknanda river in \(1970\) are few examples of hazards caused by uneven rainfall.
• 4. The most vulnerable Johnstown Flood was so massive it matched the flow of the Mississippi River in the United States due to several days of drenching rain that broke the dam.
• 5. The worst drought that hit the region of Southern India over the past \(150\) during \(2016-2018\) was a result of a shortage in the northeastern monsoon.

Summary

Light and adequate rains come as a blessing for living beings, but when an area receives prolonged heavy rains in the absence of a proper drainage system, it becomes havoc causes damage to infrastructure, and takes lives due to floods. A sudden, heavy downpour of this type is called a cloudburst. 

At the same time, a lack of rainfall in an area for a long duration leads to drought. This uneven rainfall distribution is due to geographical set-up, direction and speed of the wind, clouds’ movement, evaporation rate, etc. But, along with these natural reasons, global warming is also playing a vital role in manipulating these rainfall patterns worldwide. 

Due to an increase in the temperature of the earth, polar ice caps are melting, which increases the chance of floods due to an increase in the sea level. Also, the rate of evaporation increases due to warm climatic conditions that may lead to hazards like a cloud burst. 

Thus, there are numerous reasons for uneven rainfall that should be checked because it causes loss to lives, infrastructure, properties, food supply, as well as economic growth of a country. To conclude, we can say that “rainfall is a boon as well as a bane”.

FAQs

Q.1. What is the consequence of uneven rainfall?
Ans: Various natural calamities like drought, floods, landslides, etc., are the consequences of uneven rainfall. Poor agriculture, the slow economic growth rate are also the indirect consequences of uneven rainfall.

Q.2. What are the causes of unequal rainfall?
Ans: The places located on the windward side of the mountains receive more rainfall because when the moisture-laden winds strike the windward side of the mountains, it causes heavy rainfall, while the leeward side receives less rainfall. Other causes of unequal rainfall include monsoon trough, distance from the sea, movement of clouds, global warming, etc.

Q.3. What is irregular rainfall?
Ans: The pattern of rainfall that may include a too high or too low rate of precipitation over a certain region which may lead to heavy rainfall or very low rainfall, is known as irregular rainfall. Both droughts, as well as floods, cause great loss to life and property.

Q.4. What has evenly distributed rainfall?
Ans: A reliable and adequate amount of rainfall in a particular period of the year is known as evenly distributed rainfall. An evenly distributed rainfall is a boon for all living creatures on the earth.

Q.5. Why is precipitation unevenly distributed throughout the world?
Ans: Due to certain geographical features on the earth, precipitation is unevenly distributed throughout the world. For example, the regions located on the windward side of the mountains receive more rainfall because when the moisture-laden winds strike the windward side of the mountains, it causes heavy rainfall, while the leeward side receives less rainfall. On the other hand, the regions located on the leeward side of the mountains get scarce rainfall.

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