23 Facts about Rainwater Harvesting

The practice of harvesting rainwater has been around for thousands of years, but many people today have become dependent on tap water, bottled water, and other sources of water provided to them. However, in recent years, rainwater harvesting has become increasingly popular. This is especially the case among homesteaders, preppers, and people living off-grid.

Rainwater is one of the purest forms of water because it is naturally distilled during the evaporation process. Before people use rainwater, it should be filtered and purified to remove the chemicals and sediments it collects as it falls from the clouds. Once filtered, it can be used for drinking, watering plants, bathing, and other uses. Also, the shelf life of filtered rainwater is extended from 1 week to up to 6 months.

As climate change causes severe droughts globally, rainwater harvesting has the potential to be an international trend in the near future. It can provide millions of people with a way to secure their water supply.

Below are some interesting facts about rainwater harvesting that will help you gain knowledge and learn about the age-old practice.  

Facts about Rainwater Harvesting

• For all water uses, the average person uses 80-100 gallons of water every day. If you collect 12,000 gallons of water, you can take care of four people for about 30 days (source).
• In the United States, the average person consumes approximately 90 gallons of water per day. The toilet accounts for 24% of total daily water consumption, while the shower accounts for 20% (source).
• For every inch of rain that falls on a 1,000-square-foot roof, 600 gallons of rainwater can be collected (source).
• Rainwater is beneficial for watering your garden plants. It has nitrate, a bio-available form of nitrogen, which is essential for plants to thrive and shine a bright green. Rainwater is also free from chemicals and salt, which can be harmful to plants (source). 
• When used as drinking water, harvested rainwater has a shelf life of one week. To make it last longer, it will need to be purified through a filtration system. Once purified, it can last up to 6 months in the fridge (source).
• Acidic rainwater tainted by pollution-related pollutants will have a pH level below 4.0, which is unsuitable for plant growth. Plants only grow in a mildly acidic environment or a pH level between 5.5 and 7.0 (source).
• Virga is the term for rainwater that is evaporated before it reaches the ground (source).
• There are four ways you can clean your harvested rainwater (source). These are:
  • Filtering the water before it enters the storage tank
  • Oxygenating the water
  • Siphoning off any floating particles
  • Placing a moving fine mesh filter before the pump.

Facts about Rainfall and Precipitation  

• The average yearly rainfall across the whole Earth is 39 inches (100 cm). The wettest places are around the equator, and the places with the least rainfall are located in subtropical deserts and near the poles (source).

• Countries with the highest average annual rainfall are (source): 
• 1. Colombia (128 inches)
  2. Sao Tome and Principe (126 inches)
  3. Papua New Guinea (124 inches)
  4. Soloman Islands (119 inches)
  5. Panama (115 inches)
  6. Costa Rica (115 inches)
  7. Malaysia (113 inches)
  8. Brunei Darussalam (107 inches)
  9. Indonesia (106 inches)
  10. Bangladesh (105 inches)

• Regions with the highest average annual rainfall (source):
  1. Mawsynram, India (467 inches)
  2. Cherrapunji, India (464 inches)
  3. Tutunendo, Colombia (464 inches)
  4. Cropp River, New Zealand (453 inches)
  5. San Antonio de Ureca, Bioko Island, Equatorial Guinea (411 inches)
  6. Debundscha, Cameroon (405 inches)
  7. Big Bog, Maui, Hawaii (404 inches)
  8. Mt. Waialeale, Kaui, Hawaii (384 inches)
  9. Kukui, Maui, Hawaii (366 inches)
  10. Emei Shan, Sichuan Province, China (322 inches)

• US Cities with the highest average annual rainfall (source):
  1. Miami, Florida (67 inches)
  2. New Orleans, LA (63 inches)
  3. Birmingham, AL (57 inches)
  4. Houston, TX (56 inches)
  5. Memphis, TN (55 inches)
  6. Orlando, FL (52 inches)
  7. Nashville, TN (51 inches)
  8. Atlanta, GA (50 inches)
  9. New York, NY (50 inches)
  10. Tampa, FL (50 inches)

Facts about the History of Rainwater Harvesting

• Evidence suggests humans have been harvesting rainwater for over 7,000 years. The oldest known infrastructure dates back to 5,000 BC in the Indus Valley (source).
• Rainwater harvesting was a common practice in the Roman Empire. Communities that did not have access to Roman aqueducts relied on rooftop reservoirs and cisterns for their water needs (source).
• Venice, Italy, has a rainwater collection system since the lagoon in which the city is located is brackish water. In the past, when it would rain, water would go through the stone flooring and be filtered through a layer of sand before being collected at the bottom of a well (source).

Facts about Water Consumption

• In the US, 1% of all water consumed is for domestic consumption. 41.4% of water consumed is used for thermoelectric power, and 36.7% of water consumed is used for agriculture irrigation (source).
• Two-thirds of the global population, 4 billion people, experience some form of water scarcity for at least one month out of the year. Nearly 2 billion of those people live in India and China (source).  
• Each year, it is estimated that contaminated drinking water causes 485,000 deaths. Common diseases caused by dirty water are diarrhea, cholera, dysentery, typhoid, and polio (source).

Facts about Rainwater Harvesting Policies across the World

• Between 2003 and 2012, a number of Australian states, including Victoria, experienced severe drought. Victorian water storage levels fell by 20% in 2003, and by 2009, they had fallen to a record low of 25.9%. The Australian government introduced incentives to encourage people to recycle water and use rainwater harvesting technology in an effort to combat the drought (source).
• Following a drought in 1995, the Gansu provincial government in China launched a project to encourage rainwater harvesting. The goal of this initiative was to make sure each family would have several rainwater collection cisterns for every acre of agricultural land. Within a year of the project’s launch, 1.31 million people had gained access to domestic water (source).
• About 50% of Singapore’s land area is used as a catchment for rainwater harvesting. In Singapore, catchment areas are secured locations where no pollution-causing activities are allowed within proximity of the location (source).
• Rainwater harvesting is used by approximately 40% of Thailand’s rural population. The government heavily promoted rainwater harvesting in the 1950s. After government funding for collection tanks ran out in the 1990s, the private sector stepped in and provided several million tanks to private households, many of which are still in use today. This is one of the world’s largest examples of self-supply of water (source).
• Rainwater can be collected freely in the United States. However, some states like Arkansas, Colorado, Georgia, Illinois, Nevada, Texas, and Utah have regulations governing the people’s ways of rainwater collection (source).

Final Thoughts

All in all, harvesting rainwater has been practiced for thousands of years, and as the world experiences climate change, it is viewed as a sustainable form of sourcing water. If you intend to collect rainwater for drinking, it is important to purify and filter it before use. Rainwater exposed to sunlight and the environment can easily be contaminated and lead to illness. However, by filtering it properly, you can store rainwater for up to 6 months in the fridge.