Quick Key Facts

Water harvesting involves collecting and storing water from various sources such as rain, stormwater runoff, gray water, snow, air, and fog. It can be used for nonpotable purposes like irrigation, toilet flushing, and laundry, as well as potable use like drinking water. Rainwater harvesting can help alleviate water scarcity in densely populated areas and reduce the demand on municipal water supplies, which often affect distant communities and ecosystems.

However, rainwater collected from unclean surfaces is not suitable for drinking and needs to be purified. Water treatment processes like flocculation, settlement, and biofilm skimming can remove bacteria, organic material, and chemicals. Pre-filtered water can also be disinfected through solar water disinfection or treated with chlorine.

In some areas of the United States, rainwater harvesting is viewed as a water rights issue, leading to restrictions on the practice. However, it can also be used to recharge groundwater supplies and provide potable water during shortages, contamination events, natural disasters, and other situations where drinking water availability is disrupted.

What Is Water Harvesting?

Water harvesting involves collecting rainwater or water from the atmosphere for drinking and irrigation purposes. It has been practiced for thousands of years and is an effective way to conserve water, especially during dry seasons, while also saving money and protecting groundwater supplies. Furthermore, it provides a solution for areas facing water scarcity.

Currently, droughts are becoming increasingly common worldwide. In 2022, severe and extreme drought classifications affected large portions of the Western United States. According to the United Nations, 2 billion people lack access to clean drinking water, and an estimated 4 billion people experience severe freshwater shortages for at least one month each year. This number is projected to rise to 4.8-5.7 billion by 2050 due to factors like climate change, polluted water sources, and population growth.

Rainwater harvesting has seen steady growth, with $6 billion spent on rainwater harvesting systems in 2020. This market is projected to increase by 4% by 2027.

History of Rainwater Harvesting

Rainwater harvesting has a long history, with evidence of its practice dating back thousands of years in Asia, the Roman Empire, the Middle East, and India. Various methods, like taankas in India or trenches in indigenous U.S. cultures, were used to collect rainwater for household use, dryland farming, irrigation, and livestock. Rainwater collection lost popularity at times but regained traction in the 1950s, particularly in Australia and later in the U.S. and Africa for livestock and crop purposes.

Rainwater Harvesting and the Environment

Rainwater harvesting offers several environmental benefits:

• Reducing energy use and carbon emissions by saving energy needed for wastewater treatment.
• Replenishing groundwater supplies by releasing rainwater into the ground, recharging the soil.
• Creating healthier soil and plants by providing chemical-free water with a balanced pH.
• Reducing runoff and preventing contamination of ground and water sources.
• Reducing the overuse of groundwater in urban areas.

Where Can Rainwater Harvesting Be Used?

Rainwater harvesting can be used in various applications, from simple to elaborate systems. Simple systems involve collecting rainwater in barrels or tanks through pipes connected to rain gutters. These systems, known as “dry systems,” do not hold water in the pipes after rainfall and do not attract insects. “Wet systems” are used when pipes need to cover long distances or serve multiple areas, utilizing a pressurized system and mosquito-proof screens and filters.

Historically, rainwater harvesting has been used for domestic purposes like drinking water and household tasks. It can be collected from rooftops or the ground. Roof catchment systems collect water through gutters and pipes and store it in ground-level rain barrels.