Rainwater is one of the most common harvested water sources. Rainwater can be collected and stored for various purposes, such as using it to water plants, flush toilets, clean surfaces and even drink (although this is highly discouraged).
Most people want to store rainwater for future use or need. There are many methods of harvesting rainwater (and may be used simultaneously in different parts of the property). The best method depends on the purpose for which rainwater is needed and the available space for storage.
- Rainwater Basins/Wet Ponds
They are great for water harvesting and can hold more than enough water for multiple uses. It is easy to build one, just dig a pond around the size you want. Make it at least six inches deep if you want to use it for bathing.
To make it easier to harvest the water, make sure there are no obstructions above the basin, like tree branches or power lines. The basin will catch any water that flows over these surface areas. It may be a good idea to use clean gravel or sand at the bottom of the pond for filtration purposes. This allows for easy harvesting.
Cisterns are excellent water harvesting systems for water storage, especially for large areas that require significant amounts of harvested rainwater. They come in various sizes to fit different needs (for example one cubic meter cistern can hold up to 15 gallons) and they are very easy to build.
To build a cistern, all you need is a water-tight container and waterproof guttering. Make sure the system does not lose too much water to evaporation during the harvesting period.
- Rainwater Tanks
These can be an excellent option for those who want to store rainwater for drinking and cooking purposes only. Rainwater tanks are unlike cisterns in that they have to be elevated off the ground. Designing a rainwater tank system does not require much thinking, but remember that the larger the tank is, the more water it will store.
- Water Barrels/Drums
This method is effective for small-scale water harvesting. This method is also great for storing rainwater for small-scale irrigation tasks, like watering the garden or cleaning the car. There are many water barrels available to suit different needs.
If you want to store rainwater for irrigating fruit trees, you will need a larger container/barrel than if you just wanted to use it to water vegetables and herbs. Water barrels can be made from plastic drums, fibreglass tanks or metal tanks.
- Soil Cisterns
This method is effective for rainwater harvesting in arid regions that are unable to hold much water. This system has been around for many years, but until recently it was not well known. Water is stored in the ground under natural conditions, making this method very cost-effective.
This system can hold 400 to 600 gallons of water per 1000 square feet area. To build soil cisterns you need a pit that will be dug into the ground and lined with polyethene sheeting to prevent it from falling into the pit. To prevent the soil from leaking, it is recommended that you use an impermeable sealant. Water is collected when rain falls over the soil cistern using a drainage system installed around the pit’s walls.
- Water Walls/Hammocks
This method works in areas with slow-moving water bodies like ponds and lakes. A water wall is a dam created to trap water coming from the surrounding land areas, such as rivers and creeks (for example). If you want to store rainwater for personal use or irrigation purposes, make sure that the water body does not contain pollutants. Water stored in this way can provide 40 gallons per square foot of water wall.
- Sand Pits/Sand Traps
This method is great for catching and storing rainwater, but it requires more work than the other methods mentioned above. To build a sandpit you will need to dig a square-shaped pit approximately two feet deep and four feet wide at the top and up to 12 feet deep at the bottom of the pit. Fill the pit with clean, coarse sand and make sure it is level all around. That’s all! Now, whenever it rains your sandpit will automatically fill up with water.
- Cement Basin/Bowls
This rainwater harvesting method is very simple and effective, but if you don’t build it properly it can cause problems during the harvesting time. Cement basins are usually made out of cement, stone or brick.
To make one you need to dig a hole that is two feet deep and wide enough for the chosen material to fit into. You then fill half of the basin with sand or gravel followed by water. The basin/bowl should then be filled 3/4 full with stone or brick pieces. Cement basins are more effective if they are situated on a slope (with water flowing towards them).
- Roof Water Storage System
This method incorporates a barrel connected to a downpipe at the same level as the gutters, so your house can easily connect to the water harvesting system. To build this kind of system you need to place a barrel that is 45 gallons or larger under each downpipe outlet. It is recommended that you use food-grade barrels since they are more resistant to microbial activity and will not let contaminants through.
- Sand Filter Barrel/Rain Barrel
This method is similar to the roof water storage system, but it doesn’t require any professional help. A rainwater harvesting system using a large container is usually set up in the yard, where rainwater from your roof is stored for later use.
To make this kind of system you need a container, preferably 45 gallons or larger. It is recommended that you use food-grade barrels since they are more resistant to microbial activity and will not let contaminants through.
The container should have a hole in the bottom to ensure water can flow inside the barrel, so now all you need to do is fill it with sand or gravel, place it against your downpipe outlet, connect them using piping and connect the filters to your gutters. You must choose floodwaters a place for your rain barrel where it can be easily observed and checked for leaks, as water leakage can cause damage to the filtering system.
Benefits of Rainwater Harvesting
Harvesting rainwater helps in the conservation of groundwater.
– It decreases soil erosion and flooding in urban areas because water is collected before it can enter storm drains.
– Rainfall harvesting reduces demand for freshwater by allowing residential, agricultural, commercial and industrial buildings to carry on with normal activities even if their access to fresh water has been cut off. This can happen during water shortages, emergencies or natural disasters.
– Harvesting rainwater saves on the use of fresh water for irrigation purposes which significantly reduces the levels of saltwater intrusion in coastal regions.
– It can be used to flush toilets and wash cars with no extra effort required from the user. This contributes directly to saving energy.
– Harvesting rainwater helps in conserving energy because water is usually heated before being supplied to homes. In hot climates, there is a more significant positive impact on the conservation of energy.
– Rainwater harvesting can significantly reduce flooding of low lying areas of land by seasonal rains and heavy downpours during tropical storms and hurricanes. This also reduces the need to build dykes around coastal regions.
– Collecting rainwater helps in protecting water quality because it intercepts dirt and sediment before they enter storm drains and water bodies. This keeps domestic water supplies clean and saves on the cost of cleaning contaminated waters after a flood.
– Harvested rainwater can be stored for future use from different water sources including rivers, lakes and underground aquifers.
– The harvesting of rainwater contributes to the conservation of landscape in areas that would otherwise have been irrigated with fresh water. This is especially beneficial for desert regions where rainfall may be scarce and expensive to obtain.
– It reduces demand on groundwater resources due to the lack of water required for construction and landscaping.
– Rainwater harvesting also reduces air pollution because it curbs the emission of gases such as sulfur dioxide and nitrous oxide, which are released through the burning of fossil fuels to generate freshwater that is supplied to homes.
– Rainwater collection helps in protecting marine life by preventing erosion and sedimentation of coastal waters.
– Rainwater harvesting results in better water quality by preventing the entry of contaminants and pollutants into freshwater sources such as reservoirs and rivers. It also protects ground-based aquifers which become contaminated with polluted rainwater runoff from streets, rooftops, industry and agricultural land.
– Harvesting rainwater from roofs avoids the energy costs associated with pumping water from ground sources.
– It reduces the need to use water treatment plants because rainwater is collected before it can enter storm drains, which are usually connected to these plants.
– Harvested rainwater contributes directly to saving fuels that would have otherwise been used for pumping of groundwater and for providing freshwater supplies to homes.
– Collecting rainwater helps to protect aquatic vegetation by halting the erosion of soil and sediments into rivers, lakes and oceans. This ensures that the water bodies remain clear for other uses such as fishing, crop irrigation and swimming.
– Harvested rainwater can also be used to recharge groundwater aquifers because it percolates through the soil and recharges the water table in a process known as groundwater recharge.
– Harvested rainwater also helps in protecting wetlands by preventing runoff from entering these habitats. Wetlands provide a home to a diverse range of species, store floodwaters and help in reducing soil erosion. Their protection is important for maintaining biodiversity which contributes to ecosystems’ resilience.
What are the methods of rainwater harvesting in India?
- Roof Water Harvesting
- Surface Water Harvesting
- Ground Water Recharge
- River Surplus Flow Collection (not applicable to India).
- Water Table Recharge (not applicable to India).
- Rainfed Agriculture Recharge.
These are the most widely used methods in India. The method of rainwater harvesting that will be followed depends upon the climate and availability of water.
What are the 2 types of rainwater harvesting?
There are two types of rainwater harvesting: direct and indirect. Direct rainwater harvesting typically involves collecting water from rooftops, tiled surfaces, or other open-source areas where the water isn’t contaminated with chemicals or leaves.
Indirect rainwater harvesting uses channels to divert water away from roofs into large tanks that can then be used for crop irrigation or human consumption. This type of collection is more common in regions where drought is a problem.