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What is Rainwater Harvesting?

Updated: Apr 25

Rain Water Harvesting (RWH)

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rainwater harvesting

Rainwater harvesting is a technique used to collect, store, and manage rainwater that falls on rooftops, paved surfaces, and open areas for various beneficial uses. This method involves capturing rainwater and directing it into storage systems, such as tanks, cisterns, or underground reservoirs, where it can be stored and later used for purposes like irrigation, flushing toilets, laundry, and even drinking, after appropriate treatment.

"Don't Let Rain Go in Vain, Harvest It to Sustain!"

Rain harvesting systems can be tailored to suit the needs and capacities of different regions, whether they experience high or low levels of rainfall. Proper design, maintenance, and management are essential to ensure the safety and reliability of harvested rainwater for its intended uses.


Need for Rainwater Harvesting systems


Rain water harvesting systems are essential for several reasons, particularly in the face of increasing water scarcity and the need for sustainable water management practices. Here are some of the key reasons why rainwater harvesting systems are important:


  1. Water Conservation: Rain water harvesting helps reduce the demand on traditional water sources, such as groundwater and surface water bodies. By capturing and using rainwater for various purposes, less pressure is placed on these finite resources.

  2. Mitigating Water Scarcity: As global populations grow and water demand increases, many regions face water scarcity issues. Rain harvesting provides an additional water source that can supplement traditional sources during times of scarcity.

  3. Groundwater Recharge: In many areas, groundwater aquifers are being depleted faster than they can recharge naturally. Harvesting rainwater allows for direct recharging of these underground reservoirs, helping to replenish them.

  4. Reducing Runoff and Flooding: During heavy rainfall, excessive runoff can lead to flooding and erosion. Rain harvesting reduces the volume of runoff, easing the strain on drainage systems and decreasing the risk of flooding.

  5. Drought Resilience: Rain harvesting provides a decentralized and local water source, which is particularly valuable during droughts when centralized water supply systems might struggle to meet demand.

  6. Cost Savings: For non-potable uses such as irrigation, flushing toilets, and cleaning, using harvested rainwater can lead to reduced water bills, especially for commercial and residential buildings.

  7. Environmental Benefits: Rain water harvesting reduces the need for energy-intensive water treatment processes, decreases the energy footprint of water distribution, and helps protect water bodies from pollution caused by runoff.

  8. Sustainable Agriculture: Harvested rainwater can be used for irrigation, benefiting agricultural practices by ensuring a consistent water supply for crops, especially in regions with erratic rainfall patterns.

  9. Climate Resilience: Climate change is leading to more unpredictable rainfall patterns. Rainwater harvesting provides a locally controlled and adaptable source of water that can help communities better cope with changing climate conditions.

  10. Community Engagement: Implementing rain harvesting systems can engage communities in water management and foster a sense of ownership over local water resources.

  11. Educational Opportunities: Rain water harvesting systems offer educational opportunities to raise awareness about water conservation, sustainable living, and environmental stewardship.

  12. Regulatory Compliance: In some regions, rain water harvesting systems may be mandated by local regulations or building codes to encourage sustainable water practices.


Need for Rainwater Harvesting image view
Need for Rainwater Harvesting systems

Potentials of Rain Harvesting Systems

Rain water harvesting systems have significant potential and can offer a wide range of benefits across various sectors. Here are some of the key potentials of rainwater harvesting systems:

  1. Water Supply Diversification: Rainwater harvesting provides an additional source of water that can supplement traditional water supplies, reducing reliance on groundwater and surface water sources. This diversification enhances overall water security.

  2. Water Conservation: By capturing and using rainwater for non-potable purposes such as irrigation, flushing toilets, and cleaning, rain harvesting conserves freshwater resources and reduces demand for conventional water sources.

  3. Drought Mitigation: During droughts, when traditional water sources may become scarce, rain harvesting systems can serve as a reliable source of water for various needs, helping communities to better withstand water shortages.

  4. Local Self-Sufficiency: Rain water harvesting systems enable communities to become more self-sufficient in terms of water supply, reducing their dependence on centralized water distribution systems and enhancing resilience.

  5. Reduced Flooding: Rain harvesting reduces the volume of stormwater runoff, which can help prevent localized flooding and erosion, particularly in urban areas with impervious surfaces.

  6. Groundwater Recharge: When harvested rainwater infiltrates the ground, it contributes to the replenishment of groundwater aquifers, helping to maintain a sustainable balance between groundwater withdrawal and recharge.

  7. Sustainable Agriculture: Rain water harvesting can significantly benefit agricultural practices by providing a consistent water supply for irrigation, improving crop yields, and promoting more sustainable land use.

  8. Cost Savings: Using harvested rainwater for non-potable purposes can lead to reduced water bills, especially for larger consumers like commercial buildings, industrial facilities, and agricultural operations.

  9. Environmental Protection: Rain harvesting reduces stormwater runoff, which can carry pollutants into water bodies. By reducing runoff, the quality of local water bodies can be improved, benefiting aquatic ecosystems.

  10. Climate Resilience: Rain harvesting systems provide a decentralized and adaptable water source that can help communities better cope with changing climate patterns and more frequent extreme weather events.

  11. Educational Opportunities: Implementing rainwater harvesting systems offers educational opportunities for raising awareness about water conservation, sustainable living, and environmental stewardship.

  12. Community Engagement: Rain water harvesting systems can engage local communities in water management and promote a sense of ownership and responsibility for water resources.

  13. Regulatory Compliance: In some regions, rain harvesting systems may be required by regulations or building codes, encouraging sustainable water practices.

  14. Architectural Integration: Rain harvesting systems can be integrated into architectural designs, promoting sustainable building practices and adding aesthetic value.

  15. Resource Efficiency: By utilizing rainwater, a free and readily available resource, rainwater harvesting contributes to resource efficiency and reduces the ecological footprint of water consumption.

The potential benefits of rainwater harvesting systems extend to both urban and rural areas, and their adoption can play a significant role in addressing water-related challenges, promoting sustainability, and building climate-resilient communities.


RAINWATER HARVESTING COMPULSORY FROM BWSSB


In 2009, the BWSSB introduced an amendment to its Act and made rain water harvesting mandatory for certain sites. In

the BWSSB Act, 1964 (Karnataka Act No.36 of 1964), Section 72-A Obligation to provide rain water harvesting structure has been

inserted. The Bangalore Water Supply and Sewerage (Amendment) Act, 2009, 72A-Obligation to provide rainwater harvesting

structure states that “Within nine months from the date of commencement of the Bangalore Water Supply and Sewerage

(Amendment) Act, 2009 every owner or occupier of a building having a sital area of 2400 square feet and above or every owner

who propose to construct a building on a site area of 1200 square feet and above shall provide for a rainwater harvesting structure

in such manner, with such conditions as may be provided in the regulations, failing which the Board may cause such rainwater

harvesting structure and recover the cost from the owner or occupier, as the case may be, arrears of land revenue.”


A). Roof-based rainwater shall be harvested through a storage tank or

recharged through an open well or a bore well in the building

irrespective of the nature of sub-soil conditions.

B). Land-based rainwater from the open spaces around the buildings/

gardens parks shall be harvested using appropriate groundwater

recharge structures depending on the nature of the sub-soil conditions.

Rainwater storage (surface tank or underground sump) and ground

recharge (RCC precast ring well) of a minimum 20 liters per square

meter of roof area and a minimum of 10 liters per square meter of

paved open space provision Shell be made.


Minimum Requirements for Rain water Harvesting:


Rainwater storage (surface tank or underground sump) and ground recharge (RCC precast

ring well) of a minimum of 20 liters per square meter of roof area and a minimum of 10 liters per

a square meter of paved open space provision Shall be made.

• The open well / recharge well of depth of 3 meters (minimum) and a diameter of .9 meters

(minimum) without filling In the well (like aggregates, jelly, sand, etc.) provision shall be made.

• You may store rainwater in a tank/sump or recharge rainwater into the ground through a well

or you can use a combination of these two to achieve the stipulated capacity of ‘X’ liter.

Where X = roof area in sqm x 20 + paved Open area in sqm x10.

• The open well should be a of minimum 3 feet in diameter and 10 feet deep.


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