Effective Methods Of Rainwater Harvesting: Don’t Let It Go Into The Drain

  • July 19, 2023

Rainwater harvesting is a significant practice that contributes to the conservation of water resources. It involves collecting and saving rainwater during the rainy season from various surfaces such as roofs, yards, hills, or paved areas. By effectively harnessing rainwater, we can gather clean and safe water for different uses. Let’s explore the significance of rainwater harvesting, techniques and methods of rainwater harvesting and the key measures to make it effective.

Importance of Rainwater Harvesting

Rainwater harvesting is crucial for managing stormwater, especially in new buildings. It provides a sustainable water source for various household activities like drinking, washing, bathing, and cooking. With increasing water bills and unpredictable weather patterns, collecting rainwater from rooftops can save money and benefit the environment. Additionally, various types of rainwater harvesting methods reduce the demand for municipal water resources, thus promoting the sustainability of the drinking water supply.

Methodology of Rainwater Harvesting

To understand the method of rooftop rainwater harvesting system functions, it is essential to consider the following elements:

  • Roof Area:

    The system relies on collecting rainwater from the rooftop’s surface. The first step is determining the total square footage that will be covered by the roof and used for rainwater collection.

  • Rainfall Patterns:

    The average monthly and annual rainfall of the region where the system will be implemented should be considered. This data helps in estimating the potential volume of rooftop rainwater that can be harvested.

  • Water Demand:

    It is crucial to determine the monthly water demand and identify when it peaks. This information helps design the system’s storage capacity to meet the required water supply during peak demand.

  • Functionality Requirements:

    For a rooftop rainwater harvesting system to operate as planned, it should meet the criteria mentioned above, including sufficient roof area, appropriate rainfall levels, and storage capacity matching the demand.

Two primary methodologies of rainwater harvesting can be chosen for collecting rainwater:

Rooftop Collection:

This method of rainwater harvesting involves collecting rainwater directly from rooftops, which serve as the catchment area. The rainwater is typically directed into gutters and downspouts, leading to storage tanks or cisterns.


Surface Runoff Collection:

This method of rainwater harvesting involves capturing rainwater from paved surfaces such as driveways, pathways, or roads. The collected water is directed toward pits, wells, trenches, or shafts, allowing it to infiltrate the soil gradually. This is not possible in areas with frequent floods.

By implementing these methods and ensuring that water quality and availability are not compromised, rainwater harvesters can utilize the collected water for various purposes, just as they would with other water sources.

The Four Cornerstones of an Effective Rainwater Harvesting System

To ensure the effectiveness of a rainwater harvesting system, focus on the following aspects:

  1. Water Quality:

    The harvested water from the rooftop during the rainy season should be crystal clear, taste fantastic, have no odor or color, and be free from bacteria. Proper filtration and maintenance of the system are necessary to maintain water quality.

  2. Water Pressure:

    The system should provide water with maximum feasible pressure while staying within acceptable limits. This ensures efficient use of the harvested water for various purposes.

  3. Water Storage:

    The stored water should remain clean, odourless, and free from slime. Regular cleaning and maintenance of storage tanks and containers are essential to ensure the water’s integrity.

  4. System Design:

    A well-designed rooftop rainwater harvesting system should fulfil the local supply and demand requirements. It should be planned to optimize the collection, transportation, filtration, and storage processes.

Rooftop Rainwater Harvesting

Rooftop rainwater harvesting is a popular method that utilizes the roof as the primary catchment area. Here’s how it works:

  1. Catchments:

    The rooftop serves as the catchment area where rainwater directly falls. It can be a flat RCC/stone roof, sloping roof, courtyard, or any other suitable surface.

  2. Transportation:

    Rainwater from the rooftops is transported to the harvesting system using water pipes or drains. Properly sized pipes with UV resistance ensure efficient water flow.

  3. First Flush:

    To prevent contamination, a first flush mechanism removes the initial rainfall, which may contain pollutants from the rooftop and atmosphere. This mechanism helps maintain water quality and clears debris from the roof.

  4. Filtration:

    A reliable filtering system is crucial to prevent contamination of the stored water. Installing a filter with sand, gravel, and mesh on top of the storage tank helps remove organic matter and debris.

Rainy season

Key Components of Rainwater Harvesting Systems

  • Catchments:

    The catchment refers to the surface area that directly receives rainfall and supplies rainwater to the rainwater harvesting system. It can include various structures such as terraces with flat RCC/stone roofs or sloping roofs, courtyards, and open land, whether paved or unpaved.

  • Transportation:

    Rainwater from the catchment is transported to the rainwater harvesting system through water pipes or drains. To prevent floating materials from entering the system, it is essential to place wire mesh over each drain mouth. The water pipes should be designed to have sufficient capacity and resistance to UV degradation.

  • First Flush:

    A mechanism known as the first flush is employed to remove the initial rainwater runoff. This step is crucial for preventing contamination in the storage tank, as the catchment rooftop and the atmosphere may contain various pollutants. Additionally, the first flush helps clear out accumulated debris and dirt on the roof during dry periods. Once the initial flush is complete, rainwater flows through filters.

  • Filters:

    One common concern about rooftop rainwater harvesting is the potential contamination of groundwater if an inadequate filtering system is employed or if the underlying sewer drains are compromised. To address this concern, it is important to install a filter system. Typically, a combination of sand, gravel, and mesh filters is placed on top of the storage tank. These filters effectively prevent organic matter such as leaves, silt, dust, and other debris from entering the tank.

Techniques of rainwater harvesting

  • Maintenance of rainwater harvesting system

    It is crucial to note that the filter media requires thorough cleaning after each rainfall event. This regular maintenance ensures the continued effectiveness of the rainwater harvesting system by removing accumulated debris and contaminants.

By incorporating these key components into rainwater harvesting systems, individuals can harness rainwater effectively while minimizing the risk of groundwater contamination.

Common Rainwater Harvesting Techniques for Rooftops

  • Direct Use Storage:

Rainwater is collected from the rooftop and directed to a storage tank. The design of the tank is based on factors such as the catchment area, rainfall patterns, and water requirements. It is important to connect the tanks to an excess water overflow system. Any excess collected water can be directed to a recharge system. This technique offers energy savings by reducing the need for external water delivery and transportation.

Rooftop rainwater harvesting

  • Adding Water to Underground Aquifers:

Rather than allowing rainwater to flow onto the ground, this technique involves directing the rainfall into various structures for recharge. Some common recharge techniques include:

  • Filling up of excavated wells:

    Rainwater is directed into excavated wells to replenish the groundwater levels.

  • Replenishment of bore wells:

    The collected rainwater is treated and recharged into bore wells to enhance their water storage capacity.

  • Trenches for recharge:

    Recharge trenches, filled with porous materials such as pebbles, rocks, or brickbats, facilitate the percolation of rainwater into the ground.

  • Refilling pits:

    Pits are created to collect rainwater, which then percolates into the ground.

  • Shafts of recharge or soakaways:

    These structures are designed to allow rainwater to percolate effectively into the soil layers.

  • Filling Up Bore Wells:

          Rainwater is collected from the rooftop and directed to a settling tank for purification. The purified water is then recharged into underground aquifers through bore wells. It is important to use a rain separator to remove silt and floating debris that could clog the recharge structure. The first one or two showers should be diverted away to prevent initial contamination.

  • Filling Up of Dig Wells:

Recharge trenches are suitable for areas with shallow topsoils, such as small homes, parks, playgrounds, and roadside gutters. A trench is excavated and filled with porous materials like pebbles, rocks, or brickbats. Borewells can also be installed within the trench as recharge shafts to facilitate effective percolation. The dimensions of the trench depend on the expected runoff volume.

  • Shafts of Recharge or Soakaways:

This technique involves selecting an area with looser or less compact soil in the upper layer compared to the underlying soil. Boreholes are drilled with a standard diameter of 30 cm and a depth of 10 to 15 m. The rainwater is then directed into these boreholes for recharge.

  • Filtration Tanks:

Percolation storage reservoirs, also known as filtration tanks, are artificial surface water bodies designed to submerge a piece of land with sufficient permeability for rainwater percolation and groundwater recharge. These tanks are particularly suitable for large campuses with appropriate topography and available land for gardens, open areas, and landscaping features.

By employing these common techniques of rainwater harvesting on rooftops, individuals can effectively utilize rainwater resources while contributing to groundwater recharge and conservation.

Surface Runoff Harvesting

Capturing rainwater in confined areas such as pits, wells, trenches, or shafts and allowing it to infiltrate the soil gradually is known as surface runoff harvesting. This technique is employed when rainwater collection from roofs and paved surfaces alone is insufficient for year-round water supply. Although surface runoff harvesting does not offer immediate benefits, getting it built by your real estate developer ensures the long-term availability of groundwater resources.

Key Points to Remember:

  • A land area with a minimum slope of 5% (about 3°) is necessary for generating runoff.
  • Runoff water is collected in a small reservoir or pond created by constructing earthen bunds or embankments, directing the flow towards the lowest point.
  • Storage tanks should be equipped with pond liners to minimize infiltration.
  • The storage space and catchment area should be located in close proximity.
  • Planting tree species, shrubs, or grass along the edge of the storage area helps prevent silting and erosion.

Pros of Rainwater Harvesting:

  • Free Water:

    Rainwater collection allows for the utilization of a free water source. By efficiently collecting and storing rainwater in tanks or cisterns, individuals can reduce their dependence on municipal water supplies.

  • Environmental Safety:

    Rainwater harvesting is a socially and environmentally acceptable practice that promotes self-sufficiency and water conservation.

  • Awareness of Water Usage:

    Harvesting rainwater encourages individuals to become more conscious of their water consumption, leading to more efficient water usage habits.

  • Reduced Dependence on Imported Water:

    Rainwater collection can decrease the reliance on imported water in communities that currently rely on external sources to meet their water needs.

  • Optimal Water Use:

    By storing treated rainwater for appropriate uses, rainwater harvesting systems assist utilities in reducing peak water demand during summer months.

  • Stormwater Flow Reduction

    Rainwater collection systems help mitigate stormwater flow on properties, reducing the risk of streambank erosion and maintaining stable watercourses.

  • Energy Savings

    Using rainwater instead of municipal water reduces the amount of water that needs to be treated and pumped, resulting in decreased energy consumption.

Cons of Rainwater Harvesting:

  • High Maintenance Cost:

    Properly installed water storage tanks require regular cleaning and maintenance, which can be costly. Poor installation or unstable ground conditions may lead to tank fractures and structural issues.

  • Potential Contamination Hazards:

    Some roofs may contain lead or other hazardous substances, making rainwater from those surfaces unsuitable for certain uses, such as gardening. Floods are also an issue when it comes to rainwater harvesting.

  • High Start-Up Costs:

    The initial investment for rainwater harvesting systems can be expensive, although long-term savings can be achieved. The cost varies based on the size and type of storage tank chosen.

  • Size Restrictions:

    The capacity of rainwater harvesting systems depends on the size of the storage tank. Larger tanks are more expensive, posing challenges when balancing the demand for a larger tank against cost considerations.

  • Unpredictable Rainfall:

    Depending on rainwater as a primary water source may be challenging in areas prone to drought or irregular rainfall patterns, leading to higher costs for rainwater harvesting systems with larger storage capacities.

Summing Up

As global water scarcity worsens, it is crucial to take steps to conserve water. Rainwater harvesting at an individual level is an effective approach to water conservation. Careful consideration of the benefits and drawbacks is essential before deciding to implement rainwater harvesting systems. Choosing residential properties that prioritize rainwater harvesting, such as those developed by AsmitA India with sustainability initiatives like AsmitA Grand Maison, can contribute to a more sustainable future. AsmitA Grand Maisons are a group of luxury, sustainable apartments that perfectly balance aesthetics and functioning. By taking action now, individuals can make a positive impact on the environment and work towards addressing the impending water crisis.

By asmitarealty

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