Can  Rainwater Harvesting Contribute to Climate Change Adaptation?

We all know that 71 percent of the Earth is covered by water, 96.5 percent of which is covered by oceans, and only 2.5 percent of fresh water is used for human needs. So we have only a limited amount of fresh water on the earth. Most of the Earth’s water is saltwater, which is unsuitable for human consumption or agriculture. Of the remaining freshwater, much of it is locked up in glaciers and polar ice caps, leaving a relatively small amount available for human use. Conserving and protecting this limited resource is essential to ensure its availability for future generations. But climate change is also likely to affect this limited supply of water.

Climate change is likely to result in changes in precipitation patterns, with some areas experiencing increased rainfall while others experience drought. This can lead to changes in freshwater availability, with some areas having more water than they need while others suffer from water scarcity. And Rising temperatures can cause more evaporation from rivers, lakes, and other freshwater sources. This can lead to reduced water levels and increased salinity, making using the water for human consumption or irrigation more challenging. In addition, climate change is causing glaciers and snowpacks to melt at an accelerated rate, which can lead to flooding in the short term and reduced water availability in the long term. Many regions depend on glaciers and snowpacks as a primary source of freshwater. Also, Climate change can impact water quality. For example, increased temperatures can increase harmful algal blooms, contaminating freshwater sources and making them unsafe for human consumption.

Overall, climate change is likely to impact freshwater resources significantly, and it is essential to mitigate its effects and ensure that everyone has access to safe and clean water. Therefore, freshwater conservation is being done through various methods worldwide. One of the most effective practices in that regard is rainwater harvesting.

What is rainwater harvesting?

Rainwater harvesting is collecting and storing rainwater that runs off from rooftops, parks, open grounds, etc. This water runoff can be either stored or recharged into the groundwater. More read. Link. Archived

Rainwater harvesting helps conserve freshwater resources by reducing reliance on groundwater and surface water sources. Collecting and using rainwater can lower the water we take from these sources, which can help preserve them for future generations. It can significantly reduce our water bills by providing a water source for non-potable uses such as irrigation, flushing toilets, and washing clothes. This can lead to significant cost savings over time. Also, it can help to manage stormwater by reducing runoff and preventing flooding. By capturing rainwater on-site, we can reduce the amount of water that flows into storm drains and reduce the risk of flooding. Rainwater is generally free from chemicals and contaminants found in tap water. By using rainwater for non-potable purposes, we can reduce our exposure to these chemicals and improve the overall quality of the water in our environment. Rainwater harvesting is a sustainable practice that promotes environmental stewardship and reduces our impact on the planet. By conserving water and reducing our reliance on traditional water sources, we can create a more sustainable future for ourselves and future generations.

Why is rainwater harvesting an effective solution for climate change adaptation?

Rainwater harvesting is an effective solution for climate change adaptation because it helps mitigate the impacts of droughts, floods, and other extreme weather events that are becoming increasingly common due to climate change. Climate change is expected to lead to water scarcity in many regions, making conserving and managing water resources efficiently essential. Rainwater harvesting can increase water availability for various purposes, including irrigation, drinking, and domestic use. Also, Harvesting rainwater can help communities become more resilient to droughts by providing them with a reliable water source during dry periods. Unfortunately, climate change is also causing more frequent and severe flooding in some areas. Link. Archived.

 Harvesting rainwater can help reduce the amount of water that runs off into rivers and other water bodies during heavy rainfall events, thereby reducing the risk of flooding. With the increase in the global population, municipal water supplies are becoming strained, and water demand is expected to increase in the coming years. Harvesting rainwater can help reduce the need for municipal water supplies, reducing the strain on these resources. Many rely on water transported over long distances, leading to high energy consumption and carbon emissions. Harvesting rainwater locally can help reduce the carbon footprint associated with water transportation. So rainwater harvesting is an effective solution for climate change adaptation because it increases water availability, reduces flooding, decreases demand on municipal water supplies, increases resilience, and lowers the carbon footprint associated with water transportation. Link. Archived

Rain Water harvesting in Sri Lanka

The Lankan rainwater-harvesting forum was established in 1996 to promote the application of rainwater for domestic purposes throughout the country, develop technology, and establish guidelines for good rainwater harvesting practices. Also, National Policy on Rain Water Harvesting in Sri Lanka was officially implemented on September 27, 2005. LRWHF also represented the Steering Committee for Formulating this policy. The main objective of the National RWH Policy is to ensure that the ‘City of Tomorrow’ applies Rain Water Harvesting broadly by controlling water near its source in pursuit of becoming a ‘Green City’ in the future. Link. Archived.

In 2007 government legalized the adoption of rainwater in all new buildings in urban areas. This urban development amendment has created awareness about rainwater harvesting among people. It consists of guidelines for the constructors and the minimum quantity of water needed by each building category, such as residential, commercial, industrial, and institutional. Link. Archived.

Even though the people of Sri Lanka have been using several techniques to achieve the required quantity of water, they all can be categorized into two groups

1. Run-off harvesting

2. Rooftop harvesting

Runoff Harvesting – Gardens, driveways, landscapes, open fields, parks, roads and pavements, and other open areas of the environment are the catchment area to harvest the rainwater runoff. Specifically, this method is prospective for low rainfall areas. As this method covers a large extent as a catchment, the water collected from this method is more suitable for agriculture. Even though the urban area is shallow or nil in cultivation, the saved water can be directed to pits to recharge the groundwater. 

Rooftop Harvesting – Rooftops of houses, schools, offices, flats, and factories will be the impervious catchment areas. This system mainly focuses on water for domestic use, so the stored water should be clean and good. The design needs to adopt several components to maintain quality and estimated quantity.

The water harvested from the well-maintained rooftop can be used for drinking and other household uses, but the runoff water can’t be used for such purposes. It can only be used for agricultural purposes and to recharge the groundwater. So practically, it is tough to maintain a roof system to harvest the water for drinking water purposes. Read more.

A small tropical island close to the equator shows the critical impact of warm climate conditions. The seasonal distribution in Sri Lanka shows that droughts occur mainly in August. Most affected appear to be the Kurunegala, Puttalam, Hambantota, Moneragala, and Ampara districts. People were most affected by severe droughts that occurred in the years 2001 and 2004. The damages and economic losses due to the flood and deficiencies are very high, and it will affect many people each year. Recently, in 2017 more than 1.2 million people across 19 out of 25 districts remained affected by drought. Northern, North-Central, and Eastern Provinces are reported to have low water levels for agricultural, drinking, and household use. Therefore, rainwater harvesting can be an essential and practical idea for Sri Lanka.Link 

Rainwater harvesting is generally considered a good practice for tropical countries. In these regions, there is often a high amount of rainfall but also a need for consistent access to clean water. Rainwater harvesting allows for collecting and storing rainwater for later use, which can be particularly beneficial during dry seasons or droughts. Also, rainwater is generally free of many contaminants in other water sources, such as groundwater or surface water. Using rainwater for non-potable uses, such as irrigation or washing, can help conserve more precious clean water sources. However, it is essential to note that there may be some challenges to implementing rainwater harvesting systems in certain areas, such as areas with a high risk of flooding or landslides. It is essential to carefully assess the risks and benefits of rainwater harvesting before implementing such systems. read more 

Cost of rainwater harvesting systems 

The cost of a rainwater harvesting system can vary depending on several factors, such as the size of the system, the materials used, and the complexity of the installation. However, rainwater harvesting systems generally can be relatively inexpensive compared to other water supply options, especially in the long term. Simple rainwater harvesting systems like a basic rooftop collection system can be relatively cheap to install and may only require basic materials like gutters, downspouts, and storage tanks. In some cases, it is possible to construct a basic rainwater harvesting system using locally available materials. More complex procedures like underground storage tanks or large-scale industrial systems may require more infrastructure and specialized equipment investment and can be more expensive to install.

However, it is essential to note that the cost of a rainwater harvesting system should be considered in the context of its benefits. Rainwater harvesting can provide a reliable water source for non-potable uses like irrigation, which can help reduce demand for more expensive water sources like municipal water supplies. In some cases, rainwater harvesting is also more environmentally sustainable than other water supply options, which can offset the cost of installation over time. Read more 

“Ensure availability and sustainable management of water and sanitation for all”  SDG -06

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With Inputs from Dinesh Balasri  –