Summary Reader Response Draft 4

The webpage “Rainwater Harvesting 101” from Innovative Water Solutions LLC introduces what rainwater harvesting is (Maxwell-Gaines, 2020). Rainwater harvesting is essentially collecting run-off from buildings and other impermeable surfaces for future use. Conventionally, the rain will be collected in gutters that channel water downspouts and into a storage unit. It can range from a simplistic system like collecting water in a rain barrel to being as complicated as harvesting rainwater into a large cistern to supply an entire household. Traditionally, rainwater harvesting usually conjures up a primitive image of an old farm cistern or thoughts of developing countries (Maxwell-Gaines, 2020). The reality is that many other countries are adopting this method as it is proving to be a viable method in supplying water (Maxwell-Gaines, 2020). As stated by Housing Development Board (HDB) (n.d.), rainwater harvesting will be introduced as an alternative to boost water resource efficiency in public housing in Singapore In my opinion, even though rainwater harvesting is a viable method in supplying water for countries with a tropical climate, it cannot be the main source of water supply as it has glaring limitations like the unpredictability of rainfall and the need for regular maintenance to maintain the quality of the stored water. With Singapore implementing a water system known as the Four National Taps which compromises different ways to obtain clean drinking water, mitigating the limitation of rainwater harvesting and allowing it to be a key component in providing drinking water.

One obvious limitation of rainwater harvesting is the unpredictability of rainfall. With little or no rainfall, the amount of water harvested would drastically diminish (Rinkesh, 2013). Singapore has implemented a sturdy, diverse and sustainable water supply system known as the Four National Taps (Public Utilities Board (PUB), n.d.). Rainwater harvesting is represented by local water catchment as one of the taps, with the three taps representing other water supplying methods. One of the taps that mitigate the limitation of unpredictable rainfall is desalinated water (faced by rainwater harvesting). Desalination relies on seawater, which is readily available, to create drinking water. According to PUB (n.d.A), Singapore uses reverse osmosis for desalination. This process removes dissolved salts and minerals from seawater, making it safe for human consumption. Desalination is a highly energy consuming method, which consumes up to 3.5kwh/m3 to transform the seawater into drinking water, compared to using local catchments to collect rainwater and treating it afterwards. With the introduction of other methods such as electro-deionization which has an achievable energy consumption of 1.65kWh/m3 (PUB, n.d.A), the cost of desalination will soon be greatly reduced once it is completely implemented into all desalination plants. Hence, with the process of desalination to produce clean water not reliant on the rainfall and along with the advancement of technology, desalination will become more cost-effective. Proving to be a good counter to the limitations presented by rainwater harvesting.

Another limitation of rainwater harvesting is that the quality of the rainwater collected must be maintained. Singapore uses reservoirs (local catchments) to store rainwater which is collected through a broad network of drains, canals, and rivers, before it is treated for drinking water (PUB, n.d.). If pollutants such as organic materials are released into water bodies, this could encourage the growth of algae, wreaking the ecosystems, and ultimately complicating the water treatment process. According to PUB (n.d.B), this water pollution control is being watched over by government bodies (PUB and NEA). However, in the scenario where the water in the reservoir were to be contaminated, compromising its ability to convert the rainwater collected to clean drinking water, there are other alternatives to mitigate the effects.  Singapore uses NEWater (1 of the national taps) as another alternative water supply, where used water is recycled into high-grade reclaimed water (PUB, n.d.B). This process uses three stages to treat used water. The first stage, microfiltration/ ultrafiltration, water is channeled through membranes to filter out microscopic particles. Secondly, the water then undergoes reverse osmosis which removes undesirable contaminants such as viruses with a semi permeable membrane. Despite the water already being a high grade after the second stage, it undergoes ultraviolet disinfection, where it is exposed to ultraviolet rays which can kill bacteria and virus, disinfecting the water (PUB, n.d.C). As used water and water collected via local catchment have separate systems to transport the water, in the inadvertent case of failure, there would always be other systems that ensures a constant water supply.

Despite the limitations presented on rainwater harvesting, it still proves to be a viable water supply, especially in tropical countries like Singapore, with a higher average rainfall than countries that are in the polar climate. With the average rainfall of the wettest month (December) having 13.2 inch / 335mm of precipitation and the driest month (February) with 4.4 inch / 111mm of precipitation (World Weather & Climate Information, n.d.). Even though tropical countries have an abundance of rainfall throughout the year, completely relying on rainfall harvesting to provide water is not ideal as the unpredictability of rainfall could result in periods of droughts, which causes it to fail completely due to its absolute reliance on rain. Singapore’s implementation of the Four National taps ensures that there is always a safety net, such that in the scenario of a drought and the water catchment fails, there is 3 other methods of producing clean water.

Despite the unpredictability of rainfall and the regular maintenance required to ensure the quality of the water stored, rainwater harvesting is rather flexible and can be a steady subsidiary to other water supply methods. Due to its ability to be implemented on a small scale such as a simple rain barrel or a country-level scale like in Singapore’s case with reservoirs (water catchment) as one of the four national taps, it has proven to be a viable way to provide water to the masses. Improving water scarcity and its dependence on other water supplies methods as desalination plant and NEWater.

 

 

References

All about climate. (n.d.). National Geographic. https://education.nationalgeographic.org/resource/all-about-climate

World Weather & Climate Information. (n.d.). Average monthly rainfall and snow in Singapore, Singapore (inches). https://weather-and-climate.com:80/average-monthly-precipitation-Rainfall-inches,Singapore,Singapore

 

Friends of Reservoirs. (n.d.). Chapter 6: Water quality. Best Management Practices Manual. https://www.friendsofreservoirs.com/science/best-management-practices-manual/chapter-6-water-quality/

Iberdrola. (2022). Desalination. The process of turning seawater into drinking water. https://www.iberdrola.com/innovation/desalination#:~:text=Desalination%20is%20the%20process%20by

Maxwell-Gaines, C. (2020). Rainwater harvesting 101: Your how-to collect Rainwater guide. Innovative Water Solutions LLC. https://www.watercache.com/education/rainwater-harvesting-101

PUB. (n.d.). PUB, Singapore's four national taps. https://www.pub.gov.sg/watersupply/fournationaltaps#:~:text=Singapore%20has%20built%20a%20robust

 

PUB. (n.d.A). PUB, Singapore's four national taps. https://www.pub.gov.sg/watersupply/fournationaltaps/desalinatedwater

 

PUB. (n.d.B). PUB, Singapore's four national taps. https://www.pub.gov.sg/watersupply/fournationaltaps/localcatchmentwater

PUB. (n.d.C). PUB, Singapore's four national taps.   https://www.pub.gov.sg/watersupply/fournationaltaps/newater

BYJUS (2022). Rainwater harvesting. https://byjus.com/biology/rainwater-harvesting

Rinkesh (2013). Advantages and disadvantages of rainwater harvesting. https://www.conserve-energy-future.com/advantages_disadvantages_rainwater_harvesting.php

Housing & Development Board. (n.d.). Water. HDB Greenprint. https://www.hdb.gov.sg/about-us/our-role/smart-and-sustainable-living/hdb-greenprint/water

Encyclopaedia Britannica. (n.d.). Climate - World distribution of precipitation. In meteorology. https://www.britannica.com/science/climate-meteorology/World-distribution-of-precipitation

 Edited: 30032023