Summary Reader Response Draft 1

 

The webpage “Rainwater Harvesting 101” from Innovative Water Solutions LLC introduces what is rainwater harvesting(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. 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 HDB (n.d), rainwater harvesting will be introduced as an alternative to boost water resource efficiency in public housing. 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 regular maintenance.

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 (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. On the other hand, desalinated water mitigates the limitation of unpredictable rainfall (faced by rainwater harvesting). Desalination relies on seawater, which is readily available, to create drinking water. According to PUB (2019), 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, 2019), the cost of desalination will soon be greatly reduced once it is completely implemented into all desalination plants.

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 ,2019). 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. This water pollution control is being watched over by government bodies (PUB and NEA), but 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, 2019). 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, 2019). 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 (Average Monthly Rainfall and Snow in Singapore, Singapore (Inches), 2001). 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.

All in all, as 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, 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.

Reference:

A. John Arnfield, & Paul Edward Waggoner. (2019). Climate - World distribution of precipitation. In Encyclopædia Britannica. https://www.britannica.com/science/climate-meteorology/World-distribution-of-precipitation

Average monthly rainfall and snow in Singapore, Singapore (inches). (2001, February 3). World Weather & Climate Information. Retrieved February 3, 2023, from https://weather-and-climate.com:80/average-monthly-precipitation-Rainfall-inches,Singapore,Singapore

ByJus. (2020). Rainwater Harvesting -Process, Advantages and Disadvantages. BYJUS. https://byjus.com/biology/rainwater-harvesting/

Chapter 6 : Water Quality | Friends of Reservoirs. (n.d.). Www.friendsofreservoirs.com. https://www.friendsofreservoirs.com/science/best-management-practices-manual/chapter-6-water-quality/

Maxwell-Gaines, C. (2004, April 4). Rainwater Harvesting 101. Innovative Water Solutions LLC; Innovative Water Solutions LLC.

https://www.watercache.com/education/rainwater-harvesting-101

National Geographic Society. (2022, July 19). All About Climate | National Geographic Society. Education.nationalgeographic.org. https://education.nationalgeographic.org/resource/all-about-climate

PUB. (n.d.). PUB, Singapore’s National Water Agency. PUB, Singapore’s National Water Agency. https://www.pub.gov.sg/watersupply/fournationaltaps#:~:text=Singapore%20has%20built%20a%20robust

PUB. (2019). PUB, Singapore’s National Water Agency. PUB, Singapore’s National Water Agency. https://www.pub.gov.sg/watersupply/fournationaltaps/localcatchmentwater

PUB. (2019). PUB, Singapore’s National Water Agency. PUB, Singapore’s National Water Agency. https://www.pub.gov.sg/watersupply/fournationaltaps/desalinatedwater

Rinkesh. (2013, June 10). Advantages and Disadvantages of Rainwater Harvesting. Conserve Energy Future. https://www.conserve-energy-future.com/advantages_disadvantages_rainwater_harvesting.php

Seawater desalination: a method for combating scarcity? (n.d.). Iberdrola. https://www.iberdrola.com/innovation/desalination#:~:text=Desalination%20is%20the%20process%20by

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