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
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