Summary Reader Response Draft 2
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. 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-deionisation 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 channelled 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.
References
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
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
Rinkesh. (2013, June 10). Advantages and
Disadvantages of Rainwater Harvesting. Conserve Energy Future. https://www.conserve-energy-future.com/advantages_disadvantages_rainwater_harvesting.php
ByJus. (2020). Rainwater Harvesting -Process,
Advantages and Disadvantages. BYJUS. https://byjus.com/biology/rainwater-harvesting/
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
Seawater desalination: a method for combating scarcity? (n.d.).
Iberdrola. https://www.iberdrola.com/innovation/desalination#:~:text=Desalination%20is%20the%20process%20by
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/
PUB. (2019). NEWater. PUB, Singapore’s
National Water Agency. https://www.pub.gov.sg/watersupply/fournationaltaps/newater
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
National Geographic Society. (2022, July 19). All
About Climate | National Geographic Society. Education.nationalgeographic.org.
https://education.nationalgeographic.org/resource/all-about-climate
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
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