Summary Reader Response Draft 3
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 to
maintain the quality of the stored 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 (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 (2019A),
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, 2019A), 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, 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 ("Average monthly rainfall and snow in Singapore, Singapore
(inches)," 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.
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, 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.). https://education.nationalgeographic.org/resource/all-about-climate
Average monthly rainfall and snow in Singapore,
Singapore (inches). (n.d.). World Weather & Climate
Information. https://weather-and-climate.com:80/average-monthly-precipitation-Rainfall-inches,Singapore,Singapore
Chapter 6: Water quality. (n.d.). Friends of Reservoirs. https://www.friendsofreservoirs.com/science/best-management-practices-manual/chapter-6-water-quality/
Desalination: The process of turning seawater into
drinking water. (2021, April 22). Iberdrola. https://www.iberdrola.com/innovation/desalination#:~:text=Desalination%20is%20the%20process%20by
Maxwell-Gaines, C. (2020, July 27). 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 National
Water Agency. PUB, Singapore's National Water Agency. https://www.pub.gov.sg/watersupply/fournationaltaps#:~:text=Singapore%20has%20built%20a%20robust
PUB. (n.d.A). PUB, Singapore's National
Water Agency. PUB, Singapore's National Water Agency. https://www.pub.gov.sg/watersupply/fournationaltaps/desalinatedwater
PUB. (n.d.B). PUB, Singapore's National
Water Agency. PUB, Singapore's National Water Agency. https://www.pub.gov.sg/watersupply/fournationaltaps/localcatchmentwater
PUB. (n.d.C). PUB, Singapore's National
Water Agency. PUB, Singapore's National Water Agency. https://www.pub.gov.sg/watersupply/fournationaltaps/newater
Rainwater harvesting. (2022, June 27). BYJUS. https://byjus.com/biology/rainwater-harvesting/
Rinkesh. (2013, June 10). Advantages and
Disadvantages of Rainwater Harvesting. Conserve Energy Future. https://www.conserve-energy-future.com/advantages_disadvantages_rainwater_harvesting.php
Water conservation. (n.d.). Housing & Development Board
(HDB). https://www.hdb.gov.sg/about-us/our-role/smart-and-sustainable-living/hdb-greenprint/water
World distribution of precipitation. (n.d.). Encyclopaedia Britannica. https://www.britannica.com/science/climate-meteorology/World-distribution-of-precipitation
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