Ulsan city drinking water supply issue is contributed to by several factors. The city’s water supply is from Nakdong-river, which is not only unqualified for drinking water as its watershed involves various industrial regions, but also requires Ulsan to buy the water since the river is in other metropolitan cities. It is also a potential problem in the drought season due to over reliance. Sayeon dam was built to address the drinking water issue for residents of Ulsan Metropolitan. Historical petroglyphs were then discovered within the dam and the water reportedly causes damages to the ancient artifacts. This created a need for water in the dam to be lowered in order to preserve the cultural heritage. Ulsan city has emptied two clean dams to preserve the national treasure hemisphere petroglyphs, increasing reliance on Nakdong river. Harvesting rainwater circumnavigates these issues by allowing the dam levels to stay low and preservation of the Bangudae Petroglyphs while providing drinking water and cleaning water for residents and reducing reliance on Nakdong river.

The concept of a water smart building takes into account two parts;harvesting of rainwater from the rooftop to be used for drinking and cooking purposes and water from the sorrounding areas to be used in cleaning purposes.Secondly,it takes into account efficiency in the building plumbing systems such as water efficient taps,water saving shower heads and water efficient toilets.This concept ensures that there is minimal wastage of water in the entire building system.


Rainwater is one of the most available sources of water. It is relatively clean as it has minimal interactions with anything but the atmosphere. The annual precipitation in South Korea is 1,299.7 mm (for between 1986-2015), which is 1.6 times the global average. Ulsan city experiences an annual precipitation of 1200mm, thus rainwater is relatively available for use in this area.

Reviewing records of annual precipitation since 1905, it can be noticed that the variation range of (annual) precipitation has been increasing gradually from 754 mm (1939) to 1,756 mm (2003). Incidences of extreme drought and flood events is increasing.

The general idea is to create a rain water gathering system that collects and channels rain water to a central pipe which is connected to a filtration and water cleaning system. The water is then directed to a storage space and is accessible later through a dispensing system similar to water dispensers, that will be located in the hallway of each floor of the building or at the entrances of said buildings to serve its residents.

The collection system ideally should be set up at the roof top of each building using flat roofing material as catchment. This will create a wide surface area for gathering the water. The roofing can be set up in a butterfly roofing style to direct the water to a central gutter with screens that help prevent larger solids from getting into the storage tanks.

An example of a butterfly type of roofing system to maximize on rain water collection.

Some of the main contaminants associated with rainwater include dust, smoke and other particles like pollen. The water cleaning process will involve a filtration and treatment system to remove any impurities that may affect the quality of the drinking water. The filtration system will be decided on the basis of the height of the building, which affects the number of solid particles on the rooftop, the volume of water to be treated, the type of filters needed and the pre-filtration screening requirements.

Taking an example of a building with a rooftop area of 200 square meters using an average of 1299mm precipitation per year, the amount of water that can be collected is 259800 litres in a single year. If the building has 50 units each with 4 occupants assuming consumption of 5 litres in a single day, the water demand for the building is 1000 litres per day. Therefore the water requirements for the particular building can be partially met up to 85%.

The building should be designed to accommodate the storage of water from the rooftops and from the surrounding surfaces. The water from the surroundings with an addition from the government can be used for cleaning and other uses. Suppose the outside area of the apartment is 80 square metres then the building has an additional 103,920litres for cleaning purposes reducing the stress on the Ulsan city water levels.

The storage system should be able to hold enough water to be used by each household daily all year round. An average person drinks 5 litres of water in a day and assuming one building has 200 units with an average of four occupants per unit, the total amount of water used daily is 4000 litres a day. This translates to 1.46 million litres a year. The average rainfall in a year is 1200 millimeters in a year. This system will be adjustible to any type of building depending on the number of residents that the building can accomodate.

The dispensing system will require residents of the building to reuse recyleable plastic bottles available in their homes and the charges of using this water will be included in the monthly rent expenditures. For everytime a resident gets water from the automated machine, it does calculations for the billing. The drinking water prices would be cheaper than buying bottled water, and would be readily available and easy to access at any time of day and night.

The dispensing machine will require one to feed in the amount of water they are taking, as seen in the image, which is then credited to a card. Source:

Incorporating a point system whereby the government awards the investor with incentives for reducing plastic waste by pushing for reuse of plastic water bottles would encourage the use of such systems. The Ulsan Metropolitan City has been supporting installation of rainwater collection facilities in some places, more than 95% of which is used for landscaping, followed by cleaning and toilet. We are advocating for this water to be used primarily for drinking water. The set-up collection facilities can assist us in providing ideas for setting up adequate storage facilities and can also be incorporated with our system.

The total annual amount of rainfall has been increasing steadily over the past number of years. The system will help manage this increase in precipitation that has previously resulted in flooding, while simultaneously providing water to residents of the city, making it sustainable in the long run.


To ensure minimal wastage of water, the following suggestions have been made for this building system.

water-efficient taps -The taps in the building should have aerators that reduce the flow rates and instead of supplying water at 15 litres a minute, the taps will supply at 9litres a minute, therefore, saving 6 litres a minute per individual use. In a single month, the taps may save up to 1274 litres of water.

water-saving showerheads -An average person showers for 10-15 minutes using around 80 litres of water. In these water-smart buildings the showerhead uses 50 litres per person saving 30 litres per individual therefore per month, water savings are 900 litres of water.

water-efficient toilets -Every flash in a toilet uses up to 7 gallons(26litres) of water which should be replaced with 1.5 gallons (5.6775litres) per flash saving 20 litres of water. Considering an individual goes to the toilet 3 times a day we can save up to 60 litres of water-1800 litres in a month.


Drinking water

Assuming 30 units per building,4 individuals per unit.

Water useIndividuals(Litres)  Water demand(per annum)  Water available  Savings made (1.5l @$0.4)
Drinking water5219000250000$58400
estimated savings per building in drinking water only

Efficient plumbing fixtures

Plumbing fixtureSavings (per unit)(litres)All units (litres)(0.5 cents per 1000 litres)
Aerated taps15288458640$229.32
Efficient toilets876002628000$1314
savings in plumbing fixtures

In total the amount of water saved from the plumbing fixtures and the water collected from the surroundings of the buildings is 5782560 litres per annum.

The amount of water saved will reduce the pressure of the limited water resources in Ulan City if adopted. The evaluation can be done by experimenting with a single building and analysing the results . Acquiring funding to be able to develop this idea and create a prototype would be the first step on the road to achieving this dream of drinking water directly from the heavens.