Osaka Brand Committee
Biolgical field
Water city
Have a Seat Near the River-- Launching the "Kitahama Terrace" Project (Part 3)
Have a Seat Near the River-- Launching the "Kitahama Terrace" Project (Part 2)
Have a Seat Near the River-- Launching the "Kitahama Terrace" Project (Part 1)
Tourism in the Water Capital--Connecting and Expanding via River Cruises
Cherry Blossom in the Water Capital--A Beauty That Has Returned After a Long Winter of Hardship
Living in the Water Capital--Improving Water Quality to Make Osaka a Better Home (Part 2)
Living in the Water Capital--Improving Water Quality to Make Osaka a Better Home (Part 1)
Enjoy a Cup of Tea at the Water Capital--New Restaurants Transform the Riverfront into a Destination for Fine Dining
Future View of the Water Capital--A Prologue to Revitalization
Osaka Kaleidoscope
Water city
#3 Living in the Water Capital--Improving Water Quality to Make Osaka a Better Home (Part 1)

Are Osaka rivers really "3K"?

Women washing clothes in the Okawa River (photographed around 1936). Stone steps that led to the river near a boathouse were a perfect place to do the laundry. Photo courtesy of Osaka Castle

The driver of a water taxi, who is known for her enthusiasm for the improvement of Osaka's waterfront, once told me that the water of the rivers in Osaka is so polluted that if a woman falls in one of the rivers she won't be able to bear a baby. "I believe it's true," she insisted quite seriously as I replied to her with a doubtful look suggesting that I would only take her story as an unfounded rumor. It is still worth considering, however, the fact that Osaka's best self-proclaimed "waterfront lover" believes this gossip; as you look at the river water, it indeed appears kind of unsafe--scary enough to the eyes of us common people.

In fact, it has long been known that the rivers that run through Osaka City are prone to water contamination. The name of the Yodo River, for example, is believed to have originated from the word yodomu (to stagnate). The flow of the Okawa River (Kyu Yodo River) is slow and merges with other rivers and streams at its end. The urban development that ignored the existence of the rivers, in addition to the wastewater that the city continuously discharges, worsened the water pollution at an accelerated rate. Through the postwar period, the rivers in Osaka have turned into smelly, dirty, dangerous places and have had a negative press since then.

Improvement of city water in progress

▼Click image to enlarge

Water contamination level in Osaka City in 2005 (excerpt from White Paper on the Environment, Osaka City, 2006 edition)

So what is the actual quality of water of the rivers in Osaka today? According to the 2006 edition of the Osaka City's White Paper on the Environment, the annual average BOD (Biochemical Oxygen Demand) for the city's twelve rivers and streams was 2.8 mg/L, which, compared to 10 mg/L in the 1970s, has been dramatically reduced. In some rivers such as the Neya River and the Hirano River, however, the BOD level is still considerably high, ranging from 8.1 to 13 mg/L. At a point near the Tenjin Bridge, where those rivers merge into the Okawa River, the water contamination exceeds the environmentally acceptable level (3.2 mg/L for the Dojima River (north stream of the Okawa River); 5.4 mg/L for the Tosabori River (south stream of the Okawa River)).

Consider the Dotonbori Canal, which became infamous as a place into which fans of the Hanshin Tigers, a local professional baseball team, dived when the team won the championship. Since the development of new canal locks began in 2000, the quality of the water of Dotonbori has improved remarkably. Two canal locks, one at the downstream end of the Dotonbori Canal and the other at the Higashi-Yokobori Canal, open and close according to tidal changes in Osaka Bay, preventing the flow of contaminated water from the Neya River and releasing cleaner water from the Okawa River to the canals. The locks are also effective in maintaining the water level and protecting the city from being flooded by seawater. In 2005, the average BOD of the Dotonbori Canal was recorded at 2.3 mg/L, showing the successful improvement of the water quality. So is the canal safe and clean enough to jump in and swim in now? The answer is no--the stream still contains a high level of E. Coli and other bacteria, because the current sewage system allows wastewater from neighborhood bathrooms and kitchens to flow into the canal during heavy rain. Are there any possible solutions for this problem? According to the Public Works Bureau of Osaka City, the city expects a dramatic improvement in the water quality of Dotonbori once the ongoing construction of the Kitahama-Osaka rainwater reservoir is completed in 2010 to cease the flow of rainwater into the canal. The city has conducted other improvement projects as well, such as more frequent dredging of sewage pipes. I would say the situation regarding Osaka's symbolic canal looks promising.

BOD (Biochemical Oxygen Demand)
BOD is used as the most common gage to indicate the quality and contamination level of river water. It shows the amount of oxygen needed within a certain period of time for biological organisms to decompose organic matter contained in water. The larger the figure, the worse the contamination.

Shin-Ebisu Bridge was rebuilt in November 2007. The 1.3-kilometer-long "Tonbori River Walk" along the canal is still under construction and is scheduled to be completed in 2010.

Now, let's consider what we as residents of the ‘Water Capital’ can do to make our rivers better. First of all, the river cannot be cleaned if rainwater or wastewater is contaminated. To keep drainage water clean, we should refrain from sweeping off dirt, trash or cigarette butts into nearby drainage ditches. We should not pour grease down our kitchen sinks. In other words, we can keep the river water clean if we live an environmentally friendly life. Remember, water circulates; we need to remind ourselves to think about what may happen to the water we have just used. We cannot "let the water carry it away" and forget about it. Not to mention dumping garbage into the rivers. In the next story, we will take a closer look at what has been done to clean the rivers of Osaka. (to be continued in Part 2)

February 12, 2008
Takuji Kobayashi
member of the board of directors, Suito Osaka-Mizubenomachi Saisei Project

■Related links
Osaka City White Paper on Environment (Heisei 18 (2006) edition)
Annual environmental report by Osaka City. Data on various environmental topics are included, such as water quality, air pollution, and the heat island effect.
(only available in Japanese)

「Osaka City Public Works Bureau」
Information about the city's recent projects for river improvement, including the Dotonbori Canal and the city's sewage system. Provided by the bureau's River Department. (only available in Japanese) (brief information available in English)

Outline of Kitahama-Osaka Rainwater Reservoir
The reservoir has been nicknamed "Heisei-no Taiko Gesui (Lord's sewerage system in the era of Heisei)." Information from the former Environment and Sewerage Bureau website. (only available in Japanese) (former Environment and Sewerage Bureau English page)

Author Profile
Takuji Kobayashi
While working as a landscape designer, Kobayashi participates in various activities to stimulate community development and discover and utilize local attractions at the eye level of citizens. He is a member of the board of directors of the Suito Osaka-Mizubenomachi Saisei Project (Mizube NPO) and also a representative of the Amenicity Osaka Network. Licensed professional engineer (architecture: urban and local development, architectural environment).