As we have gained fairly much knowledge on groundwater in the past two weeks, now it would be the best to have a closer look at groundwater management by introducing theoretical concepts with a practical case study. Many countries have been faced with groundwater issues and much related to land subsidence, while Tokyo has tackled the problem quite successfully in the recent decades compared to the other nations, which makes it the main focus of this post.
How was groundwater used in Tokyo before land subsidence occurred?
Similar to many other places in the world, groundwater in Tokyo was generally used as drinking water, for domestic purposes, and also emergency response after natural disasters such as earthquakes.
v After 1910: Groundwater subsidence was first detected as a huge volume of groundwater was pumped out for factories and to serve a growing population, dominantly in the Koto area after 1910 and in Edogawa-ku and Adachi-ku in the 1920s.
v In the 1940s: Ground subsidence slowed down temporarily.
v After World War II: Economic rehabilitation along with production activities gradually intensified the topographical phenomenon and the ‘zero-metre-zone’ where subsidence at sea level or lower continued to grow.
v In the 1950s: the Industrial Water Law was enacted in 1956, followed by pumping regulations which were applied to eight out of 23 wards in Tokyo accordingly.
v 1965-1970: Water table dropped to 58m below sea level with a peak pumping rate of 1.5million m3/day.
v In 1968: Edogawa-ku in the lowlands district saw a maximum annual subsidence depth of 23.89 cm/yr, and the city of Kiyose in the high plains district witnessed a peak annual subsidence depth of 21.65 cm/yr.
v In the early 1970s: Tokyo Metropolitan Government (TMG) introduced pumping regulations for thousands of wells in the region to slow and reverse the pace of land subsidence.
v In 2003: Up to 550,000m3 of groundwater was still being pumped out daily for public water supply and other uses.
Figure 5.1: Cumulative subsidence depths at major benchmarks, 1890-2003
(Source: Tokyo Metropolitan Research Institute for Civil Engineering Technology 2004)
v Up to 2006: Water table began to rise and was at 6-10m below sea level. Subsidence rate had been slowed to approx. 1cm/year (Tokyo Standard).
v After 2011: This island country was found sinking again after the East Japan Earthquake
in March 2011 shown in the local news below.
in March 2011 shown in the local news below.
(Source: NHK World: Land Subsidence Spreads)
As land subsidence has been mostly under control in Tokyo since 2006, it arouses my curiosity to check and compare the total population in Japan up to the year of 2006. Coincidentally, Japanese population as a whole reached its climax in 2005 and began to decline afterwards (shown below). Thus, apart from appropriate and reasonable groundwater management by the Japanese government, the country’s population does pose a direct influence on its groundwater use.
Figure 5.2: Japanese total population 1600-2005-2100 (Moriyasu, 2006)
(Source: “Japanese history read from population” Kito Hiroshi (until 1846), “Analysis of the population growth” Morita Yuzo, Nippon Hyoron Sha (1847- 1870) “Our country’s population in from 1872” (1872-1919), “National Census” and “Annual Report on Current Population Estimates” (1920-2000), Statistics Bureau)
How has the Japanese government managed groundwater?
1. Measures to prevent land subsidence
After the 1950s, both Industrial Water Law (1956) and Building Water Law (1962) were introduced which are restrictions on the pumping of groundwater for industrial and building water use in designated regions respectively.
Figure 5.3: Outline of Laws concerning Groundwater Pumping Regulations (Water Resources Policy Division Land and Water Bureau Japan, 2006)
2. Implementation of Pumping Regulations
Pumping regulations were mainly targeted at the structural design of pumping facilities.
Let’s zoom into the Tokyo area:
3. Measures to preserve groundwater quality
Although uniform water quality regulations for groundwater and public water were ordained to protect human health, various standards were established for different waterbodies such as seas and coastal areas, rivers and lakes, aiming to optimise the living environment. Environmental standards were set for groundwater quality in March 1997 and Environmental Quality Standards (EQSs) under the Basic Environment Law have been specified to achieve the goals of "protection of human health" and "conservation of the living environment". 26 human-health-related substances have been listed under EQSs. Additionally, EQSs for nitrogen and phosphorus levels in lakes/reservoirs and sea/coastal areas were built up to prevent eutrophication. (Ministry of the Environment Government of Japan, Conservation of the Water Environment -Chapter 3, 1996)
4. Special Purpose Taxes
v Resource Management Tax
v Forest Conservation Tax
1. Comparison: Tokyo, Japan vs. Orange County Water District (OCWD), California, U.S.A
As the main policies applied in Tokyo were constructions of waterworks to supply technological regulations and surface water, water supply was mostly shifted from groundwater to surface water there.
A comparative analysis of groundwatermanagement in Tokyo, Japan and Orange County Water District (OCWD), California,U.S.A. has found the obvious contrast between the different policies in these two areas that, unlike Tokyo nowadays, groundwater remained an essential water resource in OCWD. Despite different socioeconomic background and time of problem recognition, their initiation stage of countermeasures was quite similar, so exactly what approach and practical solutions were used in OCWD that caused such substantial variation? Well, interestingly both places have adopted the idea of collecting taxes from citizens; however, imposition of a pump tax and artificial recharge based on the tax revenue in OCWD would not be applicable in Japan, for groundwater there is defined as part of land ownership and thus land owners have their discretion and freedom to control the groundwater underneath.
The study also researched on the main factors leading to the difference in policy responses between Tokyo and OCWD: (1) subsidy systems, (2) legal rules of groundwater pumping, and (3) local governmental authority. The Tokyo Industrial Water Law (1956) aforementioned specified well diameter limitation and well depth control which hindered the process of digging a new well due to its potentially high cost. Meanwhile, the law allowed the Japanese government to provide financial support to the construction of industrial waterworks, further reducing surface water price. Consequently, this combination managed to promote the conversion of water supply.
2. What to learn from the successful groundwater management from Tokyo?
The successful methods applied to handle groundwater issues in
Tokyo, proper countermeasures to stop or avoid land subsidence, regulate groundwater abstraction, enhance groundwater quality, and raise certain tax revenues for the sustainability of groundwater
all play a positive role in groundwater management.
3. Is the ‘Tokyo way’ applicable to the world?
Apparently every city has her own story and there is no exception for groundwater management. Although Tokyo has performed very well to prevent land subsidence, there still remain some drawbacks including some provoked byproducts, decline in diversification of water sources and local ecosystem services. Therefore, I believe other cities with groundwater problems could possibly learn from Tokyo’s experience, but it is also case-by-case that they would have to take their own geographic locations, geological formations, countries’ legal, economic and social factors, policies and regulations, as well as many other aspects into consideration.
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