Jakarta sunk 91cms in six years: Official
Jakarta sunk 91cms in six years: Official
Bambang Nurbianto, The Jakarta Post, Jakarta
Due to a greatly increased amount of construction and over-
exploitation of groundwater, the city's land has subsided up to
91 centimeters in recent years, a city official said on Tuesday.
Speaking at a hearing with the City Council's Commission C for
economic affairs, head of the city mining agency, Muzahiem
Mochtar, said that based on a study, the land subsidence in
various parts of Jakarta during the 1993 to 1999 period ranged
from four centimeters to 91 centimeters, depending on each
location.
The 4-centimeter drop occurred on Jl. Lubang Buaya in East
Jakarta, while the 91-centimeter sinkage occurred on Jl. Sunter
Kemayoran in North Jakarta.
Other significant drops occurred on Jl. Baru Arah Sunter (76.1
cm), Jl. Mundu Koja Utara (52 cm), Jl. Gadang Tanjung Priok (42
cm), and Jl. Kampung Malaka III (27 cm), which are all in North
Jakarta.
He said the continuing process of subsidence was also a
serious factor that contributed to the worsening of annual floods
in the city.
"The continuing subsidence of land here could worsen the
environmental problems, including the possibility that the annual
floods in the city will worsen in the future," he said.
Muzahiem said the impact of groundwater exploitation on land
subsidence accounted for about 19 percent, while the weight of
buildings on the land was responsible for about 80 percent, and
one percent was due to natural processes.
"Although the impact of the groundwater exploitation on land
subsidence is only 19 percent, it should be stopped. Otherwise,
it will significantly lower the ground surface (in relation to
sea-level)," he added.
"Exploitation of groundwater should be minimized to a
sustainable level. If groundwater is over-exploited, not only the
groundwater will disappear, but it will also hasten land
subsidence," he reiterated.
He said that only 7.5 percent of groundwater use was regulated
by his office, while the rest was still unregulated.
He pointed out that 44 percent of the potable water needed in
Jakarta was supplied by the city-owned company PAM Jaya, which
uses river water.
He said that there were several ways to curb the use of
groundwater. He suggested that taxes for groundwater use should
be increased. "That way, we could discourage companies from
wasting groundwater," he said.
He also suggested that PAM Jaya should be allowed to expand
its coverage because it could guarantee the water supply for the
whole city.
Haris Pindratno of the Indonesian Geological Expert
Association said the 2010 city masterplan needed to be revised as
the masterplan did not consider geological factors.
"Because there is no geological consideration, the capability
of land to support the buildings was never taken into account.
And based on the study it is proven that the weight of buildings
significantly contributes to subsidence," he added.