Water as Leverage- Setting the scene for a call for action

Water as Leverage for Resilient Cities Asia Setting the Scene for a Call for Action Content
3.2.3
Siltation of Rivers
The rivers of Semarang play an important role
in the drainage of surplus water. Due to natural
sedimentation processes and bad maintenance,
the rivers are slowly being filled with silt. Besides
their role as a drainage system, some parts of the
population use the rivers as their source of drinking
water. In the upstream areas, the rivers are also
used for washing. Taken together, the filling of the
rivers impedes Semarang’s drainage system and
will deprive parts of the population of their source of
drinking water and washing facilities.
Flash Floods Besides tidal floods,
flash floods – sudden floods due to high
amounts of precipitation upstream – also
hit Semarang on an incidental basis. The
rivers of Semarang play an important role in
drainage of surplus water. Several problems,
however, occur in the drainage system. Due
to natural sedimentation processes and bad
maintenance, the rivers are slowly being filled
with silt and occasionally with landfill. Informal
settlements are also erected in these areas,
encroaching on the riverbeds even more.
Semarang’s government recently initiated
a program to ‘normalize’ the rivers, which
implies canalization of the rivers in order to
increase their discharge speed significantly.
However, this impedes the refilling of the
shallow aquifers, contributing to further land
subsidence. Besides, ‘hardening’ the riverbeds
has negative consequences for flora and
fauna.
Most main canals have already been
normalized, except for the eastern Banjir
Kanal Timur canal. Furthermore, in lower-lying
areas, there are issues with the discharge
of floodwater as a consequence of land
subsidence. During high tide, gravitational
discharge is insufficient, which means pumps
need to be installed to get rid of surplus
rainwater. Lastly, a so-called ‘polder’, which
is a large water retention pond – not to be
confused with a traditional polder system –
was installed to deal with floods and control
the groundwater level, preventing the old city
center from waterlogging.
Drought Dry spells are expected to
become more frequent due to climate change.
Areas suffering from dry spells do not only
struggle with water scarcity, but also with
landslides. Dry spells are mainly affecting the
south of the city, such as Candisari. Although
retention ponds are set to be built around
the Semarang river and the eastern coast,
it seems that there are hardly any measures
that could deal with issues of drought and
landslides in the more southern areas.
However, research has shown that there is a
willingness among the population to revegetate
areas to improve the air quality. Revegetation
around infrastructure could be an option, given
that this could also reduce the incidence of
landslides. Another opportunity would be to
combine revegetation with socio-economic
development, since poverty rates in droughtand
landslide-prone areas are high (Gravitiani &
Kristiani, 2015; Mercy Corps, 2009).
Pollution Besides flooding,
pollution is also an issue. Pollution, because
of the dumping of industrial and household
waste in the water, creates risks of disease,
clogging of drainage canals and contributes
to issues of water scarcity. The Jatibarang
reservoir provides Semarang’s main water
supply through the Semarang river. Current
projects for the Jatibarang reservoir and the
upstream area of the Semarang river include
building a conservation zone and a trash rack.
Furthermore, preservation projects have been
planned around the waterfront, such as the
construction of an ecodistrict and collective
water management of the Kaligarang River
(Susilowati, 2006). Except for the creation of
an ecological industrial area, it seems that
there are currently few plans to reduce water
pollution from industry (WW: SSEA, 2017, in
press.).
Besides waste disposal, the rivers are also
used for washing (both humans and animals),
irrigation, sand mining, fish farming, producing
brick and, to a very small extent, drinking. Even
though outdated and specific, a case study of
the Kaligarang River from 2002 indicated that
the upstream areas are used by almost half of
the population for washing and by a third of the
population for waste disposal. Midstream, 65%
of the population uses it for waste disposal,
while 20% uses it for sand mining, fish farming
and producing brick. The downstream area,
which is the most polluted, is used by more
than half of the population for waste disposal
and by 15% of the population for irrigation,
washing, sand mining, fish farming and
producing brick (Sulisowati, 2006). Waste
management services currently manage to pick
up 34% of the waste generated in Semarang,
with informal housing districts being most
affected by the seemingly underperforming
waste management (100 Resilient Cities, 2016).
Waste is then transported to the Jatibarang
landfill, which is close by the main water
reservoir of Semarang. Here, organic waste
is composted and the remainder incinerated
to generate energy. Interestingly, several
waste management experiments are currently
underway, including the re-use of glass waste
to create water filters and community waste
management programs (most notably in Graha
Padma Estate) (Baba, Purwanto & Sunoko,
2012; Aji et al., 2015).
Pollution from household and industrial
waste is responsible for a more rapid spread
of waterborne diseases such as ringworm,
diarrhea and dengue (Ginandjar et al., 2015;
Susilowati, 2006; Widianarko, Verweij, van
Gestel & van Straalen, 2000; Baba, Purwanto
& Sunoko, 2012). These issues are interrelated
as waste clogs the waterways, allowing for
stagnant water to grow bacteria. In order to
counter these problems, Semarang is planning
to make big improvements to the water
system, including the installation of trash racks,
enhancements of the drainage systems and
dredging the canals (see the Resilient Systems
section).
Informal housing
in canal bed
Drainage canal.
Siltation
The East canal is heavily silted.
Solid Waste
254 SEMARANG
Water Issues
PART 2/Background Information on the Partner Cities
255