Download hydroclimate projections to engineering practices for water

HYDROCLIMATE PROJECTIONS TO ENGINEERING PRACTICES FOR WATER RESOURCES SECTOR ADAPTATION MEASURES Ahmad Jamalluddin S.1, Mohd Zaki M.A.2, Nurul Huda M.A.3, Y.C. Goh3
National Hydraulic Research Institute of Malaysia (NAHRIM)
Ministry of Natural Resources and Environment (NRE), MALAYSIA
ABSTRACT
Malaysia’s water resources sector is currently plagued by three major issues, namely water
excess, water shortage, and water pollution. Nine percent of the country lies in flood prone
areas. The rainfall occurring between November and January each year constitutes sixty
percent of total annual rainfall. The large rainfall amount causes widespread flooding in
riverine and coastal areas. Meanwhile, the seasonal distribution and spatial variation of
rainfall have resulted in water stress related problems in several regions in the country.
Extended periods of drought cause water supply to fall short of water demand in states
supporting large scale irrigation for rice cultivation such as Perlis and Kedah. Other
industries are not spared either. Heavily industrialized states such as Pulau Pinang,
Selangor, and the Federal Territory of Kuala Lumpur face periodic water shortages which
are exacerbated by long dry spells. On top of that, rivers and waterways are polluted by
urban, industrial and agricultural wastewater. In Klang Valley alone, 60 tons of wastes are
dumped into the rivers per day.
Behind these issues looms a larger threat – climate change. Climate change and variability
together with non-climatic drivers such as population increase, intensive land development,
and loss of forests have had physical impacts on the hydrological cycle especially in the
recent decades. Increased frequency of floods, increased catchment erosion and siltation,
inadequate environmental flows, increased pollution and deterioration of river water quality,
and limited water supply are climate change impacts that threaten the sustainability of our
water resources. The three major water resources issues – water excess, water shortage,
water pollution – together with water governance, which have always been of major concern
are expected to worsen with the stimuli of climate change.
The impacts can be modeled and projected by means of downscaling approach using the
output from Global Circulation Models (GCMs). However, to accommodate and to obtain
information of more relevance to water resources and water resources management at
watershed scale, higher, fine-resolution (spatial and temporal) and reasonably accurate
climate change projection is required. In general, there are two types of climate change
downscaling approaches: statistical and dynamic downscaling. Statistical or empirical
downscaling rely on current estimates or observations of the spatial distributions of
meteorological variables while results from dynamic downscaling method are physically
consistent but it is more computationally demanding in terms of both computer time, output
storage and cost. Adopting the dynamic downscaling approach, NAHRIM has completed the
development of the regional hydrologic-atmospheric model of Peninsular Malaysia, Sabah
and Sarawak namely RegHCM-PM (2006) and RegHCM-SS (2010) respectively, as well as
Regional Climate Model (RCM) for Peninsular Malaysia, Sabah and Sarawak using PRECIS
in 2010.
Annual daily mean temperature projection from RegHCM model for the whole Malaysia from
year 2020 up to 2099 shows the increase of surface temperature from 0.5°C in the year
1
Director General, NAHRIM Director, Research Centre for Water Resources, NAHRIM 3
Research Officer, Research Centre for Water Resources, NAHRIM 2
2020 to 3.5°C
3
at the
e end of the century. The
e climate prrojection stud
dies for prec
cipitation alsso
find that more extrem
me weather conditions in the future (2025-2050
0) may be exxpected sincce
higher maximum
m
and lower min
nimum rainfa
all are observed in the projected data.
d
Figure 1
shows th
he map of projected
p
one day maxim
mum precip
pitation from RegHCM fo
or Peninsula
ar
Malaysia
a. The proje
ection also shows incre
ease in max
ximum mon
nthly rainfall of up to 51
5
percent over
o
Pahang
g, Kelantan, and Tereng
gganu region
ns while the minimum monthly
m
rainfa
all
decrease
es from 32 to
o 61 percentt for the who
ole Peninsula
ar Malaysia.
Figurre 1: Peninsu
ular Malaysia
a Map of Ma
aximum 1 da
ay Rainfall
The mod
del output in terms of pro
ojected clima
atic parametters such as rainfall, tem
mperature an
nd
evapotranspiration iss very esse
ential for the
e quantificattion of the potential climate chang
ge
impacts on
o water ressources and
d water reso
ources mana
agement. Th
his leads to the necessity
for deve
eloping engineering me
ethodologiess for climate
e change a
adaptation particularly
p
t
to
bridge th
he gap betwe
een scientific knowledge
e and engineering practtices. In othe
er words, it is
to develo
op engineerring knowled
dge into practices in wa
ater sector, for instance
e reviewing of
o
water syystem manag
gement and
d plans to a
assess the integrity of existing
e
stru
uctures wherre
failure co
ould result in
n loss of life, reviewing d
design stand
dards for floo
od risk mana
agement in all
a
new infrrastructures including water control structures, transp
portation strructures an
nd
electricall, water and waste amenities to incorpo
orate climatte change factor, an
nd
complem
menting strucctural appro
oaches with
h non-structural approa
aches such as improve
ed
rainfall and flood fore
ecasting, dissaster warnin
ng system and flood hazzard mappin
ng as part of a
coordinatted disaster prevention and manage
ement plan.
Above all,
a these infformation need to be conveyed to policy ma
akers or pla
anners to be
b
implemen
nted or enfo
orced in the
e country. T
These are all
a part of adaptation
a
a
and
mitigatio
on
measures to cushion
n climate cha
ange impactt. Adaptation
n is primarilyy a local issu
ue as it mosttly
provides benefits at the local sccale. Adapta
ation can havve short-term
m effect on the reductio
on
of vulnerrability. In contrary,
c
mittigation is a global issue and mostly provide
es benefits to
t
mitigate the
t impact of
o greenhouse gas by m
means of em
mission reducction at glob
bal scale. Th
he
frameworks of wate
er resourcess management and wa
ater servicess evolved from adaptivve
managem
ment to reduce vulnera
ability and e
enhance sysstem resilien
ncy and rob
bustness. Th
he
framework may ha
ave a different combin
nation of tools
t
like ttechnologica
al innovation,
engineering design change, and multi-objective watershed planning and regulations. Climate
change adaptation should be given priority in water sectors as well as in health and coastal
sectors where the design, planning and operations of water resources management and
water services are required to be adjusted by water related authority.
As for an example of the proposed methodology, a case study of Sungai Kedah basin shows
that future projected rainfall indicates an increasing trend over the projected years for climate
change factor in that area, as shown in Table 1. The climate change factors are incorporated
into flood simulation models to project future peak discharge (flood) based on different
scenarios. These rainfall projections are used in flood simulation models and the results are
subsequently mapped on satellite image (Figure 2) and other information such as total
flooded area (Table 2) extracted for further analysis.
Table 1: Projected magnitude of peak floods due to climate change impacts in Sungai Kedah
Basin.
(a)
(b)
(c)
Item
Time
Horizon
Climate
Change
Factor
(CCF)
1
2
3
4
5
2020
2030
2040
2050
2060
1.05
1.09
1.14
1.19
1.25
(a) Baseline (current landuse)
(d)
1-Day
Design
Rainfall
(Baseline
= 240.6
mm)
245.2
256.5
268.0
280.0
292.6
Peak Discharges (Qp) 100 years ARI
(e)
(f)
(g)
Current
Future Landuse Adaptation
Landuse &
& Climate
value
3
Climate Change
Change
(m /s)
Scenario
Scenario
(Baseline Qp=
2047.9m3/s)
2111.2
2313.7
266
2267.9
2438.0
429
2430.2
2613.8
598
2601.9
2799.9
776
2785.3
2997.6
966
(b) 2020 (current landuse)
(c) 2060 (current landuse)
Figure 2: Generated 100 year ARI Flood Inundation Map of Sungai Kedah
Table 2: Flooded area by depth.
Flooded area by depth (km2) Landuse Scenarios 0.01 ‐ 0.5 m 0.5 ‐ 1.2 m >1.2 m Total Current Baseline 2020 2030 2040 2050 2060 50.50 50.67 50.65 50.59 49.88 48.44 41.55 42.13 43.67 45.11 47.21 49.02 35.57 36.42 38.56 40.65 43.06 45.16 127.62 129.21 132.88 136.34 140.16 142.62 Future Baseline 2020 2030 2040 2050 2060 51.10 51.24 51.01 50.51 49.13 48.16 43.30 43.91 45.18 46.86 49.17 50.00 37.07 37.92 39.90 42.00 44.20 46.95 131.47 133.06 136.10 139.36 142.50 145.10 In conclusion, this paper encompassed and deliberated water sector related issues and
problems, and also discussed methods to bridge the gap between scientific knowledge into
engineering knowledge and solution in the context of water and climate change impacts in
Malaysia. In addition, it also showed the methodology to mainstream climate change
adaptation in water sector in order to cushion and minimise the impacts of climate change
and variability and non-climatic forcing.
Keywords:
Climate change, Global Circulation Model, downscaling, regional hydro-climate model, water
resources.
Acknowledgement:
The Sungai Kedah study described in this paper is funded by Economic Planning Unit (EPU)
of the Prime Minister’s Department and the United Nations Development Programme
(UNDP).