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Richard Walker
Climate Change Case StudyWater Quality Implications
Water Safety Conference 2010
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Impact of Climate Change
2 0 7 0
S p r in g
S u m m e r
A u t u m n
A n n u a l
W i n t e r
D r ie r W e t t e r
2 0 3 0D r i e r W e t t e r
-60 -40 -20 0 20 40 60Rainfall Change (%)
Drier 2030 Wetter
Warming will change general climatic patterns and there will be greater climatic
variability
Climate Change and Water Safety Plans – Case Study
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Supply Infrastructure •Surface water source•Dam capacity 1.7 GL•Commissioned 1994•Augmentation expected 20 plus years
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Climate change/Drought•By early 2000’s supply became problematic•Pump back direct from River commenced•2002 = winter from hell
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Case Study – Scheme Supply
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Volume abstracted fromPump back(cummulative/month)
Margaret River TownshipMonthly Demand
Storage volume in TenMile (average/month)
Maximum Storage in TenMile Brook
Minimum Safe Storage inTen Mile Brook
Figure 1. River pump back, demand and storage levels 2000 to 2009.
Water Safety Plan Development•2004 – WSP’s commenced•Town scheme was reviewed•Dam catchment
- Some private land- Cattle- L3 source
• River source characterised as high risk (unsuitable)- No source protection- High E Coli detected- High C&G risk- High turbidity- High colour
•No barrier to C&G
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Water Safety Plan Action Plan
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
•Turbidity limits on pump back (immediate)
•PCP = 5NTU
•Relocate pump back pipe to back of dam
•UV on dam outlet (months)
•CCP = 40ms/cm2
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Ten Mile Brook DamCap 1,690,810m3
TWL 121.27mAHDLevel 2 Source
TransferPS
Chlorine Disinfection
Chlorine Analyser
To Reticulation
a) Margaret River scheme 1994
Ten Mile Brook DamCap 1,690,810m3
TWL 121.27mAHDLevel 2 Source
Margaret RiverUnsuitable Source
Pump Back PS
TransferPS
Chlorine Disinfection
Chlorine Analyser
To Reticulation
b) Margaret River scheme 2001
Ten Mile Brook DamCap 1,690,810m3
TWL 121.27mAHDLevel 2 Source
Margaret RiverUnsuitable Source
Pump Back PS
TransferPS
Chlorine Disinfection
To Reticulation
UV DisinfectionPump back inlet pipe relocated to back of dam
c) Margaret River scheme with the addition of UV disinfection August 2004
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Long Term Plan
The use of the high risk River pump back and reliance on a single UV barrier was a catalyst to commence planning to stabilise the long term water supply to the town.
This process was instrumental in establishing the water quality principles of the ADWG in the guidelines used by planners for selecting new sources. Relevant statements in the ADWG include:“the greatest risk to consumers of drinking water is pathogenic micro-organisms” (ADWG 1-1)
“prevention of contamination provides greater safety than removal of contaminants by treatment, so the most effective barrier is protection of source water to the maximum degree practical” (ADWG 1-2).
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Long Term Plan
This resulted in the Corporation establishing a preference order for new sources based on pathogen risk as set out below
•Confined groundwater•Unconfined groundwater•Surface water (large dam)•Surface water (small dam)•Pump back only acceptable if dam not operated for min 30 days after pump back ceases
The long term planning for the town has subsequently recommended using a confined aquifer source.
2007 Winter
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
•Low runoff to Dam
•% River water> 50%
•Breached colour and turbidity PCPs on dam outlet
•Single barrier may be compromised
•Corporate incident declared
•Stopped pumpback
•Decision to install MF on dam outlet (8-10 MLD)
Action Plan
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
•$10M for dam outlet too expensive
•$5M for pump back only (4MLD)
•Upgrade UV treatment on dam outlet
•Bought the private catchment land and fenced
•New source due 2012
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Auto shutoff when turbidity > 5 NTUTurbidity
Analyser
Ten Mile Brook DamCap 1,690,810m3
TWL 121.27mAHDLevel 2 Source
Margaret RiverUnsuitable Source
Pump Back PS
TransferPS
Chlorine Disinfection
Auto shutoff when chlorine system fails
Turbidity & Chlorine
Analysers
Auto shutoff when
turbidity > 5 NTU
To Reticulation
UV Disinfection
d) Margaret River scheme with the addition of turbidity analysers and auto shutoff 2007
Auto shutoff when turbidity > 5 NTUTurbidity
Analyser
Ten Mile Brook DamCap 1,690,810m3
TWL 121.27mAHDLevel 2 Source
Margaret RiverUnsuitable Source
Pump Back PS
TransferPS
UV DisinfectionChlorine
Disinfection
Auto shutoff when UV or chlorine
systems fail
Turbidity & Chlorine
Analysers
Auto shutoff when
turbidity > 5 NTU
To Reticulation
e) Margaret River scheme with the upgrade of UV disinfection December 2007
Auto shutoff when turbidity > 0.3 NTU or Colour >10 TCU
Turbidity & Colour
Analysers
Ten Mile Brook DamCap 1,690,810m3
TWL 121.27mAHDLevel 2 Source
Margaret RiverUnsuitable Source
Pump Back PS
TransferPS
UV DisinfectionChlorine
Disinfection
Auto shutoff when UV or chlorine systems fail
Turbidity & Chlorine
Analysers
Auto shutoff when
turbidity > 5 NTU
To ReticulationMembrane
Filter
f) Margaret River scheme with the addition of membrane filtration September 2008
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Current Situation
These actions have considerably reduced the water quality risks at the town while the long term solution is implemented (now expected in 2012).
All waters entering the dam are now considered “low risk” with respect to cryptosporidium and giardia. The UV on the outlet of the dam is a robust second line of defence for the treated water supply. The micro filtration and UV plants are both designed to “fail safe” which means failure to achieve PCP & CCP targets result in the supply shutting down automatically.
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Lessons Learnt
•Climate change/drought has seriously undermined system yield for many schemes
•New source development is expensive and takes many years
•There is pressure to use high risk sources (of unknown pedigree) to augment supply in the short term
•Application of WSP principles should be applied to those temporary sources to
•Minimise risk to customers•Demonstrate due diligence