MALKERNS CANAL Presentation.pdf - Swaziland
MALKERNS CANAL Presentation.pdf - Swaziland
MALKERNS CANAL Presentation.pdf - Swaziland
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
RDMU Investigations<br />
On behalf of the<br />
European Commission
HISTORY<br />
• Canal constructed about 54 years ago<br />
• Built very economically but could never supply the full<br />
100 cusecs to the users<br />
• Has been damaged in places by Cyclones<br />
• Has worked well and been maintained
Survey
Original Design & Construction<br />
• Canal designed for 100 cusecs<br />
• Canal is unlined for whole 29 km length<br />
• Canal has insufficient protection from stormwater and<br />
silt ingress<br />
• Canal cannot deliver more than about 50 cusecs to end<br />
users<br />
• Flume structures are at structural design limit<br />
• Construction is not up to design level
Work undertaken todate<br />
• Flow recordings at 4 sites<br />
• Topographical survey of whole canal<br />
• Structural inspection of flumes<br />
• Structural design checks on flumes<br />
• Hydraulic design checks on flumes<br />
• Inspection of sections of canal<br />
• Preparation of report on the canal<br />
• Cost estimates of proposed remedial work
Constraints in Water Delivery<br />
• Restrictions in flow at some flumes<br />
• Seepage losses through the ground<br />
• Ongoing siltation from uphill side<br />
• Losses at flumes and at under-drains
Ideal Scenario<br />
In order to deliver 100 cusecs<br />
• Concrete line whole canal to line and level<br />
• Construct access route on uphill side<br />
• Construct under-drains to prevent siltation<br />
• Install road, cattle and pedestrian crossings<br />
• Remove all trees from canal<br />
• Use syphons instead of flumes at some streams
Constraints on Repairs<br />
• Finances<br />
• Time outages on the canal – 4 weeks/year<br />
• Access to most sections
Purpose of EC Funding<br />
• Reduce risk of canal failure<br />
• Improve quantity of water delivered<br />
• Reduce maintenance costs
Issues for Rehabilitation of Canal<br />
• Short construction duration<br />
• Must have cost benefit to end users<br />
• Must be a mid to long term solution
Critical Areas along Canal<br />
• All flumes need some repair work<br />
• Flume 8 is a bottle neck to flow and likely to fail<br />
• Sections of forest area likely to fail with increased<br />
water flow due to ground crossfalls and flumes 9, 10<br />
and 11 likely to become bottlenecks when flume 8<br />
replaced.<br />
• Usutu forest area is a difficult section to maintain<br />
• Seepage losses greatest from flume 5 to 6
Proposed EC funding options<br />
• Repair the flumes and intake<br />
• Replace Flume 8 with siphon<br />
• Bypass the Usutu forest section with Siphon, which<br />
also by-passes Flumes 9, 10 and 11.
Flume repairs<br />
• Repair tops of piers<br />
• Stiffen up sections of the steel trusses<br />
• Repaint structural steelwork<br />
• Reseal end joints<br />
• Line concrete channel with an internal epoxy coating<br />
• Improve inlets and outlets to improve flow<br />
• Remove all vegetation from the flumes
Intake
Flume 2
Flume 8 replacement<br />
• Construct new flume upstream with large profile to<br />
allow for full design flow<br />
• OR construct a siphon to bypass the flume
Flume 8
Bypass Usutu Forest<br />
• Construct siphon from Research Station to Maseko<br />
farm.<br />
• (Optional siphon route.)<br />
• Total length 1.25 km for both siphons<br />
• Buried 1200 dia GRP pipeline with concrete inlets and<br />
outlets
Siphon Position
Flume & dump gate repairs<br />
• Advantages<br />
Reduce risk of canal failure<br />
Reduce risk of canal outages<br />
Reduce water losses<br />
• Disadvantages<br />
Canal will have to be taken out of commission to<br />
undertake some work (2 weeks should be adequate)
Flume 8 Replacement<br />
• Advantages<br />
Flume has high risk of failure<br />
Flume is a primary restriction in flow in system<br />
Flow can be increased by estimated 15 cusecs<br />
Can be replaced without affecting canal flow<br />
• Disadvantages<br />
Difficult access to the site<br />
Adjacent canal must also be increased in width and/or<br />
have increased fall
Bypass Usutu Forest<br />
Advantages<br />
It will omit 7 km of the canal or 24% of the canal length<br />
It will allow full design flow of canal to be transmitted<br />
It will reduce water losses by 0.5 cusecs or 2%<br />
It will ease maintenance<br />
It will reduce maintenance costs<br />
Work can be done without affecting canal operations<br />
There are no water users along this section of canal
Costs<br />
• Repair the Flumes and gates -E1.1 Million<br />
• Replace Flume 8<br />
-E3.9 Million<br />
• Siphon to omit Usuthu Forest-E16.2 Million<br />
SUB-TOTAL<br />
-E21.2 Million<br />
Allow 12% contingency -E2.8 Million<br />
TOTAL<br />
-E24.0 Million
RECOMMENDATIONS<br />
Proposed work utilising EC Funding<br />
• Repair the Flumes and gates<br />
• Replace Flume 8 with a Siphon<br />
• Install Siphon to omit Usuthu Forest section
Change language