Potential Water Supply to Morupule B

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Potential Water Supply to Morupule B

• PHAKALANE GOLF ESTATE
• 04 DECEMBER 2008
• PRESENTED BY
• NGINANI MBAYI
• TECHNICAL SERVICES DIRECTOR
• WATER UTILITIES CORPORATION

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Introduction

• The North South Carrier Water Supply Scheme (NSC)
  which is a direct result of the recommendations
  of the National Water Master Plan (NWMP) of 1992
  is in two parts
• Phase I which is currently in operation
• Phase II which is at conceptual design stage
• The objective of the scheme is to transfer water
  from the available water resources in the north
  to the bigger demand centers in the south of the
  country

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Major Dam Sites
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POTENTIAL DEMANDS ON NSC SOURCES
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NSC I

• This was the biggest water supply scheme ever
  embarked on in Botswana
• It comprises of Letsibogo Dam (100MCM capacity),
  360km pipeline, 3 pumping stations, 3 break
  pressure tanks and 3 treatment plants.
• The treatment plants are at Palapye, Mahalapye
  and Mmamashia
• The scheme has the potential to transfer 120Ml/d
  or 44MCM per annum of water from the north
• However the sustainable yield of Letsibogo Dam at
  70 Ml/d is a limiting factor
• The scheme, implemented at a cost of P1.5 billion
  at the time, was commissioned in August 2000
• NSC I was primarily earmarked to supply water to
  the Greater Gaborone area (76 of the total
  demand in 2035) with supply to demand centres of
  Palapye and Mahalapye along the route.

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NSC I Operational Challenges

• After completion, the scheme experienced
  intermittent outages
• Two pipeline materials were adopted, Glass
  Reinforced Polyester (GRP) (220 km) and welded
  Steel (140 km)
• Problems were experienced largely on the GRP
  section in couplings and rocker pipes adjacent to
  chambers
• Outages are fairly frequent lasting up to 5 days
  before repairs
• While the scheme was primarily earmarked to
  supply water to the greater Gaborone Area which
  includes Gaborone, Lobatse, Tlokweng
  Mogoditshane, Ramotswa, Mochudi as well as the
  villages of Palapye and Mahalapye, additional
  demand centres of Serowe, Kanye and Molepolole
  will be included in due course due to severe
  water shortages there.

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Morupule Water Demand Node

• Water demand projections from NSC is based on a
  50 conjunctive use with other sources such as
  groundwater.
• The demand projections cater for both Morupule
  Colliery and Power Station.
• The demand projections are estimated at a maximum
  of 2.75 Mm³/annum.
• The drawoff will initially start off with
  construction of water, which is relatively small,
  and picking up during production from 2.42
  Mm³/annum in 2014 until it reaches the maximum of
  2.75 Mm³/annum in 2020 and continues at this
  level.

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• Discussions with Morupule Colliery and BPC have
  been held with regard to their respective water
  demands.
• It appears the allocated 2.75 Mm³/annum will meet
  their requirements.

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NSC PIPELINE PROFILE AND FAILURE POINTS2000-2008
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NSC I Maintenance Issues

• A 15 year maintenance guarantee was adopted to
  allow for extended support largely to the new GRP
  pipe material.
• This arrangement has not been completely
  beneficial to WUC
• The scheme was shutdown for major maintenance in
  June 2006 and several couplings were replaced
• The scheme was subsequently used to circumvent
  the severe drought of 2005/2006 when the level of
  Gaborone reached its record lowest of 16
• Another shutdown was done in June 2007 primarily
  to install additional line valves so as to
  minimize water losses during pipe repairs
• NSC I availability has been estimated to be 70
  excluding the periods of planned shutdowns.
• Maintenance of NSC I has todate cost P12 million

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NSC II

• The NWMP projected water demands up to 2035 are
  due to exceed the current supply capacity of NSC
  I in the short to medium term
• The north eastern dams are the only source with
  sufficient capacity to meet additional demand
• Government decided that the transfer capacity of
  NSC II should be 45MCM per annum independent of
  design horizon
• It has been demonstrated that the transfer of
  45MCM per annum under NSC II over and above that
  of NSC I is adequate to meet forecast demand to
  the year 2035
• The conceptual design of NSC II allows for the
  injection of ground water from Khurutshe(Masama)
  and Palla Road well fields. These are planned as
  standby resources.

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NSC II Continued

• NSC II sources will include Shashe dam, Letsibogo
  dam and the future Dikgatlhong dam which is
  scheduled for completion in 2012.
• NSC II will generally follow the same route as
  NSC I but will be operated independently.
• Due to the NSC I experiences, it was decided that
  Steel or Ductile Iron will be the preferred
  pipeline materials
• The estimated construction cost of NSC II is P3.6
  billion
• Completion of the scheme is anticipated to be end
  of 2012

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Conclusion

• Based on the availability of both NSC I and II,
  water supply to Morupule B can be met

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• I thank you for your attention