Water resources for Botswana

Transcription

1 Water resources for Botswana David Stephenson

2 Contents The water situation Sources Demands Existing supplies Chobe Zambezi Lesotho Alternatives

3 Botswana s Rainfall distribution

4 Catchments

5 Mass balance Million Cubic Metres per annum Botswana Surface area km Mean annual rainfall mm/a 400 Inputs Rain Mm 3 /a Cross border inflow Mm 3 /a Okavango 10000, Zambesi 40000, Limpopo 500 Wastewater Mm 3 /a 50 Abstractions Evaporation, dams Mm 3 /a 700 Surface/transpiration Mm 3 /a Evaporation, Okavango Mm 3 /a River runoff across borders Mm 3 /a 150 Used from dams, rivers Mm 3 /a 140 International Rivers Mm 3 /a Zambesi, Chobe, Limpopo Ground recharge Mm 3 /a 200 Rain harvesting Mm 3 /a 1 Wastewater Mm 3 /a 40 Mined groundwater Mm 3 /a 70 Uses Farms Stock, Irrigation Mm 3 /a 80 Urban & domestic Mm 3 /a 120 Mines, energy Mm 3 /a 50

6 Botswana population distribution

7 Limit of existing sources and conveyances

8 North South Carrier Pipelines Dikgathong Letsibogo Dam PS2& BPT1 BPT2 Break Pressure Tank PS3 Pump Station BPT3 BPT & PS4g Mmamashi a

9 Water Supply and demand picture 2006 Dams Yield Ml/d Pipeline Flow Mld Demands Ml/d 25 Francistown SelibePhikwe 25 Shashe 10 Tati Mopani 5 Letsibogo 55 NorthSouth 85 PallaRd 70 MasamaWells Bokaa 5 Palapye 10 Mahalapye 5 Mmamashia wtw Gaborone 70 Tlokweng 5 65 Mogotitshane 5 Gaborone 25 Molatedi 15 Romotswa Nnywane 5 Lobatsi 10 Total Ml/d 175 Total Ml/d 170

10 Major dams DAM Capacity Mm3 95% reliable yield Mm3/a 2060 yield Comments Gaborone To act backup Shashe For Francistown Letsibogo NSC 1 Dikgatlhong NSC 2

11 District Resource Yield 95% assurance of supply (Mm 3 /annum) All sources North West Okavango Maun Wells Ghanzi Ghanzi Wells 2 2 Maitengwe Wells 2 2 Dukwi Wells 2 2 Orapa Wells 7 7 Dikgatlong Dam Central Letsibogo Dam Moshoro Paye Wells 5 5 Palapye Wells Thune Dam 3 3 Lotsane Dam 5 5 North East Kgatleng Shashe Dam Ntimbali Dam Masama Wells 9 9 Bokaa Dam Southern Jwaneng Wells South East Gaborone Dam Nnywane Dam International Molatedi Dam 7 5 Totals

12 Effect of risk on yield

13 Yield Mm3/a The more water we use from dams the less evaporates Gaborone dam draft Target Draft Evap MAR Draft Mm3/a

14 The Okovango Botswana s largest water body, holds more water than the country will use in 100 years but it is not accessible.

15 Rain water harvesting Stops evaporation Less storage than dams Pollution danger Drought shortage Costly for houses

16 Operating rules for conjunctive use

17 Imports possible ORASECO (Lesotho) 200Mm3/a Zimbabwe Nata 100Mm3/a Limpopo Molatedi 7Mm3/a Chobe 495Mm3/a

18 Effect of distance and scale on cost

19 Chobe-Pandamatenga Pipe as originally proposed

20 Route from Kazungula to Moralane

21 Meeting demands from CZ and LH phased 2 stage schemes

22 Nata weir? Could postpone major section of pipe But enviro and International repercussions

23 Assumed tariffs These tariffs are applied in the base case finance model. Customer category Base Case Tariff (P/kl) Domestic customers 4.50 Industrial customers 4.50 Irrigation customers 1.00

24 Annual Expenditure versus income, Phase 1

25 Lesotho Botswana Transfer Map of Orange Senqu Basin

26 Water sector use on Orange Senqu

27 LBWTP transfer routes Stage IV Piped all the way

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29 Allocations

30 Conclusions Sufficient water for foreseeable future Problem is cost of transmission from distant sources Environmental limitations on groundwater, Delta etc Management possibilities include; Occasional rationing, Increased tariffs to reduce consumption and pay for pipelines Reclamation Domestic management Supporting subsidies; Agricultural self sufficiency Economic advancement Life support to low income population Appointment of a regulator