Water resources for Botswana David Stephenson Profstephenson@gmail.com
Contents The water situation Sources Demands Existing supplies Chobe Zambezi Lesotho Alternatives
Botswana s Rainfall distribution
Catchments
Mass balance Million Cubic Metres per annum Botswana Surface area km 2 582000 Mean annual rainfall mm/a 400 Inputs Rain Mm 3 /a 203700 Cross border inflow Mm 3 /a 50500 Okavango 10000, Zambesi 40000, Limpopo 500 Wastewater Mm 3 /a 50 Abstractions Evaporation, dams Mm 3 /a 700 Surface/transpiration Mm 3 /a 202500 Evaporation, Okavango Mm 3 /a 10000 River runoff across borders Mm 3 /a 150 Used from dams, rivers Mm 3 /a 140 International Rivers Mm 3 /a 40500 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
Botswana population distribution
Limit of existing sources and conveyances
North South Carrier Pipelines Dikgathong Letsibogo Dam PS2& BPT1 BPT2 Break Pressure Tank PS3 Pump Station BPT3 BPT & PS4g Mmamashi a
Water Supply and demand picture 2006 Dams Yield Ml/d Pipeline Flow Mld Demands Ml/d 25 Francistown 25 25 SelibePhikwe 25 Shashe 10 Tati 10 60 5 Mopani 5 Letsibogo 55 NorthSouth 85 PallaRd 70 MasamaWells 10 85 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
Major dams DAM Capacity Mm3 95% reliable yield Mm3/a 2060 yield Comments Gaborone 140 9 7 To act backup Shashe 80 28 23 For Francistown Letsibogo 100 23 20 NSC 1 Dikgatlhong 400 66 60 NSC 2
District Resource Yield 95% assurance of supply (Mm 3 /annum) All sources North West 2015 2055 Okavango 17 17 Maun Wells 10 10 Ghanzi Ghanzi Wells 2 2 Maitengwe Wells 2 2 Dukwi Wells 2 2 Orapa Wells 7 7 Dikgatlong Dam 72 66 Central Letsibogo Dam 24 18 Moshoro Paye Wells 5 5 Palapye Wells 1-1 - 1 Thune Dam 3 3 Lotsane Dam 5 5 North East Kgatleng Shashe Dam 25.3 20 Ntimbali Dam 3.6 3 Masama Wells 9 9 Bokaa Dam 4.5 3 Southern Jwaneng Wells 13 13 South East Gaborone Dam 9.4 8 Nnywane Dam 1.9 1 International Molatedi Dam 7 5 Totals 229.1 206
Effect of risk on yield
Yield Mm3/a The more water we use from dams the less evaporates Gaborone dam draft Target Draft Evap MAR 40 30 20 10 0 0 5 10 15 20 25 Draft Mm3/a
The Okovango Botswana s largest water body, holds more water than the country will use in 100 years but it is not accessible.
Rain water harvesting Stops evaporation Less storage than dams Pollution danger Drought shortage Costly for houses
Operating rules for conjunctive use
Imports possible ORASECO (Lesotho) 200Mm3/a Zimbabwe Nata 100Mm3/a Limpopo Molatedi 7Mm3/a Chobe 495Mm3/a
Effect of distance and scale on cost
Chobe-Pandamatenga Pipe as originally proposed
Route from Kazungula to Moralane
Meeting demands from CZ and LH phased 2 stage schemes
Nata weir? Could postpone major section of pipe But enviro and International repercussions
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
Annual Expenditure versus income, Phase 1
Lesotho Botswana Transfer Map of Orange Senqu Basin
Water sector use on Orange Senqu
LBWTP transfer routes Stage IV Piped all the way
Allocations
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