Cape T own Wate r Outlook 2018 Upda te d 21 F e b rua ry 2018 De pa rtme nt o f Wa te r a nd Sa nita tio n City o f Ca pe T o wn
Cape T own’s wate r is par t of an inte gr ate d syste m Ca pe T o wn g e ts its wa te r fro m a syste m o f da ms tha t supply a g ric ulture a nd o the r urb a n a re a s. T he c urre nt syste m is he a vily de pe nde nt o n ra infa ll. T his c o mple x syste m is ma na g e d b y the na tio na l De pa rtme nt o f Wa te r a nd Sa nita tio n. Ab o ut a third o f the wa te r in this syste m is use d b y a g ric ulture a nd 7% b y o the r urb a n a re a s (sma lle r to wns).
Why is the r e a shor tage of wate r in Cape T own? T he Na tio na l De pa rtme nt o f Wa te r a nd Sa nita tio n Ca pe T o wn is e xpe rie nc ing a n is re spo nsible fo r pla nning a nd imple me nting unpre c e de nte d multi-ye a r wa te r re so urc e s sc he me s to me e t wa te r de ma nd fo r c itie s, industrie s, mining a nd a g ric ulture . dro ug ht e ve nt. T he De pa rtme nt pla ns a t a 1 in 50 ye a r le ve l o f a ssura nc e . T his me a ns tha t during dro ug hts with a se ve rity o f 1:50 ye a rs o r mo re , re stric tio ns ne e d to b e impo se d to re duc e de ma nd. T he c urre nt dro ug ht is muc h mo re se ve re tha t a 1 in 50 dro ug ht e ve nt. T he be st e stimate o f the re turn inte rval o f the me te o ro lo gic al dro ught in the re gio n o f WCWS S dams is 311 ye ars, with 90% c o nfide nc e that it ac tually falls be twe e n 105 and 1280 ye ars 1 . T he ne xt a ug me nta tio n sc he me fo r Ca pe T o wn wa s pla nne d fo r 2022/ 3 a nd is b e ing a c c e le ra te d b y the na tio na l De pa rtme nt. T his sc he me (a ug me nta tio n o f Vo e lvle i Da m) is unlike ly to b e re a dy b e fo re 2021.
Will it r ain again? Ye s. Histo ric al (gre y) and pre dic te d (pink) annual rainfall fo r Cape T o wn, ac c o rding to 16 glo bal c limate mo de ls. Ye llo w do ts indic ate rainfall inc ide nts e qual to o r lo we r than 2017 rainfall. Ra infa ll in the Ca pe T o wn a re a is va ria b le . We tte r a nd drie r ye a rs a re c o mmo n. 16 g lo b a l c lima te mo de ls pre dic t a n o ve ra ll de c line in ra infa ll fo r Ca pe T o wn in the future with mo re dry ye a rs a nd fe we r we tte r ye a rs. A sc e na rio in whic h it do e s no t ra in the future o r in whic h it o nly ra ins a t 2017 le ve ls is unre a listic . S o urc e s: 1 F ac ts are fe w, o pinio ns ple nty… o n dro ught se ve rity again (January 2018) I s Cape T o wn’ s dro ught the ne w no rmal? (1 No ve mbe r 2017) Why Cape T o wn’ s dro ught was so hard to pre dic t (19 Oc to be r 2017) www.c sag.uc t.ac .za
3000 Daily consumption MLD 2500 1028 2000 983 737 846 1500 254 451 136 28 1000 55 1218 1100 28 27 1100 27 1010 1039 979 917 884 856 500 821 794 764 368 361 201 329 284 275 184 125 94 136 0 77 83 Nov-17 Dec-17 Jan-18 Feb-18 Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Sep-18 Oct-18 Evaporation - Maximum Urban (DWS average of last 5 years) Agriculture unrestricted R E ST R ICT T O 3000 Daily consumption MLD 2500 2000 1500 411 393 295 339 1000 102 181 55 605 670 11 605 22 556 571 11 11 500 11 504 538 486 471 437 452 420 368 361 201 284 329 275 184 125 94 136 0 77 83 Nov-17 Dec-17 Jan-18 Feb-18 Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Sep-18 Oct-18 Evaporation - Maximum 45% restricted Urban Agriculture 60% restricted
Cape T own will ge t thr ough the dr ought IF r e str ic tions on dam withdr awals ar e e nfor c e d T he le ve l o f wa te r in the da ms Ove ra ll le ve l o f the Da ms supplying Ca pe T o wn will no t dro p b e lo w 10% this ye a r if re stric tio ns a re a dhe re d to a nd a ssuming a no the r lo w ra infa ll ye a r. Mo nito ring da m le ve ls (inflo w, e va po ra tio n a nd withdra wa ls) a nd ma na g ing da m withdra wa ls is a ke y to ma inta ining the inte g rity o f the syste m a nd g e tting thro ug h the dro ug ht.
Both the City and agr ic ultur e MUST adhe r e to the r e str ic tions impose d on the syste m. Ove r a b stra c tio n b y a g ric ulture is a ke y risk to the syste m. Ca pe T o wn is no t ye t me e ting its ta rg e t.
F or Cape T own, this me ans that de mand must now be manage d down to be low 450 Ml/ day. While Ca pe T o wn ha s sig nific a ntly re duc e d its de ma nd (me a sure d he re a s pro duc tio n fro m the tre a tme nt wo rks), fro m a pe a k o f 1200 Ml/ da y in 2015 do wn to b e lo w 600 Ml/ da y, a furthe r re duc tio n in de ma nd is ne e de d to b e lo w 450 Ml/ da y imme dia te ly due to no t me e ting the 500 Ml/ da y ta rg e t. De mand r e duc tion is saving 400 Ml/ day F e b 2017 = 900 Ml/ da y F e b 2018 = 500 Ml/ da y F urthe r me a sure s a re b e ing put in pla c e to re duc e de ma nd, inc luding : • punitive dro ug ht ta riffs • de ma nd ma na g e me nt de vic e s & flo w re stric to rs • mo re a g g re ssive pre ssure ma na g e me nt
Curre nt % Sa ving s: 39% NDWS T ar ge t 45% Pre limina ry Sc e na rio (a s a t Mid-F e b 2018): Antic ipate d Savings: >45% ASSUMPT IONS: - Inc r e me ntal Savings assigne d as follows: - T a riff I nc re a se s: e stima te d a t 50Ml/ da y b y e nd o f June 2018 - WMD insta lla tio ns: e stima te d a t 10Ml/ da y b y e nd o f June 2018 - Pre ssure Ma na g e me nt; T a rg e t Hig h Co nsume rs; L e a k Re pa ir: 32Ml/ da y (mid F e b rua ry to Oc t 2018) - Build Pr ogr amme - 80% suc c e ss o n b uild pro g ra mme de live ring a n a dditio na l 120Ml/ da y b y e nd Oc t 2018
Whe r e augme ntation c ame fr om: Wate r r e silie nc e e me r ge nc y pr ogr amme (May-Oc t 2017) Pro je c t list as at 24 Oc t 2017 e mise s : Pr • Assume no ra in • Build 500 Ml/ da y ne w a ug me nta tio n a s fa st a s po ssib le • No re so urc e c o nstra int
Advic e fr om Inte r national R e vie w (Nove mbe r 2017) 1. Assuming it will not r ain again is not r e alistic 2. Pr ior itise gr ound wate r 3. Do not pur sue te mpor ar y de salination and r e use 4. R e -use is c he ape r than de salination and may be quic ke r to e xe c ute 5. Plan and e xe c ute pe r mane nt de salination at a optimum sc ale oac h fo r re use a nd de sa lina tio n with a wa te r purc ha se 6. A tur nke y appr a g re e me nt will yie ld the lowe st c ost pe r unit of wate r Do not de lay de c isions o n pe rma ne nt re use a nd de sa lina tio n. 7.
Yie ld-c ost c ur ve infor ms pr ior itie s +400 MLD Augme ntation of 400 ML D mor e than 7 time s c ost of WDM supply @ R 6 000m Approximate/Target Unit costs (Rm per MLD) Yie ld ve rsus c o st 30 4 th priority 25 3 rd priority 20 1 st priority -400 MLD 15 De salination savings @ R e - < R 800m use 150 Ml/ day 10 2 nd priority 75 R 3 750 million ML D Gr ound 5 (T MG) 80 ML D R 1 500m Gr ound (Sandy) R 560m 0 +80 ML D -400 -300 -200 -100 0 100 200 300 400 Savings through demand reduction (MLD) Additional supply (MLD)
What about ne w wate r supplie s? Equivalent annual inflow (millions of m 3 ) AUGME NT AT ION 900 800 Aug me nta tio n sc he me s a re a fa r mo re 700 600 e xpe nsive so urc e o f wa te r tha n runo ff 500 fro m ra infa ll. T he vo lume o f runo ff 400 c a nno t b e e a sily a ug me nte d in sho rt 300 time pe rio ds a nd is de pe nde nt o n 200 100 ra infa ll pa tte rns. Unde r po o r ra infa ll 0 c o nditio ns like 2017 we wo uld re q uire Planned 300MLD 500MLD 2017 runoff Average Wet winter a ug me nta tio n o f ~720ML D to ma tc h the augmentation runoff runoff vo lume o f runo ff. De spite a ll a ug me nta tio n e ffo rts, the supply sc he me Estimated cost ranges for treated water treated surface water- historical is vulne ra b le to po o r ra infa ll. by source (R/kl) groundwater extraction - sandy aquifer As c a n b e se e n b e lo w the c o st pe r kl o f permanent re-use wa te r fro m o the r so urc e s va ry permanent desalination c o nside ra b ly. T he c o st o f b ulk wa te r, groundwater extraction - TMG wa ste wa te r a nd re tic ula tio n is c o mmo n temporary water re-use so the c o sts b e lo w c a n b e c o mpa re d to temporary desalination the c o st o f runo ff whic h is R 5.20/ kl vs te mpo ra ry de sa lina tio n a t >R40/ kl. R 0 R 10 R 20 R 30 R 40 R 50
Ne w wate r supplie s ar e impor tant for wate r se c ur ity going for war d but the se will have little impac t this summe r . 70.0% 60.0% I mpa c t o f Ra infa ll I mpa c t o f Ra infa ll 50.0% Urb a n re stric tio n ve ry impo rta nt 40.0% 30.0% 20.0% 10.0% Ne w supplie s ha ve a sma ll But a re ve ry impo rta nt fo r 2019 impa c t this summe r. if winte r ra infa ll is lo w 0.0% JA N- 1 8 M A R- 1 8 A PR- 1 8 M A Y- 1 8 SEP- 1 8 D EC - 1 8 JA N- 1 9 M A R- 1 9 A PR- 1 9 M A Y- 1 9 SEP- 1 9 FEB- 1 8 JUN- 1 8 JUL- 1 8 A UG - 1 8 O C T- 1 8 NO V - 1 8 FEB- 1 9 JUN- 1 9 JUL- 1 9 A UG - 1 9 O C T- 1 9 NO V - 1 9 Re stric te d, 100% 2017 600ML D, 100% 2017 Re stric te d, No Aug me nta tio n Re stric te d, 75% ra in Re stric te d, 150% ra in
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