Grow­ing wa­ter prob­lems

Poor wa­ter qual­ity is the great­est threat to South Africa’s wa­ter se­cu­rity

The Witness - - INSIGHT - ROB HART

“R IPPING off hap­less cit­i­zens” (let­ter in The Wit­ness, Oc­to­ber 16) men­tioned my knowl­edge of tax mis­use. Ex­posed here, it re­lates to more than R500 mil­lion spent by the Depart­ment of Wa­ter and San­i­ta­tion (DWS) to im­prove wa­ter qual­ity in Gaut­eng’s Hart­beespoort Dam (Har­ties).

I con­sider it tax “mis­use” as it know­ingly ap­plied a method pre­vi­ously dis­cred­ited as re­gion­ally in­ap­pli­ca­ble. Har­ties’ ma­jor wa­ter qual­ity prob­lem re­sults from nutri­ent pol­lu­tion, which is the great­est threat to wa­ter se­cu­rity na­tion­wide. To in­crease pub­lic aware­ness and com­pre­hen­sion of this prob­lem, it seems ap­pro­pri­ately in­for­ma­tive to ex­am­ine sources and con­se­quences of nutri­ent pol­lu­tion in a broad con­text, although cov­er­age is nec­es­sar­ily sim­pli­fied and in­com­plete.

DE­CLIN­ING WA­TER QUAL­ITY A GREATER THREAT

Wa­ter is South Africa’s most lim­it­ing nat­u­ral re­source, as re­cent wa­ter re­stric­tions in KZN and Cape Town’s nar­row avoid­ance of day zero surely re­minded us. De­spite over 5 000 dams across the coun­try po­ten­tially able to cap­ture and store nearly 70% of mean an­nual run-off, wa­ter sup­ply re­mains in­se­cure. How­ever, wa­ter se­cu­rity in­volves not only wa­ter quan­tity, but also wa­ter qual­ity.

Wa­ter qual­ity re­lates to the types and amounts of dis­solved chem­i­cals and sus­pended par­ti­cles (liv­ing and inan­i­mate) it con­tains — at­tributes that are of­ten in­sid­i­ously in­tan­gi­ble and some­times even sin­is­ter. Omi­nously, wa­ter qual­ity is pro­gres­sively de­clin­ing in SA — in line with pop­u­la­tion growth and its litany of as­so­ci­ated con­se­quences: more de­vel­op­ment, more waste, more habi­tat dis­tur­bance and en­vi­ron­men­tal degra­da­tion, etc.

It is im­por­tant to recog­nise that de­clines in wa­ter qual­ity of­ten pose a greater threat than di­rect wa­ter short­ages: they are of­ten cryp­tic and cu­mu­la­tive, and not nec­es­sar­ily di­rectly im­proved or re­versed im­me­di­ately by drought-break­ing rain.

Pol­lu­tion by nu­tri­ents — no­tably ni­tro­gen (N) and par­tic­u­larly phos­pho­rus (P) — is the most wide­spread of many threats to wa­ter qual­ity in SA. Termed “eu­troph­i­ca­tion” (lit­er­ally food en­rich­ment), it is the great­est threat to in­land and coastal waters glob­ally — a bizarre irony given the nat­u­ral scarcity of these es­sen­tial life el­e­ments that jus­ti­fies great ex­pen­di­ture to fer­tilise crops. The short­age of P is es­pe­cially acute in nat­u­ral fresh­wa­ters, which re­ceive only resid­ual amounts left to leach into wa­ter­courses. Con­versely, sewage is nutri­ent-rich as hu­mans ex­crete more P per unit time than leaches from scores of hectares of nat­u­ral land. With in­creas­ing and more ur­banised pop­u­la­tions, age­ing waste­water (sewage) treat­ment plants are lit­er­ally drown­ing in sh**, many un­able to meet even the lib­eral ef­flu­ent dis­charge lim­its leg­is­lated for P. Along­side nutri­ent-rich run-off from agri­cul­tural lands, nutri­ent in­puts to dams are un­sur­pris­ingly high and ris­ing. Dis­con­cert­ingly, up to 70% by vol­ume of all wa­ter stored in dams is al­ready highly or ex­tremely nutri­ent en­riched.

BRO­KEN LINK IN THE FOOD CHAIN

Eu­troph­i­ca­tion has many con­se­quences, mostly neg­a­tive. Ex­ces­sive plant growth is the most ob­vi­ous symp­tom. Pro­lific plant pro­duc­tion with no fer­tiliser cost — lots of fod­der for live­stock, or plen­ti­ful food for fish aqua­cul­ture — may sound ideal for any agri­cul­tural en­ter­prise, how­ever,

the re­al­ity is far from ideal — blooms of un­sightly, smelly and some­times toxic al­gae and cyanobac­te­ria (aka blue-green al­gae: Photo 1) and/or float­ing wa­ter plants (Photo 2). Par­tic­u­larly as this bountiful pro­duc­tion does not feed fish, but in­stead fu­els un­der­wa­ter mi­cro­bial de­com­posers that de­plete oxy­gen lev­els in wa­ter — the re­sult of a “bro­ken link” in the food chain ex­plained by my PhD stu­dent’s re­search into zoo­plank­ton feed­ing bi­ol­ogy in the highly eu­trophic Har­ties ecosys­tem in the mideight­ies.

Zoo­plank­ton are small in­ver­te­brates, mostly less than one mil­lime­tre, that act as the prin­ci­pal her­bi­vores in pe­lagic zones — broadly equiv­a­lent to an­te­lope graz­ers in sa­van­nah ecosys­tems.

He showed that the blue-green alga Mi­cro­cys­tis — the “plant” then dom­i­nant in Har­ties, sim­ply grew too large to be eaten by fil­ter-feed­ing zoo­plank­ton, par­tic­u­larly the wa­ter flea Daph­nia. Ex­cluded from the “di­rect” food chain by “im­mu­nity” to grazer re­duc­tion, Mi­cro­cys­tis pro­lif­er­ated freely to form ex­pan­sive sur­face scums (Photo 1) be­fore dy­ing and de­com­pos­ing.

Eu­troph­i­ca­tion is a global prob­lem. In nat­u­ral lakes, spe­cialised pe­lagic fish can de­plete zoo­plank­ton suf­fi­ciently for al­gae to pro­lif­er­ate unchecked by zoo­plank­ton graz­ing, lead­ing to the con­cept of “bioma­nip­u­la­tion” — pur­pose­ful food web al­ter­ation to con­trol al­gae.

In essence, in­crease the num­ber of fisheat­ing “large fish” to re­duce the num­ber of zoo­plank­ton-eat­ing “small fish”, thereby al­low­ing al­gal-eat­ing zoo­plank­ton to in­crease and con­se­quently re­duce al­gae. This seem­ingly ob­vi­ous and sim­ple so­lu­tion hinges on two cri­te­ria: zoo­plank­ton Rood­e­plaat Dam: raft of wa­ter hyacinth (photo 2). must eat and re­duce the prob­lem al­gae, and zoo­plank­ton must be too few to re­duce al­gae be­cause of their de­ple­tion by small fish pre­da­tion. Nei­ther cri­te­ria per­tain in Har­ties.

Mi­cro­cys­tis is im­mune to graz­ing and “small fish” are lack­ing (fishes in dams de­rive from river­ine species which lack spe­cialised zoo­plank­ton-eat­ing “small fish”). So bioma­nip­u­la­tion is a non-starter from the out­set.

BIOMA­NIP­U­LA­TION NOT A CRED­I­BLE TOOL TO TREAT SYMP­TOMS OF EU­TROPH­I­CA­TION

How does all this re­late to waste­ful tax use? In 2004, two ar­ti­cles on Har­ties in Wa­ter Wheel (“New hope for trou­bled waters” and “An ac­tion plan”) an­nounced DWS pro­pos­als for fu­ture eu­troph­i­ca­tion man­age­ment. Namely, to re­place con­trol mea­sures that pre­vent nutri­ent pol­lu­tion with restora­tive bioma­nip­u­la­tion to treat symp­toms of eu­troph­i­ca­tion.

Hop­ing to avoid a mis­guided fail­ure (know­ing that bioma­nip­u­la­tion is sci­en­tif­i­cally un­founded), I pre­pared a de­tailed com­men­tary and po­si­tion pa­per (pub­lished in 2006) that eval­u­ated its prospec­tive suit­abil­ity in Har­ties and SA reser­voir ecosys­tems. This negated bioma­nip­u­la­tion as a vi­able man­age­ment op­tion, ex­pos­ing it as an “il­lu­sory pipe dream” in ev­ery re­spect. The “Har­ties Metsi a me” (HMaM) restora­tion pro­gramme went ahead re­gard­less in Fe­bru­ary 2008, steered by a DWS re­gional ex­ec­u­tive and a fish-cen­tred eco­log­i­cal con­sul­tancy in Gaut­eng whose fru­gal knowl­edge of ba­sic lake ecol­ogy, and al­most to­tal ig­no­rance of dam(ned) zoo­plank­ton (re­garded as an in­con­ve­nient truth) was ev­i­dent from the pro­nounce­ments in 2004.

Was HMaM suc­cess­ful and what did it cost? Over­all, it cost “more than R500 mil­lion to 2015” (DWS 2017). DWS prin­ci­pals un­sur­pris­ingly hailed it a great suc­cess, with a ded­i­cated pub­lic web­site de­tail­ing its op­er­a­tional struc­ture and ac­com­plish­ments (e.g. re­moval of 350 tons of fish in to­tal, etc.), and sub­se­quent calls for its ex­pan­sion and ex­ten­sion.

How­ever, analy­ses of a very de­tailed record of satel­lite im­ages pro­vided no ob­jec­tive sup­port for this pur­ported suc­cess. Al­gal abun­dance dur­ing six years be­fore and four years after HMaM be­gan in 2008 did not dif­fer on av­er­age. A very slight neg­a­tive trend (de­cline in al­gae) ev­i­dent in Har­ties after 2008 can­not be at­trib­uted di­rectly and ex­clu­sively to HMaM, since par­al­lel trends oc­curred in neigh­bour­ing and dis­tant dams. All co­in­cided broadly with a sur­pris­ing, and presently in­ex­pli­ca­ble na­tion-wide de­cline of P in river wa­ter.

Re­search con­tin­ued since I re­tired in 2007 has filled pre­vi­ous knowl­edge gaps, leav­ing bioma­nip­u­la­tion with no cred­i­bil­ity as a tool to man­age eu­troph­i­ca­tion in our dams — a bland state­ment based on con­sid­er­able sub­stan­tive ev­i­dence out­side the scope of this ar­ti­cle, but pub­lished in sev­eral re­search ar­ti­cles.

SCURRILOUS AT­TEMPT TO HIDE THE DE­BA­CLE

Hav­ing spent half a bil­lion rand, DWS sur­rep­ti­tiously “plugged the plug” on HMaM in 2017. A re­gional press re­port at­trib­uted its ter­mi­na­tion to “al­le­ga­tions of cor­rup­tion, nepo­tism and in­fight­ing”.

The DWS web­site de­tail­ing HMaM ac­tiv­i­ties and achieve­ments sud­denly dis­ap­peared, sug­gest­ing a scurrilous at­tempt to hide the de­ba­cle and avoid ac­count­abil­ity by the DWS sec­tion in­volved — ne­far­i­ous cir­cum­stances, given its fund­ing from the na­tional fis­cus. While Hart­beespoort Dam it­self can­not be re­named Hart­beesgate Dam, at least its Nkandla-gate scale fi­nan­cial haem­or­rhage has been plugged. Other tax wastages must await call­ing out. Read­ers can de­cide for them­selves whether my charge of tax “mis­use” or “waste” is jus­ti­fied.

Closer to home: what ef­fect has the Khayelit­sha hous­ing scheme on Mid­mar’s shores had on wa­ter qual­ity in the Mgeni sys­tem? De­spite pre­dictable neg­a­tive con­se­quences (“Howick to Hol­ly­wood”, The Wit­ness, Oc­to­ber 16, 2002), and leg­is­lated en­vi­ron­men­tal re­stric­tions, it was driven ahead by a sub­se­quently dis­graced for­mer mayor of Howick with vested in­ter­ests in its de­vel­op­ment.

UNTESTED NEW TECH­NOLO­GIES COULD PRO­VIDE THE AN­SWER Else­where, near-coastal arid na­tions like Is­rael rely on sea­wa­ter de­salin­i­sa­tion to en­sure an ad­e­quate wa­ter sup­ply. Although tri­alled as an emer­gency mea­sure for Wilder­ness, the process (able also to mit­i­gate wa­ter qual­ity prob­lems) re­mains un­af­ford­able in SA. Re­cy­cling of do­mes­tic waste­water is eco­nom­i­cally more fea­si­ble, but un­jus­ti­fi­ably re­mains widely per­ceived as ab­hor­rent — a pub­lic mind-set that cir­cum­stances may force to change.

New and emerg­ing tech­nolo­gies (re­verse os­mo­sis and mem­brane fil­tra­tion) re­main largely untested, but may prove cost-ef­fec­tive in time. A more im­me­di­ate glim­mer of hope to com­bat eu­troph­i­ca­tion is of­fered by the grow­ing global short­age of nat­u­ral P, pro­vid­ing a po­ten­tial eco­nomic in­cen­tive to im­prove P re­cov­ery from waste­water, to fer­tilise crops more con­ser­va­tively, and even to re­trieve P ac­cu­mu­lated in lake sed­i­ment de­posits (2 000 tons in Har­ties alone), but it can­not di­rectly in­crease wa­ter sup­ply.

POTABLE WA­TER UN­DER THREAT

In the in­terim, it is cru­cial to in­crease cit­i­zen aware­ness of the threat posed by the ac­cel­er­at­ing wa­ter qual­ity de­cline in our reser­voirs — the source of potable wa­ter for most cit­i­zens. Three decades ago, South Africa was glob­ally at the cut­tingedge of reser­voir lim­nol­ogy (the dis­ci­pline of hu­man-made lake stud­ies), with highly com­pe­tent, sci­en­tif­i­cally skilled ex­per­tise avail­able to ad­dress the prom­i­nent con­cerns. The prac­ti­tion­ers re­main­ing to­day are fewer than fin­gers on a hand, and like me, all are in their twi­light years. The HMaM saga in­di­cates the present level of sci­en­tific (in)com­pe­tency in reser­voir lim­nol­ogy. Given our re­liance on reser­voirs, this is a par­lous sit­u­a­tion for which the Na­tional Re­search Foun­da­tion and Wa­ter Re­search Com­mis­sion are largely, if in­ad­ver­tently, re­spon­si­ble.

• Rob Hart, pro­fes­sor emer­i­tus, School of Life Sciences, UKZN; but writ­ten in a per­sonal ca­pac­ity. Hart is an alum­nus of the Univer­sity of Na­tal, and a Fel­low of UKZN, who holds a PhD (Rhodes) and a DSc (Na­tal). Au­thor of some 125 ma­jor pub­li­ca­tions, he has held con­tin­u­ous NRF ac­cred­i­ta­tion since 1987 and was hon­oured with the Gold Medal award of the African So­ci­ety of Aquatic Sciences in 2017.

Hart­beespoort Dam: sur­face scum of Mi­cro­cys­tis alga at wall (photo 1).

PHO­TOS: ROB HART

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