Ru­mors over wa­ter project de­struc­tive

China Daily (Canada) - - COMMENT -

The South-North­Wa­ter Di­ver­sion Project is ex­pected to be­gin sup­ply­ing wa­ter to Beijing by the end of this week, but ru­mors are do­ing the rounds that the cap­i­tal may have to wait longer for wa­ter from South China be­cause the cen­tral route canal has frozen.

In a widely cir­cu­lated blog post­ing, an “ob­server” claims to have no­ticed the “slow flow” in the cen­tral route canal, say­ing this could pre­vent wa­ter from reach­ing the cap­i­tal in win­ter. The “ob­server” also says silt­ing could dam­age the canal.

The blog­ger’s claims are ab­surd, to say the least. The blog post­ing says the cen­tral canal will trans­fer wa­ter at the rate of 22.4 cu­bic me­ters per sec­ond, or one-tenth of the de­signed ca­pac­ity, be­cause a China Cen­tral Tele­vi­sion news video shows a Rub­ber Duck mov­ing 10 cen­time­ters per sec­ond in its wa­ter.

Peo­ple with even the ba­sic knowl­edge of physics know that the ve­loc­ity of a float­ing ob­ject is not equal to that of wa­ter, be­cause the for­mer meets re­sis­tance from the lat­ter from be­low and air from above. Be­sides, the wa­ter ve­loc­ity varies with depth— a river that is calm might have fierce cur­rents flow­ing be­low the sur­face. A rough cal­cu­la­tion shows a speed of 10 cm per sec­ond means 8 kilo­me­ters in 24 hours. If the canal wa­ter in­deed trav­els at such a slow pace, as the blog post­ing claims, the wa­ter should not have crossed South China even to­day.

The fact, how­ever, is, wa­ter in the canal reached Zhengzhou, He­nan prov­ince, in Cen­tral China ear­lier this month, three days after the project’s cen­tral route was opened and flowed in­toHe­bei prov­ince in­North China a few­days ago. Does the blog­ger know th­ese facts?

The South-North­Wa­ter Di­ver­sion Project’s ul­ti­mate aim is to trans­fer 44.8 bil­lion cu­bic me­ters of fresh­wa­ter north­wards from the Yangtze River ev­ery year. The east­ern route canal will trans­fer wa­ter through Jiangsu, Zhe­jiang, He­bei and Shan­dong prov­inces, the cen­tral route to Beijing and Tian­jin, and the western route to Shanxi, Shaanxi, Gansu andQing­hai prov­inces and the In­nerMon­go­lia and Ningxia Hui au­ton­o­mous re­gions.

The blog­ger’s con­cern over silt, mainly de­posits of mud and sand, ap­pears a lit­tle more rea­son­able, though, be­cause it is un­avoid­able given the rel­a­tively slow flow of wa­ter in the Dan­jiangkou Reser­voir in­Hubei prov­ince, a ma­jor source of wa­ter for the project. But this prob­lem is con­fined to the Dan­jiangkou Reser­voir, be­cause the flow of wa­ter in the cen­tral canal will en­sure that it is not plagued by silt. Thus, there is no need to worry about the canal be­ing dam­aged by silt.

Even the silt in the Dan­jiangkou reser­voir is noth­ing se­ri­ous. The reser­voir, built in 1958, is a multi-pur­pose fa­cil­ity that serves as a ma­jor source of wa­ter for the re­gion, gen­er­ates elec­tric­ity and con­trols floods. Since the canal that sup­plies wa­ter to power plants is sit­u­ated at a lower al­ti­tude than the one which sup­plies wa­ter to the south-north project, silt in the reser­voir won’t do any harm as long as the hy­draulic power plant func­tions nor­mally.

Silt­ing is a nor­mal phe­nom­e­non, typ­i­cal of all reser­voirs. Ev­ery reser­voir has a bal­anc­ing point of silt de­posits and the vol­ume of wa­ter, and the Dan­jiangkou Reser­voir reached that point long ago. The blog post­ing didn’t con­sider this most ba­sic prin­ci­ple.

Ac­cord­ing to project au­thor­i­ties, the cli­mate varies along the canal, which stretches 1,432 km from South to North China, and the sec­tion north of Anyang in He­nan prov­ince could freeze in the win­ter. It is es­ti­mated that the rate of flow in the canal would drop by 40 per­cent be­cause of the freez­ing on the sur­face — but that will not af­fect the flow of wa­ter un­der the sur­face.

Con­cern over the South-North project is wel­come, but spread­ing ru­mors is rather de­struc­tive. Once the wa­ter from the south reaches Beijing, ru­mors will die a nat­u­ral death. The au­thor is a se­nior re­searcher at China So­ci­ety forHy­dropower En­gi­neer­ing.

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