East Alligator district centre water supply assessment : Kakadu National Park
D . Pidsley
Jamieson, M.; Pidsley, D.; Paiva, Jerome
E-Publications; E-Books; PublicationNT; Technical Report ; 26/1991
1991-02-26
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Date:1991
English
Water-supply -- Northern Territory -- Kakadu National Park; Groundwater -- Northern Territory -- Kakadu National Park; Kakadu National Park (N.T.)
Power and Water Authority
Darwin
Technical Report ; 26/1991
1 v. : ill., maps ; 30 cm.
application/pdf.
Check within Publication or with content Publisher.
https://hdl.handle.net/10070/229020
https://hdl.handle.net/10070/673451
Technical Report WRD91026 Viewed at 15:07:48 on 29/07/2010 Page 100 of 107. =r u:cATIGWrI "". .... CALQI,. lOT'L "'" ... .... ,tLmtA8L .. }.tJi(AL UU TT co, 'lAT'''' STAaa.rfT USlou( """', AS c.co) 1M SOL'" '''''''' "'"X 101t TtlS) pH-- 2!)H_"'1IIH ""'- .. ,,- .,,1. .,11. wmM {PORT' lC(ATS} ... 50 '.2 fl. I -'.9 11' .. 0 a:LYUIH tDELj$SAYIu..lJ " , " ,. 6. j 10 .2 -4.1 1 ..1 JGUIU (IATM.AU Ii.) ,. , .. > lI.1 "'S." 16.1 ICUulLJ,HII (~ IS) '" .. > 10.S .... t'5.7 NHUGUOA <4 2 ,. '.~ U.S ... , fa.o JWutc;INUG " " '.2 11 .1 ..... fl.' TIMICAU. .. 2 , '.> Itl.1 -4.' ".1 '1GPrJG::J " 2 ,., '.1 If .f. ... , !1.1 ....... -- ~ , 17 '.2 11.2 ".0 17.: """"OOLA ,. .. > It .0 .. 5 .. 1 16.1 ""'S, 1Iaf'" "t-..pwIlf'W'>M ~ frQII ,;7 '!'O 10'"'= .. -r JOIH"o::e. oK Is ot u.1. In J ....... tOl'"JP rIOt u 4.U~ .1' :ICIU"~ ,... Is me .:e'-cu"""" ~ ATUn'tM .1111 CIIC01 a" 11\. ealeta. 1Il4 .. lkIIln'tyo of ,a.'e .. CO: c.aJa".lec yalng l.bJnftl""lj pH r"iMGlnq. CQW)SJOH tIGlCU .. :.0 $aite t~~ _iii t-oI" IN"Wffal ,...,. .. 1IOI1oCC4 i .. '_ '.0 t:enQeratura am velocity, am becWe less corrcsive with increasi!'X'J .al.kalinit'/f" hardness am pH (carrier, 1965). Marri ot.'le" factor.! are invol~.. bJt the above d1araccer....sl:ics .have the major influence en t."" corrasi<ri.ty ;Jf ""tar with dissolved salts less than 1000 ng/l:. am d'!loride less than 300 m:vt.. Iohid'! applies in "''''' cases under oomideraticn. Table r lists t:'Spresentative ana.lYi;es of water frau a rutber of the supplies imrol Vi!!!!. The s~les ""re generally taken at ::he bore head or ~iving tank and. analysed in the laboratory up to several rrcnths later. Cons:a:ru1mtly, due to the effects of storage the t'eSluts do not. 4COJrately -represent the dlaracteristic::s of the water as discharged fran the sou:'ce., particularly as rega_ free CO2 in solution, and pH. These factors are int-errelated an:!. i:ritical to corrosivi ty. ~ CO., eotIbines with ;.m,te~ to prO:lJce cartcnic acid., H'":;t?j' in accordance wit.~ the following dissociaticn equilibriurt :-eLstionsh4:l: (co.) + (H20) (Hz."i53) {Stumm and Ho~n~ 1981) RTDWI STAal t. J T"Y HIlDE,( &,.a - 5.0 '.Q ... 6.0 6 .. 0 ... 1.0 1.0 - 1.:5 1.' - 1.0 "9.0 aM llf-an" KiM"" sc.i. 1.1 gft:t oSeIi ,. LIM'I. seaf. or QCITOI;iGrl 'Dlis means ti".at increases in CO2 Concentraticn result in increas~ i.n ar 3 concentt3ticn arxl a consequent reductlCfi 1.0 pH'"' Al!:hcugh t.~e laboratory pH of !:he ~les .~ .. enerally flXm 5.0 to 6.3. field tests have shewn that !:he actual pH at the bore during dis<::har<> is of the order of one unit lcwer. For exa:rple a test at Wadeye (""rt Keats) in 1981 .;ave pH values of 4.2 at site ~ared 1:0 5.4 in the laboratory. At t.'>e lower pH value t.'>e calollated ~= .. ~ concentration is approximately 500 n>;I!. to the laOoratory result of 50 mgJ'"Nabalco have also reported estimated free C:02 of appt'Oxilmtel y 500 n>;/r. in the ltlulunl1.y b5res (Egan, 1984). An exa:nination of the intar=elationships of t.~e .above factors for !;XJtablt! waters indicates that: a. one unit drq:I in pH gives ,an approxi:n~,te l!-E!nf?ld increase in free COr It 15 free CO2 :n sclutl.on and its associated effee: en pI! ud'! t. !:he critical factor in the extrene corrcsivity of the coastal undorqr=nd ",aters .", Pldicated t:y Fi'OUre 2 adaoted from f!aJ:denbergh and !b::li.. (1961). tt will be noted that for alkalinities bel"" 50 ng/l:. am free CO2 above 2 n>;I!. !:he ...ate"" are in t.~e sericus corrcsion zone. Consequently all, the coastal undergrcund .... ters . are !ughly -corrcsive. '!l"J.is itS also oonflI:med by' the ta~.l.ier and Ryznar !ndice-:s {Table I l Ioobich are all in the sericus and intolerable con'OS ion ranges 4eSp;ctively (carrier, 1965).