Ngalo (Lomlom) Island Reef Islams, Tei\4Otu Province
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.t GHOUNDWATER RESOURCES t ,OF t (LOMLOM) ii NGALO ISLAND I ll" REEF ISLANDS, TENíOTU PROVINCE by *. r: CURRY s. r23 MEMONÂNDUM TO: l.lo: ProvÍncial SecretarY, GLtd l- Temotu Province. DATE: Z/7 /85 Tel. No. Attn: I4r R Natov¡an Yor¡¡ ref: c.c. Permanent Secretary/MEP tn: Messrs ener & Patterson. PDU. c.c. Permanent Secretary/MFtA&Pc c.c. High Commissioner, Australian High Commission Attn: !'lr G Brooke. GROUND¡üATER RESOURCES OF NGALO ISLÀND As prornisedrplease find attactred a copy of the report entitled ,Groundwater Resources of l.lgalo (f.omlorn) fsland, Reef Islands, Tenrotrr Province,as prepared by the undersigned Ihe report details the study carried out on Ngalo Island frorn 5-9 June and considers the grroundrntater resource in relation to your proposed lrlater Supply Scheme requirements. As can be seen fronr the reportrsufficient grounålater exists on Ngalo Island to meet your Sctreme reguirementsralthough dranges to tìe source of water for sorne vitlages are reconuìended. Potential groundrrvater pollution problems have.been identifiecl and remedial oi alternativê actions are also outlined in the reconrnendations- 'Às mentioned in the acknov,rledgenrentsrl would like to convey my thanks to tire merùrers of your provinãe invoived in ensuring the smooth and well organised running of tÌ¡e entire trip- lfusting this report novl allovrs you proceed with the design of tÌ¡e sdteme. Snr trlater Resources Officer, for Permanent SecretarY/MNR rr att. GROUNDWATER RESOURCES OF NGALO (LOMLOM) ISLAND REEF ISLAMS, TEI\4OTU PROVINCE by R J CURRY (i) I¡üater Resources Section GeologY Division tvlinistry of Naturaf Resources GROUNDWATER RESOURCES OF NGALÐ (TCIMt,OM) ISLAND REEF ISI.,ANDS TEI\4OTU PROVIÌ.rcE June 1985 Distribution: Provincial Secretary, Temotu Provtnce PermanentSecretary,MinistryofEconornicPlannirq Permanent secretary, Mi-nistry of Health 6( Medical services HighCorrrmissioner,AustralianHiqürCorrunission High Commissioner, Nã'v Zealand High Commj'ssion ..../$i) (ii ) COI{IENTS PAGE SEgIION DESCRIPTION l_. IIVIRODUCTION 2. @or..oGY 3. Groundwater Potential 7 3.1 Recharge CaPabiIÍtY .. - 13 4. GROUNDI^JATER EVALUATTON . 4.L WeIl Tests and Resistivity Surveys " ' 16 4.1.1 BaliPa'a School WeLl t6 4.1.1.1 Well Observations l6 4.I.I.2 Earth Resistivity Results I9 4.1,1.3 PumP Test I9 4 -I.2. Laro WelI 22 4.I.2.L Well CIcservations 22 4.I.2.2 Earth Resistivity Results " " " ' 23 4 -I.3 Manuopo WeIl 25 4 .1 .3 .1 V{ell Ocservations 25 4.I.3.2 PunP Tests 25 4.I.4 Ngamanie V{el1 26 4 .I.4.I WeIl Observations 26 ñ^-! 4.I.4.2 PumP IEÞ L 28 28 4 .1 .5 Otambie Íüell 4.1.5.1 flell Ocservations 28 4.I.5.2 PunP Test 30 4.I.6 Ngival-e Well- 30 4-I.7 Napali Well 30 4.I.7 .L Well Ocservations 30 4.2 Interyretation of Resul-ts - . 32 4.3 Safe WeIt YieLd Determination 33 33 4. 3 .1 Balì-Pa'a WeIl 4.3.2 Laro füel-L 33 4.3.3 ManuoPo WelI 34 4.3.4 þamanie WelI 34 4.3.5 Otanbie lÙeII 35 /(iii) PAGE 5. RESOURCE COTfIAMINATION 6. CONCLUSTONS 37 6.1 Recharge Capability 6.2 North lþalo Village Ítater 6.3 South l.lgalo Village tlq L9! 7. RECOMMENDATIONS 39 8. ACKNOWLEDGEMENTS 39 9. /(iv) - (iv) - LIST OF FIGJRES FIG DESCRTPTION PAGE ]-. TOPOGRÀPHICAL MAP OF EASTERN SOI..OI"ION TSLANDS 2 SCAL,E l-:3,000,000 2. TOPOGRAPHICAL MAP OF NGAT,O (T.OMI..OM) ISL,AND 3 SCÀLE 1:50,000 3. GOLoGY MAP OF NGAL,O (rOt"ll,ot"l) rsleu¡ 4 SCALE l- :50 ,000 3a Map 3b Sections 4. VILLAGE AND VüELL LAYOUT, NGAI..,O ISLAND 5. IICIVIHLY AND I'IEAN I4ONTHLY RAINFALL FOR l"toHA!{K BAY, REEF ISLANDS 6. WATER hIELL PIEZTOMETRIC LEVEI.S IN REL,ATTON TO REEF ISLA¡JD TTDE LEVEI.S I8 7. BÀLIPA'A EARTH RESISTTVITY MEASUREMENIS 20 7a Site Plan.Sca1e 1:4000 7c ExampJ-e of Earth Resistivity Measurement and Fitted Model (Balipa'a Site {É2) 8. BALTPA'A WELL PUMP TEST 2I 9. LARO EARTH RESISTIVITY MEASUREI{ETIIS 9a Site Plan.Scal-e 1:4000 24 9b Example of Earth Resistivity Measurement and Fitted Model (Laro Site d+3) 10. MANUOPO VIIELL PUMP TEST 27 11. NGAMANTE I¡¡ELL PUMP TEST 29 12. O{IAI'ÍBIE WELL PUMP TEST 31 /kt - (v) - LTST OF TABLES ]- }CIHAWK BAY (REEF IS) RAINFALL RECORDS 2 CArcULATION OF POTEM]TAL EVAPO{IRANSPIRATION FDR REEF ISLANDS (SANTÀ CRUZ) USING THE THORNTHTüAITE I\4ETTTOD 3 TYPICAL SOIL l,OrSrURE - RECHARGE CAI.CULATTO¡i FOR YEAR 1984. 4 WELL WATER QUALTTY / (rl -1- GROUNDWATER RESOURCES OF NGALO (T,OM[OM) ISLAND, REEF ISLANDS, TEMOTU PROVTI{CE SOI.,OMON TSLAI'IDS R J Curry * 1. IMIRODUCITON: The Reef fslands are a small group of low-Iying reefs and terraces located 48km north-east of Nendo, the marn island of the Santa Cruz group. (Fig.I) The main isl-ands are Ngalo (tomlom), Ngawa and Fenualoa (t]:g z), the remaining islands consisting of smaller, outlying islands. In l9B3 the total population for the Reef fslands was estimated at 4200 persons. As wÍth the otìer istands in the Reefs, Ngalo Island (1¿.02fm2) rs devoid of any significant topography and so l-acks natural- surface water resources and scope for surface reser,voir development (Fiq 3b). Consequently water suppties are drawn by hand from several- natural deep groundwater wells and a few shal-low hand dug wells which are very sparsel-y l-ocated around the Island. More recently some viJ-lages have turned to roof catchment supplies for drinking water particuÌarly where groundwater sal-inity is high, however these are both expensive and limited in capacity. As with many other islands NgaÌo is experiencing an increase in population and a growing demand for water. As part of the 1984 Provincial Rolling Pl-an, the Temotu Provinciaf Executive approved in principle the construction of a rural- Water Supply project to serve 1600 persons on þalo fsland. The pro ject proposes that fresh water be pumped from natural- wells at Nimoa (naÌipa'a Schoof) and Laro by solar po\^ter to elevated storage tanks and then distrjJcuted by gravity to surrounding villages (nig. 4). Total project costs were Iocal community'and a estimated at 585900 to be shared by the Province' yet to be identified overseas aid source' Beforesuchasclremecanprocedanassessmentoftheextentofthe ensure that adequate groundwater resource must be undertaken in order to not cause salt- water is available and that the extraction of same w:-ll hrater intrusion and thus contaminate the resource' ¡.Snr Water Resources Officer lrlater Resources Section 2 (ìeology Division I'4inistry of Natural- Resources Honiara. ,tuMoN t5 . :'^--- -"ry TUVALU l¡. È\. -. .^ -\ Soìro c'.' .iÎ RÁ I. E A vl,.rulr, \i Yanø Levun "f 9 j.:'1'. l' - 1' MALA|TA (MALA) u,f ,-"uuÇ''F''' .. i - Arorf"|' I tf?Æi TONGA h o lcjvNlv t' r.¡". c"r"¿onÑ I I QUEENSLAND I P A c rF t. I AU 5 T R A L I A Fll ¡ie ¡No¡folkL 'l t'- r-t ocEANi .. Kermadec ls il ¡(.:ii I (,l "o*o"oi,*, I F-{ I NEw | $- É'. I ZEALAND \\ I !r I N up¿ni / Three Srsters ls Prlcn, !^, Grcot Rcc/ uKt I tor¡csr Ræf {AL PROVINCE \l MalauParna fcnu¡lo¿ 4-lF Loml¿m ,l-0",. Trnak"la c-- SAN CRISTOBAL (Vclcano) REET ISLANDS (MAKTRA) SANTA CRU¿ Nol¡ 1r$- o' '- .; NENDO Santa An: {r--' e .: San¡¡ Catal¡n¿ TEMOTU tONA NGrKr) MAKIRA PROV NCE Anba 'i UTUPUA RENNELL (MU NGGAVA) g:::. VANTKOLO ..\9i . --. Lì- _ . As¡rol¡bc P Mcmor¡¡l L IPROVINCE Se.o.'þ., - ! 3.o aoo li/',L -/*'t_:.i_'::i /iSl ¡' ¿J35 lndúp"n'obl. f,dft \ \ J .J .I rlDi U îì Þ A t- /ì l'\ > i¡- I Ê i\J ç I Jr iì É Laki I c t :GNIMBANGA Oi NENDE ISLAND olEp^s,h"r,'(f ,l , i' Qa l iz ln rJut'tu s.t, ln lrn lÞ lo ll- lÐ lr l.ã i0 ic t; ln In, !r t-, uptifted recrystallized corat lc lì LOMLOM E iì i i"i- lr t-\ l t¡i swamp and mud flars lF{ l;r lb EMangrove IP IJ l(,I ju l* Extensive living coral near surface ih ic It- :J I t\ ¡È i> Scale l:50,000 Qrs Unconsolidated beach sand lD rTJ P' Coral sand wilh isolaled pillars Qr I '..'"', of coral in shallow water Metres (, 1000 500 O o- sICIIONS ÄCß055 NÂMED IsI.ÀND GROIJP, OEIAINID TEOM IIVELIING TRÅVERsES. ||ORIZONTÅI fÂI-I NOT CONS]ÀNT, BUI ÂPPBOXIMÂTEI-Y ó INCHES TO 1 MItE H et res t5 lnl et res t5 l0 t0 5 SEA LEVEL 5 SEA LEVEL 14 etres Manuopo t5 (.rl t0 5 SEA LEVET Nø; bovg,iÐ FrJ l-J C, : N6ALO I o? LOMLOM I SLAND N6c 1.-, B oy . V,llaje O No*ural We,ll da @ Man-rno.le- Ndl Sc..rle-- lz50,¿)C)O N6 ALo t5 L ANb , REEtr ISLANàI Oì sÉ/owl^/ G ut_L+AçE a N_Q _ry1* _Laøl&:N S. -6- Consioerable difficulties exist in assessing the groundwater on islands such as Ngalo;with its cornparitively small area and very low topographical relíef (Iimiting groundwater l-ens developnent)' together with the cornplete lack of hydro-geological data. In order to obtain a good understanding of the underground water resources of such an rsland, many months of well loggì-ng, 1evellì-ng and geophysical testing would normal-ly be necessary,however due to its extreme isolation neither time' nor manpower and financial resources were available for such a survey' A water-resources survey team cdnprising Messrs Pule, Tickel-l- and Curry spent 5 days on the island (5 - 9 June l-985) and during th:-s time sufficient data were coll-ected to al-low predictions to be made on the maxirmrm sustainable yields frorn the various wells studi-ed' 2.