research article physicochemical characteristics of river ...e physicochemical parameters of the...

Research ArticlePhysicochemical Characteristics of River WaterDownstream of a Large Tropical Hydroelectric Dam

Teck-Yee Ling1 Chen-Lin Soo1 Teresa Lee-Eng Heng1

Lee Nyanti2 Siong-Fong Sim1 and Jongkar Grinang3

1Department of Chemistry Faculty of Resource Science and Technology Universiti Malaysia Sarawak94300 Kota Samarahan Sarawak Malaysia2Department of Aquatic Science Faculty of Resource Science and Technology Universiti Malaysia Sarawak94300 Kota Samarahan Sarawak Malaysia3Institute of Biodiversity and Environmental Conservation Universiti Malaysia Sarawak 94300 Kota Samarahan Sarawak Malaysia

Correspondence should be addressed to Teck-Yee Ling teckyee60gmailcom

Received 21 April 2016 Accepted 4 August 2016

Academic Editor Samuel B Dampare

Copyright copy 2016 Teck-Yee Ling et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Water quality in the downstream river of a hydroelectric dam may be affected by the structural design and operation To datelittle is known about the water quality downstream of the largest dam in Malaysia the Bakun hydroelectric dam Therefore theobjective of the study was to determine the water quality downstream of the dam when the spillway was closed and when it wasopened Results of the study indicate that the dam plays a significant role in regulating the water quality downstream of it Whenthe spillway was closed pH and oxygen were lower in the river where DO was below 5mgL When the spillway was opened thewater quality improved in terms of oxygen content (gt80mgL) total sulphide (TS) and chemical oxygen demand (COD) butdeteriorated in terms of five-day biochemical oxygen demand (BOD

5) total ammonia nitrogen (TAN) and total phosphorus (TP)

Additionally the intensity of the impacts particularly BOD5 COD and TAN shows a declining trend as distance from the dam

increasesThis study shows that impacts on the water quality extend to a distance of 32 km from the dam particularly turbidity andDO and opening the spillway changes the water quality significantly

1 Introduction

Dam and reservoir construction in river courses are boomingall over the world for hydropower generation flood controlirrigation and water supply In Malaysia there are about 80dams that have been built where majority of the dams arefor water supply in most of the states of Peninsular Malaysiaincluding Sabah while hydropower dams are the most com-mon in the states of Sarawak and Perak [1] Among themSarawak owns the largest hydropower project in Malaysiawith an installed capacity of 2400MW of electricity and thesecond tallest concrete rock filled dams (205m) in the worldwhich is the Bakun hydroelectric damThe dam is situated onthe Balui River a tributary of the longest river in Malaysiathe Rajang River It is impounded in 2010 and reached its fullsupply level in 2012 where the flooded area is over 695 km2[2 3]

The physicochemical parameters of the Bakun damreservoir have been studied in pre- and postimpoundmentcondition [2 3] However studies on the tropical regulateddownstream river of the dam are limited though it is alsosubjected to major environmental impacts ranging fromdownstream morphology to biodiversity of the ecosystem[4ndash10] Downstream impacts of the dam can sometimesextend up to a distance of hundred kilometers from thedam site [11] although the intensity of the impacts tends todecline with increasing distance from the dam site [12 13]Dams can change downstream hydrology by altering the flowpattern which subsequently change the water quality of thedownstream river [14ndash19] Thus it is of scientific importanceto investigate and evaluate the water quality changes inducedby dam construction and operation

Despite the substantial size of the Bakun hydroelectricdam and its potential impact on the downstream river the

Hindawi Publishing CorporationJournal of ChemistryVolume 2016 Article ID 7895234 7 pageshttpdxdoiorg10115520167895234

2 Journal of Chemistry

N

Sampling station

Bakun hydroelectric dam

Bakun reservoir

Sg Rajang

St 1St 2St 3

St 4

St 5

South China SeaPeninsular

Sabah

SarawakMalaysia

2 km

20 km

Figure 1 Location of the sampling stations along the downstream river Balui River of the Bakun hydroelectric dam in the present study inthe state of Sarawak Malaysia

water quality of its downstream river is scarcely knownRecently a study had shown that higher concentration ofFe and Mn was detected in downstream water of the Bakunhydroelectric reservoir with significant longitudinal variation[20] Structural difference between Bakun dam and otherbig tropical dams in the world may result in differences indownstream water quality Therefore the present study wasinitiated to assess the water quality of the downstream riverof the Bakun hydroelectric damwhen the spillway was closedandwhen it was openedThe findings would provide valuableinformation for the operation and management of the damfor the benefit of downstream aquatic organisms

2 Material and Methods

21 Study Area and Sampling Stations The present study wasconducted at the Balui River downstream Bakun hydroelec-tric dam in Sarawak Malaysia from Long Baagu to belowBelaga town (Figure 1) when the electrical power generationwas ongoing The river received water discharged from thereservoir of the dam after the water passed through theturbines Intake for power generation was at about 10mdepth from the surface A total of five stations were selectedalong the downstream river up to a distance of 321 kmfrom the dam (Table 1) The first sampling was conductedon 6 November 2013 when the spillway was closed Thesecond sampling was conducted in 26 February 2014 whereadditional water was discharged from the spillwaywith intakeat a depth of sim15m At the end of the spillway the waterhits the concrete barrier before entering downstream BaluiRiver The downstream river flow during second trip when

additional water was discharged from the spillway of the damwas faster than first trip It rained in the morning during thefirst trip whereas no rain was recorded for two weeks beforethe second trip

22 Field Collection and Laboratory Analysis Both in situ andex situ parameters were studied pH and dissolved oxygen(DO) were measured using an Orion 3-star Plus PortablepHmeter and aMilwaukee DOmeter respectively Turbiditywas measured using a YSI 6820 Multiparameter Sonde and aHanna Instrument in the first and second trips respectivelyWater samples were collected in triplicate for the analysisof five-day biochemical oxygen demand (BOD

5) chemical

oxygen demand (COD) total ammonia nitrogen (TAN)total phosphorus (TP) and total sulphide (TS) All samplingbottles were acid-washed cleaned and dried before useWater samples were preserved using zinc acetate for TSanalysis whereas water samples were acidified to pH lt 2 forTAN and TP analysis All water samples were placed in anice box and transported to the laboratory for further analysis[21]

Prior to the analysis the triplicate water samples werecomposited All the analyses were conducted according tostandard methods [21 22] For BOD

5analysis it began in the

field AsDOvalues in the first tripwere lowwater was aeratedby shaking in a 2 L bottle before initial DO was measuredFinal DO was measured after incubation of the sample inthe dark at 20∘C Subsequently BOD

5was calculated using

standard methods COD was determined by closed refluxtitrimetric method [21] where FAS concentration used was

Journal of Chemistry 3

Table 1 The details of the sampling location and sampling regime in the present study

Station (distancefrom Bakun dam) GPS coordinate Description 1st trip (6112013) 2nd trip (2622014)

Time Depth (m) Time Depth (m)St 1 (43 km) N02∘46101584021810158401015840 E114∘01101584041610158401015840 Long Baagu 620 pm 132 300 pm 107

St 2 (99 km) N02∘47101584002010158401015840 E113∘58101584043210158401015840 Right above Metjawah(Lubok Metjawah ) 530 pm 92 210 pm 54

St 3 (175 km) N02∘46101584005210158401015840 E113∘54101584023010158401015840 Right below longhouseLahanan Long Semuang 400 pm 45 1245 pm 41

St 4 (249 km) N02∘44101584034510158401015840 E113∘50101584021810158401015840 Right above longhouseKejaman Neh 300 pm 21 1205 pm 59

St 5 (321 km) N02∘42101584002910158401015840 E113∘46101584046310158401015840 Below Belaga Town 130 pm 79 1105 am 100

0025M TAN was determined by Nesslerrsquos method afterdistillation [22] TP was determined by ascorbic acid methodafter sulfuric-nitric acid digestion of samples [21] TS wasanalyzed using themethylene bluemethod [22] A calibrationcurve was prepared for each chemical analysis Blank andstandard solutionswere treated in the sameway as the sample

23 Statistical Analysis When data were tested for normalityand equal variance with Shapiro-Wilk test and Levenersquostest respectively it was found to be significantly differentfrom normal distribution and unequal in variances Thusnonparametric tests were used in the subsequent statisticalanalyses To determine if there was any significant differencein the results between the five sampling stations of eachsampling trip Kruskal-Wallis test was used Wilcoxon Sign-rank test was used to compare the water quality of thedownstream river between opened and closed spillway Allthe statistical analyses were conducted by using SPSS Version22

3 Results and Discussion

Figure 2 shows that the water discharged from the Bakunhydroelectric reservoir has a great impact on the in situwaterquality at the downstream river Low pH value was observedat stations near to the dam which is most likely due to thelow pHwater of the reservoir from a depth of between 10 and15m that was released into the downstream river after passingthrough the turbines [3] However the pH value steadilyincreased from 60plusmn00 to 77plusmn00 along the downstream riverdue to the dilution from the tributaries in the first samplingHowever when water was also discharged from the openedspillway in the second sampling the pH value is relativelyconstant along the downstream river ranging from 61 plusmn 00to 62 plusmn 00 In addition to the impact of the high volumeof low pH reservoir water no precipitation for two weeksbefore the second sampling could also contribute to the lowpH value up to a distance of 32 km from the dam in thepresent study Overall the pH value of the downstream riveris mostly classified as Class II according to National WaterQuality Standard (NWQS) for Malaysia except stations 4 and5 in the first trip which are classified as Class I [23]

The mean value of DO along the downstream river was43mgL and 92mgL when reservoir water is discharged

Table 2 Mean difference in water quality parameters betweenclosed and opened spillway when the Bakun hydroelectric dam isin operation (119873 = 5)

Parameters Mean difference 119901 valuepH 04 0057DO mgL minus48 0001Turbidity NTU minus190 0001TS mgL 13 0019BOD5 mgL minus05 0028

COD mgL 264 0001TAN mgL minus0065 0001TP 120583gL minus1147 0001Positive value of mean difference indicates water quality parameter washigher during closed spillway whereas negative value indicates water qualityparameter was higher during opened spillway of the Bakun hydroelectricdam The significant difference at 119901 value le 005 was indicated in bold

with the spillway closed and opened respectively Accordingto the NWQS DO is classified as Class III along thedownstream river when water is discharged from the damduring power generation with the spillway closed The DOcontent improved considerably when the spillway was openwhere the DO is classified as Class I Table 2 shows that theDO value along the downstream river is significantly higherwhen additional water was discharged from the spillway ofthe dam (119901 value le 005) but decreased steadily along thedownstream river as illustrated by Figure 2 On the otherhand when spillway was closed and the only water wasdischarged through the turbines DO value is the lowest atstation 1 which is the nearest station to the dam but steadilyincreased along the downstream river indicating the DOcontent was first impacted by the low DO content from thereservoir but was then diluted by river water with higherDO content along the downstream river Despite the dilutionalong the downstream river station 5 which is the furtheststation from the dam still showed DO of less than 5mgLBesides the low DO content in the downstream river thatraises environmental health concerns the high DO when thewater is discharged from the spillwaymay also pose ecologicalrisks to the downstream river The high oxygen level causedby the rapid aeration when water plunged from the spillwayhitting the barrier may cause the total dissolved gas (TDG)


50

55

60

65

70

75

80

43 99 175 249 321

pH ABC

BC

C

AB Abcaab

abc

Distance from Bakun hydroelectric dam (km)

Water discharged during power generation Water discharged from spillway

(a)

20

40

60

80

100

43 99 175 249 321

DO

(mg

L)

b

AAB ABC BC C

b ab ab a



(b)

200

300

400

500

600

700

800

900

43 99 175 249 321

Turb

idity

(NTU

)

AAB

C

ABC BC

ba

aba

b



(c)

000

005

010

015

020

025

030

TS (m

gL)

43 99 175 249 321


ABAB

B

A A abbcc

aab


(d)

20

25

30

35

40

45

43 99 175 249 321Distance from Bakun hydroelectric dam (km)

AB

A

B

A

B

a

ab

abcbcc

BOD

5(m

gL)


(e)

00

200

400

600

800

1000

COD

(mg

L)


A

AA

A A

aab

abc

bc

c


(f)

Figure 2 Continued


0000

0050

0100

0150

0200

0250TA

N (m

gL)


A

A AA A

aba

a

ab

b


(g)

00

500

1000

1500

2000

TP (120583

gL)


AA

A A A

aaaa

a


(h)

Figure 2 In situ and ex situ water quality parameters of (a) pH (b) DO (c) turbidity (d) TS (e) BOD5 (f) COD (g) TAN and (h) TP

at stations of downstream Bakun hydroelectric dam when the spillway was closed (dash line) and when it is opened (solid line) when thedam is in operation Different letters indicate significant difference at 119901 value le 005 along the downstream river (uppercasemdashspillway closedlowercasemdashspillway opened)

supersaturation in the downstreamwater which could lead tobubble disease on fish living downstream of dams [17 24 25]

The turbidity value (asymp40NTU) at station 1 when wateris discharged from the dam during power generation withclosed spillway is similar to the turbidity value of the Bakunreservoir which ranged from 22 to 40NTU at a depth of 10ndash15m [3] The highest turbidity value (745 plusmn 06NTU) wasobserved at station 3 and the high turbidity value at stations4 and 5 (gt60NTU) indicating the possible anthropogenicinfluences of suspended solids from adjacent area besides theimpact of the dam Turbidity value increased significantly (119901value le 005) when the spillway was opened with a meanvalue of 752mgL The high turbidity value had extended upto a distance of 32 km from the dam in the present studyWhen water is discharged from the spillway in addition toturbine outflow resuspension of deposited sediments underhigh flow rate increases the suspended solids downstreamBesides the impacts of the reservoir water discharged fromthe spillway the high turbidity value could also be due to thelow dilution from the tributaries along the downstream riveras there was no precipitation for two weeks before the secondsampling was conducted Overall most of the turbidity valueat both trips (gt50NTU) had exceeded the Class II of NWQSfor Malaysia [23] except stations 1 and 2 in the first sampling

When water is discharged from the dam during powergeneration when spillway was closed TS was very high atstations 1 2 and 3 (asymp022mgL) up to a distance of 175 kmfrom the damThe high TS concentration at the downstreamriver near to the dam indicates that it is most likely due tothe reservoir water that contains high TS concentration [26]Strong rotten egg smell indicating the presence of hydrogensulphide had been detected at Bakun reservoir during thefilling phase [2] However TS concentration was foundmuchlower at stations 4 and 5 most likely due to degassing and

oxidation of hydrogen sulphide when the anaerobic waterwas aerated [27] When the spillway is opened the waterwas aerated by the plunge and impact on the concrete wallresulting in degassing and oxidation of hydrogen sulphideand this water diluted the higher sulphide water from theturbine outflow leading to significantly (119901 value le 005) lowerTS along the downstream river The mean TS concentrationalong the downstream river decreased from 014mgL to001mgL where the TS value changes from noncomplianceto compliance with the 005mgL standard [23] The highestconcentration of TS in both samples was found at station 3indicating that station 3 which is located below the longhousemay have contributed substantial TS besides the reservoirwater

The BOD5concentration fluctuated along the down-

stream river with the highest value located at stations 3and 5 (asymp40mgL) when the spillway was closed BOD

5

concentration at the two stations is also significantly higher(119901 value le 005) than the BOD

5concentration at stations

2 (30 plusmn 01mgL) and 4 (31 plusmn 02mgL) The higherconcentration of BOD

5at the two stations indicates that high

BOD5concentration is most likely attributed to the domestic

discharge and runoff as stations 3 and 5 were located belowlonghouses and Belaga town respectively When the spillwaywas opened the BOD

5concentration increased significantly

(p value le 005) compared to when closed but significantlydecreased from 42plusmn00mgL to 35plusmn01mgL (p valuele 005)along the downstream river as distance increases as shownin Figure 2 The BOD

5concentration along the downstream

river was classified as Class III at all stations except station 2(Class II) in the first sampling

Figure 2 illustrates that the highest COD concentration(asymp85mgL) was observed at station 1 which is the neareststation to the dam in both trips The value lies between the


COD concentrations near to the Bakun dam in the reservoirat a depth between 15m and 30m [3] In the present studyCOD concentration decreased significantly (p value le 005)from 800 plusmn 80mgL to 187 plusmn 46mgL along the down-stream river when additional water was discharged from thespillway The classification of COD shows improvement withincreasing distance from the dam that is from Class IVto Class II Besides the mean COD concentration was alsosignificantly lower (p value le 005) when the spillway wasopened compared to closed spillway When the spillway wasclosed COD concentration was not significantly different (pvalue gt 005) along the downstream river although the CODconcentration decreased from 90mgL at station 1 to 63mgLat the subsequent stations as illustrated in Figure 2 Whenthe spillway was opened the high volume of reservoir waterwas aerated resulting in high DO in the river which loweredthe COD concentration substantially along the downstreamriver

The TAN concentration ranged from 0030 plusmn 0007mgLto 0125 plusmn 0024mgL and 0119 plusmn 0002mgL to 0226 plusmn0045mgLwhen the spillway was closed and opened respec-tively Similar to COD concentration the highest value ofTAN was observed at station 1 and the values are comparableto the TAN concentration in the Bakun reservoir near tothe Bakun dam at a depth of 15m and 30m which wasreported to be 014mgL and 035mgL respectively [3] Inthe present study the TAN concentration when the spillwaywas closed is similar to the reservoir TAN concentrationnear to the Bakun dam at a depth of 15m whereas TANconcentration when the spillway was opened lies between15m and 30m depths of the reservoir TAN concentrationNo significant difference of TAN concentration (119901 value gt005) was observed along the downstream river when thespillwaywas closed but TAN shows sign of decrease along thedownstream river when the spillway was opened where TANconcentrations at stations 3 and 4 were significantly lower (119901value le 005) than TAN concentration at station 1 The meanTAN concentration increased significantly (119901 value le 005)when water was discharged from the spillway (015mgL)compared to the dam (0085mgL) and the classification ofTAN changed from Class I to Class II at all stations exceptstation 1where it was classified asClass II at both samplesTheresult indicates that reservoir water and the dam operationgreatly influence the TAN concentration in the downstreamriver of the dam

Figure 2 shows that no significant difference of TP(119901 value gt 005) was observed as we moved along thedownstream river stations in both opened and closed spillwayconditions However TP concentrations were higher whenspillway was opened and values ranged from 242 plusmn 06 to451 plusmn 50 120583gL and 1447 plusmn 79 to 1782 plusmn 24 120583gL when thespillway was closed and opened respectivelyThemean valueof TP increased significantly (119901 value le 005) from 38 120583gL to1527 120583gL when the spillway was opened compared to closedspillway (Table 2) The result indicates that reservoir watercontributes substantial TP to the downstream river and theimpact extended up to a distance of 32 km in the presentstudy Nevertheless TP concentration along the downstreamriver is classified as Class I for both trips indicating that the

TP concentration is still of acceptable standard according toMalaysia National Water Quality Standard [23]

4 Conclusions

The present study indicates that Bakun hydroelectric damplays a significant role in regulating the downstream waterqualityThedownstream riverwas low in pHandDObut highin turbidity TS BOD

5 COD TAN and TP Nevertheless

the pH and DO gradually increased along the downstreamriver Opening the spillway increased themeanDO turbidityBOD5 TAN and TP significantly whereas it decreases mean

TS and COD significantly in the downstream river Thelow pH and high turbidity and TP remained along thedownstream river up to a distance of 32 km from the damwhereas the DO BOD

5 and COD decreased significantly

with increasing distance from the dam Besides the influenceof the reservoir water the water quality of the downstreamriver was also subjected to anthropogenic activities partic-ularly at station 3 and station 5 which are located belowlonghouses and township High turbidity TS and BOD

5

were observed at station 3 whereas high turbidity and BOD5

were observed at station 5 Even though opening the spillwayincreased DO and reduced toxic sulphide in the downstreamriver further studies need to be conducted to see the effectof the total dissolved gas supersaturated water on the aquaticorganisms especially fish in the area

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors appreciate the financial support provided bythe Ministry of Higher Education through Grant noFRGSSTWN01(04)9912013(32) and the facilities providedby Universiti Malaysia Sarawak

References

[1] A M Latifah and L Met ldquoAn ecological evaluation approachfor dam project development in Malaysiardquo Life Science Journalvol 11 no 7 pp 225ndash237 2014

[2] L Nyanti T Y Ling and J Grinang ldquoPhysico-chemical char-acteristics in the filling phase of Bakun hydroelectric reservoirSarawak Malaysiardquo International Journal of Applied Science andTechnology vol 2 no 6 pp 92ndash101 2012

[3] T Y Ling L Nyanti T Muan J Grinang S F Sim and AMujahid ldquoPhysicochemical parameters of bakun reservoir inBelaga Sarawak Malaysia 13 months after reaching full supplylevelrdquo Sains Malaysiana vol 45 no 2 pp 157ndash166 2016

[4] Y Yi Z Yang and S Zhang ldquoEcological influence of damconstruction and river-lake connectivity onmigration fish habi-tat in the Yangtze River basin Chinardquo Procedia EnvironmentalSciences vol 2 no 5 pp 1942ndash1954 2010


[5] M W Beck A H Claassen and P J Hundt ldquoEnvironmentaland livelihood impacts of dams common lessons across devel-opment gradients that challenge sustainabilityrdquo InternationalJournal of River Basin Management vol 10 no 1 pp 73ndash922012

[6] X Li S Dong Q Zhao and S Liu ldquoImpacts of ManwanDam construction on aquatic habitat and community inMiddleReach of Lancang Riverrdquo Procedia Environmental Sciences vol2 no 5 pp 706ndash712 2010

[7] WWildi ldquoEnvironmental hazards of dams and reservoirsrdquoNearCurriculum in Natural Environmental Science vol 88 pp 187ndash197 2010

[8] Q G Wang Y H Du Y Su and K Q Chen ldquoEnvironmentalimpact post-assessment of damand reservoir projects a reviewrdquoProcedia Environmental Sciences vol 13 pp 1439ndash1443 2012

[9] PMcCully ldquoRivers nomore the environmental effects of damsrdquoin Silenced Rivers The Ecology and Politics of Large Dams PMcCully Ed pp 29ndash64 Zed Books London UK 1996

[10] Q Lin ldquoInfluence of dams on river ecosystem and its counter-measuresrdquo Journal of Water Resource and Protection vol 03 no01 pp 60ndash66 2011

[11] R PreeceColdWater Pollution belowDams inNew SouthWalesDepartment of Infrastructure Planning andNatural ResourcesSydney Australia 2004

[12] Q Zhao S Liu L Deng S Dong Z Yang and Q LiuldquoDetermining the influencing distance of dam construction andreservoir impoundment on land use a case study of ManwanDam Lancang Riverrdquo Ecological Engineering vol 53 pp 235ndash242 2013

[13] N D Gillett Y Pan J Eli Asarian and J Kann ldquoSpatial andtemporal variability of river periphyton below a hypereutrophiclake and a series of damsrdquo Science ofThe Total Environment vol541 pp 1382ndash1392 2016

[14] Y Zhang J Xia T Liang andQ Shao ldquoImpact of water projectson river flow regimes and water quality in Huai River BasinrdquoWater Resources Management vol 24 no 5 pp 889ndash908 2010

[15] L Feng X Sun and X Zhu ldquoImpact of floodgates operation onwater environment using one-dimensional modelling system inriver network of Wuxi city Chinardquo Ecological Engineering vol91 pp 173ndash182 2016

[16] Q Zhao S Liu L Deng et al ldquoLandscape change and hydro-logic alteration associated with dam constructionrdquo Interna-tional Journal of Applied EarthObservation andGeoinformationvol 16 no 1 pp 17ndash26 2012

[17] H Guo Q Hu Q Zhang and S Feng ldquoEffects of the ThreeGorges Dam on Yangtze River flow and river interaction withPoyang Lake China 2003ndash2008rdquo Journal of Hydrology vol 416-417 pp 19ndash27 2012

[18] G L Wei Z F Yang B Cui et al ldquoImpact of dam constructionon water quality and water self-purification capacity of theLancang River Chinardquo Water Resources Management vol 23no 9 pp 1763ndash1780 2009

[19] M Wiatkowski ldquoInfluence of słup dam reservoir on flow andquality of water in the Nysa Szalona riverrdquo Polish Journal ofEnvironmental Studies vol 20 no 2 pp 469ndash478 2011

[20] S F Sim T Y Ling L Nyanti N Gerunsin Y EWong and L PKho ldquoAssessment of heavymetals in water sediment and fishesof a large tropical hydroelectric dam in Sarawak MalaysiardquoJournal of Chemistry vol 2016 Article ID 8923183 10 pages2016

[21] D Jenkins J J Connors and A E Greenberg Standard Meth-ods for the Examination of Water and Wastewater AmericanPublic Health Association Washington DC USA 21st edition2005

[22] Hach Hach Water Analysis Handbook Hach Company Love-land Colo USA 2015

[23] Department of Environment Malaysia Environmental QualityReport 2014 Department of Environment Kuala LumpurMalaysia 2015

[24] S-C Chen X-Q Liu W Jiang et al ldquoEffects of total dissolvedgas supersaturated water on lethality and catalase activity ofChinese sucker (Myxocyprinus asiaticus Bleeker)rdquo Journal ofZhejiang University Science B vol 13 no 10 pp 791ndash796 2012

[25] R Liang B Li K Li and Y Tuo ldquoEffect of total dissolvedgas supersaturated water on early life of Davidrsquos schizothoracin(Schizothorax davidi)rdquo Journal of Zhejiang University Science Bvol 140 no 7 pp 632ndash639 2013

[26] T Y Ling D P Debbie N Lee I Norhadi and J J E JustinldquoWater quality at Batang Ai hydroelectric reservoir (SarawakMalaysia) and implications for aquaculturerdquo International Jour-nal of Applied Sciencce and Technology vol 2 no 6 pp 23ndash302012

[27] J Nix ldquoSpatial and temporal distribution of sulfide and reducedmetals in the tailwater of Narrows dam (Lake Greeson)Arkansasrdquo Tech Rep E-86-14 US Army Corps of EngineersWashington DC USA 1986

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CatalystsJournal of


N

Sampling station

Bakun hydroelectric dam

Bakun reservoir

Sg Rajang

St 1St 2St 3

St 4

St 5

South China SeaPeninsular

Sabah

SarawakMalaysia

2 km

20 km

Figure 1 Location of the sampling stations along the downstream river Balui River of the Bakun hydroelectric dam in the present study inthe state of Sarawak Malaysia

water quality of its downstream river is scarcely knownRecently a study had shown that higher concentration ofFe and Mn was detected in downstream water of the Bakunhydroelectric reservoir with significant longitudinal variation[20] Structural difference between Bakun dam and otherbig tropical dams in the world may result in differences indownstream water quality Therefore the present study wasinitiated to assess the water quality of the downstream riverof the Bakun hydroelectric damwhen the spillway was closedandwhen it was openedThe findings would provide valuableinformation for the operation and management of the damfor the benefit of downstream aquatic organisms

2 Material and Methods

21 Study Area and Sampling Stations The present study wasconducted at the Balui River downstream Bakun hydroelec-tric dam in Sarawak Malaysia from Long Baagu to belowBelaga town (Figure 1) when the electrical power generationwas ongoing The river received water discharged from thereservoir of the dam after the water passed through theturbines Intake for power generation was at about 10mdepth from the surface A total of five stations were selectedalong the downstream river up to a distance of 321 kmfrom the dam (Table 1) The first sampling was conductedon 6 November 2013 when the spillway was closed Thesecond sampling was conducted in 26 February 2014 whereadditional water was discharged from the spillwaywith intakeat a depth of sim15m At the end of the spillway the waterhits the concrete barrier before entering downstream BaluiRiver The downstream river flow during second trip when

additional water was discharged from the spillway of the damwas faster than first trip It rained in the morning during thefirst trip whereas no rain was recorded for two weeks beforethe second trip

22 Field Collection and Laboratory Analysis Both in situ andex situ parameters were studied pH and dissolved oxygen(DO) were measured using an Orion 3-star Plus PortablepHmeter and aMilwaukee DOmeter respectively Turbiditywas measured using a YSI 6820 Multiparameter Sonde and aHanna Instrument in the first and second trips respectivelyWater samples were collected in triplicate for the analysisof five-day biochemical oxygen demand (BOD

5) chemical

oxygen demand (COD) total ammonia nitrogen (TAN)total phosphorus (TP) and total sulphide (TS) All samplingbottles were acid-washed cleaned and dried before useWater samples were preserved using zinc acetate for TSanalysis whereas water samples were acidified to pH lt 2 forTAN and TP analysis All water samples were placed in anice box and transported to the laboratory for further analysis[21]

Prior to the analysis the triplicate water samples werecomposited All the analyses were conducted according tostandard methods [21 22] For BOD

5analysis it began in the

field AsDOvalues in the first tripwere lowwater was aeratedby shaking in a 2 L bottle before initial DO was measuredFinal DO was measured after incubation of the sample inthe dark at 20∘C Subsequently BOD

5was calculated using

standard methods COD was determined by closed refluxtitrimetric method [21] where FAS concentration used was



















50

55

60

65

70

75

80

43 99 175 249 321

pH ABC

BC

C

AB Abcaab

abc



(a)

20

40

60

80

100

43 99 175 249 321

DO

(mg

L)

b

AAB ABC BC C

b ab ab a



(b)

200

300

400

500

600

700

800

900

43 99 175 249 321

Turb

idity

(NTU

)

AAB

C

ABC BC

ba

aba

b



(c)

000

005

010

015

020

025

030

TS (m

gL)

43 99 175 249 321


ABAB

B

A A abbcc

aab


(d)

20

25

30

35

40

45


AB

A

B

A

B

a

ab

abcbcc

BOD

5(m

gL)


(e)

00

200

400

600

800

1000

COD

(mg

L)


A

AA

A A

aab

abc

bc

c


(f)

Figure 2 Continued


0000

0050

0100

0150

0200

0250TA

N (m

gL)


A

A AA A

aba

a

ab

b


(g)

00

500

1000

1500

2000

TP (120583

gL)


AA

A A A

aaaa

a


(h)









5

















4 Conclusions







5



Competing Interests


Acknowledgments


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



















50

55

60

65

70

75

80

43 99 175 249 321

pH ABC

BC

C

AB Abcaab

abc



(a)

20

40

60

80

100

43 99 175 249 321

DO

(mg

L)

b

AAB ABC BC C

b ab ab a



(b)

200

300

400

500

600

700

800

900

43 99 175 249 321

Turb

idity

(NTU

)

AAB

C

ABC BC

ba

aba

b



(c)

000

005

010

015

020

025

030

TS (m

gL)

43 99 175 249 321


ABAB

B

A A abbcc

aab


(d)

20

25

30

35

40

45


AB

A

B

A

B

a

ab

abcbcc

BOD

5(m

gL)


(e)

00

200

400

600

800

1000

COD

(mg

L)


A

AA

A A

aab

abc

bc

c


(f)

Figure 2 Continued


0000

0050

0100

0150

0200

0250TA

N (m

gL)


A

A AA A

aba

a

ab

b


(g)

00

500

1000

1500

2000

TP (120583

gL)


AA

A A A

aaaa

a


(h)









5

















4 Conclusions







5



Competing Interests


Acknowledgments


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0000

0050

0100

0150

0200

0250TA

N (m

gL)


A

A AA A

aba

a

ab

b


(g)

00

500

1000

1500

2000

TP (120583

gL)


AA

A A A

aaaa

a


(h)









5

















4 Conclusions







5



Competing Interests


Acknowledgments


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






4 Conclusions







5



Competing Interests


Acknowledgments


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

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