Open Access Research Article Modeling the Effect of ...

World Journal of Applied Environmental Chemistry All Rights Reserved Euresian Publication © 2012 eISSN 2277-8055 Available Online at: www.environmentaljournals.org Volume 1, Issue 2: 57-66

Open Access

Research Article

Modeling the Effect of Dam Construction and Operation towards Downstream Water Quality of Sg. Tawau and Batang Baleh Zaki Zainudin, Parveen Jamal and Iqrah Akbar Department of Biotechnology Engineering, International Islamic University Malaysia Corresponding author: [email protected], [email protected], [email protected]

Abstract: Amongst all the natural resources necessary to support human civilization, water plays the most critical role.Planning and development of water resources to meet a country's need for water supply, flood control, hydroelectric power, irrigation, and navigation need to be evaluated with reference to the environmental needs and regulations. One such method is construction of dams and reservoirs which have enabled efficient usage and storage of water over the years.The intent of this study is to apply a water quality model (QUAL2E developed by USEPA)to critically examine the plausible environmental impacts of two proposed dams in Malaysia around the areas of Sg. Tawau and BatangBaleh (Sg. Baleh). Numerous operational scenarios, with and without the proposed dams were considered. Primary concerns about the effects of dam operations on water quality were physico-chemical water quality constituents such as BOD5, dissolved oxygen and TSS. Results obtained depicted that the construction process would result in a slight degradation of the water quality in Sg. Tawau elevating the BOD and TSS levels;whereas for the BatangBaleh dam, none such adverse effects were identified, however with frequent removal of organics and sediment build up behind the dam, the ill effects of dam construction on the both the rivers can be mitigated.The proposed discharge volume (compensational flow) 3 of 280 m /s should be sufficient in sustaining the ambient water quality during the operational phase of the 3 Tawau dam while as for Batang Baleh the flow should be maintained at about 2.0m /s. The results also depicted that for both Tawau and BatangBaleh dams, intermittent flow release during the reservoir storage process, particularly during the dry season should be done, to maintain water quality levels at the downstream reaches. While dams provide significant benefits to our society, their impacts on the surroundings include: resettlement and relocation, socioeconomic impacts, environmental concerns, sedimentation issues and safety aspects. The problems associated with the poor water quality commonly encountered in dams are: turbidity (mud in suspension), chemical and bacterial contamination, organic staining, and reduced oxygen (Chapra et al., 2005).However, these concerns and impacts can be reduced or eliminated by careful planning, and the incorporation of a variety of mitigation measures. From the foregoing, it is believed that serious planning is pertinent prior to the construction of any proposed dam. This investigation affirms that modeling techniques can be utilized to predict the impact of two proposed dams in Malaysia. The areas proposed for investigation in this study is the Sg. Tawau and the BatangBaleh dams.

1.0 Introduction: Throughout history dams and reservoirs have embarked the most successful usage of collecting, storing and managing water needed to sustain civilizations generations after generations. The construction of dams is one of the most efficient ways to manage water resources for human needs as they create reservoirs for water storage and future distribution. In 1999, there were about 45,000 dams higher than 15 meters throughout the world (ICOLD, 1999).While some were more than 2,000 years old, about 73% have been built in the last 50 years. The reservoirs formed by these dams store 3 approximately 3,600 km of usable water (ICOLD, 1999). Hence, the primary benefit of construction of dams and reservoirs in the world is water supply. Other major aspects of dam construction involves; irrigation for agriculture (food supply), flood control, generation of hydropower, inland navigation, and for other recreational purposes.

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World Journal of Applied Environmental Chemistry

t

2.0 Methodology: Several key factors were considered prior to the commencement of the modeling exercise, such as; the modeling assumptions, limitations, scenarios, delineation and data requirements. The general QUAL2E model assumptions and limitations applied to this study include the water quality parameters to be simulated as dissolved oxygen (DO), biochemical oxygen demand (BOD5, uBOD)and inorganic solids (total suspended solids). The model is based on ultimate cBOD, hence a 5-day measurement will be extrapolated to incur this value. This method is computed using the following formula;

yt = L0 (1 − e − kt )

= Incubation time (days)

For calculation of BOD, decay rate ‘k’ of 0.23 was assumed for the ambient stream conditions (Bowie et al., 1985). It should be noted that, besides practical considerations of time and expense, there are other benefits for using the 5-day measurement with extrapolation, rather that performing a longerterm cBOD. Although extrapolation might introduce some error, the 5-day value has the advantage that it would tend to minimize possible nitrification effects, which, even when inhibited, can begin to be exerted on longer time frames (Chapra et al., 2005). As discussed previously, the main impact from the dam operation towards ambient water quality should be towards the sensitive receptors located downstream of the project sites. However, in terms of the modeling proceedings, a direct impact is difficult to quantify, as it is correlated to a reduction in carrying capacity due to flow retention (and release) without an obvious point source input (Mills et al., 1986).

kT = k 20θ T − 20

where ; yt = BOD at time t (mg/l) = Ultimate BOD (mg/l) L0 k ,kT = Decay rate in bottle at designated temperature (1/day) k20 = Decay rate at 20°C (1/day) Ө =Temperature correction factor (typically 1.047, slight variation depending on literature)

The stream reach layout structure for the Sg. Tawau QUAL2E model is illustrated in Figure 1: Sg. Tawau

DAM SITE

F

Tributaries accounted as incremental inflows from flow balance

Fig. 1: Sg. Tawau QUAL2E Stream Reach System

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The primary impact, if any, of the dam operation towards ambient water quality shall be towards the sensitive receptors located downstream of the project site. Just like the case of the Sg. Tawau dam, modeling scenarios have been oriented towards these conditions, vis-a-vis the resulting water quality

of the downstream reaches as a result of flow retention, during the reservoir storage as well discharge during power generation. The scenarios have been designed to encapsulate these conditions as shown in Table 1:

Table 1: Scenarios designed to encapsulate conditions for the proposed dam sites i.e:Sg. Tawau and BatangBaleh SCENARIO

Sg. Tawau Dam

SCENARIO 1 SCENARIO 2 SCENARIO 3 SCENARIO 4 SCENARIO 5

BatangBaleh Dam

Baseline scenario without the presence of the dam, at normal in-stream flow. Baseline scenario without the presence of the dam, at low in-stream flow. Water quality during reservoir storage, at normal in-stream flow Water quality during reservoir storage, at low in-stream flow Water quality during dam operation at 2.0 : Water quality during dam operation at 3 3 m /s compensational flow, under normal 280 m /s compensational flow, under in-stream flow. normal in-stream flow. Water quality during dam operation at 2.0 Water quality during dam operation at 3 3 m /s compensational flow during low in- 280 m /s compensational flow during low stream flow. in-stream flow.

SCENARIO 6

The cumulative impact of other dam construction within the Batang Rajang basin was not considered for this study. Flow retention, particularly during the reservoir storage period at other sub-catchments may have a profound influence on the in-stream

water quality of the main river. The streams reach layout system for the Batang Baleh QUAL2E model in Figure 2 is as follows:

BatangBaleh

DAM SITE Sg. Mengiong

Batang Rajang

Fig. 2: BatangBaleh QUAL2E Stream System

Sg. Batu

Reach

Sg. Putai

Nanga Entawau

Kapit

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inflows) recharge them to ambient levels as seen in Scenarios 3 and 4. That being the case, the Scenario 5 and 6 results depicted the ambient levels to be higher than that of the baseline scenarios, up to 6.5 mg/L. Although, the amounts of DO in these scenarios were higher, the quantity of water requisite for aquatic life may be lower depending on seasonal variations. The heightened DO levels is a direct consequence of a mixing and turbulence from the dam release as well as a shallower stream enabling easier surface oxygen water transfer (Mohamed, 2000).

3.0 Results and Discussion: 3.1 Sg. Tawau Dam: Dam impacts (during the operational phase) towards conventional physico-chemical water quality constituents can be considered to be moderate in the downstream reaches, with the exception of Total Suspended Solid (TSS). That being the case, during the storage phase, most of the upstream reaches will have minimal flow (if any) resulting in a loss of habitat for many aquatic species. Also, since the dam will be constructed on the main-stem of Sg. Tawau itself, majority of the flow will be blocked hence depleting DO levels. During the operational phase, as long as there is sufficient compensational flow released from the dam, depletion of DO levels can be avoided. This hypothesis is further reinforced by the pristine water quality conditions in Sg. Tawau. For illustration purposes, three critical physicochemical parameters were chosen as part of the modeling proceedings, dissolved oxygen (DO), biochemical oxygen demand (BOD5)and total suspended solids (TSS).

The above scenarios show that at 90 percentile release of the mean daily flow (approximately 2.0 m3/s), the current baseline of DO levels would be maintained. Due to the decreased in-stream flow, the river is thus, most sensitive during the retention period and under low flow conditions (Scenario 4), as a direct consequence of reduced Waste Assimilative Capacity (WAC). However, since there are no significant pollution load contributors within the vicinity, the ambient levels should remain relatively unchanged. Therefore, it is absolutely critical that no new significant pollution load contributors are allowed into the catchment area during this period.

In Figures 3 and 4 below, the effect of the water storage is expected to deplete the upstream DO values (baseline levels were between 5 – 6 mg/L) before the lower tributaries confluences (and Scenario 1 (Baseline) Scenario 3 Scenario 5

8.0

Scenario 2 (Baseline Low Flow) Scenario 4 Scenario 6

7.0 6.0

DO (mg/L)

5.0 4.0 3.0 2.0 1.0 0.0 6

5

4

3 River KM

2

1

0

Fig. 3: Downstream Concentration Spatial Trend of DO current stream, the condition is more than sufficient to “neutralize” these sources thus maintaining a BOD5of less than 2 mg/L which falls under Class I water quality of the National Water Quality Standards for Malaysia (NWQS).This condition also

The low organic contribution results in the BOD5 spatial trend shown in Figure 4. There are not many organic pollution contributors within the sub-basin save apart from natural background sources (animal feaces, decay wood, leaves etc.). In the entire

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holds true for both Scenarios 3 and 4. Some further degradation in organics may occur during the release phase due to organic pollutant build-up behind the dam as can be seen in Scenarios 5 and 6. Under these circumstances, the BOD5 class denotation may deteriorate from the previous value range of less than2 mg/L to a value of 6 mg/L (Class I to Class III

6

max. of NWQS) as a result of the dam release. It would therefore be prudent to ensure that regular maintenance is carried out, to remove any organic build-up in the reservoir. The water quality in the reservoir should be preserved as close to baseline levels as possible.

Scenario 1 (Baseline)

Scenario 2 (Baseline Low Flow)

Scenario 3

Scenario 4

Scenario 5

Scenario 6

5

BOD5 (mg/L)

4

3

2

1

0 6

5

4

3 River KM

2

1

0

1

0

Fig. 4: BOD5 Downstream Spatial Trend

10,000



Scenario 3

Scenario 4

Scenario 5

Scenario 6

BOD5 (kg/day)

1,000

100

10

1 6

5

4

3

2

River KM

Fig. 5: Downstream Loading Spatial Trend of BOD5 The TSS modeling results in Figures 6 and 7, which show the spatial pattern to be quite pristine within the maximum value of 25mg/L (Class I denotation) for both baseline scenarios (Scenarios 1 and 2). This was consistent with the baseline monitoring results as only a maximum increment of up to 8 mg/L was observed. During the storage phase (Scenarios 3 and 4), some degradation is expected to occur as a consequence of reduced carrying capacity and

contribution from agricultural areas. Under these conditions, the value is expected to increase to about 10 mg/L (still within Class I). During the dam release stage (Scenarios 5 and 6), further deterioration is expected to occur due to the sedimentary build-up behind the dam as well as the disturbance of the underlying sediment from release and mixing. The TSS levels may increase to Class II denotation of about 45 mg/L before settling down to

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the bottom and eventually reaching a Class I standard of 20 mg/L in the downstream reaches. In order to reduce the impact of TSS, it would be to make sure that any sedimentary layer build-up behind the dam is effectively removed and disposed

60

off prior to discharge. It would not only help improve TSS levels on Sg. Tawau, but would also have cost benefits, in terms of reduction of other operational problemsin the long-haul.



Scenario 3

Scenario 4

Scenario 5

Scenario 6

50

TSS (mg/L)

40

30

20

10

0 6

5

4

3 River KM

2

1

0

1

0

Fig. 6: Downstream Concentration Spatial Trend of TSS

100,000



Scenario 3

Scenario 4

Scenario 5

Scenario 6

TSS (kg/day)

10,000

1,000

100

10

1 6

5

4

3

2

River KM

Fig. 7: Downstream Loading Spatial Trend of TSS Nanga Entawau. The initial drop seen just before the dam, for scenarios 3 and 4, was due to flow retention, hence ensuing in poor re-aeration. This potential compromise in carrying capacity will be rejuvenated after confluence with Batang Rajang at the downstream segment. The condition is expected to further improve when more water is released from the dam for power generation (Scenarios 5 and 6). Again, it can thus be concluded that the river is most sensitive during the retention period and under low flow conditions (Scenario 4).

3.2 BatangBaleh Dam: In Figures 8 and 9 below, the effects of the dam operation (Scenarios 3 – 6) relative to Scenarios 1 and 2 (baseline scenarios) are considered negligible. Flow retention (during the reservoir storage phase, scenarios 3 and 4) would not cause a significant DO depletion. This is because there are many other major tributaries in the Baleh sub-catchmentafter the dam such as Sg. Putai which replenishes the ambient DO levels in the downstream reaches after

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Scenario 1 9.0

Scenario 2

Scenario 3

Scenario 4

Scenario 5

Scenario 6

BALEH DAM

8.0

Dissolved Oxygen (mg/l)

7.0 6.0 INWQS Class II

5.0 4.0 3.0 2.0 1.0 0.0 127.5

115.0

102.5

Sg. Mengiong

90.0

77.5

65.0

52.5

40.0

27.5

Sg. Batu

15.0

2.5

180.0

Sg. Rajang

Nanga Entawau

Kapit

Sg. Putai River Kilometer

Fig. 8: Dissolved Oxygen (DO) Downstream Spatial Trend The low organic contribution results in the BOD5 spatial trend shown in Figure 7.During the retention phase (Scenarios 3 and 4), some further degradation in organics may occur resulting in the initial depletion of DO levels behind the dam (as shown in Figure 6). These minute changes will be eradicated once the dam starts discharging water at a rate 3 of280 m /s (Scenarios 5 and 6). The proposed compensational flow volume should be more than enough to sustain the current water quality Scenario 1 3.5

Scenario 2

conditions as shown below. Current major settlements along the river bank, such as Nanga Entawau and Kapit, should not be adversely affected by any physico-chemical organic changes. No undesirable effects is also concluded for other physico-chemical parameters not modeled here-in, such as COD, ammoniacal nitrogen, nitrate, phosphate as well heavy metals as long as there is no direct contribution of these constituents.

Scenario 3

Scenario 4

Scenario 5

Scenario 6

BALEH DAM

Biochemical Oxygen Demand (BOD5) (mg/l)

INWQS Class III 3.0

2.5

2.0

1.5

1.0

0.5

0.0 127.5

115.0

102.5

Sg. Mengiong

90.0

77.5

65.0

52.5

40.0

27.5

Sg. Batu Nanga Entawau

15.0

2.5

Sg. Rajang

180.0

Kapit

Sg. Putai River Kilometer

Fig. 9: BOD5 Downstream Spatial Trend From the field survey conducted and the modeling proceedings, it was evident that both BatangBaleh and Batang Rajang suffer from severe SS

contamination, hovering around 300 mg/l (Class IV & V of the NWQS). The SS originates from anthropogenic activities such as logging, road

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clearance and hill-side agriculture. The extent of the heightened SS levels was observed as far upstream as Long Singgut, close to the Kalimantan Border. Besides SS, other floatables such as log and wood debris were also observable in the river. The SS modeling results depicted in Figure 10 show the spatial SS levels increasing, moving upstream to downstream, with its peak reaching more than300 mg/L after the confluence with Batang Rajang for both baseline scenarios (Scenarios 1 and 2). Therefore, it can be deduced that the sediment load is far more significant in Batang Rajang than BatangBaleh. The consequence of this is far reaching, as the reservoir storage phase will result in a significant amount of flow reduction to Batang Rajang, hence decreasing the dilution effect and increasing SS levels. This outcome can be seen

Scenario 1 600

Scenario 2

clearly in Scenarios 3 and 4, where after the confluence, the constituent levels are predominantly higher than that of the baseline. Overall, an increase of about 150 mg/l was predicted on the main river. During the power generation phase; at a discharge 3 of 280 m /s, the SS levels will slightly improve under normal flow conditions (Scenario 5), whereas a significant improvement can be seen under low flow conditions (Scenario 6), compared to the baseline. In this sense, the dam can actually have a positive effect towards the in-stream SS levels, provided that a steady state discharge is maintained throughout dry season. Albeit, the sediment load in Batang Rajang is overwhelmingly large, the ambient SS levels were predicted to remain near or above 300 mg/l which denotes Class V of NWQS in both scenarios.

Scenario 3

Scenario 4

Scenario 5

Scenario 6

BALEH DAM

Total Suspended Solids (TSS) (mg/l)

500

400 INWQS Class V 300

200

100

0 127.5

115.0

102.5

Sg. Mengiong

90.0

77.5

65.0

52.5

40.0

27.5

Sg. Batu Nanga Entawau Sg. Putai River Kilometer

15.0

2.5

Sg. Rajang

180.0 Kapit

Fig. 10: TSS Downstream Spatial Trend Although some SS contamination on the upper reaches has occurred, the overall river morphology still remains natural and beautiful. The upper reaches of BatangBaleh, are quite simply breathtaking with majestic views all around. The river morphology is a good example of a “classic” river with many rock-rapids, ideal for white-water rafting and ecotourism. Not many rivers in Malaysia have such characteristics, even lesser those with good water quality. The upper reaches, host a wide variety of flora and fauna, both aquatic and land animals. Hornbills were seen in the air as well as other rare territorial animals.

4.0 Conclusions and Recommendations: For the proposed Tawaudam, the release rate at 2.0 3 m /s may alter the downstream water quality characteristics, elevating BOD5 and TSS in the downstream reaches from the baseline of Class I to Class II/III, whereas the operation of the proposed BatangBaleh dam will not adversely affect the ambient water quality (except for SS), as there are no direct or in-direct input of these species from the proposed project. However during the reservoir storage periods, the downstream reaches of Tawau’s proposed dam will be very sensitive as a result of the reduced WAC andaquatic habitation may likely be affected by reduced water quantity; and likewise, the proposed BatangBaleh dam to degradation

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(particularly in terms of SS) resulting in reduced dilution. 2) For the BatangBaleh dam, the proposed discharge 3 volume (compensational flow) of 280 m /s should be sufficient in sustaining the ambient water quality during the operational phase of the dam as long as a steady flow is maintained. While as the proposed 3 compensational flow of 2.0 m /s for the Tawaudam’s operational phase must be adhered to. The project proponent is also advised to conduct frequent removal of organics and sediment built up behind the dam to ensure that excessive discharge of these kind of constituents are avoided by performing a monthly monitoring exercise of the water quality of the reservoir for BOD5, NH3-N, P, NO3-N and TSS. However for both Tawau and BatangBaleh dams, intermittent flow release during the reservoir storage process, particularly during the dry season should be done, to maintain water quality levels at the downstream reaches. A macro-level water quality modeling study encompassing the cumulative impacts from all the proposed dam construction within the Batang Rajang basin should be conducted, enabling a holistic and sustainable management from a water quality perspective.

3)

4)

5)

(IEM), Proceedings, 11th Annual IEM Water Resources Colloquium, ISBN 978-967-5048-46-3. Betin, T. N. A. (2006).Assessing Cumulative Watershed Effects by Zig-Zag Pebble Count Method. Master of Science. UniversitiTeknologi Malaysia, Skudai, Johor, Malaysia. Bowie, G. L., Mills, W. B., Porcella, D. B., Campbell, C. L., Pagenkopf, J. R., Rupp, G. L., Johnson, K. M., Chan, W. H, Gherini, S. A. & Chamberlain, C. E. (1985).Rates, Constants and Kinetics Formulations in Surface Water Quality Modeling (Second Edition).United States Environmental Protection Agency (US EPA), Athens, Georgia, USA. Brown, L. C. & Barnwell, T. O. (1987). The Enhanced Stream Water Quality Models QUAL2E and QUAL2E-UNCAS:Documentation and User Manual. United States Environmental Protection Agency (US EPA), Athens, Georgia, USA. Chapra, S. C. (1997).Surface Water Quality st Modeling. (1 ed.). Singapore : McGraw-Hill Series in Water Resources and Environmental Engineering.

6) Chapra, S. C., Pelletier, G. and Tao, H., (2005).QUAL2K : A Modeling Framework for Simulation River and Stream Water Quality. (Ver. 2.04). Athens, Georgia, USA : United States Environmental Protection Agency (US EPA). Department of Environment, DOE, (2008).National Water Quality Standards. Environmental Quality Report 2008. 7) Department of Environment, (2006).AktaKualitiAlamSekeliling 1974 (Akta 127) &Peraturan-Peraturan Dan PerintahPerintah (Hingga 5hb Jun 2006). International Law Book Services (ILBS), Selangor, Malaysia. 8) International Commission On Large Dams (1999).Benefits and Concerns About Dams – An Argumentaire.ICOLD’s publication, 1999. 9) Malaysian Environmental Resources Center, MERC (2010). Study on Pollution Prevention and Water Quality Improvement of Sg. Kuantan Basin, Pahang. RMK-9 Special Study : Department of Environment Malaysia (DOE). 10) Mills, W. B., Bowie, G. L., Grieb, T. M., Johnson, K. M. and Whittemore, R. C. (1986).Handbook : Stream Sampling for Waste Load Allocation st Applications. (1 ed.). Washington D. C., USA : United States Environmental Protection Agency (US EPA).

Nomenclatures BOD Biochemical Oxygen Demand BOD5 BOD determined by a 5-day test cBOD Carbonaceous Biochemical Oxygen Demand uBOD Ultimate Biochemical Oxygen Demand DID Department of Irrigation and Drainage SS Suspended Solids DO Dissolved Oxygen COD Chemical Oxygen Demand INWQS Interim National Water Quality Standard of Malaysia TSS Total Suspended Solids USEPA United States Environmental Protection Agency WTP Water Treatment Plant WAC Waste Assimilative Capacity

References: 1) Baginda, A. R. A. and Zainudin, Z., (2009).Keynote Paper : Moving Towards Integrated River Basin Management (IRBM) in Malaysia , Institution of Engineers Malaysia

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11) Mohamed, M. (2000).Comparison of Field Measurements to Predicted Reaeration Coefficients, k2, in the Application of Water Quality Model, QUAL2E, to a Tropical River.Doctor of Philosophy.Colorado State University, Fort Collins, Colorado, USA. 12) Salleh, M. N. and Zainudin, Z. (2011).Potable Water Quality Characterisctics. Institution of Engineers Malaysia (IEM), Jurutera Monthly Bulletin. 12. 13) Sawyer, C. N., McCarty, P. L. and Parkin G. F. (2003).Chemistry for Environmental Engineering and Science. (5thed.). New York : McGraw-Hill Professional. 14) Zainudin, Z., (2005). Industrial Effluent Load Characterization of Sungai Perembi Watershed. Masters Dissertation, UniversitiTeknologi Malaysia (UTM), Skudai. 15) Zainudin, Z. (2008) .The Many Intricacies of Biochemical Oxygen Demand (BOD). Institution of Engineers Malaysia (IEM), Featured Article, Jurutera Monthly Bulletin (November 2008). 16) Zainudin, Z., Mazlan N. F., Abdullah, N. (2008). Sewage Pollution Impact and Characterization in Sg. Langat River Basin through QUAL2E River Water Quality Modeling Temporal Data Review. International Conference and Expo on Environmental Management and Technologies (ICEEMAT’08), Putra World Trade Center (PWTC), December 2008.

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