Download Sediment and Nutrients Balance of Bukit Merah Reservoir, Perak

Sediment and Nutrients Balance of Bukit Merah Reservoir, Perak, Malaysia
ISMAIL Wan Ruslan1，NAJIB Sumayyah Aimi Mohd1
Section of Geography, School of Humanities, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia
[email protected], [email protected]
allochthonous input of labile organic matter. Bukit
Merah Reservoir (BMR) was in category shallow lake
and manmade lake in Malaysia. The inlet water from the
tributaries was Sg Merah, Jelutong, Selarong and Kurau.
Changes in land use and vegetation cover nowadays get
result in major modification to freshwater runoff,
sediment transport, fluxes of carbon and nutrients to lake
systems. Tropical rivers may be a source of nutrients to
the lake and provide a sedimentary sink for nutrients on
the other. Generally, lakes with a long history of
eutrophication are considered to respond slowly to a
loading reduction [2].
Chemical resistance in lakes being in the recovery
phase after a reduction in the external loading of
nutrients is a well known phenomenon in both shallow
and deep lakes [2]. Emissions from non-point sources
have great importance regarding the water pollutions at
present and one of the current water quality problems
related to the eutrophication. Despite the controlling of
point sources, and nutrient removal, significant loads of
nutrients still reach surface water bodies. Nitrogen and
phosphorus enter rivers through several hydrological,
geological and biological pathways depending on the
natural and anthropogenic processes taking place in the
catchments [3].
The total quantity of nutrients
discharged into surface waters in a river basin is
normally larger than the nutrient load at the river mouth.
This discrepancy can be explained by the process of
nutrient retention, which is a collective expression for a
large number of biogeochemical and hydrological
processes that temporarily decrease, decay, degrade,
transform, or permanently retard and remove the
substance from the river channel. An understanding of
the nutrient retention process is therefore important to
prevent overloading the system and the resultant
eutrophication [4].
Basically, the recovery period and the importance of
internal loading for overall lake concentrations are
considered to depend on the flushing rate, loading history,
and chemical characteristics of the sediment [2]. If the
period with high N and P loading was relatively short, a
high flushing rate may ensure a rapid return to low in
lake concentrations after the external loading reduction.
Suitable approaches to describe the changing conditions
of a river system are important. Thus, it may be
hypothesized that the occurrence of lakes and their
Abstract: In this study the pollutants load were
evaluated for Bukit Merah Reservoir (BMR) and its
catchment area. BMR is a 40 km2 man made lake located
in the district of Kerian, Perak. BMR is divided into two
parts- the north lake and the south lake by a 4.7 km
railway line. The source of water for the reservoir came
from 4 rivers: the Kurau (83.31 km2); Merah (4.25 km2),
Jelutong (7.1 km2) and Selarong (3.1 km2) which flow
through Pondok Tanjung Forest Reserved (6718 ha).
The total amount of suspended sediment inputs from
all four rivers to the BMR were 55165 tonnes and almost
93% of the sediment input came from Kurau river. In
2007, the nutrient inputs to BMR were about 77 tonnes
of phosphate; 24 tonnes of ammoniacal-N; 3 tonnes of
nitrite and 47 tonnes of nitrate. The sediment, nitrate and
nitrite were retained in the reservoir, but ammonia and
phosphate were released from the reservoir. The
percentage retention were 78%; 63% and 34% for
phosphorus, sediment, and nitrate respectively. The
percentage of released of phosphate was about 178% and
25% for ammonia. This study shows that non-point
sources are responsible for the impact of sediment and
nutrients on the receiving water body.
Keywords: Sediment, Nutrients Balance, Bukit
Merah,
1. Introduction
Reservoirs can be considered as subsidized
ecosystems like most rivers are, promoting a continuous
and very dynamical link between terrestrial ecosystems,
running waters, and reservoirs. This is why manmade
lakes are very reactive systems to human alterations in
upstream ecosystems. On the other hand, reservoirs are
also fast responsive systems to variations in the
hydrological regime. For example illustrating the need
for an independent theoretical background for reservoirs
is the strong link between water input from tributaries
and the fact was reported that, a clear link between the
amount of water incoming from rivers and the oxygen
content in the hypo-limnetic layer of reservoirs matter
[1].
In addition to the hydrological driver, the oxygen
content in reservoirs is also greatly influenced by the
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characteristics, as well as character of main river and
tributaries, have a major influence on the retention
processes of a catchments. In general, denitrification can
be assumed to be the dominant process resulting in the
loss of nitrogen from riverine systems, and sedimentation
is of only minor importance for nitrogen retention. This
study was to assess nutrient loading tributary of the inlet
rivers, the mass balance of BMR and the retention or
production were occur in that lake.
2. Methodology
2.1 Site Description
Bukit Merah Reservoir (40 km2) in Perak, Malaysia,
is one of the oldest reservoir which was built in 1902 and
in operation in 1906. The capacity of the reservoir is 70
Million cubic meter at 28.50 feet. Bukit Merah reservoir
is divided into two parts- the north lake and the south
lake by a 4.7 km railway line. Water from the reservoir
are channeled out by gravity flow through 6 gates to two
outlet canals, the Selinsing canal and Main canal for
paddy irrigation. The capacity of water outflow is
around 1200 cusec (34 cumecs). Four gates with a
capacity of 800 cusec are channeled through the Main
canal and 400 cusec through the Selinsing canal. The
source of water for the reservoir came from 4 rivers. Sg.
Kurau system (83.31 km2) which is the largest catchment
area, Sg. Jelutong (7.1 km2) which later join with Sg.
Merah (4.25 km2) form another system flows through
Pondok Tanjung Forest Reserve (6718 ha) that feed to
Bukit Merah reservoir to the north lake on the western
side of the forest reserve. Pondok Tanjung Forest
Reserve is probably the largest remaining swamp forest
in northern Peninsular Malaysia. There is another small
river system, the Sg. Selarong (3.1 km2) that flow
through the Pondok Tanjung Forest Reserve which
consists of three main habitat types namely peat swamp,
seasonally-flooded freshwater swamp and hill
dipterocarp forests (Fig.1) [5].
Fig. 1 Bukit Merah reservoir catchment areas
and landuse of Sg Kurau.
Water quality parameters such as pH, conductivity,
dissolved oxygen (DO), temperature and total dissolved
solids (TDS) were measured in situ using YSI-556 meter.
Water samples were filtered through millipore membrane
filters (0.45 μm) for P and N determinations. Chemical
analysis was performed following APHA (1999) [6];
NO2− was determined by coupling diazotization followed
by a colorimetric technique, NH4+ and NO3− by
potentiometry. Soluble reactive phosphate (SRP) was
determined by the colorimetric molybdenum blue
method [7].
River flow was measured using propeller current
meter and discharge was calculated using a velocity-area
method [8]. Discharge in the main inlets and the outlets
was measured and the water level was recorded
continuously. Daily mean discharge was calculated by
use of stage-discharge relationships. In minor inlets and a
few outlets, discharge was measured fortnightly to
monthly and daily mean discharge was estimated by
establishment
of
relationships
between
these
instantaneous values and the calculated mean discharge
from nearby hydrometric stations. A water balance was
2.2 Field and Laboratory analysis
This study was carried out from January 2008 to
December 2008. Sampling strategy involved monitoring
water quality parameters and hydrological gauging at
four sampling sites of the river which is inlet to BMR
namely Sg. Merah, Sg. Jelutong, Sg. Selarong and Sg.
Kurau. Water quality, river cross section and flow
measurements were carried out every fortnight. Water
samples from both the upstream and downstream
sampling sites were collected at three points across the
width of the river cross section. Three replicates were
collected at each point.
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calculated including data on evaporation obtained from
the river authority.
The cross-sectional view of each station was
plotted on graph paper using the width and depth
measurements obtained in the field to obtain crosssectional area of flow. The discharge at each station was
then estimated by the velocity area method using the
relation:
L = QC
Where is:
L = nutrient load (g·s-1)
Q = discharge (m3·s-1)
C = concentration (g·m-3) [10].
Loadings of nutrients and suspended sediment
between a time intervals was calculated by multiplying
the discharge (Q) by concentration C over the time
interval K (in seconds) between samples. This is called
an average sample load [10]. The nutrient loading
calculations was carried out to look at the mass balance
between input and output. The mass balance approach
has been used extensively during recent years to study
the in-stream reactions and pollution loading patterns,
increased fluctuations in streamflow, reduced water
quality and downstream hydrological impacts would also
follow [11].
Tab. 1 A simple nutrient loading and balance of BMR.
Nutrient
Output
Utama
Canal
Selinsing
Canal
Spillway
Total
Output
(t/year)
Sg. Merah
Sg.
Jelutong
Sg.
Selarong
Sg. Kurau
Total Input
(t/year)
InputOutput
(t/year)
Percentage
Retention
(Rt)
or
Removal
(Rm)
NO3
NO2
NH4
PO4
TSS
11.15
1.14
16.79
149.83
6527.9
4.74
0.90
11.89
63.68
4422.7
1.42
0.19
1.19
0.47
1160.4
17.31
2.22
29.87
213.99
12111
4.17
0.15
2.16
5.05
2831.9
2.91
0.22
2.17
2.91
899.93
0.25
0.05
0.43
0.70
162.98
39.81
2.92
19.11
68.32
51270.
47.14
3.35
23.87
76.97
55164.
29.83
1.13
-6.01
-137
43053
63.28
33.64
-25.17
-178
78.05
Rt
Rt
Rm
Rm
Rt
3. Results
A simple nutrient loading calculation and budget is
shown in Tab. 1. The results indicate that the sediment,
nitrate-N and nitrite-N as nitrogen component were
reteined in the lake during the study period, while SRP,
ammonia were produced in the lake. The fluctuations in
the amount of the retained or production of sediment and
nutrients depend upon the river discharge and sediment
and nutrients concentrations.
The total loading of the input nitrate was 47.14
t/year and the output was 17.31 t/year resulting in a net
retention of nitrate was 29.83 t/year. Besides, the total
loading of the input nitrate was 47.14 t/year and the
output was 17.31 t/year resulting in a net retention of
nitrate was 29.83 t/year or 63 % increase.
On the contrary, ammonia and phosphorus were
produced in (or removed from) the lake. The loading of
the input for ammonia was 23.87 t/year and the output
was 29.87 t/year resulting in a net of ammonia was 6.01
t/year or 25% produced in the lake. Besides, the total
loading input of phosphorus was 76.97 t/ year and the
output was 213.99 t/year and the net produced was
137.01 t/year or 178%.
Q = AV
Where is:
Q = discharge (m3·s-1)
V = mean velocity (m·s-1)
A = area of cross-section (m2) [9].
4. Discussions
2.3 Calculation of Nutrient Loading
4.1 Nutrient retention in lake
The concentrations of nutrient were then used to
estimate the nutrient load in the water at a given time at
each station since the nutrient load is the product of
concentration and discharge, as follows:
Nitrogen retention occurred in three components
which is uptake by vegetation, sedimentation and
denitrification. Studies quantifying the proportion of
retention accounted for by denitrification, however
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relatively rare and almost exclusive restricted to lake
[12]. The principle reason why water discharge affects
the percentage of nitrogen and sediment loading is that
discharge serves as surrogate measure for water resident
time . Water resident time is defined here as the ratio of
discharge to volume of the system. The difference of
loading for each basin depends on their catchment area
[13]. Sg Kurau is the largest catchment compared to
other 3 river inlets because of that, Sg Kurau contribute
huge value of the nitrogen to BMR. From the results, Sg
Kurau contributed the highest loading of sediment and
nitrogen.
Point-source effluent discharges often enter streams
that already have elevated nutrient concentrations
because of human activity in the basin. The impact of
any point source depends on the combination of ambient
nutrient concentrations in the receiving stream, the
nutrient concentration of the effluent, and the magnitude
of the point source discharge relative to stream discharge
[14]. In our study, the effluent discharge came from
rivers inlet which is Sg Merah, Sg. Jelutong, Sg.
Selarong and Sg Kurau. Road building especially at
Kurau can substantially increase sediment concentrations
of nutrients.
Monitoring water quality of Bukit Merah reservoir is
very important as source of people who stay at this area.
This observation during sampling period shows that,
nitrogen which is nitrate and nitrite were retained in the
lake but ammonia was removed from the lake. Table 1
show that the nitrate and nitrite were retained in the lake
which is about 63% and 33 %. Oxygen concentration
within the sediments was the factor most commonly
quoted as being of importance to the retention in the lake.
The most frequently quoted significant influencing
factors were hydraulic retention time, hydraulic loading
and vegetation processes [14]. Due to the
characteristically high water discharge rates of all river
inputs (Sg Merah, Sg. Jelutong, Sg. Selarong and Sg.
Kurau), the nitrogen and sediment loads from this
systems were dramatically higher than those of the lake.
the sediment P release were higher particularly in
shallow lakes. In very shallow lakes, for example,
resuspension events increases, more or less continuously
at the contact between sediment and water [15] and
particulate nutrients settling to the bottom are most
probably resuspended several times [16]. Potentially,
resuspension of sediment can both reduce and increase
the sediment P release because the overall process
depends on the actual equilibrium conditions between
sediment and water [17]. This could explain the high P
release in the BMR. Some net P removal is expected
because of sedimentation processes or decrease
microbial activity in certain month.
Ammonia may have been converted into inorganic
compounds, release from the bottom sediments and
discharge from the lake. Increased P release may be
recorded in dense macrophyte beds and beneath
macrophyte canopies due to low oxygen concentrations
[18]. Most likely the sediment depth interacting with the
lake water is lake specific and highly dependent on lake
morphology, sediment characteristics, and wind exposure
[19,20].
5.
Conclusion
This study concludes that BMR and its catchments
area works efficiently as a nutrient and sediment trap.
The nutrient balance approach was successfully used to
determine the nutrient loading from non- point sources of
pollution using upstream-downstream sampling locations.
The nutrient and sediment balance indicated that nitrogen
component retention were 63 %, 33% and 78% for
nitrate, nitrite and sediment, respectively; while
ammonia and phosphorus production was 25% and 178%,
respectively. As nitrogen loading to freshwater systems
increases as a result of human activities, the ability to
predict the resulting impact is becoming more important.
The process began from the rivers and follow by lake.
Our finding shows that, the monitoring very important
because BMR was the sources for dringking, agricultural
etc especially for people in that area.
4.2 Nutrients removal from the lake
Acknowledgments
Phosphorus enters the lake in either in a particulate
form, which can be directly deposited in the sediment, or
as dissolved phosphate, which can be incorporated in
organic matter by primary producers that eventually sink
to the bottom in an organic form. Overall, the net release
of P observed from a sediment is the difference between
the downward flux caused mainly by sedimentation of
particles continuously produced in the water column
(algae, detritus) and the upward flux and gross release of
P driven by the decomposition of organic matter and the
P gradients and transport mechanisms established in the
sediment [15].
Wind-induced resuspension may significantly affect
This study was undertaken under the Ministry of
Science and Technology E-Science grant No: 04-01-05SF0007. We are also indebted to the Director of the
Drainage and Irrigation Department, Kerian for
permission to carry out this study in the BMR.
References
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[1] R. Marce, E. Moreno-Ostos, and J. Armengol. The role of
river inputs on the hypolimnetic chemistry of a productive
reservoir: implications for management of anoxia and total
phosphorus internal loading. Lake and Reservoir
Management, 24, 2008. pp. 87- 98.
[2] M. W. Marsden,, Lake restoration by reducing external
phosphorus loading: The influence of sediment
phosphorus release. Freshwat. Biol. 21, 1989. pp. 139–162.
[3] M. McClaim, R. E. Bilb and F. J. Triska, Biogeochemistry
of N, P, and S in Northwest Rivers: Natural distributions
and responses to disturbance. In: Naiman RJ and Bilby RE
(eds.) River Ecology and Management: Lessons from the
Pacific Coastal Ecoregion. Springer Verlag, New York,
1998. pp. 347-372.
[4] I. Nhapi , Z. Hoko , M. A. Siebel and H. J. Gigzen HJ,
Assessment of the major water and nutrient flows in the
Chivero
catchment
area,
Zimbabwe.
Proc.
ARFSA/WaterNet Symposium: Integrated Water Resources
Management: Theory, Practice, Cases. 30-31 October,
Cape Town, South Africa, 2001.
[5] S. A. M. Najib, W. R. Ismail, Z. A. Rahaman, M. A. Omar,
Trophic status of the South Lake, Bukit Merah Reservoir,
Perak. Proc. 2nd National Conference Space, Society and
Environment 2009. 2-3 June 2009.Universiti Sains
Malaysia, Penang.
[6] APHA. Standard Methods for the Examination of Water
sources of pollution in North America. Water Res. Bull. 29,
pp. 729-740. 1993.
[15] D. P. Hamilton, and S. F. Mitchell, Wave-induced
shear stresses, plant nutrients and chlorophyll in
seven shallow lakes. Freshwater Biol. 38, 1997. pp.
159-168.
[16] P. Ekholm, O. Malve, and T. Kirkkala, Internal and
external loading as regulators of nutrient
concentrations in the agriculturally loaded Lake
Pyhajarvi, southwest Finland. Hydrobiologia 345,
1997. PP. 3-14.
[17] P. S. Hansen, E. J. Philips, and F. J. Aldridge, The effects
of sediment resuspension on phosphorus available for
algal growth in a shallow subtropical lake, Lake
Okeechobee. Lake Reserv. Manage. 13, 1997. pp. 154-159.
[18] J. D. Frodge, G. L. Thomas, and G. B. Pauley, Sediment
phosphorus loading beneath dense canopies of aquatic
macrophytes. Lake Reserv. Mange. 7, 1991. pp. 61-71.
[19] D. Stephen, B. Moss, and G. Phillips, Do rooted
macrophytes increase sediment phosphorus
release? Hydrobiologia 342, 1997. pp. 27-34.
and Wastewater. 19th Edition. Port City Press, Baltimore.
[20] E. B. Welch, and G. D. Cooke, Internal phosphorus
1999.
loading in shallow lakes: importance and control. Lake
[7] J. Murphy, and J. Riley, A modified single solution method
Reserv. Manage. 11, 1995.pp. 273-281.
for determination of phosphate in natural waters, Anal.
Chim. Acta Vol. 27, 1962. pp. 31–36.
[8] N. D. Gordon, T. A. Mc Mahon, and B. L. Finlayson,
Stream Hydrology: An Introduction for Ecologists.
Chichester: John Wiley & Sons. 1992.
[9]
S. A. Schum, The Fluvial System. John Wiley and Sons,
New York. 1977.
[10] I. G. Littlewood, Estimating Contaminant Loads in Rivers:
A Review. Institute of Hydrology Report No. 17,
Institute of Hydrology, Wallingford, UK. 1992.
[11]
W. R. Ismail, A. Y. Siow, A. Ali, Water Quality and
Chemical Mass Balance of Tropical Freshwater Wetland,
Beriah Swamp, Perak. Jurnal Teknologi (F). Vol. 43, 2005.
pp. 65-84.
[12] S. P. Seitzinger, Denitrification in freshwater and coastal
marine
ecosystems:
ecological
ang
geochemical
significance. Limnol. Oceanogr. 33, 1998, pp. 702-724.
[13] W.
J. Mitsch, J. G. Gosselink, Wetlands. Van
Nonstrand Reinhold, New York, 1993. pp. 722.
[14] D. Binkey and T. C. Brown, Forest practices as nonpoint
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