Water Quality Modeling Of Indus River Biology Essay

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In this paper, the modeling of the behavior of contaminants transport in River Indus from d/s of the Ghazi to its confluence with Kabul River, is discussed. For this purpose, QUAL2K model developed by USEPA has been employed. For simulation purpose, three scenarios were developed to study the worst condition of water quality in Indus River during low flow season. Scenaro-1 was run for a low flow of 28 cumecs with the present condition of wastewater quantity and quality. In Scenario-2, flow was kept same but wastewater quantities were projected upto year 2063 with same wastewater quality as in year 2002. In case of Scenario-3, it was assumed that the wastewater quality would be further deteriorated to the extent so that BOD value would be in the range of 80 mg/l in the project life. The river flow and wastewater quantities were kept same as that in case of Scenario-2. The model results show that the DO and BOD will remain within the permissible limits (DO >4mg/l and BOD <8mg/l respectively) in case of all three scenarios.The model results show that if the BOD of wastewater increases up to 80 mg/l above the value which was at the start of the project, the quality of the Indus River floodplain will deteriorate endangering the aquatic life. In order to keep the BOD value of wastewater within the range of 80 mg/l, proper mitigations and management plans have to be evaluated and implemented.

1. Introduction

Water is prerequisite for life and development. This is the reason that from early age of the humanity, most of the population was initially settled along the rivers and streams. Every use of water generates wastewater. Natural streams are always considered as an easy way to dispose off many kinds of effluents. The philosophy behind this practice is that the wastes are diluted and washed away as well as diluted by the stream water and the same are not visible at the dumping sites.

The natural stream/river water contains substances derived from the environment, both natural and man-made. The amount of these constituents in water determines its quality. Consequently, sampling the water and measurements of the concentrations of various constituents can quantify the water quality. Such information about river water quality can be vital for determining the suitability of water for various purposes, such as domestic agricultural and industrial uses use, sustenance of aquatic life and recipient of waste water in natural streams, etc.

It is believed that only proper way for determining the quality of water, is by chemical analysis of water samples. However, other questions might arise such as understanding the different relations between the water quality parameters and properties, prediction of future water quality, estimating the effects of river flow and water quality management. Such problems cannot be solved by mere chemical analysis and it is here that models can be used to have significant and decisive role. Basically, river water quality models are tools for analyzing, extrapolating and predicting water quality.

2. Ghazi Brotha Hydropower Project (GBHP)

The Water and Power Development Authority (WAPDA) of Pakistan has recently implemented the Ghazi-Barotha Hydropower Project (the Project) on the Indus River with the financial assistance of the World Bank and other international donor agencies.

The Project was planned to utilize the hydraulic head for power generation that is available between the tailrace of the Tarbela Dam and the confluence of the Indus River with Haro River. In this reach the Indus River drops by 76 m in a distance of 63 km. This is solely a power generation project with an installed capacity of 1450 MW. The Project has three main components i.e. a barrage located about 7 km downstream of Tarbela dam forming a pond, a 52 km long concrete-lined power channel to divert the flow from barrage to a power complex, which is located near the confluence of Indus and Haro rivers.

There are a number of villages close to the left and right banks of the river downstream of the barrage which have no proper drainage system and their wastewater either discharge directly into the river or soak into the ground and reaches the river indirectly through percolation (GBHP Report on Supplementary Environmental Studies, PHC, 1992). The other nearby villages and towns, which are relatively away from the river, discharge their wastewaters into the natural streams, which ultimately join the river.

The flow to the power channel of GBHP will consist of release from Terbela Dam. During the low-flow period (from early October to mid-May), when Tarbela releases shall be less than the channel capacity of 1,600 cumecs (about 56,450 cusecs), it will not only result in reduction in the flows in the power channel but also less water will be available for releasing into the river downstream of the barrage. These releases may reach to almost nil during early 20 days of January. However, WAPDA has ensured a minimum release of 28 cumecs (about 990 cusecs) during this period. (GBHP Report on Supplementary Environmental Studies, PHC, 1992). It is apprehended that the water quality of Indus Floodplain will be adversely affected by the wastewater, which is being disposed off into the river particularly during low flow period.

The increase of contaminants concentration due to reduced flows may threat to the aquatic life especially fish. Keeping in view the alarming situation of the contaminants in river, an effort was made to model the behavior of contaminants transport in River Indus from D/S of the Ghazi to its confluence with Kabul River (about 40 km stretch). For this purpose QUAL2K model developed by USEPA was used.

2.1. Description of the Study Area

For the present research study, River Indus was selected considering change of its present status by diverting the discharge of river from Ghazi to Brotha through a channel. For this purpose a reach of about 40km between Ghazi to the point of confluence of River Indus with Kabul was selected. The study area is shown in Figure 1. There are seven wastewater cum storm-water drains on Left Bank and four on Right Bank side of the river, which are disposing of effluents into the river in the selected reach. These drains join the river at different reaches starting from km 00+750 and terminating at about km 37+000. A line diagram of the proposed study reach is shown in Figure 2.

Figure 1. Ghazi-Barotha Hydropower Project Layout.

Figure 2. Schematic Presentation of the Selected Reach of River Indus

2.2. Discharge Measurement

The discharges of drains measured on monthly basis for a year around. The table-1 shows the discharge measured at different points.

Table 1. Discharge Measurements of Potential Sources Joining Indus River in the Study Area.

Period

Potential Sources of Left Bank (Wastewater Drains/Nullahs)

 

 

 

 

 

 

Potential Sources of Right Bank (Nullahs/Drains)

 

 

 

 

 

Cumulative Monthly Discharge

(cumec)

Ghazi-I

Ghazi-M

Khalo-I

Khalo-II

Qazipur

Ghurghushti

Chel

Bada Khawar

Gadoon Amazai I

Gadoon Amazai II

Badri Khawar

Drain -I

Drain II

September

Discharge

0.0028

0.016

0.004

0.009

0.0051

1.06

0.929

0.03

0.0212

0.049

2.73

 

4.8561

October

Discharge

0.0046

0.0102

0.0019

0.0014

0.003

0.262

0.3468

 

0.0267

0.0804

2.93

0.74

0.1093

4.5163

November

Discharge

0.0036

0.0056

0.0028

0.0035

0.0034

0.21

0.188

0.0062

0.084

2.42

1.07

0.181

4.1781

December

Discharge

0.00088

0.0026

0.00028

0.0026

0.0017

0.145

0.142

0.005

0.057

2.196

0.972

0.241

3.76606

January

Discharge

0.0024

0.0038

0.0005

0.0005

0.002

0.347

0.245

0.006

0.065

2.25

0.375

0.126

3.4232

February

Discharge

0.0013

0.003

0.00098

0.00098

0.0013

0.333

0.282

0.0067

0.017

1.58

0.301

0.058

2.58526

March

Discharge

0.0068

0.0049

0.0018

0.0107

0.0021

0.444

0.409

0.0011

0.041

2.65

1.29

0.49

5.3514

April

Discharge

0.00143

0.0043

0.00187

0.00093

0.0028

0.309

0.308

0.00198

0.0386

1.65

0.70

0.375

3.39391

May

Discharge

0.001

0.0053

0.0013

0.00065

0.0025

0.252

0.333

 

0.0022

0.014

1.85

0.676

0.106

3.24395

June

Discharge

0.0014

0.0282

0.00042

0.00042

0.0021

0.23

0.199

0.0071

0.014

1.8

0.7

0.12

3.10264

July

Discharge

0.002

0.011

0.00053

0.00053

0.0025

0.388

0.141

12.13

0.0039

0.0103

1.83

0.75

0.102

15.37176

August

Discharge

0.00114

0.0136

0.00073

0.000365

0.0032

0.302

0.724

1.52

0.0011

0.034

5.32

1.38

0.415

9.715135

September

Discharge

0.001

0.0127

0.001

0.001

0.0054

0.252

0.444

 

0.009

0.01

3.41

 

0.321

4.4671

2.2. Quality Measurement

For this study, water samples were collected from river and other storm water channels/drains. The samples were taken in high-flow and low-flow stages of the streams/river to determine the variation of contaminants. The physical testing, however, remained continued with the activity of discharge measurements. Tables 2 and 3 provide the water quality results for the samples collected for left and right banks in high and low flow conditions.

Table 2. Physical, Chemical and Biological Test Results of River and Drainage Waters of the Study Area (High-Flow Period -January)

Sr. No.

Name of Sample

Temp oC

pH

E.C

µs/cm

DO

ppm

TSS

ppm

TDS

ppm

BOD

ppm

COD

ppm

Cl

ppm

Fe

ppm

1

Indus River 30 m u/s of Ghazi Drain Outfall

17.9

8.54

170

8.9

1.5

125

0

0

14.5

0.11

2

Ghazi Wastewater Drain

24.7

7.27

676

3.1

10.5

349

57

191

15

0.01

3

Indus River 30 m d/s of Khalo Drain Outfall

19.1

8.37

167

8.1

0.5

165

0

5

14.5

0.1

4

Indus River 30 m u/s of Ghurghushti Nullah Outfall

22.5

8.1

425

6.7

0.5

272

0

0

21.5

0.05

5

Ghurghushti Nullah

19.2

8.68

181

9

0.5

123

0

0

14

0.08

6

Indus River 30 m d/s of Ghurghushti Nullah Outfall

21.5

8.51

180

8.8

1.5

167

0

0

21.5

0.01

7

Indus River 30 m u/s of Chel River/Nullah

19.3

7.98

201

8

4.5

98

0

0

16.5

0.14

8

Chel River/Nullah

23.3

7.99

511

6.7

4.5

322

0

14

25.5

0.09

9

Indus River 30 m d/s of Chel River/Nullah

17.8

8.03

176

9.1

5

96

7.7

0

10

0.15

10

Gadoon-Amazi Eastern Drain

20.5

6.76

609

0.5

124

259

32

0

34

0.16

11

Gadoon-Amazi Western Drain

19.6

6.94

695

0.6

17.5

314

78

374

41

0.2

12

Bada Khawar

No flow in Bada Khwar was available at the time of sampling.

13

Indus River 30 m d/s of Bada Khawar Outfall

18

7.3

263

7.9

3.5

119

0

4

10

0.14

14

Indus River 30 m u/s of Badri Khawar Outfall

18

8.57

197

9.1

1

242

5.5

0

20

Nil

15

Badri Khawar

20

8.66

506

7.2

3.5

329

0

0

31

Nil

16

Indus River 30 m d/s of Badri Khawar Outfall

18

8.68

499

8.4

5

463

6.6

0

26.5

Nil

PEPA Standards*

=<3°C

6-9

 

 

200

3500

80

150

1000

2.0

Source: WAPDA (2003)

*As per Statutory Notification of August 2000

Table 3. Physical, Chemical and Biological Test Results of River and Drainage Waters of the Study Area (Low-Flow Period -January)

Sr. No.

Name of Sample

Temp oC

pH*

E.C

µs/cm

DO

ppm

TSS

ppm

TDS

ppm

BOD

ppm

COD

ppm

Cl

ppm

Fe

ppm

1

Indus River 30 m u/s of Ghazi Drain Outfall

13.7

8.2

242

8.6

1.5

140

6.0

0.0

6

0.05

2

Ghazi Wastewater Drain

14.6

7.45

685

3.9

133.0

340

66

107.0

58.0

0.37

3

Indus River 30 m d/s of Khalo Drain Outfall

15.2

8.68

326

7.8

0.5

150

6.0

33.0

11.0

0.04

4

Indus River 30 m u/s of Ghurghushti Nullah Outfall

11.2

8.82

260

8.3

0.5

170

15

17.0

10.0

Nil

5

Ghurghushti Nullah

14.5

7.88

393

6.3

0.5

110

15.7

0.0

6.0

Nil

6

Indus River 30 m d/s of Ghurghushti Nullah Outfall

12.5

8.3

365

7.3

0.5

170

12.3

0.0

10.0

Nil

7

Indus River 30 m u/s of Chel River/Nullah

11.5

8.55

259

8.7

0.5

110.0

3

0

9

Nil

8

Chel River/Nullah

10.3

8.06

447

6.9

0.5

200

6.0

16

18.0

0.12

9

Indus River 30 m d/s of Chel River/Nullah

12.3

8.51

267

8.5

1

120

1.5

0

8.0

Nil

10

Gadoon-Amazi Eastern Drain

10.3

7.7

784

5.4

608

440

111.0

687.0

52.0

1.69

11

Gadoon-Amazi Western Drain

20

8.65

582

5

9.5

290

112.0

354

49.0

0.18

12

Bada Khwar

No flow in Bada Khwar was available at time of sampling.

13

Indus River 30 m d/s of Bada Khawar Outfall

11.7

8.2

230

7.5

1.0

130.0

3

115.0

8

0.01

14

Indus River 30 m u/of Badri Khawar Outfall

The outfall of Chel Nullah was cut off from the river creek.

15

Badri Khawar

11.7

8.2

531

7.9

0.5

300.0

4.5

41.0

19

-

16

Indus River 30 m d/s of Badri Khawar Outfall

13.4

8.68

284

8.5

0.5

180.0

0

0

12.0

Nil

PEPA Standards*

=<3°C

6-9

 

 

200

3500

80

150

1000

2.0

Source: WAPDA

*As per Statutory Notification of August 2000

2.2. Model Description and Data Collection

The enhanced stream water quality model QUAL2K or Q2K that is intended to represent a modernized version of the QUAL2E or Q2E. The model permits simulation of several water quality constituents in a branching stream system. The conceptual representation of a stream used in the Q2K formation is a stream reach that has been divided into a number of sub-reaches or computational elements equivalent to finite differences.

QUAL2K is a comprehensive and versatile stream water quality, model. It can simulate up to 26 water quality constituents in any combination desired by user. The main constituents including temperature, conductivity, inorganic suspended solids, dissolved oxygen, detritus, slow CBOD, fast CBOD, dissolved organic nitrogen, ammonia nitrogen (NH4), nitrate, nitrogen (NO3), dissolved organic phosphorus (DOP), inorganic phosphorus, phytoplankton, bottom algae, pathogen, alkalinity, pH, TSS, NH3, Arbitrary non-conservative constituents, etc. The model has 17 worksheets of which 14 are used to enter data while 3 are output

The main data requirements for model was the discharge in each river reach, the river cross-sections at different points, bed slope of the river and water quality of main stream and tributaries. The main data used in the model included:

River discharge

River cross-sections

River bed slope

River water temperature

Wind velocity

Shade

Cloud cover

Water quality data, etc.

The cross-sections of the River Indus for selected reach were available at 43 points between barrage and point of confluence of Indus River with Kabul River, which were obtained from Pakistan Hydro Consultants (PHC), 2002. The selected cross-sections, which were used for the present study, have been plotted with the help of computer showing the water levels in different creeks. The only that part of the cross-section was used in model where water has been found in the creek. . For given reach, the average of cross-sections has been taken. The discharge for reach was also known, so velocity was calculated for every reach. The latitude and longitude of the area were taken from Atlas of Pakistan (1992). The other relevant data was collected from WAPDA Environmental Cell (WEC), 2003. For the present study, the parameters selected for the model simulation include DO and BOD as the wastewater, which is being disposed of into the river, is generated by households not industries.

3. Model Input

According to model requirements, the selected river reach of 40 km of length was divided into computational elements of different lengths. The total selected length of the river was divided into 7 reaches as shown in Table 4. Each reach is of 5 km long except reach nos. 4 and 7, which are 10 km and 6 km long respectively. Reach 1 has four wastewater-cum storm water drains namely Ghazi-I at km 00+750, Ghazi-M at km 01+000, Khalo-I at km 02+500 and Khalo-II at km 02+750. Reach 2 contains one drain i.e. Qazi Pur at km 08+000. Reach 3 has two drains i.e. Bada Khawar at km 11+500 and Ghurghusti Nullah at km 14+000. In reach 4, there is no any kind of drain joining the river that's why it is named as plane reach. In reach 5, there is only one drain i.e. Badri Khawar at km 29+000. Reach 6 also contains one drain known as Lahor Drain at km 33+000. The last reach No. 7 has two drains i.e. Todhar Drain at km 36+500 and Chel Nullah at km 37+000.

Table 4. Distribution of Study Reach into Different Computational Elements

Reach No.

Reach Name

Distance Covered (kms)

1

Ghazi-Khalo Reach

0 to 5

2

Qazi Pur Reach

5 to 10

3

Bada-Ghurghusti Reach

10 to 15

4

Plane Reach

15 to 25

5

Badri Reach

25 to 30

6

Lahor Reach

30 to 35

7

Todhar-Chel Reach

35 to 41

3.1 Model Calibration

The model was calibrated for low flow using river discharge data during January.

The wastewater discharges were taken for the same month of January. The selected water quality parameters, i.e. DO and BOD were used to simulate for the selected reach of the river. The model was made to run only for low flow discharge because at high flow there would be insignificance effect on water quality of the river floodplain from induction of the wastewater effluents as river flows will be very high to dilute these pollutions. So the model was not calibrated for high flow discharge.

The average discharge observed during January in the river floodplain was 297 cumecs (10,500 cusecs), which was used for model calibration. The DO and BOD values at 30 m d/s of different point sources observed during January that were used to compare the model out put values for calibration purposes are given in Table 5.

Table 5. Water Quality Parameters at 30 m D/S of Different Point Sources in the Study Area

Site

DO (mg/l)

BOD (mg/l)

Ghazi

8.6

6.0

Khalo

7.8

6.0

Bada Khawar

7.5

3.3

Lahor

8.7

3.0

Chel

8.5

1.5

Source: WAPDA

The data used for mode calibration included DO, BOD, water temperature and other water quality parameters provided in Table 3. The other main data used for model calibration was:

Bed Slope 0.002 m/m (as there is a drop of 76 m in a reach of 63 km, WAPDA, 2003).

Manning's 'n' 0.1 (as recommended in "Documentation and Users Manual" for natural streams).

Average wind velocity in the month of January 1.28 m/s (WAPDA, 2003).

Upstream and Downstream Latitude and Longitude values of reaches (Atlas of Pakistan, 1992).

Average Hourly air temperature for the month of January as 13.70 Co (WAPDA, 2003).

Shade values were taken zero percent as per site conditions and users manual recommendations.

Bottom Algae was taken as 20 percent as per site conditions and model manual instructions.

Cloud Cover was taken as 25 percent as per site conditions and model manual instructions.

The model was made to run for calibration purposes by selecting the other parameters to be used by the model as per guidelines provided in the manual for the model users. The comparison of DO and BOD values observed through sampling and calculated by model at locations indicated in Table 5 is presented in Table 6.

Table 6. Comparison of Observed and Calculated DO and BOD Values at Different locations in the study area

Location

Observed DO

(mg/l)

Calculated DO

(mg/l)

Observed BOD (mg/l)

Calculated BOD (mg/l)

Ghazi

8.6

8.55

6.0

5.38

Khalo

7.8

8.50

6.0

5.30

Bada Khawar

7.5

8.27

3.3

4.46

Lahor

8.7

7.50

3.0

2.98

Chel

8.5

7.30

1.5

2.58

Average

8.22

8.02

3.9

4.14

Average Deviation in DO:

Avg. DO Deviation = (Avg. Observed DO - Avg. Calculated DO)* 100

Avg. Observed DO

= (8.22-8.02)*100

8.22

= +2.4 %

Similarly,

Average Deviation in BOD:

Avg. BOD Deviation = (Avg. Observed BOD - Avg. Calculated BOD)* 100

Avg. Observed BOD

= (3.9 - 4.14) * 100

3.9

= - 6.1 %

3.2 Appropriate Water Quality Criteria

One of the important parameter relating to the river water quality is dissolved oxygen. Aquatic life will be adversely affected if the dissolved oxygen is not within the prescribed limits or there is excessive concentration of heavy metals. However, the wastewater quality results show that there is no significant contribution of heavy metals. Therefore, the decision to be based on DO concentration, minima and not on average concentrations arises from various considerations. Deleterious effects on fish seem to depend more on extremes than on averages. For example, the growth of young fish is shown markedly if the oxygen concentration falls to 3 mg/l for part of the day, even if it rises as high as 8 mg/l at other times (Bahzad, 2002).

The Australian Water Quality Guidelines proposes that DO should not be permitted to fall below 6 mg/l or 80-90 % saturation (Bahzad, 2002), this being determined over at least on diurnal cycle. This figure is recommended based on the studies conducted in Victoria Australia, which showed that DO concentrations below 5 mg/l are stressful to many specifies. The experts recommend that a DO concentration of 4mg/l should be maintained in the fresh water streams because the aquatic life is reasonably protected at 4 mg/l (Bahzad, 2002). To maintain the DO level within permissible limit, it is desirable that BOD concentration in river water be kept low. The European Community has given a maximum BOD limit for aquatic life (particularly fish) as 3.0 to 6.0 mg/l where as USSR standards are strict and allow a maximum BOD of 3 mg/l only (Bahzad, 2002).

Pakistan Environmental Protection Agency (EPA) has no maximum and minimum limits of DO and BOD for aquatic life as such. But it is restriction from EPA that the wastewater should be treated to bring BOD of the effluents up to 80 mg/l before discharging it into natural stream when enough water is available for its dilution by 10 times.

Based on above discussions, BOD values were taken in the rage of 8 mg/l and DO should not be less than in 4 mg/l for the purpose of simulation of different scenarios.

3.3 Model Simulations

Scenario -1: In this scenario, the present condition i.e. in year 2002 has been checked when there will be minimum flow of 28 cumecs (990 cusecs). The wastewater discharges with their DO and BOD inputs are shown in Table 7.

The water quality data was not available for a number of drains/ nullahs. So water quality data for the drains like Ghazi-M, Khalo-I, Khalo-II and Qazipur were assumed to be of similar nature as measured in case of Ghazi-I Drain. Similarly, for Lahore and Todhar drains, water quality was assumed to be the same as in case of Badri Khawar. While in case of Bada Khawar Nullah, the water was not available at the time of water discharge measurements in January 2002. However, two industrial estates Gadoon-Amazi Eastern and Gadoon-Amazi Western are disposing of their wastewater into Bada Khawar Nullah at a distance of about 13 Km upstream of its outfall into the Indus River. For assessment under adverse condition the discharge as well as wastewater quality data was used which was the sum of both industrial estates for Bada Khawar assuming that all wastewater is discharging into the river.

It may be noted that model allows the simulation of two forms of carbonaceous BOD to represent organic carbon. These forms are a slowly oxidizing form (CBODs) and a rapidly oxidizing form (CBODf ). Since, there are no separate values for CBODs and CBODf , so the BOD values instead of CBODs (assuming that it also covers the time of fast oxidizing material) are used. Hence the model output values for CBODs are the representing values of the BOD. The results of Scenario-1 are given in Table 8.

Scenario -2: In this scenario the river flow was the same as 28 cumecs but the discharge of the darins/nullahs was projected for the year 2063. The reason for projection of the wastewater discharge upto the year 2063 was that the project life of Ghazi Brotha Hydropower is for 60 years. The quality of the wastewater was assumed to be the same as in Scenario 1. The projected wastewater quantity and quality used for model input in Scenario- 2 is given in Table 7. The results of this scenario are given in Table 8.

Scenario -3: This scenario was the same as Scenario-2 with only difference that the BOD of wastewater was assumed to falling in the range of 80mg/l in project life, which is the worst case. The assumption for BOD upto 80 mg/l was based on the EPA restriction that the wastewater should be treated upto 80 mg/l BOD before discharging it into the natural steam and natural stream should has the discharges for ten times dilution. The projected wastewater discharge for the year 2063 and quality of the wastewater used for model input in Scenario-3 is given in Table 7. It may be noted that the BOD value was taken for Bada Khawar is the same as in case of Scenarios-1 and 2 due to reason that it is already over 80 mg/l i.e. 111.5 mg/l. The results of this scenario are given in Table 8.

Table 7. Wastewater Discharge and Water Quality data used for Model input

under Selected Scenarios- 1,2&

Site

Scenario-1

Scenario-2

Scenario-3

Discharge for the year 2003

(cumecs)

DO Model Input

(mg/l)

BOD Model Input

(mg/l)

Discharge for the year 2063*

(cumecs)

DO Model Input

(mg/l)

BOD Model Input

(mg/l)

Discharge for the year 2063

(cumecs)

DO Model Input

(mg/l)

BOD Model Input

(mg/l)

Ghazi-I

0.0024

3.9

66

0.0086

3.9

66

0.0086

3.9

80

Ghazi-M

0.0038

3.9

66

0.0135

3.9

66

0.0135

3.9

80

Khalo-I

0.0005

3.9

66

0.0042

3.9

66

0.0042

3.9

80

Khalo-II

0.0005

3.9

66

0.0042

3.9

66

0.0042

3.9

80

Qazipur

0.002

3.9

66

0.0110

3.9

66

0.0110

3.9

80

Ghurghushti

0.347

6.3

15.7

0.8632

6.3

15.7

0.8632

6.3

80

Chel

0.245

6.9

6.0

1.156

6.9

6.0

1.156

6.9

80

Bada Khawar

0.071

5.2

111.5

0.071

5.2

111.5

0.071

5.2

111.5

Badri Khawar

2.25

7.9

4.5

2.707

7.9

4.5

2.707

7.9

80

Lahor Drain

0.375

7.9

4.5

0.545

7.9

4.5

0.545

7.9

80

Todhar Drain

0.126

7.9

4.5

0.3006

7.9

4.5

0.3006

7.9

80

*Source: WAPDA.

3.3 Results of the Scenarios

Table 8 depicts the results of Scenarios 1, 2 and 3 for values of DO and BOD.

Table 8: Comparison of the Results of Scenarios 1, 2 & 3

Reach Label

Distance

(km)

Scenario 1

Scenario 2

Scenario 3

DO

(mg/l)

BOD

(mg/l)

DO

(mg/l)

BOD

(mg/l)

DO

(mg/l)

BOD

(mg/l)

Barrage

0.00

8.60

6.00

8.60

6.00

8.60

6.00

Ghazi-Khalo

2.50

8.84

4.67

8.84

4.71

8.83

4.72

Qazipur

7.50

8.90

3.65

8.89

3.69

8.89

3.71

Bada-Ghurghushti

12.50

8.67

3.37

8.61

3.58

8.54

5.18

Plan

20.00

8.75

2.27

8.69

2.41

8.45

3.47

Badri

27.50

8.65

2.63

8.57

2.17

8.04

8.30

Lahor

32.50

9.00

1.64

8.93

1.75

8.05

7.36

Todhar-Chel

38.00

9.27

1.33

9.16

1.50

7.89

7.81

Tail

41.00

9.27

1.33

9.16

1.50

7.89

7.81

As clear from above table that the DO values are almost same in first two Scenarios and there is a minor variation in case of Scenario-3. The DO values are much higher than permissible limits of 4 mg/l, so it can be assumed that there will be no danger to aquatic life due to availability of DO in river even during reduced flow, projected wastewater for the year 2063 and worst BOD of sewage up to 80 mg/l.

In case of BOD, the values are same in Scenarios-1 and 2. However, the values are higher in case of Scenario- 3 as compared to other two scenarios. But the values are almost within permissible limit of 8 mg/l for reduced flow, projected wastewater discharges and worst condition of BOD up to 80 mg/l. So, based on above results it can be assumed that there will be no adverse effect on aquatic life of the river during life of the Ghazi Brotha Hydropower Project.

4. Comments and Discussions

Model DO Output Values

It may be observed from Table 9 that the DO values from barrage to downstream are in the range of 8.60 mg/l to 7.90 mg/l, which are almost same as compared to general observations made through sampling as provided in Table 3. As per Table 3, the DO values are 8.6 mg/l at barrage and downstream of Chel Nullah i.e. 8.5 mg/l. It may be noted that at reduced flow of 28 cumecs, projected wastewater quantity and worse wastewater quality of upto 80 mg/l BOD, the model out put DO and observed DO by sampling are almost same which may be due to reason that the reduced water flow pattern in the river was taken as the same as observed during October 2002 to May 2003 at the time of river survey when the flow was varying from 297 cumecs to 770 cumecs. Since it was assumed that at reduced flow conditions the water will flow in the same creeks as observed in river survey of October 2002 to May 2003, the cross sectional area of the reduced flow is presumably more and depth of flow is lesser than the actual condition that will prevail when the discharges of the river are 28 cumecs. Ultimately, the chance of re-aeration, oxygen inhabitation, photo-synthetically available radiation is more than the actual, thus the values of DO have increased accordingly. Basically, it is not possible to predict exact path of flow, which will be followed by the reduced flow, it may require a detailed hydraulic model study.

Model BOD Output Values

It may also observed from Table 9 that the BOD value is higher at downstream of barrage i.e. 6 mg/l and it goes on decreasing further downstream and it remains as 1.85 and 1.86 mg/l in Scenarios 1 & 2 and 7.81 mg/l in Scenario 3, even though there are a number of drains/nullahs discharging their effluents into the river. This situation may be due to several reasons. One main reason is that at upstream of the barrage there are three main sewage outfalls on Left Bank, which are discharging pollutants of Main Terbela Colony, Sanober Colony and Sobra City of WAPDA into the river. Similarly, on Right Bank there are two sewage outfalls, which are contributing the pollutants of Powerhouse Colony WAPDA and GIK Institute. All these colonies and institute have their effluent treatment plants and it is assumed that the BOD value of the pollutants will be in the range of 80 mg/l. The second reason of the barrage side, higher value of the BOD may be due to stagnant water of the impoundment area as it has less chance of re-aeration and radiation due to higher depth of the water. Thirdly, the reason for less value of BOD on downstream side is that the quantities of the effluents are small and their quality is not much deteriorated. However, in case of scenario-3 where the BOD value of wastewater quality was assumed to be in the range of 80mg/l, the BOD value of river floodplain is higher than that at barrage. Fourthly, the riverbed downstream is mostly gravely thus a lot of turbulence is encountered in the flows, which results effective assimilation of pollutants.

Assumptions of Scenario- 3

At simulation of Scenario- 3, it was assumed that the BOD of wastewater would be in the range of 80 mg/l as per EPA standards. This will be the case if the wastewater is treated accordingly before discharging it into the river. The samples collected at the time of Feasibility Study at Ghazi and Khalo drains were showing that the value of BOD was over 400mg/l. During last few years, the local population has constructed septic tanks and soakage pits in their houses, due to this facility the quality of wastewater is relatively better. But ultimately the capacities of the septic tanks and soakage pits will be over and then the quality of wastewater may again deteriorate. The local administration is providing proper flush systems even to the rural areas. If such flush system was provided in the study area, the quality of wastewater will further deteriorate and it may cross the range of 80mg/l as assumed in Scenario-3. So there will be need of some mitigation and management plan to keep the BOD within permissible limits.

Some drains/nallas e.g. Ghurghashti, Chel, Bada Khawar and Badri Khawar, carry wastewater from far away and most of the water do not reach up to the river due to seepage into the ground and causes the ground water contamination. If in these villages/towns, which are contributing their wastewater into these near by drains/nullahs were also provided the flush system and the drains were lined, the contribution of wastewater of these drains will be much higher to the river as assumed in the Scenario-3. Due to higher water quantity and worst quality of the drains/nullahs wastewater, the quality of the river water may deteriorate. So there will be a need of some management plan for wastewater treatment of those villages/towns, which are even far away from the river but may affect the river water quality.

Future Industrial Development of the Area

Local Development Authority is planning to develop an Industrial Estate about 5 km downstream of the Ghazi village. For this purpose the basic infrastructure has already been developed by the Local Development Authority. If this industrial estate is developed, its wastewater will also affect the river water quality. So there will be need of some management plan to save the river water quality from further deterioration.

5. Conclusions and Recommendations

5.1 Conclusions

Based on the model results and discussions, the following conclusions are derived.

Under present conditions of quality and quantity of wastewater and minimum flow of

28 cumecs, the DO and BOD remain within permissible limits.

Under minimum flow conditions of 28 cumecs and projected wastewater quantity for the year 2063, the DO and BOD values will remain within the permissible limits.

Under minimum flow conditions, projected wastewater for the year 2063 and assumed wastewater quality in the range of 80 mg/l, the DO and BOD values will still remain within the permissible limits.

The flow pattern of the minimum flow in the river may require to be established to obtain the exact values of the DO and BOD in all three scenarios.

When capacities of the septic tanks and soakage pits are over in the concerned towns/villages, the quality of the wastewater is liable to further deteriorate by crossing the limit of 80 mg/l. Under such scenarios, some mitigation and management plan will be required to keep the river water quality within permissible limits.

By providing flush system for the households in the concerned towns/villages, if the drains/nullahs carrying the sewage water to the river are lined, the quantity of the wastewater will increase, resulting in an increase in pollution level. Therefore, in the management plan, this aspect will be required for consideration.

If the Local Development Authority develops an Industrial Estate at 5 km downstream of Ghazi, the wastewater from Industrial Estate may further deteriorate the river water quality and thus require some mitigation and management plan.

5.2 Recommendations

With reference to above conclusions, the following recommendations are made to establish the river flow pattern to mitigate the adverse effects and evaluate the management plans to ensure that the river water quality may remain within the permissible limits.

Hydraulic Model Study: It is recommended that a proper Hydraulic Model Study should be conducted to establish the river flow pattern during the reduced flow. It will help assess the values of DO and BOD near to practical situation and determine the creeks which will be severally affected due to reduced flow.

Wastewater Treatment Facilities: In order to keep the BOD values of the effluents in the range of 80 mg/l in the project life, the treatment facilities like treatment plants for big cities/towns and oxidation ponds for relatively small towns may be provided. Similarly the option for the provision of Reed-Bed Lagoons and Reed-Bed Channels may also be adopted, as it proved to be very economic and effective solution.

Release of Excessive amount of Water from Barrage to the River: If the Industrial Estate was constructed by the Local Development Authority, then a sophisticated wastewater treatment plant, to keep the BOD less than 80 mg/l, will be required to mitigate the effects on water quality of the Indus River floodplain.

References and Notes

Atlas of Pakistan, (1992). Survey Sheet No. 24, Survey of Pakistan, Murree Road, Rawalpindi, published in1992.

Bahzaz, A., (2002), "Application of QUAL2K Model to the Contaminant Transport in River Ravi", M.SC (WRM) Thesis, Centre of Excellence in Water Resources Engineering, UET, Lahore.

Brown, L.C., and T.O. Barnwell, (1987). The Enhanced Stream Water Quality Model QUAL2E and QUAL2E-UNCAS, EPA/600/3-87-007, U.S. Environmental Protection Agency, Athens, G. A.

PHC (Pakistan Hydro Consultants), (1992). Ghazi-Brotha Hydropower Project, " Report on Supplementary Environmental Studies".

PHC (Pakistan Hydro Consultants), (1991), Feasibility Report, "Environmental Assessment of Ghazi-Gariala Hydropower Project", Volume 7.

Steve, C. and Greg. P., (2003). QUAL2K, A Modelling Framework for Simulating River and Stream Water Quality "Documentation and Users Manual".

WAPDA, (2003). Ghazi-Brotha Hydropower Project, "Supplementary Environmental and Social (SES) Study for Management of Indus Flood Plain and Water Releases" (2003).

© 2010 by the authors; licensee MDPI, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).

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