Title : IMPACT OF RBOD EFFLUENTS ON RIVER INDUS

Habib Ursani , Dr. Abdul Khalique Ansari,

ABSTRACT

The Right Bank Outfall Drain (RBOD) project was started to overcome twin menace of waterlogging and salinity in the Right Bank Command Area of Guddu and Sukkur barrages of river Indus. The naturally occurring Main Nara Valley Drain (MNVD) with rehabilitation and extension will perform as Spinal Drain (RBOD).

To answer the question whether water from RBD (four stages) and D.G Khan and Muzafargarh would hamper the Indus river water quality, its was necessary to analyse the present data available on RBOD drains and Punjab drain proposed to be connected with RBOD. Present Indus river water quality and flow is important to find the river assimilative capacity.

The existing drainage units are discharging their drainage effluents via MNVD into Hamal lake and then into Manchar lake and then ultimately to river Indus through Indus link.

The analysis results of river Indus samples collected from Dadu-Moro bridge and Kotri barrage show that Total Dissolved Solids (260-416 mg/l) hardness (44-88 mg/l) and chloride (44-76 mg/l) were within the allowable WHO standard. The Indus River water quality will be deteriorated, as the effluents from RBOD outfall into the river.

The salt flow analysis was carried out by using the same method as proposed by PANEL OF EXPERTS [18] for the period of dry season (February-March, November-December). This shows that when Indus flows are minimum (3000-7000 cusecs) with E.C of 0.44 dS/m, the mixed water quality of Indus at Kotri in most cases is critical (> 1.0 dS/m). This even crosses the WHO standard (1.5 dS/m) in some cases, when RBOD flow is 1000 cusecs or above with E.C of 6.0 dS/m or above.

The toxic water having higher Total Dissolved Solids, hardness and chlorides will cause irreparable damage to all the downstream users, human as well as livestock and fisheries. The agriculture will also be affected by the effluents of RBOD as salt sensitive crops, banana and sunflower are grown in the Kotri command area.

I.I Introduction:

The province of Sindh extends over an area of 14.0 million hectare's, out of which 9 million hectare's are fit for cultivation. An area of 5.28 million hectare's is under the command of canal system of three barrages on River Indus namely Guddu Barrage, Sukkur Barrage and Kotri Barrage. The Right Bank Command system cater for 1.24 million hectares, the rest of the command is under the command of Left Bank Canal System of all three Barrages.

Before the construction of Sukkur barrage and its canal system in 1932, both Left and Right banks of River Indus were irrigated by inundation canals. Because of the irrigation supplies in summer only i.e. Kharif the Rice crop was the pre-dominant production.

After commissioning of the Sukkur Barrage and its six perennial and one non‑perennial off‑taking Canals with a culturable commanded area of 2.9 million hectares in 1932 and onwards, the ground watertable (W.T) started gradually rising. Just over three quarters of a decade, the rising watertable was showing it's ill‑effects on the fertility of the land by pushing up salts to the surface turning these into kalarish and saline tracts. The sub‑soil watertable has been classified into following four categories:

C A T E G O R Y

1. 0 ‑ 5' below ground level

2. 5 ‑ 10' below ground level

3. 10‑ 15' below ground level

4. Watertable more than 15' below ground level.

0‑5' below ground level

---------------------------------------------------

ß ß ß

Guddu Barrage Sukkur Barrage Kotri Barrage

1,03,408 Hectars 3,76,644 Hectars 4,45,336 Hectars

To overcome the twin menace of waterlogging and salinity, drainage projects were started in both the Right Bank and the left bank of the Indus. The drainage projects are called as Left Bank Outfall Drain (LBOD) and Right Bank Outfall Drain (RBOD).

The Left Bank Outfall Drain catchment covers about 5 million acres. The basic surface drainage facility has been provided throughout the project area for the disposal of tubewell or tile effluent and for the removal of surplus irrigation water and storm water. During periods of heavy rain the tubewell and tile discharges can be stopped and the full capacity of the drain will be available for storm water runoff.

The Right Bank Outfall Drain (RBOD) caters for the development of approximately 1.8 million hectares, generally irrigated by the Right Bank canals of the Guddu and Sukkur Barrages. The implementation period of this plan spans over 26 years [5].

There is little natural drainage on the Right Bank. The command of Sukkur Barrage slopes generally to the west, away from the Indus, until it reaches the Main Nara Valley, a historic river course forming a natural drainage line, west of the main Nara valley, the land rises again towards the Khirthar Hills. The designers of Sukkur Barrage exploited this natural drainage line to construct a large drain called the Main Nara Valley Drain (MNVD). This drain was part of the Manchar Drainage Scheme (Government of Bombay:1933). It linked two natural depressions, Mirza Khan Reservoir (Now called Hamal Lake) and Manchar Lake, and in addition, catered for escape flows from the Rice Canal, via the Pritchard Escape, there was no agricultural drainage facilities were provided.

II.I WHO GUIDE LINES FOR WATER QUALITY:

WHO DRINKING WATER STANDARDS

Parameters

Units

WHO 1984 guidelines

TDS

mg/l

1000

6.5 - 8.5

Detergents

mg/l

1.0

Oils

mg/l

0.30

Total Hardness

mg/l

500

Calcium

mg/l

200

Iron

mg/l

0.3

Chloride

mg/l

250

Sulphate

mg/l

400

Nitrate

mg/l

11.3

Source: World Health Organization, Geneva.

GUIDELINES FOR INTERPRETATION OF WATER

QUALITY FOR IRRIGATION

Parameter

Units

Degree of restriction of use

None

Moderate

Severe

Salinity

ECw or

TDS

dS/m

mg/l

< 0.7

< 450

0.70 - 3.0

450 - 2000

> 3.0

> 2000

Infiltration

SAR = 0 - 3 & Ecw =

= 3 - 6 =

= 6 - 12 =

= 12-20 =

= 20-40 =

> 0.7

> 1.2

> 1.9

> 2.9

> 5.2

0.7 - 0.2

1.2 - 0.3

1.9 - 0.5

2.9 - 1.3

5.2 - 2.9

< 0.2

< 0.3

< 0.5

< 1.3

< 2.9

Sodium (Na)

SAR

< 3

3 - 9

> 9

Chloride (Cl)

me/l

< 4

4 - 10

> 10

p^H

Normal range 6.5 - 8.5

Source: Food and Agricultural Organization.

WATER QUALITY GUIDELINES FOR

LIVESTOCK AND POULTRY USES

Water Salinity

mg/l

Rating

Remarks

1000

Excellent

Useable for all classes of livestock and poultry

1000 - 3000

Very

Satisfactory

Useable for all classes of livestock and poultry. May cause temporary diarrhoea in livestock not accustomed to such water, watery droppings in poultry.

3000 - 5000

Satisfactory for livestock

Unfit for poultry

May cause temporary diarrhoea or be refused at first by animals not accustomed to such water.

Often causes watery faeces,

increased mortality and decreased growth, especially in turkeys.

5000 - 7000

Limited use for livestock

Unfit for Poultry

Useable with reasonable safety for dairy and beef, cattle, sheep and horses. Avoid use for pregnant or lactating animals.

Not acceptable for poultry.

7000 - 10000

Very limited use

Unfit for both livestock and poultry.

> 10000

Not recommended

Risks with such highly saline water are so great that it cannot be recommended for use under any conditions.

Source: Food & Agricultural Organization.

III.I WATER QUALITY OF RIVER INDUS:

After completion of the RBOD project, the drainage effluent will be discharged into the river Indus via Indus link. Therefore, the samples of Indus water were collected from two locations one at Dadu-Moro Bridge and the other from upstream of Kotri barrage, the analysis results are presented in Table III.9 & III.10.

The results of Indus River from Dadu-Moro Bridge and Kotri barrage show that pH was about 7.6 in each sample. The Total Dissolved Solids were between 200-400 mg/l within the WHO acceptable level (1000 mg/l).

The salinity data obtained during the months of February 1997 to June 1997 has been compared (Table III.11) with the SMO WAPDA data during the same months of 1995 and 1996.

The Table 3.1 shows:

For Indus Flow at Kotri 3000 cusecs:

· The mixed E.C goes beyond 1.0 dS/m when RBOD flow is at 300 cusecs with E.C of 9 dS/m.

· The mixed E.C is above 1.0 dS/m when RBOD flow is above 1000 cusecs even with lowest E.C of 3.0 dS/m. With RBOD E.C of 6.0 dS/m and above the mixed E.C crosses the WHO standard of 1000 mg/l (1.5 dS/m).

· The mixed E.C becomes high when RBOD flow is 2000 cusecs and RBOD E.C is 3.0 dS/m or higher. This mixed E.C is much higher than the WHO standard (1.5 dS/m).

For Indus Flow at Kotri 5000 cusecs:

· The mixed E.C is within 1.0 dS/m when the RBOD flow is 300 cusecs.

· The mixed E.C is above 1.0 dS/m when RBOD flow is 1000 cusecs with E.C of 6.0 dS/m or higher.

· The mixed E.C is above 1.0 dS/m when RBOD flow is 2000 cusecs. When RBOD E.C is 6.0 dS/m or higher the mixed E.C value crosses the WHO standard.

For Indus Flows at Kotri 7000 cusecs:

· The mixed E.C is within 1.0 dS/m when RBOD flow is 300 cusecs.

· The mixed E.C is above 1.0 dS/m when RBOD flow is 1000 cusecs with E.C of 6.0 dS/m or higher.

· The mixed E.C is above 1.0 dS/m when RBOD flow is 2000 cusecs with E.C of 6.0 dS/m or higher.

· Here again the WHO standard is violated when the RBOD flow is 1000 cusecs or higher if the incoming E.C is 9.0 dS/m.

For Indus Flow at Kotri 10000 cusecs:

· The mixed E.C is below 1.0 dS/m when the RBOD flow is 300 cusecs

· When RBOD flow increases to the value of 1000 cusecs with E.C of 9.0 dS/m the mixed E.C value goes beyond 1.0 dS/m.

· The mixed E.C is above 1.0 dS/m when RBOD flow is 2000 cusecs with E.C of 6.0 dS/m and above.

· Here again the mixed E.C would cross the WHO limit if RBOD incoming E.C is 9.0 dS/m.

For Indus Flow at Kotri, 15000 cusecs:

· Here the mixed E.C is above 1.0 dS/m when the RBOD flow is 2000 cusecs with E.C 6.0 dS/m or higher.

IV.I IMPACT OF RBOD EFFLUENTS ON RIVER INDUS:

The most crucial period is dry season, which approximately starts from the month of October and ends in the month of June. It is this period the flow of river Indus is less and E.C as a result increases. From fifteen year data (1982-97) of river Indus discharge at Kotri (during dry season), it is clear that the average flow is as minimum as 2000 cusecs (February 1984). This year wise data is presented in two graphs: IV.1 (February-March) and IV.2 (November-December). The graph IV.1 show that the flow at Kotri was 10000 cusecs or below in March in most of the years. This flow was below 20,000 cusecs in February for atleast seven years. The graph IV.2 show that the flow was again below 20,000 cusecs for the month of November for almost all the years.

The Indus at Kotri have encountered a dry spell of 10,000 cusecs or below in the end of years 1984, 85, 86, 87 and 89. It is worth mentioning that the March of 1983, 85, 86 and 97 have witnessed the minimum discharges, (5000 cusecs or below) at Kotri upstream of river Indus. This has given the ample reason of selecting the Indus flows at Kotri as 3000, 5000, 7000, 10000 and 15000 cusecs to find the impact of RBOD effluents during the dry season.

During the dry season (February-March & November-December) the value of E.C as found by Panel of Experts is around 0.44 dS/m (Table A.4). This also matches reasonably with the weighted average measured value of E.C as given in Table A.3. Therefore, in the present study the value of E.C at Kotri has been used as 0.44 dS/m throughout. The impact of RBOD effluents on the Indus River water quality has been found by following the same dynamic salt flow analysis procedure.

The Panel of Expert report (Tables A.1 to A.5) and SMO, WAPDA data (Tables A.6 and A.7) for the period 1995-96 shows that MNVD flow would approximately vary from 300 cusecs to 2000 cusecs in the months of February-march and November-December when the RBOD Project is fully developed. The corresponding RBOD E.C have been measured/Projected by SMO/POE and approximately range from 3 to 9 dS/m.

4.0 CONCLUSION:

· Disposal of RBOD drainage effluents into the river Indus above Kotri Barrage can affect the water quality badly for downstream users. Therefore, the ultimate objective of water quality analysis was to determine the impact of Effluent disposal on the quality of the river Indus above Kotri.

· In dry season, the Indus River at Kotri witnessed the minimum flow of 3000 cusecs or even lower during the month of March and December of atleast two years 1985 and 1986. If Indus at Kotri is at the above flow with E.C of 0.44 dS/m, the mixed water quality would cross the WHO standard even with the RBOD flow of 1000 cusecs and E.C of 6.0 dS/m. This is a negative impact of RBOD on Indus River water quality.

· In dry season, even at high flow of Indus (10,000 cusecs and E.C=0.44 dS/m), the mixed water quality of river Indus at Kotri is critical (>1.0 dS/m). And violates the WHO standard (1.5 dS/m) when the RBOD flows into it beyond 2000 cusecs with E.C of 9.0 dS/m.

· Even at high flow of Indus (10000 - 15000 cusecs) one can expect negative impact if RBOD flow is 2000 cusecs or above with E.C of 6.0 or above.

V.I MITIGATION MEASURES:

Pakistan has World's largest contiguous irrigation network in the form of canals, distributaries and watercourses. With its own inherent benefits and operational and management problems. There have been concerns in the recent past about increasing the system efficiencies through options as lining of canals and on-farm watercourse improvement.

Once the land become saline and waterlogged, it is very difficult to reclaim it easily. Drainage is the method to reclaim the affected land, but the safe disposal of drainage effluent is difficult. Safe disposal requires large areas of abandoned lands or an outfall into an ocean. As far the effluents of Right Bank Outfall Drain are concerned, there is vast abandoned land on the western side of the project, but the hilly terrain does not allow feasible passage towards the abandoned lands. Construction of tunnel will be much costly. As for the disposal towards the sea is concerned, there are two options i.e. either through the river Indus or via Left Bank Outfall Drain [19].