Title : IMPACT OF RBOD
EFFLUENTS ON RIVER INDUS
Habib Ursani , Dr. Abdul Khalique Ansari,
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 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 |
PH |
- |
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 |
pH |
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].