Assessment of variation in water quality at Right Bank Outfall Drain, including Manchar lake, Sindh, Pakistan

The effluent water brought by RBOD (Right Bank Outfall Drain) is not only threat to the aquatic life of Manchar Lake but also the fertile agricultural lands which are being cultivated by use of lake water through Danastar Wah are at risk of salinization. The farming community of the area is scary of continual use of irrigation waters received through the Danastar Wah; they are of the view that the constant use of this water will ruin their fertile lands into salt-affected soils. Thus, keeping in view the fears of the farmers of the command area of Danastar Wah, a study was carried out to investigate the water quality of the Manchar Lake, RBOD MNV (Main Nara Valley) drain and Danastar Wah, and to examine soil salinity status of the area using Geo-referenced field and satellite imagery data for Kharif season of the year 2015. The results of the study showed that the EC (Electrical Conductivity) of the Danastar Wah water was below 1.2 dS/m. Thus, the water was suitable for irrigation purpose. In all the water samples, Na+, Ca2+ + Mg2+ and CO3 concentrations were found within the permissible limits, while no concentration of HCO3 was found in any of the water samples. In the command area, clay texture was dominant down to a depth of 60 cm soil profile. In the area about 37, 28, and 30% of the soils were normal (non-saline), saline and sodic, respectively; while only 5% of soils were saline-sodic. The cotton crop was identified as the major Kharif crop, occupying about 13.76% (2,844 ha) of the total command area, followed by rice crop grown on about 5.21% (1,078 ha) of the command area. The overall accuracy of image classification was 90% with a kappa coefficient of 0.86. Based on this study, it can be concluded that the water of the Danastar Wah can be used for irrigation purpose during Kharif season only with the condition that adequate land drainage is maintained. It is also suggested that before using the water of Manchar Lake, RBOD and Danastar Wah for Rabi season, analysis for water quality be conducted. GeoInformatics (GIS and RS) tools can be employed for spatial and temporal monitoring of water quality of the Manchar Lake.

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Impact of Right Bank Outfall Drain-I (RBOD-I) / Main Nara Valley Drain (MNVD) on Manchar Lake, Sindh, Pakistan

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.3219 ◽

2019 ◽

Vol 9 (6) ◽

pp. 5074-5079

Author(s):

A. A. Mahessar ◽

K. Ansari ◽

G. M. Arain ◽

S. M. Kori ◽

S. Qureshi ◽

...

Keyword(s):

Water Quality ◽

Water Supply ◽

Lake Water ◽

Polluted Water ◽

Mountain Range ◽

Indus River ◽

Lake Water Quality ◽

The Right ◽

The Impact ◽

Manchar Lake

The lakes of Sindh are in poor environmental condition due to the massive disposal of effluents. This paper presents the impact of water quality in Manchar Lake due to climate change and anthropogenic intervention. The lake is one of the biggest natural lakes in Sindh, Pakistan. The lake has three major sources of water supply: Indus River, hill torrents from the Khirthar Mountain range and the Right Bank Outfall Drain (RBOD-I)/Main Nara Valley Drain (MNVD). The water supply of the lake from the first two sources has been reduced due to morphological and climate changes. Hence, there is only one, and polluted, water supply to the lake, the RBOD-I/MNVD. At the same time, the use of poisonous materials for fishing has further contaminated the lake’s water. The RBOD system is connected with RBOD-III, RBOD-I/MNVD, Indus Link and RBOD-II on the right side of Indus River for safe disposal of wastewater into the Arabian Sea, which is still not functioning. Hence, more than 4500 cusecs of wastewater from the catchment area of RBOD have directly been discharged into the lake causing severe impact on flora, fauna and the livelihood of locals. In order to analyze the lake water quality impact, the water quality index (WQI) model was used. The results indicate that the water quality of four samples was very poor, while the fifth sample was unsuitable for drinking. The results of statistical analysis of parameters such as TDS, EC, SO4, Cl, Na, and hardness are higher to their permissible limits. Consequently, lake water possesses a high potential risk to local consumers and aquatic ecology.

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