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

A A Mahessar,G M Arain,A L Qureshi,S M Kori,S Qureshi,K Ansari

doi:10.48084/etasr.3219

Abstract

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.

Highlights

Lakes are natural water bodies that serve as sources of recharging groundwater reservoirs while improving its quality, but have significantly been degraded due to growing population and economic development
They are broadly categorized as mountainous lakes, tropical freshwater and salt lakes, Indus River, coastal wetlands and manmade reservoirs [2], but only 46 of them are listed as protected areas including 19 Ramsar sites which have international importance [3]
The results of water quality index (WQI) indicate that the water quality of the collected samples is very poor and unsuitable for drinking

Summary

Introduction

Lakes are natural water bodies that serve as sources of recharging groundwater reservoirs while improving its quality, but have significantly been degraded due to growing population and economic development These lakes are natural water providers, flood storages, natural habitats and breeding homes for indigenous and migratory birds including endangered species. Sindh holds the privilege of hosting Wildlife Protected Ramsar sites as they serve as sanctuaries for waterfowl migratory and local birds such as Keenjhar Lake (Ramsar Site No 99), Haleji Lake, (Ramsar Site No 101), Drigh Lake (Ramsar Site No 100), Jubho Lagoon (Ramsar Site No.1067), and Narri lagoon and Guddu to Sukkur stretch of Indus river (Ramsar sites) These lakes are almost under threat due to fresh water scarcity, less drainage, less rainfall, polluted water, increased sedimentation and eutrophication [4]. Manchar Lake, which is the biggest lake of Sindh, was developed along with Himalaya, Karakorum and Khirthar www.etasr.com

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