Manchar Lake Image source Wikipedia
by Abdul Waheed Bhutto 15 May 2023
The devastating impact of the monsoon season and floods on farmers in Sindh highlights the urgent need for floodwater management. Freshwater lake especially the Manchar Lake has the potential to play a crucial role in storing floodwater and promoting sustainable agriculture in the region.
Sindh has several freshwater lakes, including Keenjhar, Haleji, and Manchar, primarily fed by rainfall and Indus water. However, the water quality of these lakes may be unsuitable due to pollution, especially Manchar Lake. Manchar Lake was once the largest freshwater lake in Pakistan, but pollution, waterlogging, and salinization have severely impacted its ecosystem and surrounding communities’ livelihoods.
Manchar Lake covers an area of around 200 square miles when full and fed by multiple sources, including the Indus River, hill torrents, and drainage channels. The average depth of lake is 2.5 to 3.75 meters. It is 6 meters lower than the bed of the Indus, and catches floodwater from the river, while in winter when the river is low, water flows from the lake into the Indus.
The wastewater and pollutants from agricultural fields, fish and livestock farms, and urban areas also flow into the lake, and it has already degraded its water quality. All these sources of pollution have contributed to a decline in water quality and the health of the lake’s ecosystem. The resulting pollution has also had negative impacts on the health and livelihoods of the surrounding communities.
Manchar Lake has suffered significant pollution in recent years, with major contributors including agricultural runoff containing chemicals, industrial waste from nearby factories, domestic sewage from surrounding communities, and deforestation in nearby hills causing sedimentation and water quality issues.
To address drainage issues on right bank of Indus River and to protect the Indus River, Manchar Lake, and other freshwater lakes in Sindh, Right Bank Outfall Drain (RBOD) a drainage project was originated. Initially it was comprising on RBOD-I and RBOD-II, however later RBOD-III was added to the project. The objective of the project was to divert wastewater and agricultural runoff from upper Sindh and Baluchistan to the Arabian Sea.
RBOD-I, also known as the Main Nara Valley Drain (MNVD), is a 168 km long drainage channel that carry drainage water. It starts from Miro Khan in Qambar Shahdadkot district to Sehwan. Originally MNVD which constructed in 1932 with Sukkur Barrage command area. It is an old abundant distributary of Indus River. MNVD also connect Hamal Lake and Manchar lake.
The Danister Wah, Aral Head, Aral Tail and Main Nara Valley Drain (MNVD) are irrigation systems that have been developed around Manchar Lake. The Danister Canals are a network of small canals that are connected to the Aral Canal and are used to irrigate the lands near the lake. These canals were built to provide a continuous flow of water to the lake and also to maintain the water level by redirect excess water back into Indus.
The Indus Link Canal connects RBOD-I to RBOD-II and facilitates the transfer of water between the two systems. The RBOD-I system was designed to manage the drainage and wastewater generated by agriculture in the Nara Canal command area. The system collects, transports, and discharges drainage water into Manchar Lake. The RBOD-I system includes a sub-system called the Darawat Dam Spillway Drain (DDSD), which carries excess water from the Darawat Dam and other water sources in the area into Manchar Lake through the Aral Wah channel.
RBOD-II is a 273km-long drain designed to carry effluent from RBOD-I to the sea. Its capacity was enhanced to 3,500 cusecs due to the addition of Balochistan’s effluent. RBOD-I and RBOD-III was completed by WAPDA, while RBOD-II is currently being executed by the Irrigation Department of the Government of Sindh. The project has faced several challenges, including issues with the construction and maintenance of the drainage channel. Despite these challenges, the RBOD project is still being expanded to increase its capacity and improve its efficiency.
Manchar Lake’s capacity varies with the season and rainfall. It can expand to 250 sq miles during monsoon and shrink to 100 sq miles in the dry season. At maximum, it can store about 5 billion cubic meters of water, mainly for fishing and irrigation. To comparison of magnitude of capacity, Tarbela Dam is a man-made reservoir with a capacity of 13.7 billion cubic meters, used for hydroelectricity and irrigation purposes. The current power generation capacity of Tarbela Dam is 4,888 MW.
Likewise, under construction Diamer-Basha Dam Project is expected to generate 4,500 MW of electricity and will have a water storage capacity of 8.1 billion cubic meters. estimated cost of around 14 billion US dollars. Project is estimated to complete in 2028.
It is important to note that the capacity of Manchar Lake has been significantly reduced due to siltation and sedimentation caused by the erosion of the surrounding hills and deforestation. Additionally, the diversion of water for irrigation and industrial purposes has led to a decrease in the lake’s water level and volume over the years. As a result, the lake’s capacity and overall health have been severely impacted, highlighting the urgent need for conservation and restoration efforts.
The devastating impact of the monsoon season and floods of 2022 in Sindh highlights the urgent need for floodwater management. Freshwater lakes specifically Manchar Lake has the potential to play a crucial role in storing floodwater and promoting sustainable agriculture in the region. To store floodwater in the lake, controlling the inflow of water from the Indus River during periods of high rainfall and flooding is crucial. This can be achieved by building spillways and diversion channels to redirect excess water to the lake while also ensuring the stability of the lake’s embankments. Moreover, removing sediment from the lake by dredging it may also enhance its capacity to store more water.
Storing floodwater in Manchar Lake could be a potential solution for utilizing the water for irrigation, domestic use, and recharging groundwater tables. However, the success of this strategy would depend on several factors, including the lake’s water level, rainfall, and water inflow from the Indus River.
To use Manchar Lake for storing flood water, it is crucial to ensure its proper condition and infrastructure. This involves repairing embankments, dredging the lakebed, and upgrading water management structures. Additionally, a floodwater management plan could coordinate efforts of stakeholders to capture and store flood water in the lake.
Work is also needed to address the underlying causes of pollution in the area and promote sustainable water management practices. This includes improving agricultural practices, promoting the use of wastewater for irrigation, and implementing stricter regulations on industrial pollution. Water-efficient agricultural practices should be promoted to maximize crop yields while minimizing water use. Establishing effective governance mechanisms, such as water user associations, can ensure sustainable water use. Implementing these strategies can enable the storage of flood water in Manchar Lake for agricultural purposes and promote sustainable development in the region.
There are several agricultural areas downstream from Manchar Lake that could benefit from the use of its water for irrigation. These include Dadu District, which produces cotton, wheat, and sugarcane; Jamshoro District, which produces crops such as wheat, rice, and cotton, Thatta District, which produces wheat, cotton, and vegetables; and Badin District, which produces rice, wheat, and cotton. By supplementing existing water sources with water from Manchar Lake, crop yields could potentially increase, and sustainable agricultural development could be supported in the region. The biggest benefit of remodeling Manchar for water storage shall be controlling seawater intrusion.
In addition to providing water for irrigation, Manchar Lake can also support aquaculture activities, particularly the cultivation of fish. The lake has traditionally been a major source of fish for the local population, and aquaculture activities can help to sustainably manage the lake’s fish populations while also providing economic opportunities for local communities.
However, the lake has been facing severe environmental degradation over the years, mainly due to pollution from industrial and agricultural activities, as well as water diversion for irrigation purposes. The excessive growth of water hyacinth, a non-native invasive plant species, has also contributed to the lake’s degradation, affecting the lake’s ecology and threatening the livelihoods of the local communities who depend on fishing and agriculture.
Remodeling freshwater lakes for floodwater Storage and Protecting Sindh’s Freshwater Ecosystems requires a collaborative effort involving the government, local communities, and environmental organizations. Key measures that could be implemented include raising public awareness of pollution’s impacts, constructing wastewater treatment plants, implementing solid waste management practices, dredging and desilting the lake, planting aquatic vegetation, and establishing a monitoring system to assess water quality. A comprehensive approach is crucial for successful and sustained cleanup efforts.
The task of rehabilitating and renovating freshwater lakes for floodwater storage, agriculture, and domestic use is too massive for the Sindh government to handle alone. There is a need to revisit Water Apportionment Accord of 1991 to tackle evolving water resource issues, climate changes, and to improve infrastructure and institutions for efficient water management. The federal government must provide financial and technical assistance to Sindh for the identified projects and other potential water infrastructure. Collaboration between federal and provincial governments is essential to implement sustainable water management policies and practices that ensure sufficient water availability.