Left Bank Outfall Drain

Location It starts from Ghotki district, which is located on the Sindh-Punjab border, and flows through the districts on the left bank of River Indus before ending in the Sir Creek of Arabian Sea on Badin's coast. Capacity Its designed capacity is 4,500 cusecs The canal's effluent disseminates into Dhoro Puran Outfall Drain (DPOD) with capacity of 2000 cusec and Kadhan Pateji Outfall Drain (KPOD) having capacity of 2500 cusec. The DPOD empties into Shakoor Lake located both in Pakistan and India whereas effluent of KPDO is directly discharged into sea through 41 km long Tidal Link Canal. Drainage capacity of canal has been increased to 9000 cusecs after 2011 floods by de-silting of bed of drain, raising banks up to two feet, repairing damaged hydraulic structures and by clearing vegetative growth. Purpose LBOD is located in the catchment area of the Old Nara River which is a left bank delta channel of Indus River. Old Nara River streams are used to collect the saline water generated from irrigated lands and the industrial effluents. In the middle reach (i.e. Nara canal) of this river, saline and polluted water flowing into the river are diluted by feeding main Indus River water from Sukkur barrage and supplied by gravity canals for irrigation and industrial needs. The saline water generated from the irrigated lands and the industrial effluents are collected by the LBOD canal network from the lower reaches of the Old Nara River or Puran River to discharge by gravity flow to the sea. Also bore wells are used to pump saline water into the LBOD or the Old Nara River streams to depress the saline ground water level at safe depth or prevent waterlogging. As most of the cultivated lands are located on the left side of the Indus River, LBOD would be the predominant means of discharging the river salt load to the sea once the Indus River waters are fully put to use without letting the Indus River water overflow to the sea from the Kotri barrage which is the last barrage across the river. Effective usage of LBOD is crucial to preserve/enhance the soil fertility in lower reaches of Indus basin area or Sind province or Indus River Delta for discharging adequate salt load to the sea. ==Issues==

Doubtful efficacy of the LBOD system However, the efficacy of the LBOD remains a point of contention. During extreme weather events, such as the floods of 1999, 2011, and 2024, the system suffered catastrophic failures. Rather than reaching its maritime outfall, high-intensity tidal surges and backwater effects caused toxic saline water to overflow into the surrounding drainage basins and Shakoor Lake. This recurring failure has significantly increased the salinity levels of the remnant Nara River system, degrading the local freshwater ecosystem and the livelihoods of communities dependent on these wetlands for agriculture and fishing. Collapse of Cholri Weir The Cholri Weir of LBOD system, constructed at the "Cholri dhand" (Cholri wetland/lagoon), was a critical hydraulic regulator designed to control the backflow of seawater and protect the freshwater dhands (lagoons) of the Ramsar wetlands from the saline effluents of the Left Bank Outfall Drain (LBOD). However, almost immediately after its completion, the structure suffered a catastrophic failure when a 250-foot section collapsed due to design faults and tidal pressure. This degradation culminated in May 1999, when a severe tropical cyclone almost completely destroyed the weir and breached the Tidal Link embankments in dozens of places. The collapse effectively turned the drainage system into a conduit for sea intrusion, allowing seawater to flow inland and devastating the local ecosystem, including the contamination of groundwater and the destruction of indigenous flora and fauna. Despite various repair attempts, the failure of the Cholri Weir remains a central point of environmental and technical criticism regarding the LBOD's impact on southern Sindh. Environmental impact The creation of the canal has been said to have a negative impact on wetlands in the area, especially in India's Great Rann of Kutch area, and by releasing LBOD's salt water into the purposefully built Chotiari Reservoir in Sindh in Pakistan. ==See also==