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5-km stretch of Assonora river water non-potable

NT NETWORK

Panaji

A 5-km stretch of river Assonora, which is the main source of drinking water for many residents, is not even fit for drinking due to fecal pollution.

The situation is worse during pre-monsoon (January-May) and monsoon (June-September) wherein the Total Coliform exceeds the desired level of 5000 MPN/ 100 ml two to five times in the five kilometre polluted stretch of River Assonora.

The 22-km long River Assonora, one of the main tributaries of Mandovi River, originates near Mencurem village in Bicholim taluka, and flows through areas like Assonora, and Sirsaim. 

The Goa State Pollution Control Board (GSPCB) monitors its water quality at one location (that is Assonora, near water works) between the polluted stretches of the Assonora River (Assonora to Sirsaim) which is 5 km
long.

This polluted stretch of the River Assonora between Assonora to Sirsaim is classified as Class C (for drinking water source after conventional treatment and disinfection) and categorised as priority V based on BOD level of 3.3 mg/litre.

The water monitoring carried out from April 2015 to December 2018 found BOD levels in the polluted river stretch between Assonora and Sirsaim are well below the desired level of 3 mg/l required for bathing water quality / drinking quality and also DO levels are well above the desired level of 5 mg/l indicating well oxygenated water but the levels of Total Coliforms (TC) exceeds the prescribed limits to make it fit for consumption.

During the survey conducted for identification of pollution sources, it has been observed that the untreated domestic sewage outfalls mainly from the Assonora, and Sirsaim are contributing to the values of total coliform in the polluted stretch. The outfalls during monsoon from the mining areas of Shirgao and Corjuem are also polluting the river to some
extent.

Apart from making use of the river water for irrigation, people living on the river banks make use of the river for bathing, and washing clothes, causing pollution.

The higher values of TC are observed during pre-monsoon season in Assonora River which varies from 350 MPN/ 100ml to 24000 MPN/ 100ml and 330 MPN/ 100ml to 9200 MPN/ 100ml during monsoon due to surface runoff and during lean period between October and December, the TC values are well within the desired limit of 170 MPN/ 100ml to 2400 MPN/ 100ml.

There are in all three bandharas constructed on the Assonora river till Assonora water works (from Assonora to Mandovi river) to fulfill the water demand in the surrounding areas. The flow in the Mandovi tributaries reduces drastically in summer (non-monsoon season) and to overcome shortfall, water is pumped from the mining pits into the river.

The river rejuvenation action plan has set six months time for the health department to ensure that the residents living along the banks of Assonora to Sirsaim stop direct discharge of sewage into nullah and sewage is diverted to septic tank and soak pit in order to restore the water quality to the desired drinking water quality level.

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