GUWAHATI, Aug 25 ? The Kopili, which has become infamous for its fury this time, was not that infamous as an incensed one till past mid-July this year. It was a serene, quiet river unlike the ones frequently shifting courses and hurtling through the north bank of the Brahmaputra in this geologically nascent part of the earth. Then what made the Kopili so furious this time that it has detached itself from its tradition? The State Government has explained this in the following manner.
On July 17, 2004 the water level of the Kopili dam of the NEEPCO rose to a height of 8.40 metres above the Full Reservoir Level (FRL). This excess water rushed downstream and was responsible for the flood that created a catastrophe in Morigaon and Nagaon districts of the State. The State Government explained the reasons for the unprecedented flood caused by the Kopili in Nagaon and Morigaon districts this year thus in the State Assembly on August 6. It further stated that the volume of water released by the NEEPCO dam that day was 5,000 cubic metres. This water was joined by the 3,000 cubic metres of water coming down from the Mynteng river. And together, the waters of these two sources created havoc for the people of the two districts of the State.
The Government statement in the Assembly also pointed out to the size of the dam and structural defects. ?The dam height is 40 metres and the reservoir area is about 15 square kilometres and surprisingly there is no controlled system with operation of gates. Such situation obviously is very serious since without any gate operation for release of control discharge during the flood is not possible. Gate control operation of reservoir is a must for saving the life and property in the down stream,? the Government said in its statement. The statement was based on the report of a team of experts that visited the site and held discussion with the senior officials of the Kopili Hydro-Electric project of the NEEPCO.
The team of the officials suggested, among others, remodeling of the ?operation structure of the reservoir regarding release of water with gates which can be controlled/regulated for flood moderation to avoid flood devastation in the downstream areas. It also called for steps to materialise the proposed 150 MW hydel project at the downstream of the river for generation of power as well as moderation of flood of the river. Besides, it suggested steps to discourage deforestation and earth cutting.
In fact, the Kopili was made to roar, giving up its mellifluousness and behave irately, in 1976 when works on the NEEPCO dam were started. Dr Ranjan Saikia, a former Professor and Head of the Department, Geography, Cotton College found this during his research on the river for eight years between 1976 and 1984.
According to Dr Saikia, a teacher of geomorphology, the Kopili, a principal river on the southern bank of the Brahmaputra, rises from the Barail range near Sherpai Peak at an altitude of 1525 metre. The river, after flowing for a distance of 290 km from its source, meets the Kollong at Hatiamukh near Jagibhakat Gaon.
Four major left bank tributaries namely ? the Killing, the Barapani, the Myntang and the Kharkar, feed the Kopili. Two right bank tributaries ? Diyung and Jamuna also feed it. These rivers drain a total area of 14,760 square km. All the tributaries of the Kopili originate from Meghalaya and the Karbi plateau, except the Diyung, which originates from the Barail range of the North Cachar Hills. Unlike the braided north bank tributaries of the Brahmaputra, the Kopili exhibits a meandering course in its lower reaches. The rivers of the south bank do not change their courses frequently and cause less flood havoc during the summer.
A study of runoff behaviour of the Kopili and its tributaries reveals that rate of runoff increases during the period of heavy rainfall. The relationship between the percentage of rainfall and runoff during the winter and the summer months stands as, ? November to February, ? annual rainfall 4 per cent and annual runoff 1.13 per cent; March to October, ? annual rainfall 96 per cent and annual runoff 98.87 per cent, Dr Saikia said. It needs mention that the average annual rainfall in the catchment areas of the river is 178 cm.
The study reveals that though there is decreasing pattern of channel flow in the Kopili and its tributaries, since 1976 onwards the Kopili plains or the Nagaon plains have been continuously subjected to floods, he said. He attributed this to the environmental degradation in the form of deforestation, soil erosion etc in the upper catchment areas of the Kopili system.
Explaining, Professor Saikia said that the effect of exploitative land use in the hills and the resultant mass movement to the flood plains had created a situation of rapid aggradations of the drainage channels, swampy areas and beels etc. The accelerated soil erosion and devastating rate of deforestation has resulted in high sediment load.
The accelerated increase in soil erosion, soil aggradation and surface runoff due to renewed exposure of landform have together converted the Kopili plains into a flood-prone area, Dr Saikia said. He also regretted the fact that the initial proposal for the Kopili multi-purpose project was turned into that of a hydel power project ignoring the above aspects concerning the river and its basin.