WATER RESOURCES

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Manipur receives heavy rainfall from the SW and NE monsoons, the average annual rainfall readings were 1116 mm in 1972 and 2646 mm in 1983 and 2887.6 mm in 1995. This amounts to richness of surface water resource in the state even though much has to be done in tapping the resource and saving it from being drained out due to the peculiar drainage pattern over the rugged terrains of the state. The surface and groundwater potentials of the state have been assessed by various departments like the Irrigation and Flood Control Department (I.F.C.D.), Minor Irrigation Department (M.I.D.) and Public Health Engineering Department (P.H.E.D.) in consultation with other agencies like CWC, CEA and CGWB etc.

Surface Water

The total water discharge from the two river basins viz. The Barak River basin draining the western part and the Manipur River Basin draining the eastern half of the state including the Manipur Valley has been estimated to be 1.8545 M hectare meters (15.04 M acre ft.). Manipur River Basin accounts for 0.5192 hectare metre of annual run off against a total catchment area of 6332 sq.km. The Barak Basin has a greater discharge capacity with 1.3295 M hectare metre against a catchment of 9042 sq.km. The sub-basin wise break up of the water discharge is shown below:

MANIPUR RIVER BASIN

BARAK RIVER BASIN

Source: I.F.C.D. 1984, Govt. of Manipur.

Groundwater

The area covered by valleys that can be investigated for groundwater potentials in Manipur is about 1800 sq.km. forming roughly 8% of the total geographical area. The important valleys are the Manipur Central Valley and Western Jiribam of Imphal District, Khuga valley in Churachandpur District and Khoupum valley in Tamenglong District. The Central Ground Water Board (CGWB) so far has covered an area of 6,600 sq.km. out of the total land area of 22,346 sq.km. in hydrogeological survey.The valleys have superficial alluvium which are underlined by tertiary rocks of Barail series in Imphal valley and the Tipam formations in Jiribam valley. Ground-water in top sandy and clayey formations occurs under water table conditions with the depth of water varying from 3 to 4 metres bgl. Groundwater is mostly exploited through open wells. Ground water in the deeper aquifers occurs under sub-artesian and artesian conditions.Granular zones are encountered at a depth of about 150 m in Imphal valley and at about 220 m in Jiribam valley. Tubewells have been installed at various places of the valley areas with the yields ranging from 0.6 to 4 cu.m./hr. On the basis of the monitoring of water level in key/dug wells network stations in the area, an annual recharge of 44 M.cu.m. has been estimated. Considering the clayey nature of formation in the top aquifer, development of this resource is not considered promising on a large scale either in irrigation of watersupply. However, it can be exploited for local water supply through open wells dug-cum-bore wells and tubewells. The potable water quality has been shown by partial chemical tests of these water samples.

Quality of Ground water in Central Manipur Valley, Khuga Valley & Jiribam Valley

Knowledge of hydro geological conditions prevailing in the valleys of Manipur is too limited. Fuller detailed investigations have yet to be done. The present constraints are the drilling hazards like gas encounters and sand rushing etc.

Water requirements and Potentials

1. The total water requirement per annum for Major and Medium Irrigation from surface water resources has been estimated to be 97,231 hectare metre or 0.097 M hectare metre.
   
   
2. Total water requirement per annum for Minor Irrigation schemes upto 2000 AD from surface water resources works out to be 0.426 acre ft. i.e. 0.0526 M hectare metre.
   
   
3. Water requirement per annum for domestic consumption and industrial uses in the state is estimated as under:
   a) Domestic consumption - 0.0757 M acre ft.
   b) Industrial uses - 0.1206 M acre ft.
   Total: - 0.1963 M acre ft.
   
   
4. Anticipated potential from Surface Water Resources for water supply is as indicated below:
   a) From Major and Medium Irrigation
   Project = 46.5 mgd = 0.062 M acre ft. per annum
   b) Balance requirement to be met from the Schemes of Public Health Engineering Department = 0.1343 M acre ft.
   Putting together = 0.1963 M acre ft.
   
   
5. Potential from Ground Water Resource is estimated around 44 M cum per annum i.e. 0.0044 M hectare metre.
   
   
6. Additional requirement of surface water per annum for power generation upto 2000 AD is estimated to be around 0.939 M hectare meter.

Water Balance

The above calculations have revealed that against a total availability of 1.8487 M hectare metre of water there will be an annual requirement of 1.1121 M hecatre metre upto 2000 AD. The water balance thus works out to 0.7366 M hectare metre in the annual budget. With prospects of water recycling, the IFCD is optimistic of a sufficient water reserve beyond 2000 AD.