Barak River criss crossing through the hills of Manipur
For the state of Manipur, 2.85% of total geographic area is under different types of wetlands like lake / pond (61.5%), river/steam (26.2%), waterlogged (5.5%) and aquaculture ponds covering an area of 63,616 ha according to the National Wetland Atlas 2010, developed by Space Application Centre. The wetlands of the state are mostly confined to three valley districts of Bishnupur, Thoubal and Imphal West. The state has 15 major rivers / streams covering a total area of about 166.77 sq. km. (i.e. 0.75 % of the total geographical area of the state). The three major rivers namely Imphal River, Nambul River and Iril River supply around 90% of the drinking water in the urban areas of the state. Average availability of surface water of the Barak and Manipur river basins and the lakes has been assessed at 18487 million cum per annum (Barak Basin- 3295 million cum against a total catchment area of 9042 Sq. km and Manipur Basin – 5192 million cum against a total catchment area of 6332 Sq. km) as per CWC's report. Groundwater in the state is mostly exploited through open wells along with tube wells which are installed at various places of the valley areas. Considering the clayey nature of formation in the top aquifer, development of this resource is not considered promising on a large scale.
Manipur receives heavy rainfall from the South West (SW) and North East (NE) monsoons with average annual rainfall readings of 1435 mm during the last 5 decades (1961-2010). However, due to the global climate change phenomena, the water balance in different parts of the state has been affected due to changes in precipitation and evapotranspiration. Increased rainfall intensity during the rainy season may lead to higher runoff and the existing topography of the state would possibly reduced recharge. The rainy days during the 1950s and 1960s have a regular pattern but since the early ‘70s Manipur began to experienced uneven distribution of the annual rainfall. It began to vary widely among the districts too. The precipitation level has increased for most of the year with increasing intensity but with gradual decline in the number of rainy days. There has also been an increase in the pre-monsoon rain over the last few years. The variation in the pattern of rainfall in the last ten years has tremendous affect on the overall climatic condition of the region.
Percentage of area under different water bodies in Manipur
Source: National Wetland Atlas, 2010, SAC, ISRO
Annual rainfall in Manipur (1956-2017)
Source: Directorate of Environment, Govt. of Manipur
The frequent floods experienced mostly in the Imphal valley areas have brought much harm to the people. The flash floods are common phenomena owing to high intensity of rainfall within a short spell in the hilly areas which are the upper catchments areas of various rivers draining the valley, the poor drainage conditions and overflowing of rivers caused by uncontrolled rainwater run-off in the hills due to degradation of forests.
Flash flood is a major cause for inundation in many areas of the valley districts
The erratic nature of rainfall coupled with the rise in average maximum and minimum temperature observed in the state will have a significant impact on the water resources. As temperature increases, evaporation increases and sometimes resulting in droughts. Frequent flood and occasional drought have become part and parcel of the residents of Manipur. The valley areas of the state are flooded many a times before the onset of monsoon rain whereas the hill regions are facing severe water scarcity throughout the year mainly during the lean season. With water scarcity and extreme weather events projected to increase under climate change, water security could be a major challenge for the rural populace whose primary source of livelihood is agriculture. Besides rural areas, the urban areas including Imphal city is getting affected by urban floods and scarcity of water for drinking and sanitation. Management of the water resources in an integrated manner would be essential as it would affect the social, economic as well as the environment. Climate change adaptation has become an important issue in the water sector for a sustainable future.