![\"Tehri](\"https:\/\/tibetnature.net\/en\/wp-content\/uploads\/2015\/01\/Tehri_dam.jpg\")
<\/a><\/p>\nTehri dam and reservoir (Image by Ministry of Water Resources, Government of India)<\/p>\n<\/div>\n
Similarly, the western region, which includes the states of Gujarat and Maharashtra, has 22 reservoirs with total storage capacity of 24.54 BCM. The storage recorded on January 14, 2015 is 14.48 BCM, 59% of the reservoirs\u2019 total capacity and less than both the previous year\u2019s figures as well as the average of the last 10 years.<\/p>\n
The eastern region, including Jharkhand, Odisha, Tripura and West Bengal, has 15 reservoirs with total storage capacity of 18.83 BCM. The current water stored is 13.61 BCM, or 72% of the total. This is less than the corresponding period of 2014 but higher than the average storage of the last 10 years.<\/p>\n
The central region, which includes Uttar Pradesh, Madhya Pradesh and Chhattisgarh, has 12 reservoirs with total storage capacity of 42.30 BCM. The stored water available is 28.64 BCM, or 68% of their total storage capacity of these reservoirs. Here, as in the case of the eastern region, the storage during the current year is less than the storage of last year but better than the average storage of last 10 years.<\/p>\n
Himanshu Kulkarni, executive director of Pune-based Advanced Centre for Water Resources and Management (ACWADAM) said, \u201cThe decline in reservoir storage could be a consequence of many factors, both natural and anthropogenic because the inflow into a reservoir depends upon the precipitation (snow, hail and rain) as well as the state of the catchment. Outflows, similarly could be natural \u2013 infiltration and leakage \u2013 and human-driven in the form of releases and pumping.\u201d<\/p>\n
\u201cIt is a complex situation,\u201d said Himanshu Thakkar, who heads the Delhi-based NGO, South Asia Network on Dams, Rivers and People (SANDRP). The CWC data on 85 reservoirs, Thakkar told thethirdpole.net, \u201cgives a limited picture\u201d as it represents barely 1.5% of the over 5,000 large reservoirs and hundreds of thousands of small, medium and big dams in the country.<\/p>\n
Six months ago, in May 2014, the CWC had warned of declining water reserves across India. Analysts had noted at the time that a decline in water storage was expected during the hot summer months ahead of the monsoon. Traditionally, water levels pick up during the monsoon period, especially the peak July-August period.<\/p>\n
But that didn\u2019t happen. Two months later \u2013 almost midway into India\u2019s monsoon season from June to September and with the India Meteorological Department (IMD) forecasting a weak monsoon \u2013 the CWC\u2019s figures showed continuing low storage levels.<\/p>\n
According to Thakkar, India in 2014 recorded two deficit monsoons for the first time in 10 years \u2013 the main southwest monsoon with a 12.3% deficit, and the retreating northeast monsoon with 33%. This would have exacerbated the water deficit.<\/p>\n
In Thakkar\u2019s view, reservoir storage capacity should not be viewed in isolation as it is linked to groundwater availability and use. \u201cSo much water is being used upstream of rivers that it will impact flows downstream, which in turn will impact storage reservoirs,\u201d he said, adding that downstream reservoirs do not get filled.<\/p>\n
India, he said, was building too many storage reservoirs, \u201cbeyond the hydrological carrying capacity of river basins.\u201d<\/p>\n
\u201cThe relationship between reservoir storage and aquifer storage is complex and is a function of many factors, the foremost being the characteristics of aquifers and the extent to which these are used,\u201d says Kulkarni, who was member of a working group on sustainable groundwater storage at India\u2019s erstwhile Planning Commission. Local and regional geology also plays a role.<\/p>\n
A compounding factor is the increasing instances of floods in the country. Hydrology experts caution that floods aggravate groundwater scarcity as more water is lost during rapid run-offs instead of rainwater seeping into the soil and aquifers. Key Indian Himalayan states have been witnessing devastating floods in recent years \u2013 Uttarakhand in 2013 and Himachal Pradesh and Jammu and Kashmir in 2014.<\/p>\n
The decline in reservoir water adds to the growing concern over depleting groundwater in northwest India, mainly due to over-exploitation. In 2009, a satellite-based study by US scientists published in Nature warned of over-exploitation of groundwater.<\/p>\n
\u201cGroundwater depletion was equivalent to a net loss of 109 cubic km of water, which is double the capacity of India\u2019s largest surface-water reservoir,\u201d stated the team, comprising scientists from the US National Aeronautics and Space Administration (NASA), University of California, California Institute of Technology and University of Italy. The study covered the period of August 2002 to October 2008.<\/p>\n
Annual rainfall was close to normal during the study period, it said. \u201cAlthough our observational record is brief, the available evidence suggests that unsustainable consumption of groundwater for irrigation and other anthropogenic uses is likely to be the cause.\u201d<\/p>\n
\u201cIf measures are not taken soon to ensure sustainable groundwater usage, the consequences for the 114,000,000 residents of the region may include a reduction of agricultural output and shortages of potable water, leading to extensive socioeconomic stresses,\u201d it cautioned.<\/p>\n
The International Water Management Institute (IWMI) too argues for a rethink on water storage policies and says a mix of storage options, including aquifer recharge, restoring natural wetlands, enhancing soil moisture, and small ponds and tanks should complement reservoir storage to increase water availability.<\/p>\n
Experts highlight the crucial role of water storage in coping with variations in water supply and demand, supporting agriculture and livestock production during dry spells and generating power. A 2010 report by IWMI says that per capita water storage is lower in Africa and Asia compared to other regions and lack of water storage infrastructure is a major constraint to poverty alleviation and economic development in many developing countries.<\/p>\n
Rainfall apart, the additional important factor affecting water storage in reservoirs globally is sediment deposition. In September 2013, a team of Dutch, German and American scientists reported in the Water Resources Research journal that \u201cthe storage capacity and the lifetime of water storage reservoirs can be significantly reduced by the inflow of sediments.\u201d<\/p>\n
The team estimated the loss in reservoir capacity for a global data set of large reservoirs from 1901 to 2010 using data from computer-modelled sediment fluxes. It also used population data sets as a proxy for storage demand to calculate storage capacity for all river basins globally.<\/p>\n
Their study identified major river basins in India and China among \u201cmost vulnerable\u201d.<\/p>\n
It said the declining net reservoir capacity as result of sediments deposits \u2013 estimated at about 5% of the installed capacity \u2013 challenges the sustainable management of reservoir operation and water resources management in many regions.<\/p>\n
Source: www.thethirdpole.net<\/p>\n
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