A recent study by IIT Kharagpur found that the Ganga River water levels are declining in several lower reaches in the last few summer seasons, as groundwater storage around the river is depleting.

Findings of the study
• Unprecedented low water levels: The summer of 2015 and 2017 witnessed an unprecedented low water level and flow in the middle and lower reaches of the Ganga.
• Rate of water level change over the years: Water level in River Ganga depleted at a rate of -0.5 to -38.1 cm/year between the summer of 1999 and 2013. The constant reduction in water flow in downstream states was possibly caused by groundwater depletion in the adjoining aquifers.
• Significance of the adjoining Gangetic aquifers: The present day base flow (part of total river flows which represent groundwater seepage into a stream channel from natural storage) to the Ganga from the adjoining aquifers may be a third or more of the total river water volume in pre-monsoon (summer) months. The base flow might have dipped by 50 per cent from the beginning of irrigation-pumping phase in 1970s.
• Average groundwater contribution to the river can substantially decrease in future: In the forthcoming summers, for the next 30 years, groundwate contribution to river Ganga will continue decreasing.
• Climate change and the Himalayan glacial retreat: would further contribute to degradation of riverine ecosystem.
• Factors controlling the process of ground water change: Surface water irrigation for cropping accounts for 27 per cent of the total irrigation in the region.
Anthropogenic stress through expansion of cities by the river, denudation of forests, encroachment of floodplains and excess groundwater extraction had affected the river severely.
• Previous studies have shown that embankments constructed to protect the cities from floods elevate the river resulting in more runoff during the rains and lesser percolation to recharge the aquifers.

Effects of declining water levels of Ganga

• Would severely affect domestic water supply, irrigation water requirements, river transport and ecology of the densely populated northern Indian plains because of low water level.
• Impact of river water depletion on food security in the region: Over 120 million residents in downstream region got affected and larger population would experience substantial reduction in food production if extraction of groundwater continues at the current unsustainable rate. By 2050, the total carbohydratebased food would be unavailable for almost 20% of the total inhabitants in the region studied.
• Possibility of surface water crisis: it poses a much bigger crisis along with ongoing ‘groundwater drought’ in the Indian subcontinent.
• Affects economic activities: for instance, in 2016, a NTPC plant near Farakka barrage was shut down after flow dipped.
• Contamination of ground water: According to the Report of Central Ground Water Board, more than half of India’s groundwater is contaminated with a high level of fluoride, nitrate and arsenic among others.
• Impact on living organism: May have severe impact on biodiversity including on the population of endangered Gangetic Dolphins.

Causes of Groundwater Depletion

• Increase in Irrigated Area and Politics of subsidy: Politics of subsidies has led to volatile extraction of ground water leading to its scarcity. Farmer tends to use water for irrigation without any restriction due to availability of cheap, subsidized electricity, thanks to politics of populism.
• Indiscriminate water-tapping: Due to the uninterrupted exploitation of ground water by deep wells and tube wells to meet the shortage of water, the level of ground water is continuously decreasing.
• Decreasing forests: Trees absorb up to 18 inches of precipitation before gradually releasing it to natural channels and recharging ground water.
• Melting glaciers: According to scientists, glaciers of the Himalayan region have been melting at an average rate of 131.4 sq km per year. When glaciers melt, they initially contribute more water to the rivers they feed. After this there is a decline in water contributed to the seasonal melt cycle, as shrinking
glaciers provide a smaller contribution to the overall river flow.
• Global warming and Climate change accentuate water stress as it reduces useable groundwater availability for agriculture globally.
• Wrong Agricultural practices: In rural India, water scarcity is also the result of untested agricultural practices, such as cultivating more water-consuming crops – paddy, cotton and sugarcane – in areas riddled with water scarcity.

Prevention and Way Forward

• Limiting of water-extraction and Protecting and enriching water resources: Illegal exploitation of ground water should be banned.
• Diverting River Streams and Building reservoirs: There is a need to deepen old reservoirs along with building new reservoirs, besides increasing the depth of boring of new tubewells.
• Plantation drives: extensive afforestation can help restore water tables.
• Increasing awareness: among the people regarding sustainable utilization of water resources.
• Implementing adaptation options related to either food production or water use in agriculture: waterefficient agricultural practices (modification of existing food irrigation techniques), conversion to watersaving crops, agro-climatic farming practices, reduced groundwater pumping, aquifer rejuvenation and managed recharge must be implemented.
• Results of this study could be used to understand groundwater-linked river water depletion as well as the regional water security in other densely populated regions of the world