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Groundwater Resources of India

@IndHydrogeology

23 Dec

Thread:
What do our aquifer's rocks look like, when dry?
What are the different aquifer types in India?

Here is an aquifer map of India by ACWADAM. The pink Indian Craton is the base, overlain by the green volcanics, blue sediments, & yellow alluvium.

<Gross Generalizations>

Indus-Ganga Plains aquifer is the most prolific, consisting of alluvium (गाद). The most recent, the thickest, the most porous, & most transmissive!

Contrasting other types, this is "soft rock". When saturated, ~10% is filled with water (CGWB).

Pic: Columbia University

It's 15 million years old, 0.3% of earth's age.

Erosion of the Himalayas (left in pic) has been filling the basin between them & the Indian Craton (right).

While the aquifer is ~250m thick, deeper waters are saline bcoz of ancient seas and high evaporation.
PC: Bonsor (2015)

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Groundwater Resources of India

@IndHydrogeology

31 Aug

While the 2018 NITI Aayog report saying Delhi will run out of groundwater by 2020 was a misunderstanding, a district less than 100 km from Delhi has almost exhausted its freshwater.

Here is a #thread on salinisation of GW of Mewat/Nuh district of Haryana. Dilli zyada door nahi:

Map from a recent paper by Krishan et al (2020) in the reputed Journal of Hydrology.

Salinity of more than 2 gm/L is considered unfit of drinking & general irrigation.

Only blue in map is freshwater and it REDUCES from 14% to 1% of the area over the monsoon! Why reduce?

Freshwater region reduces because pumping is happening in central/freshwater area reducing its water level, saline water from south increases further in monsoon, and ingresses the freshwater.

This is a very dangerous trend that Dr. Himanshu Kulkarni has predicted for Punjab too.

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Groundwater Resources of India

@IndHydrogeology

6 Aug

#Thread on India's #CarbonateAquifers:

Aquifers may be divided as unconsolidated (alluvial) or consolidated (hard-rock).

Among the consolidated - carbonate aquifers (made of Limestone/Dolomite) are special, as they are often very productive. Map - Shah et al (2018).

#Retweet

@CGWB_CHQ

Limestone often dissolves in the groundwater (a process called karstification), creating much more space & hydraulic conductivity. Space for water is denoted by Specific yield = % of vol of water/rock.

@CGWB_CHQ here gives values for Specific Yield for as carbonates 2-15%:

Some widely used carbonate aquifers are in Chhattisgarh, Cuddapah & Vidhyan sedimentary basins; and in Kashmir.

Kashmir is famous for prolific springs ('nags') some of which discharge at over 3000 lps! These are basically underground rivers curring through limestone like butter.

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Groundwater Resources of India

@IndHydrogeology

30 Jun

@CGWB_CHQ

Thread: Delhi has a lot of GW, as its on a thick alluvial aquifer formed by Yamuna. But the GW situation is grave because most of the GW is salty (Orange in map) & unusable!

Snippets from the recent National Project for Aquifer Management (NAQUIM) report by @CGWB_CHQ

This map shows thickness of fresh-water left. If you have lived in areas of west Delhi like Dwarka you would know how salty the groundwater is.

This map shows how over a decade the water levels (top/freshwater) have decreased. Decrease of ~ 2 meters on an average.

Unsustainable considering that the remaining freshwater thickness is less than 10 meters in many areas.

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