Hydrogeologist Vivek Grewal (https://www.linkedin.com/in/viveksinghgrewal/) joins host Pavan Srinath (https://www.linkedin.com/in/pavansrinath/?originalSubdomain=in) once again to unpack the basic science of groundwater and to explain how groundwater behaves in one of India’s most important hydrogeological regions.

Where does groundwater fit in the water story? Vivek explains why most of the world’s liquid freshwater exists underground, how rainfall becomes groundwater, and how rivers like the Ganga are sustained by flows beneath the surface.

The episode then breaks down how aquifers work from porosity and fractures to recharge and baseflow - while debunking common myths about “hidden underground rivers.”

Finally, the discussion turns to the Indo-Gangetic aquifer, explaining how it was formed and why regions like Punjab, UP, Bihar and Bengal face very different challenges - from depletion and salinity to arsenic contamination.

Drawing from both field experience and hydrogeological research, Vivek also explains why western India faces severe depletion despite large underground storage, why eastern India may have more water but different access and quality challenges, and how a better understanding of groundwater is essential for managing agriculture, drinking water and long-term water security.

Vivek Grewal (https://welllabs.org/vivek-singh-grewal/ ) is the Managing Partner with the Technical Consulting programme at WELL Labs. He has around 9+ years of experience in the water sector. He is passionate about taking the science of hydrology to the grassroots organisations.

Pavan Srinath (https://welllabs.org/our-team-pavan-srinath/) is the Managing Partner for Communications and Development at WELL Labs. Pavan is a communications and public policy professional who has spent over 14 years working in Bangalore's not-for-profit sector.

This episode is essential viewing for anyone interested in groundwater, hydrology, Indian geography, water security, agriculture, geology, and the science behind how water moves beneath the surface.

The WELL Labs Show features rich conversations on water, environment, land and livelihoods, from the people and partners of WELL Labs. Hosted by Pavan Srinath and occasionally guest-hosted by colleagues from WELL Labs, each episode explores complex environmental and social issues and helps you understand the systems and the dynamics better.

For all references and further readings related to the episode, visit https://welllabs.org/twls-vivek-grewal-pt3/

Subscribe to the WELL Labs YouTube channel @welllabs and watch all episodes on the official playlist here (https://open.spotify.com/show/6fDa6X5XqsHjUXZsWuDhkq)

Recording by Nabina Chakraborty and Vraj Acharya. Video editing by Ranjith Kumar S. Graphics and artwork by Aparna Nambiar and Kanishka Goyal. Podcast production and management by Nabina Chakraborty and Pavan Srinath.

Chapter markers:

00:00 Highlights

00:54 Intro

03:05 Understanding Groundwater

05:41 How does rainfall recharge groundwater

09:46 Misconception about the Hidden River Saraswati

11:13 Groundwater and Perennial Rivers

13:55 Aquifer Systems and their Characteristics

17:25 Check out the Water Data Podcast

17:46 India’s Groundwater Systems: 6 Aquifer Types Explained

21:12 How the Indo-Gangetic Aquifer Was Formed

23:54 How Punjab Went from Water-Rich to Water-Stressed

32:11 Subscribe to our YouTube channel

32:28 Lower Gangetic Aquifer: Water, Clay and Quality Issues

39:33 Why Groundwater Has Arsenic in Bihar & Bengal

41:25 Closing