Monday, June 14, 2010

Sinking Deeper And Deeper For Groundwater In Pune

This is a sight becoming common in Pune.


A drilling rig is often the first order of business for many new constructions on commercial and residential premises. It reflects both an increased consumption of water due to affluent lifestyles and a growing uncertainty about water security often due to lack of piped water supply especially in the suburbs and despite claims from the Pune Municipal Corporation that surface water reservoirs have enough capacity to provide for future population growth and increased use.

I guess people want to ensure that they have a water supply under their control in case of future inability of the city to provide them with piped water. I talked recently with a geologist with years of experience in the groundwater situation in Pune and I heard the same ominous story that is reverberating all over India.

The deeper aquifer in Pune which means drilling to depths of 150-200 feet seems to be experiencing overdraft as unregulated bore-wells extract more than natural recharge. The city is trying to address the problem by proposing that it will limit the number of bore-wells based on surveys of aquifer capacity. This kind of aggregate limit however will not regulate current and future use by individual wells already in operation. Indian groundwater law allows the owner of a property unlimited use of the groundwater and increased reliance on groundwater in the future will keep depleting the resource if not managed scientifically.

And therein lies the problem because just how much water lies underneath is at best only sketchily understood. Any blanket limit going by watersheds  imposed on extraction makes little sense because the deeper aquifers in Deccan basalts are not congruent with the surface water contours. They show extreme laterally variability and are compartmentalized. So for proper groundwater management the underlying aquifers need to be mapped, monitored and a scientific database on aquifer capacity needs to be built before any allocation plan that is sustainable is finalized.

Besides understanding the limits of extraction, just how the city is going to regulate individual use of groundwater remains a thorny issue. There is extreme reluctance to price the use of groundwater by metering bore-wells. The reasons are manifold. It will be an "enforcement headache" (read we are too lazy) is one excuse I have heard. Besides, there is a cultural tendency in India to look at groundwater as a free resource. The focus for long on groundwater use as been on rural consumption for agriculture. Making farmers pay a price for electricity and water is considered political Harakiri in India. So politicians keep tip-toeing around making any serious amendments to groundwater law.

Indian cities however are growing and reliance on groundwater by urban users is bound to increase. There needs to be a sensible re-look at groundwater laws for the urban consumer. Water allocation for well owners based on the aquifer capacity, the need to limit new well permits, mandating artificial recharge structures to augment refilling, and getting urban consumers to pay for the water they are pulling out of the aquifer are all ideas that need to be debated and thrashed out if we want to move towards a more sustainable use of this resource.

Tuesday, June 8, 2010

Budding Geologists On The Rugby Pitch

Every weekend one of the coaches gives a word quiz to our soccer and rugby kids, ages 8 to 10. Last Saturday it was my turn and I asked about Gondwanaland. .. tell me all about it.

Come Monday and I got three correct answers... the kids had read up and got the right ideas about continents being in different places and attached to other continents in the past.. they also told me that the present arrangement of continents will change in the future.. impressive for 10 year old's

Here are the winners (they do it for the chocolate bars):


Meanwhile we had our first pre-monsoon thunderstorms last week. It was just a massive cloud burst turning the ground into a swimming pool.


All set for rugby season over here.

Friday, June 4, 2010

Mineralogy And Deep Subduction Of Indian Continental Crust

Science Daily describes some work on eclogites found in the Ladakh region of the Himalayas and its implications on the subduction of the Indian continental crust underneath the Asian plate.

The paper appeared in last month's Geology and uses the mineral majorite - a high pressure variety of garnet - to estimate the depth of mineral formation. The pattern in which atoms are arranged in a lattice structure and the ratio of certain elements in a mineral are often sensitive to changes in temperature and pressure and can be used to estimate and develop a history of change of these parameters as plate subduction drives crust deeper and mineral growth takes place at higher and higher temperatures and pressures . The results indicate a depth of around 200 km for the formation of the mineral majorite.

So the study throws light not on just on how deep the Indian crust sank during continental collision with Asia but also how quickly it has been exhumed during the formation of the Himalayan mountains. The mineral and its chemical ratios which were stable at 200 km depth have been essentially frozen in that state as the enclosing rock was brought to the surface geologically quickly along thrust faults and through rapid erosion and removal of overlying crust preventing majorite from completely altering to a lower temperature and pressure analog.

Rocks at depths of 200 km formed tens of millions of years ago are today on the surface at great heights of about fourteen thousand odd feet. These ecologites are exposed in the Lake Tso Moriri area of Ladakh in the high Himalayas. It is difficult terrain. Field seasons are restricted to a couple of months in summer. The altitude takes some getting used to.



Lake Tso Moriri / Source: Wolken Berge Wasser Wiese   Author: Jochen Westermann

A faculty friend has a graduate student working on this very same eclogite complex. I hope this publication by a different group does not mean a setback to her work. Finding that you have been scooped after you are in your third year of PhD can be demoralizing but my friend is sure that there are parallel stories of mineral genesis to be wrung out of these ecologites.

Last month's Accretionary Wedge threw open the diverse interests of the geology community... from the microscopic to the continental scale. Discoveries like the one on the Tso Morari ecologites makes you reflect on the fact that these geological features and processes that encompass such vast differences in scale don't occur as independent events not affected by or having no relation to or having no effect on processes larger or smaller.

The secrets of plate tectonics are sometimes hidden in one tiny mineral. I find it fascinating that the chemical ratios found in one mineral reveal a story of continents colliding, the subduction and burial of crust to great depths and its later ascent to icy heights, part of the geological saga of the great Himalayan mountains.

Gulf Spill: Hear What You Want To Hear

Worst case scenarios and political fallouts:


Source: xkcd comics

Tuesday, June 1, 2010

Me And Tafoni

A most healthy obsession with rocks:


Location- Korlai village, west coast India, south of Mumbai. Exposures of Tafoni in the intertidal wave cut basalt benches.

Photo courtesy Daniel MEGE.