Krishna delta front is increasing in area, according to Geological Survey of India

Syed Akbar
Hyderabad:  The Krishna delta is constantly growing at a “rapid
pace” gaining as much as 28 sq km of area in the last five decades.

A detailed analysis of the research data on the Krishna delta by the
Geological Survey of India reveals that the delta is regularly gaining
land at the “front” region. Delta front is the area that protrudes
into the sea. This in other words means that the Krishna delta has
projected further into the Bay of Bengal since the early 1960s.

The Krishna River divides into two main branches, a few kilometres
downstream of the Prakasam Barrage in Vijayawada. One branch joins the
Bay of Bengal at Hamsaladivi, while the other branch further divides
into three distributaries, which later join the sea downstream of
Nagayalanka.

According to GSI, the Krishna delta front is “constantly growing at a
rapid pace on both sides of all the three distributaries, particularly
the western most, through sand deposits (spits and bars). Over the
past half century, the Krishna delta has gained about 28 sq km of
area”. Since the growth is more in the western most distributary that
borders Repalle, the Krishna delta front is adding new area from the
Guntur district side.

The growth of the Krishna delta further into the sea (progradation)
has been noticed at Kaikaluru- Bapatla strandline, Gudur strandline,
Machilipatnam strandline and the Koduru strandline. The delta front is
sandy or marshy in nature with a vast stretches of wild grasses or
protected mangrove forests. The mangrove forests have gained some of
this newly added area.

The Krishna delta is “lobate” (lobe like) and unique in having the
greatest protuberance of 37 km from the adjoining coast, points out
“GSI Memoirs”, containing the summerised data of the research work
done by GSI scientists at its Hyderabad centre. As new land is added
to the delta front, the protuberance into the sea increases. The
deltaic shore is about 90 km long.

A delta is highly sensitive to any change, natural or manmade. Changes
in the Krishna delta started after the construction of dams in the
upstream. This has reduced the sediment carrying capacity of the
river. With the outflow into the sea coming down drastically in the
last few decades, the sea is depositing sands, increasing the area of
the delta front.

The coastal region in Andhra Pradesh is fast changing with the area under beaches either increasing or decreasing, and rivulets shifting their course. The sea is eating into lush green lands at certain places

Syed Akbar
Hyderabad: The coastal region in Andhra Pradesh is fast
changing with the area under beaches either increasing or decreasing,
and rivulets shifting their course. The sea is eating into lush green
lands at certain places.

The geomorphology data for the last four decades available with the
city unit of the Geological Survey of India indicate that the mouth of
the Upputeru rivulet has unidirectionally shifted very rapidly
westwards by about 3 km in the last 30 years, eroding more than 100
hectares of high-yielding coconut gardens near Chinnagollapalem. There
has been a growth of about 3 km long beach near the Upputeru river
mouth and formation of bars and shoals in the vicinity.

The coastal tract between the two distributaries channel mouths of the
Gautami Godavari at Malatithippa is subjected to both erosion and
accretion, though the latter is dominant.  The prominent bar, which
existed in 1971, and the northeastern side of the Gautami-Godavari
mouth disappeared. Spits are developing on left mouth of the
Vainateyam and the Vasishta.

The GSI has summerised the research works (GSI Memoirs) since the
opening of the Hyderabad centre in 1973. An analysis of the data
reveals that the delicate geomorphology of the coastal region is
undergoing visible changes at a rapid phase. According to the GSI
data, beach growth up to 1 km wide has been noticed along the 10 km
stretch from river mouth of Gautami towards west, while the shoreline
near Machilipatnam is subjected to erosion. The tidal creek mouth is
constantly shifting northwards with respect to the Machilipatnam Port.

The GSI city team has found erosion of bars on one side and accretion
on the other side of the estuary of the Penna River. A spit is
emerging on the Swarnamukhi River mouth. There is beach accretion
further south near Kondurupalem.

“Accretion in the form of bar and shoal is seen at the confluence of
Vainateyam, Vasishta, Krishna River northeast distributary and also
the outfalls of Enamadurru drain- straight cut, Kunavaram straight
cut, Peddalanka drain etc. Due to the formation of the Kakinada spit,
a vast area of shallow sea is being separated from the main sea,” the
GSI Memoirs points out.

The GSI has noticed sea erosion north of Uppada village, where 100 m
wide beach was eroded in 14 years. Besides, presence of a wave-cut
platform at 2.5 km southwest of Uppada, and erosion of beach at
Mulapeta are the important evidences of sea erosion.

After oil and natural gas, the offshore of Krishna River now holds prospects for diamond mining

Syed Akbar
Hyderabad:  After oil and natural gas, the offshore of Krishna
River now holds prospects for diamond mining. The diamond search in
the State has extended to areas beyond Vijayawada and up to the
estuary of the river Krishna with the Geological Survey of India
finding evidence for the presence of precious stones in this hitherto
unexploited region.

So far, the area between Sangam (confluence of Tungabhadra and Krishna
in Mahbubnagar district) and Prakasam Barrage in Vijayawada is
recognized as the diamond zone. Recent studies by the GIS have
revealed that the diamond zone well extends beyond Vijayawada and up
to near shore in Avanigadda and Nagayalanka in Krishna district and
Repalle in Guntur district. Penna River, downstream of Somasila, is
another new area with prospects of diamond reserves. The region may go
well into the sea, offshore of Krishna and Penna.

The mapping of the geological terrain of coastal areas dating back to
the last glacial maximum (18,000 years ago) and beyond shows that the
palaeo-channels and channel bars comprising diamond bearing gravels
extend into the lower part of the Krishna delta and even into the near
shore area.

According to GSI, about 18,000 years ago Krishna as well as the Penna
rivers had extended courses joining the sea at lower levels. “The
palaeo-channels of Krishna and Penna in their delta and offshore areas
may also form important diamond prospects, in select zones,” GSI’s new
“Quaternary Maps” point out. Quaternary is the current period in the
Cenozoic era on the geological timescale. These diamonds were formed
during this period. Diamond-bearing gravels are also found in Chennuru
and Kanuparthy, located along the upper reaches of the Penna.

GIS believes that Quaternary studies of the river basins of Penna,
Hagari and Handri might help in delineating their palaeo-drainage
channels and in locating new diamond bearing terrace/gravel zones. The
existence of a few old pits and dumps near these gravel beds indicates
that terrace gravels were excavated to recover diamonds in the past.

Diamond constitutes the most important economic mineral of the Quaternary
fluvial gravels of AP. The alluvial tracts around Kolluru, Ustapalle,
Paritala, Chandralapadu and Venkatayapalem areas in Guntur and Krishna
districts along the banks of the Krishna River, have yielded many
world famous diamonds.

Besides diamonds, precious stones like transparent to translucent ruby
corundum have been found around Salebhanjar village in Khammam
district. Corundum is also found in an area of about 50 sq km up to
Lalguda in the south, Tummalapalle in the west and Lallurgudem in
Kadapa district.

Gem variety garnets are noticed in the Muneru river around Tekugudem.
Semi-precious stones including chalcedony, agate, carnelian, jasper
and opal have been found in abundance in the older gravel bed as well
as recent channel/ point bars of the Godavari river around Bhadrachalam.

NGRI develops methodology to pinpoint the ground water potential in rocky areas

Syed Akbar
Hyderabad: Scientists at the city-based National Geophysical
Research Institute have developed a methodology to pinpoint the ground
water potential in rocky areas. A large portion of area in and around
Hyderabad is a hard rock terrain and ground water is trapped in
fractures of the bed rock.

The NGRI team utilised geospatial and geophysical techniques to
develop the model for assessing ground water potential. The
methodology has been successfully demonstrated in Maheshwaram
watershed in the city outskirts. Whether ground water is available in
a given rocky terrain and if so to what extent can be found out using
the NGRI system.

It will help people easily identify suitable locations for ground
water withdrawal. The demand for ground water in Hyderabad and
neighbouring Rangareddy district has increased in the recent past
thanks to scanty rainfall, rainwater runoff, and largescale
urbanisation and industrialisation of the region.

NGRI team comprising Dr Shakeel Ahmed, Ms Mehnaz Rashid and Mr Mahjoor
Ahmed Lone developed the methodology by integrating a number of
important indications of ground water like soil structure, rain water
drainage density, aquifer resistivity and thickness, and the pattern
of land use in the area.

"The results reveal that the area falls in four ground water potential
zones ranging from poor to very good. The poor zone is indicative of
the least favourable region for ground water prospecting, while the
good to very good zone indicates the most favourable region," the
scientists noted.

It is a foolproof system that can be adapted in any part of the globe.
In fact, the NGRI's work serves as a guideline for further research on
complex terrains all over the world. According to the scientists, the
methodology based on the GIS can be utilised for sustainable
management of ground water resources in any area for artificial
recharge.

The team utilised the data from the Indian remote sensing satellite,
Resourcesat-1, and other remote sensing and geophysical information.
It is also an effective tool for identifying ground water potential in
diverse hydrogeological terrains.

The ground water resources in the country are depleting fast and in
certain regions it is as high as four cm per year. In Hyderabad and
surrounding areas the thickness of the top layer of the soil is
between 0.1 and 4.1 metres. Below is the weathered granite with
thickness going up to 35.7 metres. The third layer is highly fractured
granite ranging between 0.3 metres and 31 metres. Ground water is
trapped in these fractures.

Ground water is just 150 ft deep in Hyderabad; further down is hard rock which does not yield any ground water

By Syed Akbar

Hyderabad: How deep one should dig a bore well in Hyderabad and Secunderabad to extract 
ground water? As builders and house owners vie with one another to go deeper into the 
soil for “perennial source” of ground water, geologists clarify that the water table in 
twin cities is just 150 ft deep. They warn that any drilling into the earth beyond this 
point will only harm the ground water table and affect its prospects as time passes by. 
It’s waste of money and labour.

The geology of Hyderabad and its surrounding areas is peculiar in the sense that the 
depth up to which it can withhold water is about 150 ft or a little more in certain 
pockets. Beyond 150 ft one encounters the bedrock, which does not hold any ground water, 
unless it has some fractures. Going deeper and deeper may give temporary benefits, but in 
the long run spoils the water table.

According to Dr VVS Gurunatha Rao, deputy director, National Geophysical Research 
Institute, hard rock is encountered in twin cities up to depths up about 150 ft. This is 
the lower limit for drawl of ground water. “Our studies have shown that hard rock is 
encountered in many places in and around Hyderabad at 30 meters deep or a little below. 
The upper loose soil and the area below it are the potential sources of tapping ground 
water. Below it the ground water potential is relatively less. And lower further down is 
the bedrock, which is hard and impermeable. The rain water that percolates the ground 
will not seep further down the hard rock,” he clarifies.

Explaining the reason for drying up of many bore wells in Hyderabad despite the increase 
in ground water table in the last three years, Dr Gurunatha Rao blames the culture of 
constructing cellars and double cellars. “The first few metres of top soil have the 
greatest potential of withholding water. But by constructing cellars and double cellars 
we are robbing of a large portion of this potential ground water zone,” he adds. A cellar 
occupies about six metres of this important water holding area. Double cellar means 
occupation of 12 to 15 metres of the top soil.

The NGRI scientist suggests that one should avoid constructing cellars to ensure more 
recharge of ground water. He also points out that going deeper into the earth will not 
yield ground water perennially at least in twin cities.

According to the city-based International Water Management Institute and Jawahar Lal 
Nehru Technological University, the Musi sub-basin is mainly
covered by Archaean granites with Deccan Traps. As in a typical hard rock
aquifer region, the yield of the bores decreases with depth due to the  reduction of the 
fracture density. The risk of water scarcity in case of
a drought year is thus exacerbated.

A joint study by teams from IWMI and JNTU has revealed that the ground water resource in 
Hyderabad and its surrounding areas is mostly represented by typical unconfined shallow 
aquifers in hard rock which generally occupy the upper 20 metres of the subsurface 
profile. “These composite aquifers derive primarily from the geomorphologic processes of 
deep weathering and
erosion. They can therefore be considered as a multi-layered system,” the study points 
out.

The upper layer is unconsolidated weathered mantle (saprolite or regolith), which is from 
negligible to several tens of metres thickness. When saturated, this layer constitutes 
the reservoir of the aquifer (water source). Instead of tapping this zone, builders are 
going deeper to the second layer, which is fractured-weathered layer, characterised by a 
fracture density that decreases with depth. This in other words means as one goes deeper 
the potentiality of ground water decreases. The lower layer is fresh basement, which is 
permeable only locally where deep tectonic fractures are present.

The study found that in the last two decades, natural recharge from rainfall in Musi 
sub-basin accounted for 9.4 per cent of the total annual rainfall. But the exploitation 
was much higher leaving a wide deficit. In certain places, however, there are deeper 
aquifer systems thanks to major joints, fractures or crevices. At these places ground 
water can be harnessed up to 700 feet. But only a fortunate few will get such deeper 
aquifer systems. But as Dr Gurunatha Rao argues the average depth of bore wells in twin 
cities should not cross 150 ft, and to ensure perennial source of ground water, 
scientifically-test rain water harvesting methods should be adopted.
====================
AP virtually sits on well explosion
====================
Andhra Pradesh virtually sits on a well explosion. In the last three decades 
the number of wells in the State has gone up by four times, up from 8 lakhs to 24 lakhs. 
And hold your breath. The well population in Andhra Pradesh is increasing at the rate of 
50,000 a year. But what’s worrying is that scientific steps are not taken to ensure that 
the quantity of water drawn from ground water is properly replenished by rain water.

According to official figures, area irrigated through groundwater increased from 10 lakh 
hectares to 28 lakhs hectares since 1990. Ground water constitutes about 45 per cent of 
the total area irrigated. Interestingly, almost 80 per cent of the drinking water needs 
are met through ground water and just 20 per cent from rivers and lakes.

With increasing concretization, recharge of ground water during monsoon has been hit in 
the last 10 years. Adding to the problem, the number of rainy days has come down. 
Geologists point out that the more the number of rainy days the more the recharge of 
ground water. Heavy rains only lead to run off. For ground water to be recharged fully, 
rain should be moderate and spread over a number of days.

Predicting the “future scenario”, the State ground water department forecasts that by 
2020 the number of wells will be touch 36 lakhs, mostly deep bore/tube wells, irrigating 
about 36 lakh hectares.

While bore wells may meet the water needs of people in Telangana and Rayalaseema, they 
will harm the delicate ecological balance in the coastal regions. “If ground water is 
over exploited in coastal regions, there’s the threat of sea water intrusion into the 
ground water. This will make the soil salty and unfit for agriculture,” warns Dr VVS 
Gurunatha Rao, deputy director of NGRI.

In case of Hyderabad and Rangareddy district, of the 40 ground water micro basins 
present, only 10 can be declared as safe. The remaining fall under over-exploited and 
critical categories, meaning there’s danger to the water table if immediate steps to 
recharge it are not taken. There’s the problem of ground water pollution too thanks to 
the use of fertilizers and pesticides and unscientific disposal of waste by chemical 
units.

Himalayas are twice older than believed!

By Syed Akbar

How old are the Himalayas, the snow-covered mountains that wall the northern India? Existing scientific records and evidence show that the Himalayas are less than eight million years old. But a group of scientists from India and the United Kingdom has negated this widely held belief and established with latest scientific evidence that the mountains are twice as older. In short, the Himalayas took their birth about 15 million years ago.

The Indo-British team has found evidence for early uplift of Himalayas within the central Indian Ocean. "The discovery that the Earth's strong outer shell - the 'lithosphere' - within the central Indian Ocean began to deform and fracture 15.4-13.9 million years ago, much earlier than previously thought, impacts our understanding of the birth of the Himalayas and the strengthening of the Indian-Asian monsoon," says Dr KS Krishna of the Goa-based National Institute of Oceanography.

According to an official release from the National Institute of Oceanography,
India and Asia collided around 50 million years ago as a result of plate tectonics - the large-scale movements of the lithosphere, which continue to this day. The study was published in "Geology", a scientific magazine published by the Geological Society of America.

"The ocean floor has been systematically transformed into folds 100-300 kilometres long and 2,000-3,000 metres high, and there are also regularly spaced faults or cracks that are evident from seismic surveys and ocean drilling," points out Dr Krishna in the research study.

The onset of this deformation marks the start of major geological uplift of the Himalayas and the Tibetan Plateau, some 4,000 km further to the north, due to stresses within the wider India-Asia area. Some studies indicate that it began around 8.0-7.5 million years ago, while others have indicated that it started before 8.0 million years ago, and perhaps much earlier.

This controversy has now been addressed by Dr Krishna and his British colleagues Prof. Jon Bull of the University of Southampton, and Prof. Roger Scrutton of Edinburgh University. They have analysed seismic profiles of 293 faults (vertical cracks in the ocean floor) in the accumulated sediments of the Bengal Fan. This is the world's largest submarine fan, a delta-shaped accumulation of land-derived sediments covering the floor of the Bay of Bengal.

The NIO statement points out that the team demonstrated that deformation of the lithosphere within the central Indian Ocean started around 15.4-13.9 million years ago, much earlier than most previous estimates. This implies considerable Himalayan uplift before 8.0 million years ago, which is when many geologists believe that the strong seasonal winds of the India-Asia monsoon first started.

"However," says Dr. Krishna, "the realisation that the onset of lithospheric deformation within the central Indian Ocean occurred much earlier fits in well with more recent evidence that the strengthening of the monsoon was linked to the early geological uplift of the Himalayas and Tibetan plateau up to 15-20 million years ago."

Scientists believe that intensive deep-sea drilling within the Bengal Fan would provide better age estimates for the onset of deformation of the lithosphere in the central Indian Ocean and concretise the recent findings. There are more weighty geological questions related to the geodynamics of the Indian Plate yet to be understood.

Principal among these being the issue of how exactly did the ocean floor buckle and crack in space and time, and what will be the future course of this compressional activity in the central Indian Ocean.

The NIO statement said further scientists would like to gather new evidences for understanding of 1) why and how the central Indian Ocean region has now become site where mountains are rising up from the ocean floor and cracks are propagating within the crust; and 2) whether the present process could be a pre-cursor to the formation of a subduction zone in the central Indian Ocean.

Himalayas are twice older than believed

2009
By Syed Akbar

How old are the Himalayas, the snow-covered mountains that wall the northern India? Existing scientific records and evidence show that the Himalayas are less than eight million years old. But a group of scientists from India and the United Kingdom has negated this widely held belief and established with latest scientific evidence that the mountains are twice as older. In short, the Himalayas took their birth about 15 million years ago.

The Indo-British team has found evidence for early uplift of Himalayas within the central Indian Ocean. "The discovery that the earth’s strong outer shell — the ‘lithosphere’ — within the central Indian Ocean began to deform and fracture 15.4-13.9 million years ago, much earlier than previously thought, impacts our understanding of the birth of the Himalayas and the strengthening of the Indian-Asian monsoon," says Dr K.S. Krishna of the Goa-based National Institute of Oceanography.

According to an official release from the National Institute of Oceanography, India and Asia collided around 50 million years ago as a result of plate tectonics — the large-scale movements of the lithosphere, which continue to this day. The study was published in Geology, a scientific magazine published by the Geological Society of America.

"The ocean floor has been systematically transformed into folds 100-300 kilometres long and 2,000-3,000 metres high, and there are also regularly spaced faults or cracks that are evident from seismic surveys and ocean drilling," points out Dr Krishna in the research study.

The onset of this deformation marks the start of major geological uplift of the Himalayas and the Tibetan Plateau, some 4,000 km further to the north, due to stresses within the wider India-Asia area. Some studies indicate that it began around 8.0-7.5 million years ago, while others have indicated that it started before 8.0 million years ago, and perhaps much earlier.

This controversy has now been addressed by Dr Krishna and his British colleagues Prof. Jon Bull of the University of Southampton, and Prof. Roger Scrutton of Edinburgh University. They have analysed seismic profiles of 293 faults (vertical cracks in the ocean floor) in the accumulated sediments of the Bengal Fan. This is the world’s largest submarine fan, a delta-shaped accumulation of land-derived sediments covering the floor of the Bay of Bengal.

The NIO statement points out that the team demonstrated that deformation of the lithosphere within the central Indian Ocean started around 15.4-13.9 million years ago, much earlier than most previous estimates. This implies considerable Himalayan uplift before 8.0 million years ago, which is when many geologists believe that the strong seasonal winds of the India-Asia monsoon first started.

"However," says Dr Krishna, "the realisation that the onset of lithospheric deformation within the central Indian Ocean occurred much earlier fits in well with more recent evidence that the strengthening of the monsoon was linked to the early geological uplift of the Himalayas and Tibetan plateau up to 15-20 million years ago."

Scientists believe that intensive deep-sea drilling within the Bengal Fan would provide better age estimates for the onset of deformation of the lithosphere in the central Indian Ocean and concretise the recent findings. There are more weighty geological questions related to the geodynamics of the Indian Plate yet to be understood.

Principal among these being the issue of how exactly did the ocean floor buckle and crack in space and time, and what will be the future course of this compressional activity in the central Indian Ocean.

The NIO statement said further scientists would like to gather new evidences for understanding of 1) why and how the central Indian Ocean region has now become site where mountains are rising up from the ocean floor and cracks are propagating within the crust; and 2) whether the present process could be a pre-cursor to the formation of a subduction zone in the central Indian Ocean.