Will the flow end? Artesian wells of Uttarakhand’s Tarai

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A preliminary study in the Tarai
region of Uttarakhand has revealed a depleting water flow in the
artesian wells used for agricultural purposes, due to over exploitation
of the aquifers. This coupled with deforestation, global warming and
unpredictable weather patterns could damage an otherwise sustainable and
eco-sensitive agricultural practice.  

A K Vashisht (akvashisht74@yahoo.com)
is at the Department of Soil and Water Engineering at the College of
Agricultural Engineering and Post-Harvest Technology, Central
Agricultural University in Gangtok, Sikkim.

Human beings  have traditionally built settlements near the source of
water – ancient civilizations’ presence near major rivers of the world
bears proof of this. For fulfilling the ever increasing demand for water
by domestic, agricultural, and industrial sectors, human beings learnt
to extract groundwater. Probably the open wells are the ancient
structures that were developed for abstracting groundwater from
unconfined1 aquifers and the water from these wells was
raised to the surface level by man or animal power using indigenous
techniques. Later on, the advancements in mechanisation in the 20th
century made it more convenient to abstract groundwater even from
deeper aquifers. The introduction of diesel-engine/electricity operated
centrifugal pumps has completely changed the irrigation scenario of
agriculture. Depending on the depth of aquifer and the quantity of water
required, pump size in terms of its horse power (hp) is selected.
Increased input of energy has also increased the production cost of the
crops.

A sustainable agricultural practice

However, there are regions all over the world where abstraction of
groundwater does not require a pump. Once the drilling of bore-hole to
the specific aquifer (essentially artesian2) is completed,
the pressure within the aquifer forces the groundwater to rise above the
ground surface naturally without using a pump. These types of wells are
known as flowing artesian wells. Flowing wells are an uncommon
manifestation of geological activities (Swamee et al: 2000). Expansion
of water due to release of pressure and compression of aquifer formation
material are responsible for the water flow from such wells (Jacob:
1940). In Uttarakhand, such type of wells – of width up to 25 km and
having a general slope less than 1%, is restricted only to the Tarai zone. .

The formation of the Tarai region is dependent on the evenly
sorted finer material that was washed away by the streams from the
hilly tracts. The northern limit of the Tarai belt is in contact with the Bhabar zone which is bound by the lower Shiwalik range of Himalayas in the north. The Bhabar
zone can also be referred as piedmont alluvial terrain that comprises 
ill-sorted sediments ranging from big boulders to silt. Since this zone
is very porous and permeable it forms the recharge area of the artesian
aquifer system in the Tarai zone. Moreover, the region between Bhabar and Tarai
belts forms the spring line (the landmass with marshy conditions). This
spring line is of the source of various perennial streams in the
region. Since the slope of Bhabar zone varies from 1-2%, the elevation difference between the recharging area in Bhabar zone and water withdrawing position (i.e. well) in Tarai zone creates the artesian head in the aquifer which is directly responsible for the existence of flowing wells.

Tarai soils are rich in clay and organic matter and that is
why this belt is considered  one of the highly productive agricultural
areas in India. Availability of irrigation water from flowing wells
without spending any energy on its withdrawal is one of the factors that
could reduce agricultural costs.. The introduction of highly mechanised
agricultural practices since the last two to three decades has
encouraged the farmers to adopt the intensive cultivation in the region.
Consequently, the demand for irrigation water has increased
significantly. The trajectory of water resources development has thus
been following a simple principle of “developing”, which in the case of
groundwater means extracting more water to produce more grain (Kulkarni
and Shah: 2013). Other than this, the rising domestic and industrial
needs for water have further stressed the existing groundwater
resources. Collectively, it has resulted in the development of more
number of bore wells which has increased the density of flowing wells in
the Tarai belt. As expected, the discharge rates of these wells have drastically decreased and are declining further with time.

Overexploitation and environmental damage

A preliminary study on the thermal characteristics of water sampled
from the seven flowing wells located in a radius of more than 15 km has
revealed that all the wells are installed in the same aquifer.
Definitely, the installation of more wells in this stretch will directly
affect the yield of other wells. It can be judged from the fact that in
year 1970, the water pressure of these flowing wells at the ground
surface was over 2 kg/cm2 (Michael: 2006) which now has dropped to ~ 0.2 kg/cm2.
Moreover, the figures mentioned are  for the monsoon season only which
would be lesser than this value during the dry season. Presently, the
flowing behaviour of wells in certain pockets of the region have become
seasonal (see Figures 1) and few others are completely dried (Figure 2a)
and are abandoned now.

Other than the over exploitation of groundwater due to overall development and industrialisation in the Tarai
zone, haphazard felling of trees for converting forest land into
industrial/agricultural land, reduction of water pressure in the
artesian aquifers due to increased leakage of water from confined to
unconfined aquifers through the increased number of bore-holes for
developing tube wells, and unattended flowing of these wells without any
beneficial purpose (Figure 2b below) are the additional causes for
their changed behaviour. The current scenario will further worsen with
the reduction in recharging of these artesian aquifers in Bhabar zone due to changed rainfall pattern in Himalayan (Vashisht and Bam: 2013) and Shiwalik
foothill regions. For proper recharging of the aquifers, rainfall
intensity should be less than the water intake capacity of the land
surface.

According to a World Bank report,
global mean warming is approaching 4°C. This will result in a 10%
increase in annual mean monsoon intensity and a 15% increase in a
year-to-year variability of Indian summer monsoon precipitation is
projected compared to normal levels during the first half of the 20th
century (World Bank: 2013). The report further emphasises that these
changes imply an extreme wet monsoon. This is projected to occur every
10 years by the end of the century compared to the currently probability
of it occurring only once in 100 years. These extremes of weather
conditions are likely to affect flowing wells adversely. With the number
of flowing wells dwindling, abstraction of water will be dependent on
the diesel engine or electric motor operated pumps. This increase in the
energy cost will be added to the production cost of the crops. To
equalise the profit margin, it is likely that food prices will be
increased which will affect the end consumer adversely.

Nevertheless, the impact of the above mentioned factors can be
drastically reduced by strengthening the farmers’ knowledge regarding
the groundwater hydraulics with special attention on the groundwater
movement from the recharging zone to flowing artesian wells in their
fields. But, the immediate action that is required at this stage is to
increase awareness so that the farmers in the region can install control
valves on the flowing wells to avoid water loss. The farmers who are
aware of the consequences of this water loss have already adopted these
measures by using end plugs or end plates for the purpose. However,
these measures are not so effective in completely controlling the water
loss (see Figure 3 below). Lack of general maintenance of control
valves, non-replacement of end-plug gaskets at appropriate intervals,
and improper tightening of the nuts and bolts of the pipe are the main
reasons of this major water loss.

Additionally, there is a need to demarcate the major recharging zones in Bhabar belt
and any kind of development other than the construction of water
conservation/harvesting structures should be restricted on it.
Environmental isotope techniques can be efficiently used for the purpose
(Shivanna et al: 2008). Conserving groundwater resources at this stage
is crucial in the Tarai and Bhabar belt before it’s too late.

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