WATER RESOURCES ORGANISATION
PLAN FOR ‘ARTIFICIAL RECHARGE TO
RECHARGE TO GROUND WATER’ IN TAMIL NADU’
as a dependable source and its proximity to various users has led to
indiscriminate extraction of this precious natural resource for agricultural,
domestic and industrial uses. The speedy and uncontrolled usage of ground water
has caused many problems. The intensive ground water development has resulted in
depletion in water levels, deterioration in water quality and availability of
this scarce resource. Proliferation in ground water extraction resulted in
increase in the stage of development in Tamil Nadu from 63% to 85% between 1992
and 2004 as per the ground water assessment made by the Ground Water Wing of
TNPWD. Similarly the nos. of over-exploited and critical blocks has increased
from 89 blocks to 175 blocks. Groundwater quality in coastal area has also been
affected due to excessive groundwater development. Also over exploitation near
the coast has led to sea water intrusion. The development of groundwater
resources in these areas therefore need to be regulated and augmented through
suitable measures to provide sustainability. Rainfall being the main source of
recharge to groundwater, it is essential that substantial volumes of surplus
monsoon run-off that flows out into the sea has to be conserved and recharged to
efficacy of the surface water bodies such as tanks, canals as a means of natural
recharge to groundwater has drastically reduced simply because the water levels
in those areas are too deep. Hence the need of the hour is for ‘Artificial
Recharge’ systems that convey the fresh rainwater into the aquifer. In
other words, the basic purpose of artificial recharge of ground water is to
restore supplies from the aquifers depleted due to excessive ground water
development. The artificial recharge to ground water aims at augmentation
of ground water reservoir by modifying the natural movement of surface water
utilizing suitable civil construction techniques.The Artificial recharge
techniques inter-relate and integrate the source water to ground water
reservoir. The benefits are rise in water level and consequent increase in
storage of the ground water reservoir.
of augmenting ground water or sub surface reservoir:
sub surface reservoirs are very attractive and technically feasible alternatives
for storing surplus monsoon run off. The sub surface storages have advantages of
being free from the adverse effects like inundation of large surface area, loss
of cultivable land, displacement of local population, evaporation losses and
sensitivity to earthquakes. No gigantic structures are needed to store water.
The structures required for recharging ground water reservoirs are of small
dimensions and cost effective such as check dams, percolation tanks, surface
spreading basins, pits, sub surface dykes etc.
requirement for Artificial Recharge projects:
The basic requirements for artificial
recharge to ground water are: -
Availability of non-committed surplus run-off in space and time
Identification of suitable geological environment and sites for creating
sub-surface reservoir through cost effective artificial recharge techniques.
of Water availability:
source water availability, one of the prime requisites for ground water recharge
can be assessed by analyzing the monsoon rainfall pattern, its frequency, number
of rainy days maximum rainfall in a day and its variation in space and time. The
variations in rainfall pattern in space and time can be considered for assessing
the surplus surface water availability.
knowledge of geological and hydrological features of the area is necessary for
adequately selecting the site and the type of recharge structure. The
hydro-geological situation in each area needs to be appraised with a view to
assess the recharge capabilities of the underlying hydro-geological formations.
For assessing the requirement of water for sub-surface storage, the entire
thickness of the vadose zone upto 3 m below ground level is to be considered as
the upper 3 m of unsaturated zone may cause adverse environmental impact viz.,
water logging, soil salinity etc.
for Artificial Recharge Projects:
natural recharge of ground water is very slow and could not keep pace with the
excessive continued exploitation of ground water. This over-exploitation of
ground water resulted in declining ground water levels and depleted the ground
water resources in some of the areas. In order to augment the natural supply of
ground water, the artificial recharge of ground water is essential.The rainfall
occurrence is limited to a few days in a year. The natural recharge to ground
water reservoir in restricted to this period only. The artificial recharge
techniques aim at increasing the recharge period in the post monsoon season and
provide additional recharge. This results in providing sustainability to ground
water development during the lean season.Thus there is a need for a systematic
implementation of artificial projects for augmenting ground water under various
of Artificial Recharge Projects:
Artificial Recharge projects are site specific and the replication of the
techniques from areas are to be based on the local hydro-geological and
hydrological environments. The first step in planning the project is to
demarcate the area of recharge.The Artificial Recharge of Ground Water is
normally taken in areas i) where the water levels are declining on regular basis
ii) where the substantial amount of aquifer has already been de-saturated iii)
where availability of ground water is inadequate in lean months and iv) where
salinity ingress is taking place. In Tamil Nadu, the potential recharge areas
have been identified from the zonation maps prepared using Remote Sensing and
GIS techniques by Institute of Remote Sensing, Anna University in association
with Department of Rural Development, Government of Tamil Nadu and Tamil Nadu
Water Supply and Drainage Board.
to be considered:
on rainfall intensity, number of rainy days etc. help in deciding the capacity
and design of the artificial recharge structures.
details like quantity of water available for artificial recharge as source water
for recharge have to be worked out by carrying out hydrological investigations
in that area viz., water shed/sub basin/basin.
information on the infiltration capacity of the soil at a particular point under
given set of conditions is important while adopting water spreading methods for
artificial recharge. The infiltration capacity depends on soil type moisture
content, organic matter, vegetable cover season air entrapment, formations of
surface seals crusts etc.
The hydrogeology of an area is of prime importance in successful
implementation of any 'Artificial Recharge Scheme'. The data on sub-surface
hydro-geological units, their thickness and depth of occurrence are essential to
decide on the location and type of structures to be constructed in the field.
techniques are highly suitable and effective means of determining the
characteristic formational features for suitable site selection for artificial
recharge structures. Also this technique is mostly adopted to assess the unknown
sub-surface hydro-geological conditions economically, adequately and
The quality of raw waters available for recharge should be free from
chemical and bacteriological effects. Also the water should be silt free.
The impact assessment studies carried out on the already
constructed artificial recharge structures reveal that percolation tanks, check
dams, recharge shafts are effective structures in hard rock areas whereas
recharge trench and recharge tube wells are effective in case of alluvial areas.
In coastal areas tidal regulators are effective in controlling seawater ingress.
In case of urban areas and hilly terrains with high rainfall rooftop rain water
structures are effective. These aspects are to be kept in mind while formulating
the artificial recharge schemes.
Artificial Recharge Techniques can be broadly categorized as follows:-
of Artificial Recharge Structures:
Artificial Recharge Structures are to be proposed to suit different
hydro-geological conditions as below:-
Check dams are constructed across small streams having gentle slope and
are feasible both in hard rock as well as alluvial formation. The site selected
for check dam should have sufficient thickness of permeable bed or weathered
formation to facilitate recharge of stored water within short span of time. The
water stored in these structures is mostly confined to stream course and the
height is normally around 2 metres.
structures are artificially created surface water body submerging highly
permeable land areas so that the surface run-off is made
to percolate and recharge the ground water recharge. The percolation tanks
should be located on the downstream side of run-off zone with land slope between
3 to 5%.The capacity of a percolation tank should be governed by the percolation
capacity of the strata in the tank rather than the yield of the catchment. These
structures are suitable for both in alluvial and hard rock areas. In the case of
hard rock areas submergence area should have high permeability with the degree
and extent of weathering of rocks should be uniform and not just localized.
Percolation tanks with wells and shafts can also be constructed in areas where
shallow or superficial formations are highly impermeable or clayey.
tanks are normally constructed on second order or third order steams since the
catchment so also the submergence area would be smaller.Designed capacity should
not normally be more than 50% of the total quantum of rainfall in catchment. The
benefited area should have sufficient number of wells and cultivable land to
develop the recharged water.
as Recharge structures:
top rain water harvesting:
Nadu scenario of Ground Water:
Nadu is an agrarian state spreading over an area of 1,30,300 sq.km
and has been divided into 31 districts, which are further divided into
385 blocks. The State is characterized by diverse climatic, physiographic and
hydro-geologic conditions 73% of the geographical area is underlain by hard rock
formations and 27% occupy sedimentary formations.
predominant source of water for the State is rainfall from both the southwest
and northeast monsoons. The average rainfall in the state in a water year (June
to May) is 961.8 mm. The utilizable surface water resources are 23,371 MCM (825
TMC). The annual replenishable ground water resource in the state is 23,070 MCM
(815 TMC). In Tamil Nadu 95% of the surface water resources have been utilized
and the only alternative is 'Ground Water'. The Ground Water Development
in the State has shown a phenomenal increase from 7.9 lakhs wells to 20 lakhs
wells between 1951 to 1990. This has further increased to 37 lakhs during 2004.
The increase in number of ground water abstraction structures is due to
implementation of technically viable schemes for development of the resource
backed by liberal funding from institutional finance agencies, improvement in
availability of electric power and diesel, good quality seeds, fertilizers,
Government subsidies etc.
stage of ground water development as on March 2004 in the State is 85% and the
quantum available for future development is 3076 MCM (15%). Based on the stage
of development, the blocks have been categorized in terms of its exploitation
for various uses in 385 blocks of the State. They are as below: -
(>90% but < 100%)
(>70% but <90%)
of ground water has resulted in declining ground water levels, shortage in water
supply increased pumping lifts and consequent increase in power consumption.
stage of ground water development of this magnitude viz. 85% with such optimal
planning has resulted in creating deleterious effects in terms of ground water
depletion and quality deterioration.The combination of these challenges needs a
suitable management approach. Augmentation of ground water through Artificial
Recharge is one such approach to overcome the problems of ground water scarcity.
for a Master Plan for Artificial Recharge:
Tamil Nadu various departments like PWD, Agricultural Engg.Dept. Tamil Nadu
Water Supply and Drainage Board, Rural Development, Metro Water and Forest
Department have been implementing different 'Artificial Recharge Schemes'
like Check Dams, Percolation Ponds, Recharge Shafts, Tidal regulators, Recharge
tube wells and rain water structures. So far the Agricultural Engineering Dept.
has implemented 4753 check dams, 10996 Percolation ponds and 12564 Farm ponds
since 1984. Similarly, TWAD Board has implemented 3666 check dams since 2001.
The Forest Department has executed 25600 check dams and 2540 percolation ponds
so far under various projects. The impact assessment studies conducted by the
TWAD Board on some of the artificial schemes revealed that there was a
substantial increase in water level from 2.50 metres to 12 metres in those
areas. Similarly the impact assessment studies conducted by the Agricultural
Engineering Department and Forest Department also revealed that there was a
substantial increase in water levels and in turn indicating the increase in
groundwater potential. These success stories emphasize the need for taking up
the Artificial Recharge Schemes in a larger way so as to augment the ground
water through Artificial recharge so as to prevent the semi-critical areas
numbering 57 blocks becoming critical blocks. Also the implementation of
Artificial Recharge Schemes will improve the ground water potential which will
enable the over-exploited and critical blocks to revert back to semi-critical
and safe blocks. Hence the Artificial Recharge schemes are to be taken in a
large scale wherever feasible for which a systematic approach based on a Master
Plan is the need of the hour.
for preparation of the Master Plan:
The most favourable areas for artificial recharge structures are
identified and prioritized based on the ‘Stage of Ground Water development’
of that area.
The numbers and suitable types of structures are proposed based on the
storage capacity and efficiency considering the storage space and available
source water for recharge.
The cost estimates of different types of artificial recharge structures
were worked out to arrive at the total cost.
of feasible areas and types of structures to be
several areas of the state where rainfall is high, considerable variability of
rains in terms of their onset, distribution and amount over space and time
result in uncertainty about availability of water for rain fed crops. In hilly
terrains, steep slopes result in heavy run-off and low infiltration, resulting
in shortage of water during summer season. In all such areas, there is an urgent
need to take steps for augmentation of ground water resources through
appropriate techniques to provide assured supply of water for irrigation,
industrial and domestic needs.
areas characterized both declining trend and depletion in depth to water table
are ideal sites for ‘Artificial recharge to Ground Water’.
potential recharge areas and the type of recharge structures to be provided are
being identified with the help of zonation maps prepared using Remote Sensing
and GIS techniques by the Institute of Remote Sensing, Anna University and
funded by the Department of Rural Development and TWAD
structures proposed depending upon the topography, hydro-geological conditions,
check dams, percolation ponds will be appropriate for recharging the aquifer. It
has been considered that 70% of the available sub storage would be recharged
through percolation ponds and the remaining 30% through check dams. In certain
areas, for example, in Cuddalore district, the terrain is not suitable for check
dams and hence only percolation ponds are to be adopted. In urban areas, roof
top rainwater harvesting is to be adopted. Apart from these sub-surface
barriers, providing recharge shafts/pits, Farm ponds, Recharge tanks, Desilting
of Tanks etc. can also be adopted depending upon the site conditions.
of Artificial Recharge Schemes in Tamil Nadu:
implementation of Artificial Recharge schemes has to be carried out in
systematic and holistic manner as per the Master Plan by the respective agencies
like PWD, Agricultural Engineering Department, TWAD Board, Chennai Metro Water
Supply and Sewage Board and Forest Department in a period of three years. As
already indicated different departments have been implementing the 'Artificial
Recharge of Ground Water' schemes, to make the schemes of this nature well
planned on scientific basis and also to create data base, it is desirable to
notify the 'State Ground & Surface Water Resources Data Centre (SG&SWRDC)
WRO as a nodal department at the state level. The Nodal Agency identified as the
'State Ground and Surface Water Resources Data Centre, WRO has to monitor
the implementation of all the recharge schemes. To popularize these schemes in a
big way and to ensure their success, this programme has to be made a people's
implementation of Artificial Recharge Schemes in a systematic and scientific
manner will enhance the ground water potential in the affected areas. The
problems like depletion in water levels and deterioration in water quality
caused due to over-exploitation will be tackled by augmentation of ground water
through Artificial Recharge. In our State, out of 385 blocks, 175 blocks are
over-exploited and critical where the stage of ground water development is more
than 90%. The situation in these over-exploited and critical blocks constituting
45.45% will improve by the implementation of the proposed artificial recharge
schemes. The augmentation of the ground water through the Artificial Recharge
measures coupled with management and regulatory measures will improve the ground
water scenario in the State and these affected blocks may revert back to
semi-critical and safe blocks respectively. Apart from this, immediate steps are
required to be taken to prevent the semi-critical blocks numbering 57 blocks
(14.80%) from becoming critical and over-exploited blocks. In Tamil Nadu,
various departments like PWD, Agricultural Engineering, TWAD Board, Panchayats
were implementing artificial recharge schemes. Forest department is implementing
similar schemes in the Reserved Forests. The sectoral allocation of water to various uses will
be supplemented and go a longway in tackling the problems of over-exploitation
of ground water in the State.
total cost of artificial recharge structures to be taken up in the years
2008-09, 2009-10 & 2010-11 will
be Rs. 550 Crores of which the
amount sanctioned for the year 2008-09
will be Rs. 100 Crores.
Excellency, the Governor of Tamilnadu addressed in the Legislative Assembly on
23.01.2008 that the schemes for implementation in the water deficit areas for
storing the unutilized water in rivers, river lets and streams and utilizing it
round the year for drinking water and agricultural purposes. Hence this Master
Plan is prepared.
Administrative Sanction for this scheme has
been issued by the Tamilnadu Government vide
its order mentioned below.
Ms No 198, PW(R2)Dept. dt
break up details of the amount sanctioned for 2008-09
for different Government Agencies are as follow.
a) Water Resources Organaisation (PWD) Rs
b) State Ground and Surface Water
Resources Data Centre (PWD)
Rs 2 Crores.
c) TWAD Board
d) Agricultural Engineering
e) Forest Department
Rs 100 Croress.