The document discusses groundwater recharge techniques, emphasizing the importance of groundwater as a vital resource and the need for effective recharge methods due to declining water levels from urbanization. It outlines various artificial and natural techniques for recharging groundwater, including recharge pits, wells, and check dams, and presents methods for estimating groundwater recharge, such as water level fluctuation and ground water balance methods. The impact of climate change on groundwater systems and the reliance on effective management of this resource are also highlighted.

2. Groundwater
Recharge Techniques
By
CH.APPARAO
BEM-12-001

3. Introduction
Ground water is a precious and the most widely distributed resource of the
earth and unlike any other mineral resource, it gets its annual replenishment
from the meteoric precipitation.
At present nearly one fifth of all the water used in the world is obtained
from ground water resources. Agriculture is the greatest user of water
accounting for 80% of all consumption. (H.M. Raghunath , 2006).
Due to rapid urbanization, infiltration of rainwater into sub-soil has
drastically decreased, and recharging of groundwater has diminished over the
years.

4. This creates serious impact on socio-economic and environmental degradation of
the area.
It has therefore, become imperative to promote in-situ water harvesting to
augment groundwater recharge.
Out of 400 Mha.m rainwater, although 215 Mha.m percolates into the ground
(about 165 Mha.m is retained as soil moisture), but only 50 Mha.m joins the
groundwater (Michael, 1990).

5. Ground water recharge is the process where by the amount of water present in
or flowing through the interstices of the sub-soil increases by natural or artificial
means.
Rainfall is the principal source for replenishment of recharge of ground water.
Other sources include recharge from rivers, streams, irrigation water etc.

6. An unconfined aquifer is recharged directly by local rainfall, rivers, and lakes,
and the rate of recharge will be influenced by the permeability of overlying rocks
and soils.
A confined aquifer, on the other hand, is characterized by an overlying bed that
is impermeable, and local rainfall does not influence the aquifer. It is normally
recharged from lakes, rivers, and rainfall that may occur at distances ranging
from a few kilometers to thousands of kilometers.

7. Groundwater in Hydrologic Cycle

8. Fig. 1 A graphical distribution of the locations of water on Earth.

9. Fig.2: Ground water Resources Availability and Utilization in India
Source : Ministry
of water resources,
Central ground
water board(2009)

10. Dynamic Ground Water Resources
Annual Replenishable Ground water Resource 36.50 BCM
Net Annual Ground Water Availability 32.95 BCM
Annual Ground Water Draft 14.90 BCM
Stage of Ground Water Development 45 %
http://cgwb.gov.in/gw_profiles/st_ap.htm
Groundwater resources of Andhrapradesh

11. Groundwater accounts for small percentage
of Earth’s total water, groundwater
comprises approximately thirty percent of the
Earth’s freshwater.
Groundwater is the primary source of
water for over 1.5 billion people worldwide.
Depletion of groundwater may be the most
substantial threat to irrigated agriculture.
(Alley, et al., 2002)

12. Impact of Climate Change on Groundwater
 It is important to consider the potential impacts of climate change on
groundwater systems.
 Although the most noticeable impacts of climate change could be fluctuations in
surface water levels and quality.
 Because groundwater aquifers are recharged mainly by precipitation or through
interaction with surface water bodies, the direct influence of climate change on
precipitation and surface water ultimately affects groundwater systems.

13. Methods and techniques for ground water recharge
Urban Areas Rural Areas
• Recharge Pit
• Recharge Trench
• Tube well
• Recharge Well
• Gully Plug
• Contour Bund
• Gabion Structure
• Percolation tank
• Check Dam/ Cement Plug/ Nala Bund
• Recharge shaft
• Dugwell Recharge
• Ground Water Dams/Subsurface Dyke

14. 1. Gully plug
•These are built using local stones, clay
and bushes across small gullies and
streams.
•Gully Plugs help in conservation of soil
and moisture.
2. Contour bund
•To conserve soil moisture in watershed
for long duration.
•These are suitable in low rain fall
areas.
Fig. 3: Gully plug and Contour bund
Ground Water Recharge in Rural Areas

15. 3. Gabion structure
•A small bund across the stream is made by putting locally available boulders in a mesh of
steel wires and anchored to the stream banks.
•The excess water over flows this structure storing some water to serve as source of
recharge.
Fig.4: Gabion structure

16. 4. Percolation tank
•Percolation tank is an artificially created surface water body, submerging in its
reservoir a highly permeable land, so that surface runoff is made to percolate and
recharge the ground water storage.
Fig. 5: Percolation tank

17. 5. Check dams
• Check dams are constructed across small streams having gentle slope.
• The site selected should have sufficient thickness of permeable bed to facilitate
recharge of stored water within short span of time.
Fig. 6: Check dams

18. 6. Recharge shaft
This is the most efficient and cost effective technique to recharge unconfined
aquifer overlain by poorly permeable strata.
By constructing recharge shaft in tanks, surplus water can be recharged to
ground water.
Fig. 7: Recharge shaft

19. 7. Dugwell recharge
•Existing and abandoned dug wells may be utilized as recharge structure after
cleaning and desilting the same.
•The recharge water is guided through a pipe from desilting chamber to the
bottom of well or below the water level to avoid scouring of bottom and
entrapment of air bubbles in the aquifer.
Fig. 8: Dugwell
recharge

20. 8. Ground Water Dams or Sub-Surface Dykes
It is a subsurface barrier across stream which retards the base flow and stores
water upstream below ground surface.
Since the water is stored within the aquifer, submergence of land can be avoided
and land above the reservoir can be utilized even after the construction of the
dam.
Fig. 9: Ground water dams or sub-surface dykes

21. 1.Recharge Pit
•In alluvial areas where permeable rocks are exposed on the land surface or are
located at very shallow depth, rain water harvesting can be done through
recharge pits.
•These are constructed for recharging the shallow aquifers.
2. Recharge Trench
•Recharge trenches are suitable for buildings having roof area of 200-300 sq. m.
and where permeable strata is available at shallow depths.
•Trench may be 0.5 to 1 m wide, 1 to 1.5m. deep and 10 to 20 m. long depending
upon availability of water to be recharge.
Ground Water Recharge in Urban Areas

22. 3. Tube Wells
•In areas where the shallow aquifers have dried up and existing tubewells are
tapping deeper aquifer, rain water harvesting through existing tubewell can be
adopted to recharge the deeper aquifers.
4. Trench with Recharge Well
•In areas where the surface soil is impervious and large quantities of roof water or
surface runoff is available within a very short period of heavy rainfall, the use of
trench/ pits is made to store the water in a filter media and subsequently recharge
to ground water through specially constructed recharge wells.
•This technique is ideally suited for area where permeable horizon is within 3m
below ground level.

23. Recharge pit Recharge trench
Tube wells Trench with recharge well

24. The following methods are commonly in use for estimating ground
water recharge:
1) Ground water level fluctuation method
2) Ground water balance method
3) Hydrochemical (chloride mass balance)

25. GROUND WATER LEVEL FLUCTUATION METHOD
This is an indirect method of deducing the recharge from the fluctuation of the
water table.
The rise in the water table during the rainy season is used to estimate the
recharge, the rainfall recharge, Ri is given by,
Ri = Sy∆s + Tp RT
Where , Sy = specific yield,
Tp = The abstraction during the rainy season divide by the study area,
and
RT = The return flow due to any irrigation which occurs during the rainy
season.
The basic limitation of the above equation is that it neglects the subsurface inflow
and outflow and assumes that every inflow and outflow is uniformly distributed
over the area.

26. GROUND WATER BALANCE METHOD
I – O = ∆W / ∆t
Where, I = inflow (m3
/day) during time ∆t, O = Outflow (m3
/day) during time ∆t, and W =
Change in water volume (m3
).
Considering the various inflow and outflow components, the ground water balance
equation for a time period ∆t is given as:
Ri+Rc+RT+Rt+Si+Ig = Et+Tp+Se+Og+ ∆W
Where, Ri = Recharge from rainfall Rc = Recharge from canal seepage
RT = Recharge from field irrigation Rt = Recharge from tank
Si = Influent recharge from rivers Ig = Inflow from other basins
Et = Evapotranspiration Tp = Draft from ground water
Se = Effluent recharge to rivers Og = Outflow to other basins
∆W = Change in ground water storage.
The above equation is the general ground water balance equation for an
unconfined aquifer.

27. Chloride Mass Balance Recharge Estimation
To determine the mean annual recharge using the chloride method it is assumed
that the only possible source of chloride ion in groundwaters of the study area is at
the soil surface (either in precipitation or as dry fallout) and that there is no
contribution from weathering.
Recharge as shown in the following relationship developed by Eriksson and
Khunakasem (1969):
Recharge (mm) = rainfall (mm) × Cl concentration in rainfall (mg/L)/Cl
concentration in groundwater (mg/L)