Subsurface dams

1. A Seminar Of Special Topic On
Subsurface Dam
Presented By
Sambhaji P.Harwandkar
Under The Guidance Of
Prof. S.L.Bodas

2. Introduction
Need of subsurface dam
Diversity of the country
Population & water supply needs
Agricultural requirements

4. Need
 The Nakajima Subsurface Dam is located on
Nakajima Island, one of the hilly Islands in
the Sea of Japan.
 Low average annual rainfall of 1,473 mm,
 The island constantly needs more water,
especially in the summer for agricultural and
household uses.

5. Location & hydrogeology of the dam
Site located at 200 m from the coastline in a valley
plain in the southeast part of the island
The bedrock at the dam site and the storage area is
andesite, ryolite and granite.
Alluvial deposits overlying the bedrock valley consist
of gravel, sand, silt, clay, and volcanic ash.
The maximum thickness of alluvium was 26 m
The coefficient of permeability was 1.01x10-2 cm/sec
in the upper strata and 1.74x10-3 cm/sec in the lower
strata.
The coefficient of permeability ranged from 1 to
3.5x10-5 cm/sec in the fresh andesite.

6. Dimensions of the Nakajima Subsurface
Dam
Catchment Area 0.62 km2
Crest Length 87.7 m
Height of Dam 24.84 m
Average Thickness of Wall 0.55 m
Cutoff Wall Area 1,357.09 m2
Height of Overflow Zone 1.3 m
Volume of Reservoir 277,000 m3
Specific Yield 0.10
Active Storage Capacity 27,000 m3

7. Method of construction
The Soil Mixed Wall (SMW) Method consists of
cutting and mixing the in-situ soils with cement grout
using auger flights and mixing paddles attached to
three axis auger shafts.
The soil mixing produces overlapped soil-cement
columns, 55 cm in diameter and 145 cm long per
panel of three columns which forms the cutoff wall.
The soil-cement column has a minimum 28 day
unconfined compressive strength of 5 kg/cm2 and a
maximum coefficient of permeability of 1x10-6
cm/sec.

8. Pumping Test
Two long-term pumping tests of 18 days and
30 days were performed to study the function
of the subsurface dam and the nature of the
salt water intrusion before and after
construction.
The pumping volume was 100 m3 per day.

9. Subsurface dam in India
 Located at Chirayinkil Block , Trivandrum
District, Kerala
 The average rainfall is 1963 mm of which
about 70% is received during south-
western monsoon.
 Sub-surface dyke is being constructed to
arrest the sub-surface ground water
outflow.

10. Subsurface dam in India
The Central Ground Water Board has sited
and constructed a number of sub-surface
dams in Kerala in the 1980s.
Presently, Shri Vivekananda Research and
Training Institute (SVRTI), under the
guidance of K C B Raju is involved in
constructing groundwater dams in Kutch
district of Gujarat.

11. Concept & principle
A system to store groundwater
Storage in geological strata
A dam constructed under ground
Necessity for water-pumping facilities

12. Types of subsurface dam
 Under ground dam
 Sand storage dam
&
combination of these two types

13. Under ground dam
sand storage dam

14. sand storage dam

16. Advantages of a subsurface dam
A water storage system without land
submergence
Prevention of evaporation of reserved water
Clean, safe water
A stable, secure dam
Utilization of renewable resources

18. Disadvantages of a subsurface
dam
Difficulties in site selection
Low effectiveness of water storage
Interception of downstream groundwater flow
Salinization in reservoir area

19. Basic Requirement for Subsurface dam
Projects
Source Water Availability
Hydrogeological Aspects

20. Planning of subsurface dam projects
Identification Area
Scientific Inputs
Hydrometeorological Studies
Hydrological Studies
Soil Infiltration Studies
Hydrogeological Studies
Geophysical Studies
Chemical Quality of Source Water
Suspended matters
Assessment Of Sub-Surface Potential For
Ground Water Recharge

21. Requirements for a subsurface dam
site
Presence of shallow groundwater with high
fluidity
Presence of a porous layer (aquifer) for water
storage
Presence of the surrounding basement rock
with low permeability
Presence of a gorge of basement rock with
low permeability

22. Monitoring mechanism for Subsurface
dam projects
Water Level Monitoring
Tracer Technique For Demarcating Zone
Of Benefit
Water Quality Monitoring

23. Impact Assessment
Conservation and harvesting of surplus monsoon
runoff
Rise in ground water levels
Availability of water in lean months
Cropping pattern in the benefitted zone will undergo
marked change
Quality of ground water may improve due to filtration
Indirect benefit in terms of decrease in soil erosion,
improvement in fauna and flora, influx of migratory
birds, etc.

24. FORMAT FOR PREPARATION OF SUBSURFACE DAM PROJECT
Base Information of Problem Area
1. Location State
District
Block
Basin/Sub Basin/Watershed
Lat. & Longitude
Area Extent
No. of Villages/Towns
2. Population (i) Human - Urban & Rural Livestock
3. Land use (i) Cultivable & Non-cultivable Area Forest
4. Agriculture (i) Soil Type, thickness and extent
(ii) Cropping Pattern
(iii) Area under irrigation (a) Surface water
(b) Ground water
5. Climate (i) Type of Climate
(a) Humid
(b) Sub-Humid
(c) Arid
(d) Semi-arid
(ii) Rainfall
(a) Average annual
(b) Rainfall Distribution
(c) No. of Rainy days
(d) Temperature
(e) Humidity
(f) P.E.T.
(g) Wind

25. 6. Topographic Features (i) Elevation range (Maximum,Minimum & General)
(ii) Landform
(a) Hilly Area
(b) Highly Dissected Platea
(c) Moderately Dissected Plateau
(d) Foot Hill Zone
(e) Piedmont Zone
(f) Valley Slopes
(g) Plain Area
(h) Sand dune Area
(i) Delta Region
(j) Coastal Plains
(k) Karstitic Terrain
7. Surface Water Bodies: (i) Rivers/Streams - Perennial, Ephemera
(ii) Average Discharge & Duration of flow
(iii) Canal - Lined / Unlined
(iv) Length and capacity of canal and duration of
canal flow
(v) Number and Area of Natural Lake & ponds.
(vi) Reservoirs, their number and storage capacity
(a) major
(b) Medium
(c) Minor.
8. Hydrogeology (i) Geological Formations
(ii) Major Rock Types
(iii) Structural Features

26. (iv) Nature of unsaturated zone
(a) Moisture conditions
(b) Presence/Absence of imperviousLayers in vadose zone
(v) Aquifer systems
(a) Phreatic
(b) Semi-confined
(c) Confined
(vi) Depth of Aquifer Zones Hydraulic Characteristics of Aquifers:
(a) Transmissivity
(b) Storativity /Specific yield
© Hydraulic Conductivity
(viii) Aquifer boundaries
(ix) Depth of Water level and its seasonal fluctuation.
(x) Ground Water Structures
(a) Type, Number
(b) Depth range
(c) Yield range
(d) Aquifer tapped
(xi) Ground Water Resources
(a) Annual Recharge
(b) Annual Draft
(c) Stage of Ground Water Development
(xii) Ground Water Level trends.
9. Water Requirements
(i) Present requirement for different uses (Domestic Industrial
and Irrigation).
(ii)Projected requirement after 10 years 20 years
(Domestic, Industrial and Irrigation)
10. Ground Water
(i) Unconfined & confined aquifers

27. (a) Potable
(b) Brackis
(c) Saline
(ii) Any special quality problem,(Seawater intrusion, pollution, high
fluoride etc.).
11. Nature of problem requiring
(i) Quantity Problem Artificial Recharge of Ground Water
(a) Quantification of Water shortage for different purposes.
(b) Period of Shortage
(c) Location of deficit areas.
(ii) Quantity Problem
(a) Control of Sea Water Intrusion
(iii) Special Problem
(a) Control of Land subsidence
(b) Waste water reclamation through SAT System.

28. 12. Source Water Availability
For Artificial Recharge Purpose:
______________________________________________________________________________________
Source Location Quantity Period of Physical
Availability & Chemical
Quality
______________________________________________________________________________________
Rainfall
River
Canals
Reservoirs
Municipal Waste Water
13. Sub-surface Potential for Ground Water Recharge
(i) Thickness of un-saturated zone(below 3 mbgl).
(ii) Total runoff in the catchment
(iii) Committed flow…..
(iv) Surplus available for recharge

29. Thank You