Water and Development
Minor Structures
Milind Sohoni
www.cse.iitb.ac.in/∼sohoni email: sohoni@cse.iitb.ac.in
January 28, 2018 1 / 50
So far...
The organization of the village.
Farmlands and crops -Kharif, Rabi and Summer
The demand for water. The deficit or the surplus.
How do we meet it?
Watershed interventions
Different types-Drain and Area.
Larger - Percolation tanks and KT weirs
January 28, 2018 2 / 50
The Design Cycle
Development Bio-physical Designs and
Outcomes ⇒ Outcomes ⇒ Plans
Development Outcomes
Socio-economic, concerns such as equity, access.
More cropping area. More certain and more secure water.
Good quality drinking water. easy to maintain systems.
Bio-physical Outcomes
Science and Technology Choice, Sustainability.
Water requirements, norms.
Design and Plans
Interventions, Efficiency. Cost-Benefit: Metric, Rs./TCM, Labour, Social contribution.
Overall plans. Major and minor structures. Where to do.
January 28, 2018 3 / 50
.
0 0.225 0.45 0.9
Kilometers 1:20,000 SCALE - ACTIONPLAN MAP (Watershed No:- GP-8/4/14)
PREPARED BY::
Maharashtra Remote Sensing Applications Centre, Dept. of Planning,Nagpur,
Govt. of Maharashtra.
And GSDA,Pune DATA SOURCES::
Village Map:Directorate of Land Records Linaments/Dyke:Derived from SatelliteData MRSAC, Actionplan: MRSAC Contour 5mt:Derived from SRTM data MRSAC, Watershed -AISLUS & GSDA, Drainage:GSDA,Pune
Village-Daregaon ,Taluka -Fulambari, District -Aurangabad
Location Map 710
685
690
695
680
675 715
725720 665
660 655
650
745
715
735
725
735
730 GP-8/ 04/14
GP-8/ 04/12
D a r e g a o n D a r e g a o n
83
90 126
39
68 58
66 53
85 139
74 4
69 26
2
97
59
70 24
1 27
99 146
43
100
60 44
65 136
177
52
81 111
29
50
180 17
89 87
164
73 151
75 77
57 157
56 104 131
40 152
164
119
55 96
116 117
41 35 162
187 143 185
174 37
163
36 19 155
183 20
34
106 173 175
105 494847
173
46 23 3231
33 30
67 162
179 172
125
64 72 181
129
63 142
71 62 127 148
54 178
120 124
21
76 128
78 141 138
150 161
84 107 135
42 149
160
93
165 156
171
91 167
118 145144
79 88
173
92 131 132
109 51
170
114 186 153
61 188
98 159
94 137
134 22 166 168
101
16
121 123
103 182
122 9
112
5
133 179
15 18
113 169
115
158
127 162
38 29
140 3 13
108 130
165 158
184 28
147
75°29'0"E 75°29'0"E
75°28'30"E 75°28'30"E
75°28'0"E 75°28'0"E
75°27'30"E 75°27'30"E
75°27'0"E 75°27'0"E
75°26'30"E 75°26'30"E
75°26'0"E 75°26'0"E
20°5'30"N 20°5'30"N
20°5'0"N 20°5'0"N
20°4'30"N 20°4'30"N
20°4'0"N 20°4'0"N
20°3'30"N 20°3'30"N
PREPARED FOR::
Vasundhara Watershed Development Agency, Maharashtra, Pune-1 AndDirector of Soil and Water Conservation Maharashtra, Pune-1
Sillod Kannad Vaijapur
Paithan GangapurAurangabad
Fulambari Soegaon Khuldabad
Soegaon
Part of Jalna District
Part of Vaijapur PuneBid
Nashik
Solapur Satara
Jalgaon Thane JalnaYavatmalGadchiroli
Latur Amravati
Sangli Nagpur Nanded Dhule
Buldana Chandrapur
Ratnagiri Raigarh
Kolhapur Gondiya
Osmanabad Nandurbar
Sindhudurg Bhandara Legend
Linaments/Dyke Contour 5 Meter Watershed Boundary Survey/Gat No. Boundary Village Boundary Drainage Line Treatment
Gully Plug or LBS Earthen Nalla Bund/ Gabian Bandhara Nala Desilting/C.N.B./K.T.
Area Treatment Dry land Agriculture/Contour Bunding/ Farmpond Afforestation/ Dry Land Horticulture/Plantation CCT/Deep CCT/WAT/Forest Pond Compartment Bunding/Graded Bunding/Fram Pond/Well Recharge River/ Waterbody
Village Area Page Size:A1
JALYUKT SHIVAR ABHIYAN (2017-18)
In Map Show Existing Activities with Red Colour and Proposed Activities
with Green Colour
(For Official Use Only)
January 28, 2018 4 / 50
Variable Access to Water
January 28, 2018 5 / 50
Interventions and their influence
January 28, 2018 6 / 50
Classification by Purpose
We may classify structures/procedures by their primary objective.
Groundwater Recharge: To enhance the recharge of groundwater or to improve soil moisture. Usually done either by
(i) reducing the velocity of water-flow
(ii) increasing the infiltration coefficient
(iii) explicit groundwater recharge structure
Examples: Contour bunding, furrowing, well-recharge structures, percolation tanks.
Reducing Soil Erosion: To improve agriculture, protect building etc., or to protect downstream water
structures. Examples:
Terracing, contour bunds.
Gabions and gully plugs.
Surface Storage: To store water on the surface. Some examples are:
Check-Dams, Weirs Rainwater harvesting Bunds, Farm-ponds.January 28, 2018 7 / 50
Contour Trenches
source:FAO
Hill
Contour Lines
L
w d Berm Pit Saturated
region
Parameters L,d,w depend on the slope, rainfall etc.
Working: Pits fill with water and remain so till the end of monsoon.
This creates a local saturated layer which helps percolation. Also used alongside tree-plantation.
January 28, 2018 8 / 50
Contour Trenches
source:FAO
On forest and common lands.
Slope less than 20%. Risk of lanslides.
Intercept sliding sheet of water and capture and infiltrate.
2-3 fillings per season. 1000 running meters per hectare.
Roughly 2000-3000 cu.m.
infiltration. Rs. 60-120 /cu.m.
January 28, 2018 9 / 50
Hill-sides
Baner, Pune. source:http://stuffido.wordpress.com/2009/07/
January 28, 2018 10 / 50
Contour-bunds
This is formed by firming the berms to create obstructions to water flow. It is especially useful for tree-planting.
source: Ray Weil, Picasa January 28, 2018 11 / 50
Terracing
This is largely about preventing soil-erosion and utilizing the land for agriculture. It is used when the gradients are small.
source: FAO
January 28, 2018 12 / 50
Terracing and gullies
Top view source: FAO
Terracing: Delicate construction. Special care must be taken for the inlet and outlet of water.
Example of gully formation in an agricultural field.
Gullies may form in a single monsoon in fields with even a small gradient. These get reinforced and cause
substantial damage.
source: FAO January 28, 2018 13 / 50
Bunds and channels
Rice-fields have bunds to maintain submergence.
Fields in Black Cotton soils have channels to drain excess water, esp. for cotton or soyabean.
Water management: must for dry-spells. Ensure soil moisture.
January 28, 2018 14 / 50
Contour Bunds
To bring fallow land into agriculture, esp. horticulture.
Broad trences of 2-3m and bunds of 1m in height.
Moves about 20-30mm of run-off into infiltration. Rs. 7000/Ha.
January 28, 2018 15 / 50
Furrowing
Soil may get compacted by overgrazing and animal/human use. This reduces infiltration coefficients substantially. For level lands,
furrowing is a useful technique for increasing infiltration. In fact, agricultural land is excellent for recharge.
source: FAO January 28, 2018 16 / 50
Farm Ponds
from TN agri. univ.
January 28, 2018 17 / 50
Farm Ponds-Design
Need
Protective irrigation during Kharif
Support for critical Rabi/Crop crop
Recharge and Storage How is it filled? Is it lined?
Ideal Use: Fill from run-off/base-flow or from canal-side wells.
Not from groundwater.
Lined if protective, unlined if community recharge.
Rs. 1 lakhs, if unlined, Rs. 2 lakhs if lined.
January 28, 2018 18 / 50
Locations
January 28, 2018 19 / 50
Detail
January 28, 2018 20 / 50
Count Them!
January 28, 2018 21 / 50
This needs analysis
January 28, 2018 22 / 50
Tanks and Bunds
source:
http://forest.ap.nic.in/Sparks of Success
APFD-02-05/007-Nallavally.htm
Dug-outs or obtained by bunding an existing flow to create a pond.
If bunded, then the design of the bund needs some care. It should have a spillway, and usually afoundation.
Primary objective is to recharge groundwater by holding it during the monsoons and after it.
Also serves as farm-ponds to protectkharif crops.
Periodic de-silting important for purpose. January 28, 2018 23 / 50
Tanks and Check-Dams
source:
http://test1.icrisat.org/
satrends/ jan2006.htm Note the spillways and pitching.
Most dry up in 3 months.
source:http://washim.nic.in/DOC/ Egs files/image007.jpg
Acheck-dam is designed differently.
The bund is deeper with a clay core.
January 28, 2018 24 / 50
Vanrai Bandhara
Temporary, must be installed after every monsoon.
<2m in height, and may be used on top of existing bunds.
Installed just after monsoons get over, but stream flows remain.
Mainly to achieve/increment some recharge and some storage.
source: http://washim.nic.in/DOC/ Egs files/image010.jpg
January 28, 2018 25 / 50
The principle
During the monsoons, connect the WT and the pond.
Increase recharge during the monsoons.
Helps reduce crop stress in lean periods.
Post-monsoon, a perched WT.
Increases soil moisture.
Silts have low conductivity.
Must be removed from tank bottoms to aid percolation.
Evaporation losses about 5mm/day.
Poor ambient conductivity
=⇒Wet longer
WT
monsoon
region saturated
post−monsoon
January 28, 2018 26 / 50
Gabions
Gabions are loose rock structures to prevent soil erosion.
Located along/across gullies or stream banks.
They trap soil and reduce water velocities.
They help maintain and control stream flow.
Typically built using wire-meshes.
A cage is built which encloses rocks suitably arranged.
Manual construction.
Porous, does not hold water. source:
http://lh4.ggpht.com/ KsQX iKm6hw/SMZgiE V4HI/AAAAAAAAACA/2JBdx7LQUO8/01062008(002).jpg
January 28, 2018 27 / 50
Across streams: an overflowing gabion
source: http://www.bridgetrust.org/images/Gabion (1).jpg
January 28, 2018 28 / 50
Masonry Structures
source: http://www.gomukh.org/images/index 02.jpg
Ground Breaker
Silt Water Wall
Boulder and concrete wall with a concrete breaker.
Foundation and Key-wall to prevent leakage around the wall.
Overflow structure, used as storage and silt trap.
January 28, 2018 29 / 50
Concrete Nala Bunds
Vented structure at Adoshi.
January 28, 2018 30 / 50
Design Principles
Storage/Recharge. To create small storages within river beds.
Soil Conservation. To obstruct water and reduce velocity of water. To trap silt.
Design: RCC Overflow structure, compact and with foundation.
3-4m high, with apron. Roughly Rs 1-2 lakhs per meter.
Storage created: 3m× 20m ×300m = 18000 Cu.m. Adequate for 18 Ha. protective irrigationthrough pumps or through well-recharge.
Serious Issues: Flooding of banks!Silting. Cost: Rs.
5K-10K/cu.m.
January 28, 2018 31 / 50
Adoshi vents operating
No silting, but more complex structure.
January 28, 2018 32 / 50
Kurlod structure
Useful for agriculture.
January 28, 2018 33 / 50
Needing Repairs
January 28, 2018 34 / 50
Manipada
Broken, reported to Collector.
January 28, 2018 35 / 50
Manipada repiared: in Monsoons
January 28, 2018 36 / 50
Manipada Upstream
January 28, 2018 37 / 50
Nalla deepening and widening
Create storage within river bed. Behind an existing or new CNB.
Length × cross-section=10-20TCM.
Make sure depth no more than3m or less.
Make sure that berms are made and that it doesnt close flows from farms into stream. water-logging.
January 28, 2018 38 / 50
Desilting
Soil: 3 grades-Top to bottom. Sand. Silt. Clay.
Move silt back to farms.
Estimate silt to be removed. Estimate farm-lands to receive.
5cm thick layer is 500 cu.m., i.e., 50 trucks per Ha.
About Rs. 60-100 per cu.m. for removal. Rs. 50 for transport.
January 28, 2018 39 / 50
Dams and Weirs-The Kolhapur Type Bandhara
source: http://www.maharashtra.gov.in/english/ gazetteer/
Nanded/images/kholhapur-dam.jpg
January 28, 2018 40 / 50
The principle
source:
http://ahmednagar.nic.in/html docs/
images Ralegan.png
Concrete structure within the river bed.
Gates open in monsoons and shut just after.
Creates a storage used for agriculture/DW.
The storage is largely confined to the river bed.
No land need be acquired.
Used by upstream people!
Appear in a sequence Fairly cheap and useful.
Very popular in India.
January 28, 2018 41 / 50
A typical caluclation
.
Height and length of KT weir: 30m×3m.
Length: 1000m and therefore volume: 100,000 cubic meter, i.e., 0.1MCM.
At 10cm watering, we get 100 hectares of irrigation.
About 30-40km of river gives us 4MCM per discharge.
Dimbhe Storage is 375MCM.
About 20-30 weeks of discharge gives about 100MCM through KT weir.
January 28, 2018 42 / 50
Reservoir+Earthen Dam
Objectives
Increase surface storage in system. Increase recharge and total GW stored. Improve surface water flows.
Improve drinking water security and allow for livelihood water.
Costs
Land acquisition, submergence. Considerable amount of earth.
Sophisticated engineering design. Labour and fuel costs.
January 28, 2018 43 / 50
A Small Dam
90
100
100 100
90
100
90 90 bund
maindam
stream stream
spillway
The FSL (full storage level) of the dam is the height at which water is stored, in this case, 100.
The dam and the bund are higher.
The bund was needed to achieve an FSL of 100.
The storage is the modified contour at 100.
The spillwayis at 100 and cuts into the old contour at 100. Excess water overflows from here.
The Key-wall protects the dam from the spillway.
January 28, 2018 44 / 50
Alignment
January 28, 2018 45 / 50
Storage or Silt Calculation
92
90 94
FSL=95
Storage=A90+. . .+A95. Height of dam=6m+safety. Silt=
A90+A91.
January 28, 2018 46 / 50
Cross-Section
Core
Drains Storage
Water Water Table
Iso−heads
Hard Rock COT
Casing
Core : a wall of clay/low conductivity soil.
COT : To insert into hard-rock.
Drains : To keep the dam dry and prevent seepage flows.
Casing : Muram like soil, supports the core.
Note the water-table and the iso-head lines.
Note the rapid drop in the water table in the core.
January 28, 2018 47 / 50
Section at alignment
January 28, 2018 48 / 50
Gudwanwadi Dam
85m long, 8m high, earthen.
Storage 2 acres, 20K cu.m.
Cost: 24 lakhs.
Construction time: 6 mo.
Note Spillway, and Key-wall.
Note Pitching (stones) on the dam walls.
January 28, 2018 49 / 50
Thanks
January 28, 2018 50 / 50
