The runoff from the watershed will be 34.606 mm or 0.34606 m.

2. Planning and design of water harvesting structures in a
watershed
Dr. Pawan Jeet
Scientist, Division of Land and Water Management
ICAR-Research Complex for Eastern Region
Patna, Bihar-800 014
Presentation

3. ?
• Basin, catchment and watershed
• Hydrologic, hydraulic and structural design of
structure
• Irrigation and drainage
• Infiltration and percolation
• Rainfall and drizzle
• Surface water and ground water
• Groundwater recharge and groundwater extraction
• Conjunctive use and consumptive use

4. • Basin/Catchment/Watershed: Geo-hydrological unit which drain water into a
common point/outlet.
• Surface Runoff: Rainfall in excess to the interception, surface storage and
infiltration flows as overland flow and reaches to the outlets as surface runoff.
• Groundwater recharge: Groundwater recharge is a process by which infiltrated
water moves through the vadose zone and joins the water table. Amount of water
reaching to the water table under specific geo-hydrologic and orographic conditions
can be termed as the groundwater recharge potential.
• Water harvesting: capture, diversion, and storage of water obtained from different
freshwater sources for irrigation, domestic, industrial, groundwater recharge and
other uses.
• Rainwater harvesting : system of collection and concentration of rain water and its
runoff and its productive use for Irrigation of annual crops pastures and trees,
domestic and livestock consumption and groundwater recharge.

5. Introduction
• India commands approx. 4% of the global freshwater
resources for supporting 17% of the world’s population.
• Water is a crucial limiting factor for increased food and fibre
production to supply an ever growing population.
• Rainwater is the major source of water and it’s current use
efficiency for crop production ranges between 30 to 45 per
cent and annually 300 to 800 mm of seasonal rainfall is lost as
surface runoff or deep drainage (Wani et al., 2003).
• Every square mile of developed land causes 60.57 million
litres of rain water to directly enter the rivers on a rainy
day!
• India has been divided into 6 Water Resource Region, 35
Basin, 112 Catchments, 550 Sub catchments and 3257
Watersheds (Watershed Atlas of India, Department of
Agriculture and Cooperation ).

6. Conte...
• A watershed can be symbolized as 1A2B3 where “1” stands
for Water Resource Region, “A” designates the Basin in that
river resource region, “2” indicates the Catchment within the
basin, “B” indicates Sub-catchment and “3” stands for the
watershed number in the sequence of stream hierarchy.
Average size and size ranges for each Hydrological Units
Category of Hydrologic Units Size Range (ha)
Water Resource Region 270,00,000-1130,00,000
Basins 30,00,000-300,00,000
Catchments 10,00,000-50,00,000
Sub-catchments 200,000-10,00,000
Watersheds 20,000-300,000
Sub-watersheds 5,000-9,000
Micro-watersheds 500-1,500

7. Need for efficient storage and utilization of water
 Major parts of our country have been facing continuous failure
of monsoon and consequent deficit of rainfall over the last few
years.
 Also, due to ever increasing population of India, the use of
ground water has increased drastically leading to lowering the
level of groundwater table causing drying up of ponds, wells and
tubewell.
 In some places, excessive heat waves during summer create a
situation similar to drought.
 It is imperative to take adequate measures to meet the drinking
water needs of the people in the country besides irrigation and
domestic needs.
 Out of 8760 hours in a year, most of the rain in India falls in just
100 hours.

8. Water can be harvested in a variety of ways
Directly from roof tops and stored in tanks.
Monsoon run off and water in swollen streams during
the monsoon and storing it in underground tanks.
Water from flooded rivers can be stored in small
ponds.
Collection and transfer of rainwater into percolation
tanks so as to facilitate discharge into ground.
Interlinking of river project.
Proper planning and hydrological modelling.

9. Conservation of water for it’s efficient use
• Appropriate crops
• Improved varieties
• Cropping systems
• Nutrient and pest management options for increasing
the productivity
• Conserving the natural resources
Results
• Increased productivity is achieved through doubling the
rainwater use efficiency (67 vs 37%) and reducing the soil loss
by 75 per cent as compared to the traditional methods of
cultivation (Wani et al., 2003).

10. Hariyali Guidelines (2003)
• New projects under the area development programmes shall be
implemented in accordance with the Guidelines for Hariyali with effect from
1.4.2003.
Criteria may be used in selection of the watersheds:
• Watersheds where People’s participation is assured through contribution of
labour, cash, material etc. for its development as well as for the operation
and maintenance of the assets created.
• Watershed areas having acute shortage of drinking water.
• Watersheds having large population of scheduled castes/scheduled tribes
dependent on it.
• Watershed having a preponderance of non-forest wastelands/degraded lands
and common land.
• Watersheds where actual wages are significantly lower than the minimum
wages.
• Watershed area may be of an average size of 500 hectares, preferably
covering an entire village.

11. Benefits
• To intercept the runoff and moderate peak
flow and volume of runoff
• To increase the time of concentration
• To provide irrigation potential
• To trap sediment
• To increase groundwater recharge
• Reclamation of additional land in down
stream

12. Water harvesting structures
• Percolation Tank
• Check Dams/ Cement Plug/ Nala Bunds
• Pond/ Tank
• Gabion Structure
• Ground Water Dams or Sub-surface Dykes or
Underground Bandharas
• Nadis
• Khadin
• Tanka/ Kund/ Kundi
• Doba (Developed by ICAR-RCER, Patna)

13. Doba water harvesting technology
• Low cost water harvesting technology in Eastern
Hills and Plateau region.
• Size: 3 x 1.5 x 1 m
• Life: 2-3 years
• Cost of construction (Rs): 1000-1200
• Storage capacity: 4500-5000 litres
• Benefit–cost ratio: 2.3 : 1
• Applicability: provide life-saving irrigation to 10
orchard fruit crops for 6 months.

14. Planning concept
• Check dams
 This is constructed across rivulets and gullies to control
erosion, prevent gully formation and to arrest the flow of water
to allow it to go underground.
 Inexpensive, temporary structures can be constructed using
vegetation, stone or brushwood, available at the site.
 Large numbers can be provided to reduce erosion and
formation of gullies.
 Permanent check dams can be located at the junction of one or
two streams or gullies using masonry structures.

15. Conte...
• Percolation ponds
 It should not be located in heavy soils or soils with impervious
strata, otherwise the top soil should be porous.
 The ideal location of the pond will be on a narrow stream with
high ground on either side of the stream.
 Simple, economic and efficient surplus arrangement should be
possible.
 Pond size should be decided on the basis of the catchment
area.
• Irrigation tanks/ponds
 The location should be such that it should receive water from a
large catchment area.
 There should be land below the site suitable for irrigation.
 The location should be such that it will be a narrow point with
high ground and wide open space in front of the tank location
so that a large quantity can be stored with minimum cost.

16. Collection of data
Data Type Sources
Land Use Land Cover (LULC) NBSS&LUP/Agriculture Department/ Forest
department/NRSC Bhuvan Centre/NGO/Revenue
department/IWMI
Soil Type Harmonized World Soil database
(HWSD)/NBSS&LUP/NRSC Bhuvan Centre/FAO
Topography Shuttle Radar Topography
Mission (SRTM)/Advanced Spaceborne Thermal
Emission and Reflection Radiometer (ASTER)
Groundwater Level, Water quality Central Ground Water Board (CGWB)/National
Geophysical Research Institute (NGRI), Hyderabad
Climate (i.e., Rainfall, Temperature,
Humidity, Radiation and wind speed),
Crop information
India Meteorological Department (IMD),
Department of Agriculture, Bihar
River flow gauging, Sediment load Central Water Commission (CWC), India WRIS,
Department of Water Resources, Bihar
River Basin Information Central Water Commission (CWC), India WRIS,
Department of Water Resources, Bihar

17. Land use land
cover
Soil
Set up and run SWAT
model
Hydrologic response
unit (HRU)
Rainfall
Climatic
data
Relative
humidity
Land Slope
Temperature
(Min/max)
Digital elevation
model (DEM)
Solar
radiation
Watershed delineation
Wind Speed
Model output
Calibration/Validation/Sensitivity
analysis
River flow
Results
Flow chart for delineation of HRU and estimation of surface runoff

18. Design criteria for water harvesting structures
• Selection of water harvesting site:
 Cost of construction, utility and the life of structures depends
on the site.
• Catchment area/ drainage area:
• Water spread area:
• Height of the structure:
 function of the availability of runoff water.
 Water harvesting structures of heights 1, 2, and 2.5 m are
suitable for the catchments of less than 10, 10 to 20, and 20 to
30 hectares.
 He = height of stored water + settlement allowance + freeboard
 Settlement allowance is provided 10% of height.

19. Conte...
• Freeboard:
 1.5-2m freeboard is provided depending upon the catchment
area.
• Top width:
 Tw = 0.6 x H0.5 + 1 m, where H is the maximum height of dam.
 By thumb rule, minimum top width of dam should be 2.5 m.
• Bottom width:
 Bw = 4 x H x Tw
• Side slope: depends upon the soil texture of sites.
• Storage capacity: using Prismodial formula/ Trapezoidal
formula
 Storage capacity= 1/3 x water spread area x height of stored
water

20. Computation of volume
• It is used when odd number of section
are there.
Trapezoidal formula

21. Conte...
• Design of emergency spillway:
 Key component in any water storage structure as it protects the
whole construction in case of surplus runoff.
• Calculation of Peak Runoff:
 Peak runoff can be computed by the rational formula.
Qp = (C x I x A)/36
Where, Qp= peak runoff rate (m3/sec);
C=runoff coefficient (dimensionless); I= rainfall intensity (cm/hr)
for the design recurrence interval and for the duration equal to
the time of concentration of the watershed; and
A=catchment size (ha).
 The values of runoff coefficient (C) are dependent on the
vegetative cover, soil texture and slope.
• Time of concentration of a watershed: Kirpich formula

22. Extent of savings in water and yield improvement due to the improved
management practices in watershed
Technology/Practice Crop Avg. Water
saving (%)
Avg. Increase in
crop yield (%)
Ridge and furrow method Soyabean, cotton,
maize, cowpea,
colocassia
27 8-24
Broad bed furrow Soyabean - 81
Sowing across the slope Soyabean - 33
Compartmental bunding Sorghum - 52
Conservation furrow Cotton, Pigeon pea - 8-60
Sub soiling Groundnut - 11
Plastic mulching - 4.7-45 7.5-22
Rice straw - 30 -
Trench cum bunding - 15 -
Laser levelling Rice-wheat, rice 25 2-5

23. Emerging Issues
• No starting and end point for watershed activity and
continuous training of the farmers and community need to be
sustained.
• How to institutionalize technical backstopping for the
watersheds?
• How to harmonize existing village institutions with watershed
committees and self-help groups and increase their efficiency?
• Policy options for ground water harvesting; issues like bore
wells, use of working strategies and maintenance.
• Sustainable management of watershed strengthening of village
institutions, policies and increased awareness of communities
need to be achieved.
• Need to study on-site and off-site impacts of watershed
development programs.

25. Problem
• Calculate the runoff from a watershed of 50 Ha for the
following data using SCS-CN method. Depth of
rainfall=150mm; Antecedent Moisture condition, AMC I. Row
crop, good condition in 30 Ha; Woodland, good condition in
20Ha.
• Type of crop CN at AMCII AMCI Row crop, good 82 82x0.8=
65.6 Woodland good Woodland, good 55 55x0 65= 35 75
55x0.65= 35.75 Weighted CN = (65.6 x 30 + 35.75 x 20)/ 50 =
53.66
• Using ; S= 219.35 S CN 254 25400 Q = 34.606 mm; Runoff
in response to 150mm P S rainfall