Accepted Papers - 3.pdf - UNESCO

National Seminar on Rainwater Harvesting and Water Management 11-12 Nov. 2006, Nagpur
60. Planning and Design of a Rain Water Harvesting System
for a Watershed of Uttaranchal
INTRODUCTION
In modern concept of planning and
implementation of programmes for enhancing and
sustaining the land productivity and efficient
rainwater utilization; watershed - a geographical unit
has been accepted as the most rational unit. The
word ‘watershed’, introduced in 1920, was used for
the ‘water parting boundaries’. Watershed is that
land area which drains or contributes runoff to a
common outlet. In physical terms, a watershed refer
to the area lying above a given drainage point.
Watershed management involves management of
land surface and vegetation so as to conserve the
soil and water for immediate and long-term benefits
to the farmers, community and society as a whole.
It is an integration of technologies within the natural
*P. K. Gupta *H.C. Sharma *Vinod Kumar
ABSTRACT
The Henwal watershed is located in Tehri Garhwal district of Uttaranchal,
between 30° 15' to 30° 20' N latitude and 78° 25' to 78° 30' E longitude, at an altitude
of about 1500 m above msl. Most of the area is under rainfed agriculture, due to lack
of irrigation facilities. The daily rainfall data of 14 years, of the watershed area, were
analyzed for probability distribution at different levels. The analysis of estimated daily
runoff values for 14 years showed that the annual runoff, more than 500 mm, was
observed in 4 years, between 400 mm and 500 mm in 5 years and less than 400 mm in
4 years. The average annual and seasonal runoffs were found to be 431.7 mm and
292.4 mm, respectively. The average seasonal runoff was found to be 70 per cent of
annual runoff. The expected runoff and seasonal runoff during the first excess period
was 665000 m 3 and for second excess period was 175000 m 3 . On the basis of above the
rainwater-harvesting pond was designed for Henwal watershed having a catchment
area of 351 ha and command area of 315 ha. The bottom width, top length and height
of the designed pond were 2.5, 16.6 and 3 m, respectively. The pond would have a
storage capacity of 5027.4 m 3 . The total cost (excavation cost, LDPE sheet and stone
pitching) of the pond was estimated to be Rs. 146689 and the cost per m 3 of stored
water comes to be Rs. 29/m 3 .
boundaries of drainage area for optimum
development of land, water and plant resources to
meet the basic needs of people in a sustained
manner. The main objective of watershed
management is “Proper use of all the available
resources of a watershed for optimum production
with minimum hazards to natural resources”. How
can we, under such constraints, manage to boost
agricultural production in these areas in order to
satisfy the multiplying food demand of our growing
population, whereas, irrigation would certainly be
the best method, it requires much water, which is
scare in arid and semi-arid countries. Water
harvesting may be one of the solutions to overcome
the problem of scarcity of water for irrigation. Water
harvesting in its broadest sense may be defined as
Department of Irrigation & Drainage Engineering, College of Technology
G. B. Pant University of Agriculture & Technology, Pantnagar- 263145, District Udham Singh Nagar (
Uttaranchal)
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