Accepted Papers - 3.pdf - UNESCO

Table 1. Present land use of watershed.
Area under Area under Area not available
Forest (%) cultivation (%) for agricultural
use (Roads,
habitation and
waste land) (%)
34.7 62.37 2.93
The information on crops being grown in
the watershed was collected by interviewing farmers
of the catchment area and from the revenue records.
Maize, sorghum and black-gram were the commonly
grown crops in kharif season, whereas, in rabi
season, wheat, barley, gram and mustard were the
commonly grown crops.
Probability Analysis of Rainfall
The daily rainfall data of 14 years, of the
watershed area under study, were collected from the
agro-meteorological observatory, Ranichauri. The
collected rainfall data were analyzed for probability
distribution at different levels, using the technique
proposed by Weibull (1939).
Surface Runoff and Irrigation Water
Requirement
The surface runoff from the watershed area
and irrigation water requirement were estimated by
SCS Curve Number Method and CROPWAT
software, respectively. Crop evapo-transpiration and
effective rainfall were also determined by using the
CROPWAT software. The whole year was divided
into four periods i.e. mid-June to mid-September,
mid-September to December, January to March and
April to mid June. The first and third periods are
surplus ones while second (autumn) and fourth
(summer) are the deficit ones. Thus, the irrigation
is required mainly during autumn and summer,
except in abnormal years when irrigation may be
required due to prolonged dry spell during surplus
period.
Water Harvesting System
Due to wide variability in terrain and
topography in hilly region, a single design cannot
serve the purpose and harvesting water efficiently.
Keeping this in view, following two types of
irrigation systems were designed to suit different
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topographic conditions :
i. irrigation system based on runoff recycling; and
ii. irrigation system based on very low discharge
springs and streams (1 to 10 lpm).
i) Irrigation System Based on Runoff
Recycling
The design criteria of runoff recycling based
irrigation system includes size of tanks and
catchment command area ratio (n). The final size
of tank can be determined as follows :
VT = IA * A + Losses
...(1)
Subjected to
RW * N * A > IS*
A + losses
where
V = capacity of tank (liter);
T
I = gross irrigation requirement during summer
S
crop (April to mid June) (mm);
A = command area (m2 );
R = runoff during winter surplus season;
W
N = catchment command ratio; and
I = gross irrigation requirement during autumn
A
...(2) crop.
It is assumed that the tank will be full after
monsoon, and the water needed during summer will
be met by runoff during winter.
Model development for optimal pond design :
The pond is considered as partially
excavated and partially embankment type. Thus is
mainly to avoid unnecessary disposal of spoil and
transporting extra earth from borrow pits. Therefore,
the volume of excavation is considered to be equal
to the volume of embankment to design
economically. This was considered as one constraint
for the optimization model. The geometrical
formulae used for determination of design
components were derived based on principle of solid
geometry.
The classical optimization model, using
Lagrange multiplier, was used to obtain the optimal
design of pond. The objective function of the model
is to maximize, the storage capacity of pond subject
to the constraints that the volume of earthwork is
equal to volume of embankment. Mathematically,