ASSESSMENT OF MORPHOMETRIC CHARACTERISTICS OF SHETRUNJI RIVER BASIN USING REMOTE SENSING AND GIS 1635
Loading...
Files
Date
2012-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
JAU,JUNAGADH
Abstract
The study area i.e. Shetrunji basin falling in the district of Bhavanagar, Amreli
and Junagadh, is a major one among 71 river basins of Saurashtra region of
the Gujarat state, India. The agriculture is the major social, cultural and
economic activity of the people in this basin. The water is the most important
input resource in the agriculture. The major share of monsoon rainfall
concentrated during July and August month. Therefore, the scope for the
natural recharge is very less. The existing surface water resources in the
study basin include three dams (i.e. Khodiyar and Shetrunji on main river and
Munjiasir on its tributaries), and thus present surface water resources are not
enough to meet real water demands of this basin area. The major part of the
rainwater runs away to Gulf of Khambat Sea, hence there is a need of
additional water harvesting structure across existing streams of different
orders. Planning of any surface water resources development needs runoff
characteristics of the basin to decide various kinds of water harvesting
structures. Effective functioning life of such water harvesting structures
depends on the sediment loads, carried by input runoff water. This sediment
load of the runoff water should be inevitably minimized by taking appropriate
soil conservation measures under watershed development plan. Planning any
soil and water conservation requires the complete knowledge and quantified
indicators reflecting true hydrological behaviour of contributory watershed.
Hydrological behaviour of any natural w/atershed or basin depends on its
geomorphological characteristics which need to be assessed and quantified
properly. The determination of the morphometric characteristics of any
watershed requires intensive survey, which is a tedious, difficult and time
consuming activity if done by adopting traditional methods. Present study was
undertaken adopting remote sensing and GIS technology to ease the task
keeping with a view to explain the possibility of below given objectives in
background;
1. To prepare the thematic maps of Shetrunji river basin.
2. To determine the morphometric characteristics of Shetrunji river basin.
3. To estimate the runoff potential.
Using the remotely sensed images of the IRS P6 LISS III and Cartosat
satellites, the maps for the theme of land use/land cover, soil, drainage, slope
and contour were prepared adopting the PCI Geomatica 10.1 software. The
GIS analysis was made for the said themes using the ArcMap V9.2. The
linear parameters like stream order, stream length, bifurcation ratio, stream
length ratio and length of overland flow stream frequency, areal parameters
like stream frequency, drainage density, texture ratio, elongation ratio,
circularity ratio, form factor and compactness coefficient and relief parameters
relief, relative relief,relief ratio, channel slope and ground slope or watershed
average slope were determined using GIS. The daily runoff was determined
using the SOS ON method using daily rainfall data of monsoon months (June-
October) for the year 1961-2010. The time series of monsoon rainfall, runoff
and runoff volume were analysed for the preparation of relevant frequency
curves.
The Shetrunji basin was found as 7^^ order basin. The mean bifurcation ratio
was found as 4.51 for the basin and it varied from 1.8 to 4 for the 17
watersheds which indicated that the geological structures did not amply
disturbed the drainage pattern. The length of overland flow for watersheds of
the basin was found varying from 0.1919 to 0.4419 km. while 0.3132 km for
the basin.
The drainage texture for watersheds of the basin varied from 3.3 to 10.7. For
watershed 5G2B4a. 5G2B4b 5G2B4c and 5G2B6c it was greater than 8
reflecting texture as very fine in nature, while 5G2B5d. 5G2B5c, 5G2B6a.
5G2B6d were moderate in nature. Remaining watersheds remained coarser
in nature while for basin it was found as 19.3 indicating it as fine in nature.
The drainage density of the basin was found as 1.5965 km/km^ while for its 17
watersheds it ranged between 1.14 to 2.60 km/km^, indicating highly
permeable subsoil region, dense vegetation cover and low relief. The
elongation ratio of the watersheds varied from 0.45 to 0.85. The watersheds
5G2B2b, 5G2B2C, 5G2B4a, 5G2B4b, 5G2B4c, 5G2B5b, 5G2B5c, 5G2B6a
and 5G2B2d were more elongated in nature, while remaining one were less
elongated in nature. For the basin as a whole it was 0.6206 indicating less
elongation. Similarly the form factor for basin was found 0.3023 and for basin
watersheds it varied from 0.16 to 0.56. These low values of form factor
indicate the existence of flatter peak flows for longer duration. The circularity
ratios for watersheds were found in the range of 0.37 to 0.77 and 0.3853 for
basin as a whole, which all together reflects elongated shape, low runoff and
high permeability of the subsoil. The compactness coefficient for watersheds
was found in between 1.14 to 1.79 and 1.6106 for basin as a whole. In
general watersheds of study basin had elongated shape showing the fact
there remains enough time for discharge of end runoff or indirectly a sufficient
value of time of concentration to facilitate easy disposal of watershed runoff
yield.
The relief, relative relief and relief ratio for watersheds ranged from 0.095 to
0.445 km, 0.0915 to 0.5399 and 0,00273 to 0.019 and that of for the basin as
0.605 km, 0.1410 and 0.004427 respectively. These values of relief ratios
indicate that the discharge capability of watersheds is very high and
simultaneously the groundwater recharge potential is meagre. The ground
slope and channel slope for different watersheds of study basin were found
varied from 0.00307 km/km to 0.0192 km/km and 0.001549 km/km to 0 01224
km/km; and for the basin 0.004427 km/km and 0.002820 km/km, respectively.
According to severity ranking of each watershed the compound parameters
were estimated by averaging the priorities. The final priority was allotted to the
watersheds according to the values of compound parameters. The value of
compound parameter for all 17 watersheds varied from 6 to 11.50. The
watershed 5G2B5d (compound parameter value 6) receives the highest
III
priority value and so it becomes potential and prioritized candidate for
applying soil conservation measures, in contrast to the other watersheds with
low priorities are subjected to lower degree of erosion. Such kind of
watershed prioritization becomes helpful to overall watershed management
planning. The area weighted runoff depth from the basin at 25%, 50% and
75% dependability was found 332mm, 127mm and 68mm respectively. The
runoff potential of the basin at 75% dependability was found 388MCM which
can bring additional area of 38800 ha under irrigation during winter season if
harvested (assuming 50% storage losses and 50 cm seasonal irrigation
requirement of crop).
The morphometric properties determined for this basin as whole and for each
watershed will be useful for the sound planning of water harvesting and
groundwater recharge projects on watershed base.
IV