MAPPING OF GROUNDWATER RECHARGE POTENTIAL ZONES OF OZAT RIVER BASIN 3427
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Date
2021-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
JAU,JUNAGADH
Abstract
The Ozat river basin is located in the southern Saurashtra region of Gujarat,
India. The Ozat river basin covers an area of 3176.24 km2
and flows radially through
the plains for 127.97 kilometres to run into the Arabian Sea. Since the area falls under
semi-arid climatic conditions, there is a need to construct more groundwater recharge
structures to augment the groundwater recharge. Hence, in this study, an attempt has
been made to demarcate the groundwater recharge potential zones, propose suitable
groundwater recharge structures (check dams, farm ponds, open wells, and tube wells)
as wells as soil conservation structures (vegetative barrier & tree plantation, contour
trench & staggered trench, and gully plug & gabion structure), and estimate the project
cost in specific areas. Remote sensing and Geographical Information System were used
to identify the groundwater recharge potential zones considering parameters such as
Geology, Geomorphology, Lineament Density, Drainage Density, Soil, Rainfall, Slope,
Land use/ land cover. Suitable weights to the thematic layers and their features were
assigned and normalized by the use of the Analytical Hierarchy Process. All the
thematic layers were integrated into the ArcGIS environment using the weighted
overlay method. The groundwater recharge potential zones were classified into 5
different zones of 'Excellent' (220.14 km2
, 6.93%), 'Good' (2094.81km2
, 65.95%),
'Moderate' (430.05 km2
, 13.54%), 'Poor' (430.81 km2
, 13.57%), and 'Very Poor' (0.36
km2
, 0.01%) based on their recharge potential. The SCS-CN technique was used to
estimate the rainfall-runoff potential. The weighted average rainfall and runoff of the
Ozat river basin were observed to be 835.08 mm and 383.80 mm respectively. The total
runoff of the Ozat river basin was estimated to be 1219.03 MCM. Natural groundwater
ii
recharge from precipitation was estimated using an empirical equation suitable for the
Saurashtra region and representing 204.53 MCM. The total groundwater recharge and
project cost were estimated against the various density of structures. After conducting
probability analysis, it is suggested to construct the groundwater recharge structures at
the density 61.72%, 49.24%, and 20.87% for the 60%, 75% and 90%. At 60%
probability of exceedance, 61.72% of structure density is suggested to recharge the
runoff volume of 764.72 MCM, it’s estimated project cost is Rs. 653.86 crores. In the
case of 75% probability of exceedance, 49.24% of the structure density is proposed to
recharge the runoff volume of 610.18 MCM, it’s estimated project cost is Rs. 521.73
crores. While in the case of 90% probability of exceedance, 20.87% of the structure
density is proposed to recharge the runoff volume of 258.54 MCM, it’s estimated
project cost is Rs. 221.06 crore