IMPACT OF CLIMATE CHANGE ON GROUNDWATER RECHARGE IN SHETRUNJI BASIN 1696
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Date
2012-10
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JAU,JUNAGADH
Abstract
The global warming has changed the climate worldwide. However, the nature
and magnitude of the climate change vary in space and time. Its impacts also vary in
space as well as time. The climate change will have different impacts in different
places on rainfall amount, its intensity, frequency, rainy days, evapo-transpiration
etc. These rainfall characteristics and evapo-transpiration ultimately impact on runoff
and groundwater recharge also. Therefore, the location specific studies on basin
scale are required to assess the impact of climate change on rainfall, runoff and
groundwater recharge.
The study was undertaken for Shetrunji river basin having an area of 5646.98 km^.
Satellite images of IRS P6 of sensor LISS IV and Awifs digital data and GIS software
namely PCI Geomatica V10.1 and ESRI ArcMap were used. The daily minimum and
maximum temperature records (1973-2009) were collected from the Agricultural
Research Station, JAU, Amreli. The daily rainfall data records (1961-2010) were
collected from State Water Data Centre, Gandhinagar and the daily runoff data from
Irrigation Department, Junagadh. The climatic data records (1965-2010) required for
the estimation of daily reference evapo- transpiration was collected from the JAU
Agro meteorological Observatory. The water table data records (1985-2010) before
and after monsoon for the different gauge stations of the study area with aquifer
properties were collected from the Central Groundwater Board, Ahmedabad.
The daily maximum and minimum temperature data were used to generate the time
series of monthly, seasonal and annual average of daily maximum, minimum and
mean temperature. The runoff was estimated using the SCS curve number
I
technique for each watershed of the basin and the area weightage method was used
to estimate the runoff depth for the basin. The crop water evapotranspiration from
different crops was estimated by Penman-Monteinth method as per FAO-56 (Allen et
aL, 1998) method. The evaporation from bare soil was estimated by Russel (1989)
method. The groundwater recharge estimated by different methods like water
balance, Krishna Rao (1970) and water table fluctuation were compared. The
groundwater recharge depth for the entire basin was obtained by area weightage
method. The trend analysis for all the time series was carried out by Mann-Kendall,
Sen's slope and best fit trend line method.
The significant trend in monthly average of daily maximum temperature could not be
found during any month except March in a year while that of daily minimum
temperature indicated increasing trend in 4 month in a year viz. February, March,
May, June whereas significantly decreasing trend in November month. The monthly
average of daily mean temperature indicated increasing trend in 3 month in a year
viz. February, March, April while significantly decreasing trend in November month.
The seasonal average of daily maximum and minimum temperature showed
increasing trend during summer. The seasonal average of daily mean temperature
showed significant increasing trend during monsoon and summer. The significant
increasing trend in annual average of daily maximum, minimum and mean
temperature was observed. The annual extreme maximum and minimum
temperature showed no trend.
The climate change impacts on rainfall favors to increase the rainfall significantly in 6
out of 17 watersheds while the runoff is found increasing in 5 out of 17 watersheds of
the basin. The rainfall and runoff in Shetrunji basin is found increasing at the rate
45.85 and 17.7 mm per decade respectively. The groundwater recharge estimated
by water balance method was found higher as compared to Krishna Rao (1970) and
water table fluctuation method. The groundwater recharge estimated by water
balance, Krishna Rao (1970) and water table fluctuation methods is found increasing
in 13, 9 and 6 watersheds out of 17 watershed of the basin. The groundwater
recharge in the basin during monsoon is found increasing at the rate of 36.47 mm,
8.86 mm. and 13.01 mm per decade by water balance, Krishna Rao (1970) and
water table fluctuation methods respectively due to climate change impacts.
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Keywords
Soil and Water Engineering