Introduction
70% of earth is covered with water, but 1% of fresh water is readily
accessible for human beings. For use of 1 % fresh water, 99% is
available as ground water resource. When the replenishment amount of
groundwater is less than the withdrawal amount, the area will experience
the negative change of groundwater storage termed as Groundwater
depletion. Due to lack of rainfall, different places of Globe are
interacted through scarcity of groundwater. Several regions over the
globe are depending on groundwater resources for usage of agricultural,
industrial and domestic purposes. Groundwater depletion leads to water
scarcity, land subsidence, increment of pumping costs, decrement of
water quality, affecting environment, sea level rise. Groundwater
replenishment depends on aquifer parameters, geology, soil structure,
rainfall and surface water of a particular region. Growth of population
and necessities demands preservation of the groundwater resources, which
necessitates the groundwater storage. Places of Middle East region,
North China, Colorado River basin, Bengal basin, Central valley of
California and plain aquifer are experienced under Groundwater depletion
since last 15 years. Many places of India are also interacted to
deficiency of groundwater. According to Central Ground Water Board
(CGWB), our country consuming 230 billion cubic meters of groundwater
for irrigation, domestic and industrial purposes annually.
North western states (Rajasthan, Punjab and Haryana) are experienced
4.06±1.0 cm/year of groundwater depletion during study period of August
2002 to October 2008 [1]. The main reason of depletion through
evapotranspiration loss is due to high temperatures and hot climatic
conditions. Meerut and Lucknow regions have depletion rates of 2.76 ±
0.87 cm/year and 1.46 ± 0.74 cm/year respectively [2] due to the
urbanization and land use changes. Kandivalasa River sub basin (Andhra
Pradesh) experienced 5.6 MCM of groundwater depletion during 2013-2015
[3]. Depletion rate of groundwater in Tamilnadu during 2002-2012 was
observed to be 21.4km3/year [4]. The depletion
rate of groundwater happening in India majorly affected due to
agriculture. The farmers are depending on groundwater for cultivation in
post monsoon kharif and rabi seasons.
In present days, finding groundwater accessibility is not an easy
process. It is partly due to the difficulties such as less observing
stations, deficiency of insufficient measureable data. Therefore, many
scientists have started researching on remote sensing methods to explore
more about groundwater. Remote sensing has its own advantages and
limitations over the local observed well data. In recent days,
researchers using this type of approach and validating the results with
local monitoring well data results to know how compatible it is. Most of
the studies succeeded to correlate these two methods.
They estimated confining layer depletion, as well as procedures for
approximating confining layer hydraulic conductivity and specific
storage using geologic information [5]. [6] GRACE, Lake
Altimetry, and model soil moisture are included to decrease scaling
factor bias and compare estimated groundwater storage changes in East
Africa. GRACE is applied to determine extract changes in groundwater
storage [7]. Various time series models are applied to forecast
groundwater level in Kashan plain, Iran [8]. They projected
groundwater storage across Alberta river basin, Canada using an
arrangement of GRACE, surface water and GWSAsat data [9]. [10]
They highlighted uncertainties in GWD estimating and importance of
incorporating prior information to refine spatial patterns of GRACE
signals which could be more useful in groundwater resource management.
[11] Long-term groundwater storage variation re-assessed in
Northwest India using an extended record of GRACE time-variable gravity
measurements method. [12] Ability of satellite measurements through
GRACE is evaluated to trace seasonality and trend in groundwater storage
for Bengal Basin of Bangladesh. [13] Soil moisture and snow by GLDAS
is simulated to isolate groundwater storage from GRACE for the
Mississippi River basin. [14] Feasibility of downscaling GRACE
satellite data is investigated for prediction of changes in groundwater
level. [15] Changes in regional groundwater storage in North China
from GRACE satellites data and field data from 2003 to 2010 are
estimated. [16] Monthly changes in total water storage via GRACE
data is appraised across the Middle East.
In the current study, GRACE (as a remote sensing method) and GLDAS is
used to evaluate variations in groundwater storing in the Bankura
district region of West Bengal during for a period of November 2007 to
January 2017.