International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August-01 September 2012, Melbourne, Australia
347
ing part is built-up land both industrial and residential. Change
detection analysis carried out in 3km buffer zone around Bandi
river indicated areas of impact on land use/ cover particularly,
agriculture activity - cropped area has reduced around 23.58%
and increase in fallow land. Increase in wasteland -salt affected
land & waterbodies by 3.86 & 3.08%, respectively. Normal
ised difference vegetation index found to have negative corre
lation with pollution level.
Hydrogeological Map: The hydrogeological conditions of the
terrain are depicted by the ground water potential maps, pre
pared by Ground Water Department, Pali. Well locations are
plotted as GIS layer for depicting zoning pattern of water level
and water quality. Rhyolite, granite, younger alluvium, older
alluvium and phyllites form the major aquifer in this area.
Borelog data have been analysed, isopach map (joining of
similar lithologial unit) generated to get the thickness and
multi-log 3D lithological model generated for input to hydro-
geological boundaries in modelling. Aquifer cross section
showing water column thickness along with strip log of bore
wells indicating lithological horizons is shown in Figure-2.
Figure-2 Cross section of aquifer along river Bandi
Pollution monitoring : The pollution of ground water is a
slow but intrinsic process and it may take years together and
lot of efforts to regain the natural quality of the ground water,
with analysis of existing data the variation in the spatial layer
and database preparation of water quality and depth of well
along the polluted river. Water quality zoning for selected pa
rameters of polluted water is done using data often wells.
2.2.2 Ground water modelling
Conceptual model: A conceptual model was developed based
on the analysis of available data (litholog, GW levels, hydro
geomorphology, aquifer material). A multilayered structure
based on hydrological properties was conceptualised defin
ing the model geometry. Initial hydrological properties viz.
three dimensional hydraulic conductivity, transmissivity, stor
age property (specific yield) were estimated along with time
series rainfall, well level data. The boundary condition estab
lishment helped in confining the model domain. DEM as upper
layer and Surface generated by litholog data, minimum and
maximum water levels & maximum depth of well log formed
the structure. Towards flow boundary, eastern boundary has
crystalline rock (Rhyolite). North and South are having
streams. Bandi river flow is modelled as river. General head
boundary condition towards Eastern part signifies dam. Trans
port boundary condition in the form of rainfall recharge zones
generated using land use, slope and vegetal cover into consid
eration.
Numerical modelling (Flow model): Both steady state and
transient model run for the period of 10 years (1995-2005),
five years water level data used for calibration and rest for va
lidity, prediction were carried out till 2010. Steady state flow
occurs when the magnitude and direction of flow is constant
with time throughout the entire domain. Conversely, transient
flow occurs when the magnitude and direction of the flow
changes with time. This is precursor to migration study. Dur
ing calibration run higher calculated values are shown above
equal calculated & observed line in the 95 confidence range for
layer one (wells shown in red symbols) indicates model is over
predicting.
Figure-3 Comparison of calculated and observed well head
Contamination migration: General migration pathways
commonly used in investigating conceptual aquifer model are
the floaters (immiscible contaminants), mixers (contaminants
with uniform dissolution and movement in the aquifer), and
sinkers (contaminants that move vertically due to density
makeup). Copper and other heavy metals which are essential
nutrient to plant & animal can be toxic at higher concentration.
Initial concentration of contaminant assigned in GW modelling
software. Advective flow model uses particle tracking based
Eulerian-lagrangian method and explicit finite-difference
method for dispersion.
Fundamental difficulty in advection-dispersion modelling is
both co-exist in transportation governing equations. While the
miscible contaminant is transported at the same rate as that of
ground water hydrodynamic dispersion is also governed by
sorption property and concentration gradient of contaminant.
Substantial part (sinkers) of the contaminant is likely to perco
late down was also evident during the field visits.
Pump test & resistivity for aquifer parameters:
Pumping test is performed to estimate specific aquifer proper
ties and resistivity survey carried out to get the local clay en
riched zone with reduced hydraulic conductivity.
Surface geophysical method is most suitable for depth wise
scanning of subsurface as input to distributed numerical
model. Resistivity profiling is done to know the depth of
weathered zone granite/rhyolite and slate/phyllite terrain.