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Baswa-Bandiqui, Dausa District, Rajasthan
Groundwater studies
In this area, groundwater occurs under unconfined to confined conditions:
in the sand and gravel layers overlying the hard rocks in the Quaternary Alluvium,
in the weathered zones, and
in the underlying fractured zones in the hard rocks.
The sand layers in the alluvium are the main water bearing formations. The topographic features and physical characteristics of the rock formations underlying the alluvium control the occurrence of groundwater.
The average yield of wells, fitted with pump sets, in the alluvium varies from 60,000 to 75,000 litres per day whereas the average rate of discharge of tube wells varies from 13 to 15 m3 / hour. In hard rock areas of the watershed, average yield of wells, fitted with pump sets varies from 35,000 to 45,000 litres per day and average discharge of bore wells is 10 m3 / hour.
Figure 4.12: Hydrogeological map of Baswa – Bandkui watershed, Dausa District.
Water level
As a part of the Aquifer Mapping studies in this Pilot Area, 35 observation wells are established for monitoring of ground water levels on a monthly basis. In general groundwater level monitoring is carried out by CGWB and the State agencies. Locations of monitoring stations are shown below.
Water level data for the period 2001-2011 show that:
The depth to water in the alluvium varies from 9.45 m bgl (Gol village in Lalsot Block) to 47.60 m bgl (Morodi village in Bandikui Block).
In hard rocks, it varies from 8.30 m bgl (Nabhewala village in Dausa Block) to 43.60 m bgl (Baswa village in Bandikui Block).
Water level variation, as observed at Bandikui, is presented in the following hydrograph. Fall of water level by more than 12 m in a span of 10 years is noticed at Bandikui.
Figure 4.13:
The trend of ground water levels in different aquifers of younger alluvium, older alluvium and quartzites are presented in the following hydrographs.
Figure 4.14: Pre and post monsoon trends in Younger Alluvium.
Figure 4.15: Pre and post monsoon trends in Older Alluvium.
Figure 4.16: Pre and post monsoon trends in Quartzites.
Figure 4.17: Pre and post monsoon trends in Gneisses.
The general gradient of water table is from northwest to southeast direction.
Figure 4.18: Location map of monitoring stations.
Figure 4.19: Ground Water Table - Feb. 2013
Figure 4.20: Monthly ground water level monitoring in Baswa – Bandikui Pilot study area, Rajasthan.
Geophysical studies
Vertical electrical soundings (VES) have been carried out in some parts of the watershed to estimate the alluvium thickness and identify the aquifers. The locations of VES are shown below.
Resistivity values for some of the VES indicate saturation at depths, which, depending on the groundwater level, can be considered as an aquifer.
Figure 4.21: Vertical Electrical Sounding in the Baswa – Bandikui watershed, Rajasthan.
Figure 4.22: Location map of VES.
The cross-sections, along two directions in the watershed, showing different resistivity layers based on vertical electrical soundings, are presented.
Figure 4.23: Geo-elecrical sections in X-Y and X-Z directions in the Baswa – Bandikui watershed.
Figure 4.24: Geo-electrical section in X – Y direction
Figure 4.25: Geo-electrical section in X – Z direction
CGWB has drilled 39 boreholes in Banganga basin, of which 10 are in and close to the study area.
In the alluvium, the average yield of shallow wells varies from 2.5 m3/hr to 3.1 m3/hr whereas the average yield of deep tubewells varies from 13 to 15 m3/hr. The transmissivity of alluvial aquifers ranges from 200 to 500 m2/day. At some places the transmissivity is found to be low due to a lack of adequate granular thickness. At places, the bottom part of the alluvium immediately overlying the bed rock forms a highly productive aquifer and wells tapping this aquifer yield over 50 m3/hr.
In hard rocks, the average yield of shallow wells varies from 1.5 m3/hr to 1.9 m3/hr and the average yield of deep bore wells is 10 m3/hr. Towards west in Jaipur district, the yield from fissured aquifers in the hard rocks ranges from 3.6 to 43 m3/hr.
Figure 4.26: Location of exploratory wells and piezometers.
Groundwater quality
The area suffers from fluoride contamination and salinity at places.
Water samples collected from piezometers show that:
EC ranges between 790 and 7950 micro Siemens/cm
TDS ranges from 399 to 4573 ppm
Chloride ranges from 64 to 2864 ppm
Fluoride ranges from 0.5 to 2.24 ppm
For EC, TDS and Chloride, the highest values are observed only in one SGWD piezometer located at Rampura in Bandikui block.
Fluoride concentration over the permissible limit was found in SGWD piezometers at Pichupara, Bandikui Jagir, and Badiyal Kalan in Bandikui block.
Groundwater resources
The aquifer system is classified into several ground water potential zones based on the average discharge and water level conditions for the purpose of ground water resource assessment. The broader classification is Younger Alluvium (A), Older Alluvium, Quartzite and Gness. The dynamic ground water resources of each of these zones have been estimated jointly be Central Ground Water Board and Rajasthan State Ground Water Board for the year 2009.
It is estimated that there is a net annual ground water availability of 40 million cubic metres (MCM) in the Bandikui block and the annual ground water draft is 60 MCM. The stage of ground water development is 173% and the area is categorised as Over-Exploited. Due to this over exploitation of ground water resources, the ground water levels are declining continuously (by more than 4 m from 1998 to 2008) both in pre-monsoon as well as in post-monsoon seasons.
Ground water resource and its stage of development in different aquifer systems of the watershed show a variation with higher potential in older alluvium and least in gneisses. The state of ground water development is maximum (235%) in phyllites in the western part of the watershed.
Figure 4.27: Ground water resources in different aquifer zones.