197 Chapter 8 Subsurface Water Conditions 8.1 Justification of the Study Seasonality of rainfall is the major character of Indian monsoon. So, it is considered as the barrier against multi cropping all through the years. But to meet the need of the growing demand of the crops, multi cropping practices in the limited land resources is necessary. Analysis of subsurface water condition may create proper database regarding ground water availability, water yield capacity, trend of ground water status, spatial pattern, potentiality for ground water use etc. In the extreme upper and lower catchments of Kuya river basin, where, there is no provision of canal water irrigation, for non monsoon agriculture, people have to depend on the ground water. In this context, this chapter is relevant. 8.2 Ground Water Table Lowering Dynamics 8.2.1 Long Term Dynamics Satyakam Sen in his article “The Importance of Drainage in Agriculture of West Bengal” reportedly mapped the water table as per the survey of May, 1965 and shown that average water table depth was 6.09 m. at Kandi block which is at the confluence stream of Kuya river. But, on May, 2011, average water table depth is about 14 m. So, the rate of water level lowering is about 18cm. per year which is Major Themes: 8.1 Justification of the Study 8.2 Ground Water Table Lowering Dynamics 8.3 Spatio-temporal Water Yield Dynamics 8.4 Relation Between Ground Water Table (GWT) and Ground Water Yield (GWY) in the Lower Catchment 8.5 Methods for Ground Water Estimation 8.6 Topographical Control on Ground Water Level
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197
Chapter 8
Subsurface Water Conditions
8.1 Justification of the Study
Seasonality of rainfall is the major character of Indian monsoon. So, it is considered
as the barrier against multi cropping all through the years. But to meet the need of the
growing demand of the crops, multi cropping practices in the limited land resources is
necessary. Analysis of subsurface water condition may create proper database
regarding ground water availability, water yield capacity, trend of ground water
status, spatial pattern, potentiality for ground water use etc. In the extreme upper and
lower catchments of Kuya river basin, where, there is no provision of canal water
irrigation, for non monsoon agriculture, people have to depend on the ground water.
In this context, this chapter is relevant.
8.2 Ground Water Table Lowering Dynamics
8.2.1 Long Term Dynamics
Satyakam Sen in his article “The Importance of Drainage in Agriculture of
West Bengal” reportedly mapped the water table as per the survey of May, 1965 and
shown that average water table depth was 6.09 m. at Kandi block which is at the
confluence stream of Kuya river. But, on May, 2011, average water table depth is
about 14 m. So, the rate of water level lowering is about 18cm. per year which is
Major Themes:
8.1 Justification of the Study 8.2 Ground Water Table Lowering Dynamics 8.3 Spatio-temporal Water Yield Dynamics 8.4 Relation Between Ground Water Table (GWT) and Ground Water Yield (GWY) in the Lower Catchment
8.5 Methods for Ground Water Estimation
8.6 Topographical Control on Ground Water Level
198
threateningly high. Similarly, water level was very near to surface (within 2 m.)
during monsoon, but at present water level has lowered down to about 6.5 m. on the
said period (As per the records of SWID and Pal, 2010).
8.2.2 Seasonal Dynamics
The table (Table 8.1) describes the block wise variation of ground water level during
monsoon and pre-monsoon periods for 1990 and 2011.
Water table depth has rapidly declined since 1990 to 2011. Growing water lifting
from underground storage is largely responsible for such steady water lowering rate.
Table 8.1: Average Ground Water Level in Different Periods (Below Ground
Level or bgl.); value in m. Block 1990 2011 Change of GWL
Since 1990-2011 Yearly Rate of GWL
Lowering Ground Water Level (bgl, m.)
Ground Water Level (bgl, m.)
Sept May Sept May Sept May Sept May Kundhit 2.05 3.2 4.8 6.2 -2.75 -3 -0.14474 -0.15789 Suri II 2.17 3.3 5.1 6.37 -2.93 -3.07 -0.15421 -0.16158 Rajnagar 3.15 7.11 4.5 7.35 -1.35 -0.24 -0.07105 -0.01263 Khayrasole