GROUND WATER RESOURCES OF KERALA          [Back] [Home]

Ground Water Recharge      

       The groundwater recharge was computed separately for monsoon and non-monsoon season as given in the methodology.  While calculating the monsoon recharge the normalisation was done as per the guidelines.  The infiltration rates were taken as per the recommended norms and wherever corrections needed, were done considering the field conditions and data availability.  Since the computation was done block wise, the details of the normalization/modification etc were also carried out block wise for greater accuracy. The district wise figures of monsoon and non-monsoon recharge are given in Appendix 1 and in Appendices 2 to 15.
       The recharge computed using the 1997 methodology is found to be less by 1059.48 MCM when compared to that of the 1984 methodology.  Table 4.1. gives a comparison of the same.
 

Table 4.1   Comparison of the recharge figures of 1992 (1984 methodology) and 1999 (1997 methodology)

      The maximum deviation is shown by Idukki (-41.26%) followed by Calicut (-29.55%) and Wayanad (-23.59%) districts.  This is mainly due to the omission of the hilly area where the slope is more than 20%.  All other districts have deviation of less than 20%.  The less recharge by other districts is mainly attributed to the non-inclusion of potential recharge in the 1997 methodology.
       Thus it can be seen that the recharge from rainfall is 5693.6 MCM (both monsoon and non-monsoon seasons) and that of canal and irrigation fields are 1147.20 MCM.  The total recharge thus came to 6840.80 MCM.
       The district wise recharge figures are given in Appendix-1 and block wise monsoon and non-monsoon recharge figures are given in Appendices from 2 to 15.

Net Ground Water Availability  

       The net groundwater availability was calculated as per the norms recommended in the 1997 methodology.  From the block wise figures of recharge 10% was deducted as unaccounted losses and natural discharge if the recharge was computed based on rainfall infiltration method and 5% if the recharge was computed based on water level fluctuation method.  From the block wise figures the district wise figures were computed.  The district wise figures are given in Appendix 1 and the block wise figures are given in the Appendices from 2 to 15.   The net ground water availability of the State is 6229.04 MCM.

Ground Water Draft

       The existing domestic and Industrial groundwater draft were computed as per the methodology and the district wise figures are given in Appendix I and block wise figures in Appendices from 2 to 15.  The existing districtwise gross ground water draft for irrigation is given in Appendix I and table 1 and block wise figures in Appendices from 2 to 15.  In the earlier methodology, the domestic draft was computed separately and deducted from the total recharge to arrive at utilizable recharge.  In the present methodology the domestic draft is also taken along with the other drafts.
        The gross ground water draft for all the uses is computed as 2693.38 MCM for the State.  The domestic and the industrial drafts account for 40.73% of the total draft (1097.36 MCM), the irrigation draft accounts for 59.27% of the total draft (1596.02 MCM).  These figures are given in Appendix 1.
       The block wise figure computed under various category of draft along with the total gross draft is given in Appendices from 2 to 15.

Net Ground Water Availability for Future Irrigation Development  

        The balance ground water available for future irrigation was computed after deducting the gross draft for irrigation and allocation for domestic and industrial water supply for next 25 years from the net annual ground water availability.   A balance of 3221.23 MCM is available for future irrigation development as per the new methodology.  The district wise figures are given in appendix 1 and the block wise figures are given in Appendices from 2 to 15.

 Stage of Development

       The stage of development was computed for each block separately and it indicates that 7 numbers of block show development of more than 100%, 6 show development between 90 and 100%, 6 between 80 and 90% and 12 between 70 and 80%.  The district wise stage of development is given in Appendix 1 and the block wise figures are given in Appendices from 2 to15.

Categorisation of Blocks

       The categorisation of 151 blocks based on development and the long term trend in water level is given in the Appendix-16. The long term water level trends of pre- and post-monsoon were taken to categorise the blocks.  Following is the list of over-exploited, critical and semi-critical blocks of the State (Table 4.6.1).  The remaining 136 blocks are falling under safe category.

Table 4.6.1      Details of over-exploited, critical and semi-critical blocks

                            Over exploited (3 Nos)

•    Chirayinkil                    :           Trivandrum district

•    Kasaragod                   :           Kasaragod district

•    Kodungallur                 :           Trichur district

                               Critical (6 Nos)

•         Tallicherry                    :           Cannanore district

•         Parassala                    :           Trivandrum district

•         Athiyannur                    :           Trivandrum district

•         Mukhathala                  :           Kollam district

•         Anchalumoodu            :           Kollam district

•          Balusseri                     :          Calicut district

                                Semi- critical (6 Nos)

•        Pampakuda                :           Ernakulam district

•        Paraur                          :           Ernakulam district

•        Mulanthuruthi              :           Ernakulam district

•         Mala                             :           Trichur district

•         Calicut                         :           Calicut district

•         Nemom                       :           Trivandrum district

Domestic and industrial needs for 2025

       The figures were computed for each block. The total projected demand for domestic and industrial needs worked out as 1411.79 MCM.  The district wise data is presented Appendix 1.  The blockwise figures are given in Appendices from 2 to15.

Potential recharge

        The potential recharge was computed for all the blocks underlain by coastal alluvium where the pre-monsoon water level is less than 5.0 m bgl.  The potential recharge computed is 1989.47 MCM.  The details of district wise figures are given in are given in Appendix-17 and the block wise figures for each district are given in Appendices from 17.1 to 17.14.  These figures are not considered for computation of gross recharge.  This can also be considered for computation in order to give a realistic figure of the stage of development of certain blocks, especially over- exploited and critical blocks.

Static ground water resources

       The static ground water resource is computed considering the fluctuation as 20 m.  In the hard rock it is assumed that the potential fractures exist upto 100 mbgl. In the sedimentary basin, the actual thickness of potential zones were computed and average figures were worked out.  This was done block wise.  The brackish water potential also was computed separately for sedimentary areas.  The fresh water static resource is 5576.55 MCM and the brackish water resource is 679.00 MCM. The details of district wise figures are given in Appendix-18 and the block wise figures for each district are given in Appendices 18.1 to 18.14.