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Right to Information Presantation on RTI Act The Act No 22 2005 RTI Directory IGNB


Basic Data/ Information Required for Hydrological Design
  1. General: Brief History of the Project giving salient features related to the Dam & spillway.
  2. Data Required
  • Maps & Plans: Catchment Area Plans Scale 1:50,000 or 1:25,000 showing contour lines
    1. River course & tributaries to be shown with their names
    2. Location of all gauge & discharge sites
    3. Location of water storage structures intercepting the catchment
    4. Location of ordinary & SRRG raingauge stations in & around the vicinity of the catchment of dam site / G.D. site
    5. Location of nearby minor medium and major dams
    I-Flood Studies

    Following basic data are required for flood computation studies.

  • Critical Flood Events: Rain fall & corresponding run off data for three or four flood events with date & time experienced in the catchment.
    1. Hourly gauge /discharge data at the nearest G & D station preferably on the same side of ridge
    2. Corresponding hourly rainfall data of rain gauge station including data & charts of SRRG located in the catchment or in the close vicinity of it
    3. If observed short duration data are not available, then respective sub zone reports published by CWC is to be referred & used
    4. Generalized P.M.P. (Probable Maximum Precipitation) Atlas for those river basins for which CWC have prepared & published
    5. Type of strata of bed and sides of Nalla /River
    6. Other Miscellaneous data like silt load etc.
  • Drawings:
    • L - Section of longest stream in the catchment for computing equivalent slope
    • The suitable cross sections upstream and downstream of proposed dam axis including L- section with observed HFL marked with time & date
    II-Yield Studies

    Following basic data are required for Yield Studies

    • Rainfall Data:
      • Monthly rainfall data for all the rain gauge stations in and around the catchment for minimum 25 years.
    • Run-off Data:
      1. Monthly Runoff Data at the location nearest gauge & discharge sites for maximum available period
      2. Monthly average data of all the water storage structures intercepting the catchment
      3. Monthly volumes of out flows from spillways of intercepting storage structures
      4. Monthly data of storage/spillway in nearby two tanks for comparison of data


  1. Steps For Computation of Yield Based on Observed Discharge Data at G&D Site:
    1. Mark the location of proposed Dam site on G. T. sheet.
    2. Mark the Catchment Area on G.T sheet & measure it by Planimeter or by any other method.
    3. Mark rain gauge stations in and around the catchment & construct "Thiessen's polygon" by drawing perpendicular bisectors to the lines joining rain gauge stations.
    4. Measure effective catchment area of each rain gauge
    5. Calculate influence factor for each rain gauge station

      Effective Catchment Area

      Influence Factor = ----------------------------

      Total Catchment Area

    6. Collect monthly rainfall data (for monsoon period) of the considered rain gauge stations for minimum 25 - 30 years
    7. Arrange rainfall data month wise for monsoon period i.e. from June to October
    8. Compute weighted rainfall by multiplying monthly rainfall with Influence Factor
    9. Compute month wise total weighted rainfall (Pd)) in the catchment.
    10. Select nearby G&D site where discharge data for minimum 25-30 years are available.
    11. Collect runoff data (Rg) at G&D site for the months June to Oct.
    12. Compute month wise total weighted rainfall at G&D site (Pg) by repeating step a to i
    13. Compute month wise linear relation between weighted rainfall (Pg) & Runoff (Rg) at G&D Site by using "Linear regression analysis"

    14. Compute month wise linear relation between observed weighted rainfall at G&D site (Pg) and observed weighted rainfall at dam site (Pd)
      Pd= CPg + D
    15. Compute modified total weighted rainfall at dam site (Pm) using correlation computed in step n for each month
      Pm= CPg + D
    16. Compute runoff at dam site (Rd) using modified total rainfall at dam site (Pm) and correlation computed step n for each month .
      Rd= A Pm + B
    17. Convert runoff (Rd) to volume in cubic unit
      Yield(Y) = Rd * Catchment area
    18. Arrange yield (Y) in descending order
    19. Compute probability of every year from (N+1) years, where N is number of years for which runoff data are available.
    20. Considering yield at 50% dependability, the yield is calculated using formula. {M/(N+1).}x 100




Nodal Officer

Nodal Officer :Vimal Kumar Meena, S. E. (PMU), RWSRP, 5167550  Email :

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