The Governing Body of the NWDA Society has constituted a Technical Advisory Committee (TAC) of NWDA under the Chairmanship of Chairman, Central Water Commission, for examination and scrutiny of the various technical proposals framed by the Agency. Governing Body of NWDA, during its 48th meeting held on 10.3.2006 has approved inclusion of Engineer-in-Chief, Water Resources Department, Govt. of Chhattisgarh; Chief Engineer, Irrigation Department, Govt. of Uttarakhand; and Engineer- in-Chief, Water Resources Department, Govt. of Jharkhand as Special Invitees in the TAC. Forty two meetings of TAC of NWDA have been held so far.

Compilation of Technical Guidelines Provided by TAC, NWDA

During deliberations in different TAC Meetings of NWDA a number of guidelines on the procedures/practices to be adopted on various important aspects for preparation of Water Balance Reports, Pre-feasibility/Feasibility Reports etc. have been approved from time to time. Date on which various TAC Meetings were held (since inception of NWDA) is given at Annexure-I.

The guidelines provided by various TAC Meetings of NWDA are:

I. Soils, Land Use, Delta and Water Use:

•  The permanent pastures and other grazing land need not be included in the culturable area of the basins / sub-basins and no separate provision would be necessary for irrigating the permanent pastures and other grazing lands (9th TAC).
•  The present practice of obtaining land use data of the basins from the land use statistics collected by the Directorate of Economics and Agriculture Statistics of various states may be continued by the NWDA (9th TAC).
•  Fodder crops should be included in the cropping patterns recommended by the NWDA in the water balance studies (9th TAC).
•  The procedure adopted by the NWDA for arriving at the proposed cropping pattern of major and medium projects may continue (10th TAC).
•  The overall delta for major, medium and minor projects should be computed based on Climatological data of the stations present in or adjacent to the basin/ sub-basin. To work out the delta of minor projects, an irrigation efficiency of 80% and evaporation losses at 10% of the water withdrawals from the storages may be assumed (10th TAC).
• The culturable command area (CCA) need not be projected to 2025 AD and it would be adequate to consider the maximum culturable area of recent years (11th TAC).
•  If the variation in catchment area of any basin/ sub-basin between NWDA and State Govts. figures is within 5% there is no need to revise the figures (12th TAC).
•  The IMD values of Potential Evapotranspiration (PE) published by IMD may be used for computing crop water requirement of future identified major, medium and minor projects (12th TAC).
•  It was agreed that in case of such future projects for which project reports have already been approved by CWC, the cropping pattern as given therein should be considered and for other future projects cropping pattern will be based on the availability of water and carrying capacity of soils (15th TAC)..

•  In case of future studies conveyance efficiency of 65% for major and medium projects and 80% for minor projects will be considered while working out GIR for paddy crops. The studies already completed by NWDA need not be revised in view of insignificant change with the existing and proposed methods (17th TAC).
•  The water requirement may be worked out on the basis of suggested cropping pattern and by the climatological approach as per the present practice (22nd TAC).
•  The practice of providing 20% of Rabi area with 50mm for pre-sowing irrigation in future project would be enough for planning purposes (24th TAC).

II. Computation of Yield

•  The yield studies carried by using the rainfall-runoff correlations taking monsoon months as a whole would be continued by the NWDA at present. Wherever monthly rainfall-runoff correlations are obtained by the NWDA for any sub- basin, multiple correlations should be considered (9th TAC).
•  In  case  where  there  are  no  G&.D  sites  or  the  existing  G&D  sites  cover  only  a small  portion  of  the  catchments,  rainfall-runoff  relationship  obtained  for  the adjoining  hydrometeorologically  similar  basin/  sub-basin  may  be  adopted  (10th TAC).
•  Separate  hydro logical  and  water  balance  studies  would  not  be  necessary  at  the State boundaries for various basins/sub-basins (10th TAC).
•  Regeneration  from  upstream  utilization  of  both  in basin  and  imported  waters should be considered in the assessment of virgin yields (10th TAC).
•  While  presenting  the  requirements  of  projects  present  within  sub-basins  and basins, the allocations indicated by the awards/agreements will be retained in the studies without any change (10th TAC).
•  The  surface  water  yield  need  not  be  worked  out  at  the  state  boundaries.  The existing  procedure  for  deciding  the  best-fit  equations  on  the  basis  of  the minimum standard error of estimate might continue (11th TAC).
•  Hydro logical studies  may be updated after a period of 10  years when additional data will be available (17th TAC).

III. Water Availability

• The  water  balance  study  of  the  NWDA  may  project  water  availability  at  both 75% and 50% dependability. However, the proposed schemes should provide for a 75% success rate (7th TAC).
• The NWDA reports might consider the water resources available in the basin to be the sum of gross monsoon surface water yield and replenishable groundwater potential. For any transfer of surplus water outside the basin, the monsoon flows in the basin will figure in practice (10th TAC).
• The  water  balance  studies  may  be  updated  after  a  period  of  10  years  when additional data become available (17th TAC). Water  availability  upto  the  project  site  to  be  checked  on  the  basis  of  the following

I. Flow   series   are   based   on   observed   data   and   corrected   for   existing utilization.

II.Extended flow series are based on rainfall-runoff correlations for the project site.

III. Extended  flow  series  based  on  rainfall-runoff  correlations  for  the  nearest hydrometeorologically similar watershed.

IV. Prorata Basis

• 50%  and  75%  yield  computed  as  above  may  further  be adjusted  for  the ultimate  utilization  upstream,  exports  and  imports  to  compute  50%  and 75% dependable availability.
• Water  utilization  for  any  project  should  be  restricted  to  a  maximum  of 75%  dependable  availability  in  case  of  diversions. However,  for  storage projects   requirement   may   exceed   75%   dependable   availability   with provisions of carryover storage.
• Suitability of dam site: This aspect may be accepted as per the information provided by the State Governments/Master Plan (22nd TAC).

IV. Groundwater

• The groundwater potential may be left to the states and may not be considered as an  available  resource  for  the  water  balance  studies  being  done  by  NWDA  (7thTAC).
• While the water balance reports  may  deal with the groundwater availability, the existing and projected uses etc. as in the earlier reports, data and findings should be presented state-wise and no attempts should be made to assess or identify any surplus  or  deficit  in  groundwater  availability  in  any  basin.  The  groundwater should be left entirely to the concerned states for use (9th TAC).
• The   NWDA   studies   might   consider   the   groundwater   resources   potential estimated  by  the  CGWB  as  per  the  recommendations  of  the  Groundwater Estimation  Committee,  1984,  wherever  no  specific  study  or  findings  were available  on  the  extractable  groundwater  in  any  basin.  No  corrections  will  be made  for  base  flow  since  the  CGWB  have  already  incorporated  necessary corrections in base flow in the groundwater assessment made by them (9th TAC).
• Efforts  should  be  made  by  the  NWDA  to  prepare  groundwater  maps  for  the basins/sub-basins depending upon the availability of data (10th TAC).
• The  NWDA  studies  may  consider  the  gross  groundwater  potential  of  the  basin/ sub-basin assessed from the statistics supplied by the CGWB/State Groundwater Boards  (SGWB)  and  subtract  the  domestic  and  industrial  uses  estimated  by  the NWDA  to  be  met  from  groundwater  resources  for  obtaining  the  groundwater potential available for irrigation use (10th TAC).
• The  present  practice  of  computing  the  groundwater  potential  from  Tehsil wise/ districtwise    statistics    on    the    groundwater    potential    supplied    by    the CGWB/SGWB will continue. Results of any special studies in respect of basins/ sub-basins are also available, the same should be considered by the NWDA (10th TAC).
• The NWDA reports might consider the water resources available in the basin to be the sum of gross monsoon surface water yield and replenishable groundwater potential. For any transfer of surplus water outside the basin, the monsoon flows in the basin will figure in practice (10th TAC).
• The  groundwater  should  be  continued  to  be  indicated  as  separate  statewise resource.  The  water  resources  available  for  estimating  surplus/deficit  of  any basin/ sub-basin should be taken only as the monsoon and non-monsoon surface flows.  For  such  estimation  the  awards  made  by  various  tribunals  for  concerned basins should also be kept in view (11th TAC).
• Water balance studies of deficit sub-basins/basins should be reviewed by NWDA to account for groundwater potential (15th TAC).
• It was agreed to indicate groundwater as a separate resource (16th TAC).
• In   view   of   difficulties   to   assess   and   quantify   the groundwater   annual replenishment etc.  TAC took a decision not to consider groundwater in the water balance  studies  of  NWDA.    Therefore,  NWDA  should  continue  the  existing practice  of  considering  surface  water  resource  only  while  estimating  water balance in their studies(32nd TAC).

V. Water Requirements

Domestic and industrial water requirement

• The NWDA studies would consider consumptive use of domestic and industrial uses  as  20%  and  2.5%  respectively  of  the  surface  water  diverted  or  lifted  from the rivers, reservoirs, storages, canals etc. (7th TAC).
• The  per  Capita  consumption  for  rural  and  urban  population  may  be  assumed  as     70 lts. and 200 lts. respectively, which are based on the recommendations of the Ministry of Works and Housing (10th TAC).
• The 50% of the rural water requirement and entire livestock water requirement is proposed  to  be  met  from  groundwater  sources.  The  urban  water  requirement  in full  and  50%  of  the  rural  water  requirement  is  to  be  met  from  surface  water sources (11th TAC).
• Entire  industrial  water  requirement  is  to  be  met  from  surface  water  sources       (11th TAC).
• The  per  Capita  water  requirements  @  200  lts.  and  70  lts.  for  urban  and  rural population adopted in the NWDA studies may be continued for the present, as it made  better  impact  on  the  overall  water  availability  with  80%  of  the  water returning back to the system (15th TAC).
• In order to update the water balance studies it was decided that while revising the studies population projections (which are presently upto 2025 AD) may be made upto 2050 AD (22nd TAC).

VI. Salinity Control

• It  was  decided  as  per  the  clarifications  of  NWDA  to  Kerala  Govt.  that  a  lump sum  provision  of  10%  of  the  75%  dependable  yield  will  be  earmarked  for salinity control tentatively pending detailed studies in this area (14th TAC).

Water releases in the river for environment and ecology

• Regarding   how   much   quantity   of   water   to   be   released   in   the   river   for environment and ecology, it was decided that this issue may be finalized through an expert committee or by the Ministry of Environment and Forest (17th TAC).
• After meeting downstream requirements a minimum lean season flow of 10% of the  inflow  at  diversion  structures  should  be  maintained  for  environmental  and ecological  purposes  with  storages.  This  could  be  of  the  order  of  10%  of  the average lean season natural flow downstream of the storage (23rd TAC).

VII. Annual Irrigation

• The intensity of irrigation in the case of existing and ongoing projects will be as per  the  present  use.  Under  Peninsular  river  development  component  for  the future projects, the intensity may be assumed as 150% for major projects, 125% for  medium  projects  and  100%  for  minor  projects.  The  studies  should  also consider  possibility  of  augmentation  in  the  existing  storages  to  increase  the present intensity of irrigation, wherever this is less than the percentages indicated above for the future projects (7th TAC).
• Any surplus surface water for transfer should be assessed only after considering the water needs of the basin for extending irrigation to 60% of net culturable area    (10th TAC).

VIII.   Area to be Brought under Irrigation by 2025 AD

• In  water  deficit  areas,  the  first  attempt  should  be  to  cover  at  least  30%  of  the culturable area of the basin/ sub-basin by irrigation from surface water (9th TAC)
• In  case  of  deficit  basins/sub-basins,  where  the  percentage  of  existing  irrigation from  surface  water  is  around  30%  of  the  culturable area,  the  NWDA  may consider  extending  irrigation  facilities  to  60%  of the  culturable  area  and  the additional  area  to  be  brought  under  irrigation  would  be  for  a  single  dry  crop without  considering  any  high  water  consuming  crop  like  sugarcane  and  paddy (9th TAC).
• Extension  of  irrigation  from  30%  to  60%  of the  culturable  area  in  the  deficit areas  by  way  of  transfer  from  other  basins  should  also  stand  the  scrutiny  of economic criteria (9th TAC).
• Before  diversion  of  water,  bringing  irrigation  level  of  at least  60%  of  the culturable  area  as  annual  irrigation  as  being  followed  in  the  NWDA  studies  as decided by the TAC earlier was in order (18th TAC).
• The  command  area  of  each  proposed  project  may  be  examined  with  regard  to availability  of  culturable  area  overlap  with  other projects  etc.  at  the  time  of updating the water balance studies (22nd TAC).

IX.     Irrigation Water Requirement

• The  water  requirement  for  irrigation  should  be  worked  out  on  climatological approach and reasonable provisions made for the field and transmission losses as well as evaporation from the storages (7th TAC).
• The  NWDA  should  prepare  a  brief  note  on  the  losses in  irrigation  canals,  both lined  and  unlined  and  circulate  the  same  among  the members  of  the  TAC  for further consideration. The NWDA may meanwhile, continue to adopt a figure of 60% for irrigation efficiency for the water balance studies in respect of major &, medium projects (9th TAC).
• The evaporation losses may be based on the available data for the existing major and  medium  reservoirs  in  and  around  the  basin.  It  was  also  decided  that  any figure   for   evaporation   losses   which   is   accepted   in Tribunal   Awards   or agreements  between  the  states  may  be  taken  for  the NWDA  studies  for  the concerned basin/ sub-basin (9th TAC).
• It was decided to adopt 20% of the withdrawals from the reservoir as evaporation losses  in  the  absence  of  actual  data.  TAC  recommended  same  figure  for  minor schemes also (11th TAC).
• The NWDA  might adopt an irrigation efficiency  of 55% for  major  and  medium irrigation  projects  with  a  regeneration  value  of  10%  and  an  irrigation  efficiency of 70% for minor projects without considering any regeneration (11th TAC).

X.       Regeneration

• In  the  water  balance  studies  carried  out  by  the  NWDA,  a  value  of  10%  for regeneration from utilization by all major, medium and minor projects should be adopted (7th TAC).
• In  the  case  of  Krishna,  Godavari  and  other  basins, where  Tribunal  Awards  are available,  the  estimated  regeneration  to  the  stream  for  irrigation,  domestic, industrial  and  other  uses  for  the  NWDA  studies  might  be  as  specified  in  the Award.  In  the  case  of  other  basins/sub-basins,  the estimated  regeneration  in  the NWDA studies might be at the rate of 10% of the irrigation use from surface and groundwater and 80% from both of the domestic and industrial uses from surface water resources.  No regeneration would be assumed for domestic and industrial uses from groundwater resources (9th TAC).
• Regeneration  would  be  considered  as  (i)  10%  of  the net  water  utilization  for irrigation  from  all  the  existing,  ongoing  and  future  major  and  medium  projects including those from imported water and (ii) 80% of the domestic and industrial water  use  met  from  surface  water  resources  and  that  no  regeneration  would  be considered  from  minor  irrigation  schemes  and  domestic  and  industrial  use  met from groundwater (11th TAC).
• So  far  as  NWDA  studies  are  concerned,  regeneration at  the  rate  of  18%  of  net utilization  should  be  considered  in  respect  of  existing  projects  and  10%  for ongoing  and  proposed  major  and  medium  projects  in  sub-basins  of  Cauvery basin         (15th TAC).

XI.      Special Technical Points related to Himalayan Component Studies

• Intensity of irrigation:

Considering  availability  of  considerable  groundwater  potential  in  the  basins  of the  Himalayan  rivers,  it  was  decided  that  the  areas  where  existing  irrigation intensity  is  less  than  100%,  the  same  maybe  increased  to  level  of  l00%  from surface  water.  Wherever,  the  existing  intensity  of irrigation  is  more  than  100% the  intensity  can  remain  at  the  same  level.  Additional  intensifications  over  and above  those  indicated  above  may  be  carried  out  by  using  groundwater  to encourage  conjunctive  use  and  to  avoid  the  problems  of  water  logging  and salinity (20th TAC).

• Irrigation in the en-route areas:

The  areas  en-route  of  the  link  canals  not  covered  by  any  other  irrigation  scheme may be provided with irrigation to the extent of 100% intensity from the surface water and any additional irrigation by groundwater (20th TAC).

• Irrigation in the target areas:

The target area should be covered by extensive irrigation and an intensity of not more than 100% should be provided from the transferred water (20th TAC).

• Water requirements downstream of diversion points:

While  carrying  out  water  balance  studies  at  the  point,  where  diversions  are contemplated, the water requirements will also include the committed utilization and additional requirements of downstream areas, which cannot be met from the water available downstream (20th TAC).

• Seasonal water balance:

Water balance study  at diversion points where reservoir is contemplated will  be carried  out  on  annual  basis  as  most  of  the  flows  can  be  considered  to  be regulated.  However,  at  diversion  point  where  reservoirs  are  not  contemplated, water balance study will be carried out on a seasonal basis (20th TAC).

XII. Optimum Lifting of Water for Inter Basin Water Transfer Links

• It was decided to continue to retain 120 m lift as maximum for planning links, as at present, till more information or report of any special studies is available to the TAC of NWDA  (25th TAC).

XIII    Guidelines regarding the extent of Surveys and Investigations Necessary for Preparation of Feasibility Report

• Inter-State links

The  guidelines  as  prepared  by  NWDA  regarding  the  extent  of  Surveys  and Investigations  necessary  for  preparation  of  Feasibility  Report  accepted  by  the TAC (25th TAC).

• Intra-State link proposals

Regarding  technical  guidelines  for  preparation  of  PFR/FR  of  Intra-State  links, Director  General,  NWDA  proposed  to  follow  same  technical  guidelines  as adopted  for  surveys  and  investigations  for  preparation  of  feasibility  report  of Inter basin water transfer proposal prepared and got approved from TAC in 1996.   TAC agreed to use these guide lines for preparation of Feasibility Report of Intra State link proposals also (37th TAC).