TECHNICAL SESSION : WATER AVAILABILTY AND ISSUES IN DEVELOPMENT OF HYDRO POWER/THERMAL POWER
YIELD SERIES FOR HYDRO ELECTRIC PROJECTS IN RAINFALL VARIABILITY SCENARIO
by N. N. Rai Director Central Water Commission
Introduction Huge hydro power potential in Himalayas Limited G&D data on main rivers only and huge
variability in rainfall Most of the HE Projects on Tributaries For power potential study of ROR projects at least 10
years water availability (yield) series is essential The water availability series can not be computed by
catchment area proportioning Yield correction factor along with catchment area
proportioning is essential
Objective To develop yield series for HE Projects in rainfall
variability scenario by developing an yield model at a G&D site of the basin
Input data and data validation
Catchment area map Hypsometric details of catchment Permanent snowline Transitional snow zone Upstream diversion/ other consumptive& non-consumptive use Catchment representative rainfall Observed Discharge at some locations Rainfall and discharge data Validation is must : Mass curve, double mass curve, concurrent plots, annual plots, multi station plots, yield comparison, runoff coefficient, rainfall runoff correlation, runoff-runoff correlation etc may be used
Case Study – Kameng Basin (Arunachal Pradesh) Data availabilty Discharge data Bhalukpong G&D Site
(CA-10450 sq.km) Bichom dam site G&D Site
(CA-2277 sq.km)
Rainfall data –Lower Kameng
Bhalukpong, Kimi, Lumdung Sebu Lanka
Rainfall data (East Kameng)
Seppa, Lamino
Rainfall data (West Kameng)
Bichom, Jameri, Bomdila, Dirang, Dibbin
Hypsometric Curve of Bhalukpong G&D Site
Yield model at Bhalukpong G&D Site
Catchment
Catchment Area (sq.km)
Annual Rainfall (mm)
Snowmelt during six months @ 5 mm/day
Runoff from rainfall (MCM)
Snow melt runoff (MCM)
Permanent snowfed
136
SB1 and SB2 excluding permanent snowfed
3915.8
1440
5074.88
SB3 and SB4 excluding permanent snowfed
3679.2
2400
7947.07
SB5
2719
3914
9577.95
Area between EL 3000m-5000m
1778
1548
912.5
Total Average annual runoff from rainfall and snowmelt (MCM) Total Catchment Area (sq.km) Average annual yield (mm)=1000* [runoff (MCM)/CA (sq.km)]
Observed yield (mm) at Bhaluk-pong during (1993-2010)
124.1
2752.34 22599.90
2876.44
25476.34 10450 2437.90
2437.90
Hypsometric Curve of Bichom dam G&D Site
Testing of Yield model at Bichom G&D site Catchment
Catchment Area (sq.km)
Annual Rainfall (mm)
Permanent Snowfed
23.45
SB1 excluding permanent snowfed
2253.55
1515
Area between EL 3000m-5000m
766
1548
Snowmelt during six months @ 5 mm/day
Runoff from rainfall (MCM)
912.5
Snow melt runoff (MCM)
Observed yield (mm) at Bhaluk-pong during (1993-2010)
21.40
3072.72 1185.77
Total Average annual runoff from rainfall and snow melt (MCM)
3072.72
Total Catchment Area (sq.km)
2277.00
Average annual yield (mm)
1879.61
1207.17
4279.88
1878
Application of yield model to derive 10-daily discharge series at Pachuk-I HEP diversion Catchment CatchAnnual Snowmelt Runoff Snow melt site ment Area Rainfall during six from runoff (sq.km)
(mm)
Permanent Snow fed
42
SB3 excluding permanent snowfed catchment
974
2100
Area between EL 3000m5000m 296
1548
months @ 5 mm/day
rainfall (MCM)
912.5
(MCM)
38.33
1840.86 458.208
Total
1840.86
Average annual runoff (MCM)
2337.39
Total Catchment Area (sq.km)
1016.00
Average annual yield (mm)
2300.58
496.53
Yield Series for Pachuk-I To develop 10 daily series at Pachuk-I,
discharge data of Bichom G&D site has been used Correction factor for 10-daily Bichom series
has been calculated as follows: 10 daily series at Pachuk-I = 10 daily series at
Bichom *(1016/2277)*(2300/1878) CA Ratio
Yield correction factor
Conclusions  2 or 3 years measured discharge data at a project
site does not give appropriate idea of a catchment yield  Yield model at those G&D sites where long term
measured data is available can be prepared  The same based on the catchment hypsometry and
spatial variability of rainfall can be applied at other locations to get an estimate of yield and develop long term water availability series
Thank you