SECONDARY VALIDATION - RAINFALL DATA PRIMARY VALIDATION ALREADY DONE ON INDIVIDUAL STATION BASIS SECONDARY VALIDATION IDENTIFY SUSPECT VALUES BY HAVING

HYDROLOGY PROJECTTechnical Assistance

SECONDARY VALIDATION - RAINFALL DATA

• PRIMARY VALIDATION ALREADY DONE* ON INDIVIDUAL STATION BASIS

• SECONDARY VALIDATION* IDENTIFY SUSPECT VALUES BY HAVING COMPARISON

WITH NEIGHBOURING STATIONS

• DIVISIONAL DPCs* TO CONTINUE AT SDPCs

• RAINFALL NOT HIGHLY CORRELATED IN SPACE & TIME !!

* NOT A ONE-TO-ONE - COMPARISON DIFFICULT

* BETTER CORRELATION - LARGER TIME INTERVALS

* MISTAKES & SUSTAINED SYSTEMATIC ERRORS

OHS - 1


SPATIAL CORRELATION

• MAJOR INFLUENCING FACTORS– LEVEL OF AGGREGATION IN TIME

– DISTANCE

– TYPE OF PRECIPITATION

– PHYSIOGRAPHIC FACTORS

OHS - 2


KHEDA CATCHMENT - SABARMATI

OHS - 3


Spatial Correlation - Daily Rainfall (Kheda Catchment)

Distance (km)120110100908070605040302010

Cor

rela

tion

1.0

0.8

0.6

0.4

0.2

0.0

OHS - 4


Spatial Correlation - 10 Daily Rainfall (Kheda Catchment)

Distance (km)12011511010510095908580757065605550454035302520151050

Cor

rela

tion

1.0

0.8

0.6

0.4

0.2

0.0

OHS - 5


Spatial Correlation - Monthly Rainfall (Kheda Catchment)

Distance (km)12011511010510095908580757065605550454035302520151050

Cor

rela

tion

1.0

0.8

0.6

0.4

0.2

0.0

OHS - 6


Spatial Correlation - Monthly Rainfall (Region A)

Distance (km)252423222120191817161514131211109876543210

Cor

rela

tion

1.0

0.8

0.6

0.4

0.2

0.0

OHS - 7


REGION A

OHS - 8


Spatial Correlation - Extended Region

Distance (km)80757065605550454035302520151050

Cor

rela

tion

1.0

0.8

0.6

0.4

0.2

0.0

OHS - 9


EXTENDED REGION

OHS - 10


USE OF SPATIAL CORRELATION

• PREVAILING SPATIAL CORRELATION– AS BASIS FOR TESTING SPATIAL CONSISTENCY

– SPATIAL INTERPOLATION

• THERE IS LIKELIHOOD OF– REJECTING GOOD BUT ANAMOLOUS DATA

– ACCEPTING BAD DATA

• RELIANCE ON STATION REPUTATION– TYPE OF STATION

– PAST RECORD ON QUALITY

– OBSERVER SINCERITY & PAST RECORDSOHS - 11


SECONDARY DATA VALIDATION

• SCREENING OF DATA• MULTIPLE TIME SERIES GRAPHS• DAILY RAINFALL TABULATION FOR

NEIGHBOURING STATIONS• APPLYING DATA LIMITS AT LONGER

DURATIONS• SPATIAL HOMOGENEITY TEST• VERY COMMON ERRORS

– ACCUMULATION OF RAINFALL OR MISSED ENTRY

– MISSED RAINFALL ON LOW RAINFALL DAYS

• DOUBLE MASS ANALYSIS– LONG TERM SYSTEMATIC SHIFTS

OHS - 12


DATA VALIDATION

• SCREENING OF DATA– SCREENING AGAINST DATA LIMITS

– TABULAR OUTPUT

– BASIC STATISTICS

• OBJECTIVES– REVIEW PRIMARY VALIDATION

– HARD COPY * MEDIUM FOR SCRIBBLING REMARKS/ DATA VALIDATION

NOTES

OHS - 13


Daily data and statistics of series MEGHARAJ MPS Year = 1997

Day Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May 1 .0 .0 192.5* .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 2 .0 .0 15.0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 3 .0 .0 1.0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 4 .0 .0 .0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 5 .0 .0 .0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0*

6 .0 .0 .0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 7 .0 .0 1.0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 8 .0 .0 32.0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 9 .0 .0 1.0 25.0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 10 .0 .0 .0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0*. . .. . .. . .

26 132.0* 4.0 54.5 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 27 38.0 312.0* 1.0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 28 54.0 32.5 .0 .0 .0 -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* -99.0* 29 .0 4.5 .5 .0 .0 -99.0* -99.0* -99.0********** -99.0* -99.0* -99.0* 30 .0 12.0 .5 .0 .0 -99.0* -99.0* -99.0********** -99.0* -99.0* -99.0* 31********* 22.0 .0 ********* .0 ********* -99.0* -99.0********** -99.0********** -99.0*

Data 30 31 31 30 31 30 31 31 28 31 30 31 Eff. 30 31 31 30 31 0 0 0 0 0 0 0 Miss 0 0 0 0 0 30 31 31 28 31 30 31 Sum 397.0 401.0 474.5 76.0 5.5 -99.0 -99.0 -99.0 -99.0 -99.0 -99.0 -99.0 Mean 13.2 12.9 15.3 2.5 .2 -99.0 -99.0 -99.0 -99.0 -99.0 -99.0 -99.0 Min. .0 .0 .0 .0 .0 -99.0 -99.0 -99.0 -99.0 -99.0 -99.0 -99.0 Max. 138.0 312.0 192.5 27.5 5.5 -99.0 -99.0 -99.0 -99.0 -99.0 -99.0 -99.0

High 130.0 130.0 130.0 130.0 130.0 .0 .0 .0 .0 .0 .0 .0 Numb 2 1 1 0 0 0 0 0 0 0 0 0 Low .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 Numb 0 0 0 0 0 0 0 0 0 0 0 0

Annual values: Data 365 * Sum 1354.0 * Minimum .0 * Too low 0 Effective 153 * Mean 8.8 * Maximum 312.0 * Too high 4 Missing 212

Exceedance of: - Lower bound ( .00) marked with * - Upper bound ( 130.00) marked with * - Rate of rise ( 320.00) marked with + - Rate of fall ( 320.00) marked with -

OHS - 14


Comparison of Daily Rainfall at Multiple Stations

PH_ANIOR PH_BHEMPODA PH_RELLAWADA PH_MEGHARAJ

Time

15/08/96

14/08/96

13/08/96

12/08/96

11/08/96

10/08/96

09/08/96

08/08/96

07/08/96

06/08/96

05/08/96

04/08/96

03/08/96

02/08/96

01/08/96

31/07/96

30/07/96

29/07/96

28/07/96

27/07/96

26/07/96

25/07/96

24/07/96

23/07/96

22/07/96

Rai

nfa

ll (m

m)

240

220

200

180

160

140

120

100

80

60

40

20

0

OHS - 15


OHS - 16


Tabulation of series, Year 1984

==========Data========== Year mth day hr si KAPADWANJ KATHLAL MAHISA SAVLITANK VADOL PH PH PH PH PH 1984 8 1 .0 .0 .0 .0 .0 1984 8 2 .0 .0 .2 .0 .0 1984 8 3 152.4 99.3 157.4 .0 39.3 1984 8 4 104.1 50.2 87.0 150.0 59.2 1984 8 5 7.7 12.0 18.0 76.0 13.1 1984 8 6 1.5 35.0 .0 16.0 .0 1984 8 7 .0 .0 .0 3.0 .0 1984 8 8 1.3 .0 .0 .0 .0 1984 8 9 .0 13.0 .0 .0 .0 1984 8 10 231.2 157.0 179.0 .0 17.3 1984 8 11 43.2 18.3 64.0 201.0 63.2 1984 8 12 .0 .0 .0 26.0 33.3 1984 8 13 .0 .0 .0 .0 13.1 1984 8 14 .0 .0 20.0 .0 .0 1984 8 15 .0 .0 .0 30.0 .0 1984 8 16 2.6 8.3 16.5 .0 16.3 1984 8 17 .0 .0 .0 20.0 20.2 1984 8 18 32.0 50.3 25.6 .0 37.2 1984 8 19 16.5 8.2 15.0 27.0 19.3 1984 8 20 .0 .0 .0 13.0 .0 1984 8 21 .0 .0 .0 .0 .0

OHS - 17

SCRUTINY BY TABULATION


Plot of Yearly Rainfall with Data Limits

Vadol Lower Warning Level Upp. Warning Level

Time9897969594939291908988878685848382818079787776757473727170

Rai

nfal

l (m

m)

1,400

1,300

1,200

1,100

1,000

900

800

700

600

500

400

300

200

100

0

OHS - 18


SPATIAL HOMOGENEITY TESTING

• SPATIAL CORRELATION– CONSISTENCY BETWEEN NEIGHBOURING STATIONS

– COMPARISON OF * OBSERVED VALUE

* VALUE ESTIMATED ON THE BASIS OF NEARBY STATIONS

OHS - 19


TEST & BASE (NEIGHBOUR) STATIONS

OHS - 20

+

+

+ I

III IV

+ Neighbouring stations

Test station

Selected neighbouringstations

II etc.

Quadrant

II

+++

++

++

+

+

++

+

+


• SPATIAL ESTIMATE - WEIGHTED AVERAGE– WEIGHTS : INVERSE OF DISTANCE POWER

N

ib

iD

biDt

N

i iPtestP

1/1

/)(1)(

– TEST : ABSOLUTE & RELATIVE

Pobs(t) - Pest(t) Xabs

Pobs(t) - Pest(t) Xrel * S Pest (t)

2

1)( ))()(( tPtPS ii

N

itPest

OHS - 21


OHS - 22


Spatial homogeneity check Test station SAVLITANK PH

Year mth day hr si P_obs flag P_est Stdv n

1984 6 14 0 1 9.00 + .00 .00 6 1984 6 15 0 1 14.00 + .00 .00 6 1984 6 16 0 1 23.00 + .00 .00 6 1984 7 2 0 1 52.00 + 14.52 9.71 6 1984 7 6 0 1 47.00 + 2.13 4.51 6 1984 7 25 0 1 25.00 + .32 1.21 6 1984 8 3 0 1 .00 - 96.59 65.70 6 1984 8 4 0 1 150.00 + 78.44 38.47 6 1984 8 5 0 1 76.00 + 20.64 36.20 6 1984 8 10 0 1 .00 - 128.36 93.57 6 1984 8 11 0 1 201.00 + 59.25 42.04 6 1984 8 15 0 1 30.00 + .50 1.89 6 1984 8 19 0 1 27.00 + 16.81 4.91 6 1984 8 28 0 1 8.00 + .00 .00 6 1985 6 13 0 1 9.00 + .00 .00 6 1985 6 14 0 1 14.00 + .00 .00 6 1985 6 16 0 1 8.00 + .00 .00 6 1985 7 2 0 1 21.00 + .07 .37 6 1985 7 6 0 1 47.00 + .73 3.73 6 1985 7 19 0 1 60.00 + 16.05 15.49 6 1985 7 21 0 1 29.00 + 10.41 7.93 6 1985 7 23 0 1 12.00 + .15 .75 6 1985 7 25 0 1 25.00 + 3.15 3.78 6 1985 8 1 0 1 10.00 + .48 1.97 6 1985 8 4 0 1 150.00 + 82.57 76.84 6 1985 8 5 0 1 76.00 + 15.06 37.51 6 1985 8 11 0 1 201.00 + 11.39 53.59 6 1985 8 15 0 1 30.00 + .29 1.49 6 1985 8 17 0 1 20.00 + 1.09 5.59 6 1985 8 19 0 1 27.00 + 1.75 8.94 6 1985 8 28 0 1 8.00 + .00 .00 6 1985 9 14 0 1 17.00 + .00 .00 6 1985 9 15 0 1 3.00 + .00 .00 6 1985 10 8 0 1 145.00 + 70.17 67.38 6 1985 10 9 0 1 .00 - 86.03 116.43 6OHS - 23


COMMON ERRORS - SHIFT IN ENTRIESSpatial homogeneity check ====================================

Test station VADAGAM PH

Radius of circle of influence : 25.000 (km)

Station weights proportional to : 1/D^2.00

Admissible absolute error : 50.000 Multiplier to stdv of neighbours: 2.000

Selected neighbour stations: Quadrant Station Distance (km)

1 RAHIOL PH 12.606 1 MODASA PH 18.689 4 BAYAD PH 12.882 4 ANIOR PH 21.829


1988 8 1 0 1 .50 - 8.32 3.83 4 1988 8 5 0 1 .00 - 181.97 45.70 4 1988 8 7 0 1 161.00 + 14.23 8.32 4 1988 8 8 0 1 4.00 - 11.98 3.06 4 1988 8 9 0 1 18.00 + 7.12 1.72 4 1988 8 11 0 1 4.20 + .59 1.43 4 1988 8 25 0 1 32.00 + 1.97 4.34 4 1988 9 6 0 1 9.50 + .00 .00 4 1988 9 29 0 1 12.00 + 1.09 1.30 4OHS - 24



==========Data========== Year mth day hr si ANIOR BAYAD MODASA RAHIOL VADAGAM PH PH PH PH PH

1988 7 12 .0 .0 .0 .0 .0 1988 7 13 .0 .0 70.0 .0 .0 1988 7 14 33.0 65.0 75.0 30.0 14.0 1988 7 15 8.0 17.8 12.5 5.0 3.0 1988 7 16 26.8 14.0 31.0 60.6 40.0 1988 7 17 5.4 1.2 10.0 2.0 1.0 1988 7 18 .0 2.0 .0 .0 1.0 1988 7 19 40.0 57.8 2.5 50.8 35.0 1988 7 20 54.2 46.0 60.0 32.8 46.0 1988 7 21 7.0 17.0 4.0 4.0 19.0 1988 7 22 113.0 78.4 124.0 91.8 82.0 1988 7 23 .0 11.2 15.0 6.8 16.3 1988 7 24 13.0 .0 29.0 7.4 .0 1988 7 25 8.0 14.0 43.5 35.8 23.1 1988 7 26 18.0 27.0 1.0 .0 4.2 1988 7 27 31.0 1.0 .0 3.4 1.2 1988 7 28 29.0 42.0 7.0 10.0 23.0 1988 7 29 .0 14.0 15.0 4.0 10.0 1988 7 30 13.4 .0 43.0 2.0 .0 1988 7 31 4.2 17.0 6.0 .0 .0 1988 8 1 8.0 3.0 13.0 11.4 .5 1988 8 2 4.0 .0 2.0 .0 .0 1988 8 3 .0 .0 17.0 22.0 4.0 1988 8 4 .0 1.0 1.0 .0 .0 1988 8 5 253.0 135.0 161.0 212.8 .0 1988 8 6 139.0 94.0 112.0 110.6 140.0 1988 8 7 20.0 24.0 4.0 7.6 161.0 1988 8 8 11.2 8.0 11.0 16.5 4.0 1988 8 9 9.0 8.0 9.0 4.8 18.0 1988 8 10 2.6 3.0 8.0 1.0 1.2 1988 8 11 3.5 .0 1.0 .0 4.2 1988 8 12 .0 .0 3.0 .0 3.0 1988 8 13 .0 .0 .0 .0 .0OHS - 25


COMMON ERRORS - ACCUMULATIONS

• RAINFALL OBSERVATIONS– TO BE MADE DAILY WITHOUT FAIL

– ABSENCE DUE TO PRACTICAL REASONS* SICKNESS

* HOLIDAY(S)/WEEKENDS

– OBSERVERS TENDENCY* DISTRIBUTE RAINFALL BASED ON OWN GUESS

* RECORD ACCUMULATED VALUE ON THE LAST DAY WITHOUT MENTIONING IT

* RECORD ACCUMULATED VALUE ON THE LAST DAY WITH PROPER REMARKS (NOT PRACTICED NORMALLY)

• DETECTION OF SUCH ERRORS– USING RECORDS OF NEARBY STATIONS

OHS - 26


Spatial homogeneity check ====================================

Test station DAKOR PH

Start date: 1995 6 1 0 1 End date: 1995 9 30 0 1

Radius of circle of influence : 25.000 (km)

Station weights proportional to : 1/D^2.00

Admissible absolute error : 50.000 Multiplier to stdv of neighbours: 2.000

Selected neighbour stations:

Quadrant Station Distance (km)

1 THASARA PH 8.252 1 VAGHAROLI PH 18.976 2 MAHISA PH 13.948 2 KATHLAL PH 22.216 2 MAHUDHA PH 22.694 2 SAVLITANK PH 23.403


1995 7 15 0 1 .00 - 56.64 20.50 6 1995 7 18 0 1 .00 - 8.79 3.34 6 1995 7 19 0 1 .00 - 21.24 8.73 6 1995 7 20 0 1 .00 - 36.82 15.42 6 1995 7 28 0 1 97.50 + 18.12 13.28 6 1995 7 30 0 1 6.80 - 48.59 16.20 6OHS - 27



Year mth day hr si DAKOR KATHLAL MAHISA MAHUDHA SAVLITANK THASARA

1995 7 11 .0 7.0 10.0 1.5 27.0 9.0 1995 7 12 .0 .0 3.0 2.0 3.0 17.0 1995 7 13 .0 45.0 .0 .0 .0 .0 1995 7 14 .0 10.0 20.0 7.5 .0 7.0 1995 7 15 .0 14.0 50.0 33.5 24.0 77.0 1995 7 16 .0 .0 8.0 9.5 25.0 8.0 1995 7 17 .0 20.0 4.0 1.0 .0 22.0 1995 7 18 .0 10.0 8.0 1.0 6.0 11.0 1995 7 19 .0 23.0 20.0 43.0 27.0 16.0 1995 7 20 .0 .0 35.0 32.5 14.0 48.0 1995 7 21 .0 57.0 27.0 23.0 14.0 56.0 1995 7 22 .0 .0 6.0 7.0 4.0 .0 1995 7 23 .0 .0 4.0 12.0 2.0 27.0 1995 7 24 .0 10.0 .0 .0 .0 .0 1995 7 25 .0 11.0 10.0 3.0 6.0 3.0 1995 7 26 .0 25.0 .0 10.0 5.0 8.0 1995 7 27 .0 18.0 3.0 4.0 25.0 9.0 1995 7 28 97.5 25.0 24.0 46.0 3.0 12.0 1995 7 29 16.7 40.0 4.0 6.0 .0 .0 1995 7 30 6.8 45.0 34.0 22.0 62.0 52.0 1995 7 31 .0 10.0 3.0 13.0 39.0 9.0

OHS - 28


COMMON ERRORS - MISSED ENTRIESSpatial homogeneity check ==================================== Test station BHEMPODA PH Admissible absolute error : 40.000 Multiplier to stdv of neighbours: 2.000

Quadrant Station Distance (km)

1 MEGHARAJ PH 20.897 2 RAHIOL PH 17.898 3 ANIOR PH 4.535 3 BAYAD PH 23.253


1997 6 9 0 1 9.00 + .00 .00 4 1997 6 14 0 1 3.00 + .00 .00 4 1997 6 22 0 1 20.00 + 4.79 2.38 4 1997 6 23 0 1 17.00 + 2.11 4.20 4 1997 6 25 0 1 165.00 - 205.65 33.94 4 1997 6 27 0 1 173.00 + 71.55 37.77 4 1997 7 10 0 1 .00 - 1.31 .65 4 1997 7 20 0 1 3.00 + 1.34 .65 4 1997 7 21 0 1 29.00 - 80.48 34.46 4 1997 7 26 0 1 1.00 - 12.73 4.42 4 1997 7 27 0 1 125.00 - 225.13 58.75 4 1997 7 28 0 1 280.00 - 376.98 153.43 4 1997 8 2 0 1 94.00 + 36.15 21.21 4 1997 8 8 0 1 .00 - 20.98 5.32 4 1997 8 9 0 1 .00 - 2.37 .56 4 1997 8 11 0 1 .00 - .44 .22 4 1997 8 14 0 1 .00 - 2.66 1.14 4 1997 8 19 0 1 .00 - 48.96 18.63 4 1997 8 24 0 1 .00 - 87.56 42.17 4 1997 9 11 0 1 .00 - 18.50 6.03 4 1997 9 13 0 1 .00 - 15.36 5.79 4

OHS - 29



Year mth day hr si ANIOR BAYAD BHEMPODA MEGHARAJ RAHIOL

1997 7 25 .0 .0 .0 1.0 .0 1997 7 26 13.0 11.0 1.0 4.0 16.0 1997 7 27 225.0 147.5 125.0 312.0 209.5 1997 7 28 420.5 194.5 280.0 32.5 60.0 1997 7 29 4.0 1.5 3.0 4.5 5.5 1997 7 30 16.5 9.0 13.0 12.0 7.0 1997 7 31 3.0 4.0 3.0 22.0 1.5 1997 8 1 290.0 257.0 275.0 192.5 129.5 1997 8 2 38.5 57.5 94.0 15.0 2.5 1997 8 3 11.5 28.5 24.0 1.0 11.5 1997 8 4 .0 .0 .0 .0 .0 1997 8 5 15.0 .0 23.0 .0 .0 1997 8 6 .0 .0 .0 .0 .0 1997 8 7 1.0 1.5 .0 1.0 .0 1997 8 8 20.5 25.0 .0 32.0 18.0 1997 8 9 2.5 2.0 .0 1.0 1.5 1997 8 10 .0 .0 .0 .0 .0 1997 8 11 .5 .0 .0 .0 .0 1997 8 12 4.0 1.0 .0 7.0 8.0 1997 8 13 2.5 6.0 .0 1.0 .0 1997 8 14 3.0 1.0 .0 .5 .0 1997 8 15 .0 .0 .0 1.0 .0 1997 8 16 .0 2.0 .0 .0 .0 1997 8 17 .0 .0 .0 .5 1.0 1997 8 18 .0 .0 .0 .0 3.0 1997 8 19 54.0 33.0 .0 12.0 7.0 1997 8 20 .0 7.0 .0 1.0 30.0 1997 8 21 1.0 .0 .0 6.5 .0 1997 8 22 .0 .0 .0 .0 .0 1997 8 23 3.0 .0 .0 9.5 19.5 1997 8 24 91.0 13.5 .0 125.5 50.0 1997 8 25 16.5 33.0 .0 11.0 31.0 1997 8 26 29.0 19.0 .0 54.5 .0 1997 8 27 2.5 5.5 .0 1.0 .0 1997 8 28 .0 .0 .0 .0 .0 1997 8 29 .0 .0 .0 .5 .0 1997 8 30 15.5 33.0 .0 .5 31.5 1997 8 31 .0 .0 .0 .0 .0

OHS - 30


DOUBLE MASS ANALYSIS• DETECTION OF SYSTEMATIC SHIFTS IN TIME

– PERSISTENCE FOR LONG TIME PERIODS

– ABRUPT OR GRADUAL CHANGE

• TEMPORAL INCONSISTENCY: FACTORS– SHIFTING OF STATION TO ANOTHER LOCATION

– CHANGE IN EXPOSURE CONDITION

– CHANGE IN EQUIPMENT OR PRACTICES

– UNATTENDED FAULT IN EQUIPMENT

– CHANGE IN REGIME: MAN-MADE TOO

• IN-HOMOGENEITY IN DATA SET– NOT ACCEPTABLE IN STATISTICAL ANALYSIS

– RELATING SERIES TO DESIRED SITE/REGIME

OHS - 31


DETECTION OF INHOMOGENEITY

• COMPARING BEHAVIOUR OF TEST STATION WITH RESPECT TO NEARBY STATIONS– BASE STATION(S) ASSUMED TO HOMOGENEOUS

– ANY SIGNIFICANT & PERSISTENT DIFFERENCES IN MUTUAL RELATIONSHIP INDICATES SHIFT

– RANDOM VARIATION IN RELATIONSHIP TEND TO COMPENSATE IF AGGREGATED IN TIME

– SYSTEMATIC VARIATION TENDS TO SHOW UP

OHS - 32


DOUBLE MASS CURVE

• SIMPLE TEST PROCEDURE– ACCUMULATE IN TIME

* OBSEREVED TEST SERIES

* ESTIMATED BASE SERIES

– COMPARE THE TWO ACCUMULATED SERIES

– SIGNIFICANT & PERSISTENT DEVIATION SHOWS IN-HOMOGENEITY IN THE TEST SERIES

i

jj

i

jj

i

X

Y

rc

1

1

OHS - 33


Double Mass Curve

Base Series (%) - (Megharaj & Bayad)10095908580757065605550454035302520151050

Tes

t Ser

ies

(%) -

(Vad

agam

)100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0

OHS - 34


Double Mass Curve (1970 - 1996)

Base Series (%) - (KAPADWANJ, MAHISA, THASARA)10095908580757065605550454035302520151050

Tes

t Ser

ies

(%) -

(VA

DO

L)100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0

OHS - 35

Documents

SECONDARY VALIDATION - RAINFALL DATA PRIMARY VALIDATION ALREADY DONE *ON INDIVIDUAL STATION BASIS SECONDARY VALIDATION *IDENTIFY SUSPECT VALUES BY HAVING

SECONDARY VALIDATION - RAINFALL DATA PRIMARY VALIDATION ALREADY DONE ON INDIVIDUAL STATION BASIS SECONDARY VALIDATION IDENTIFY SUSPECT VALUES BY HAVING