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
HYDROLOGY PROJECTTechnical Assistance
SPATIAL CORRELATION
• MAJOR INFLUENCING FACTORS– LEVEL OF AGGREGATION IN TIME
– DISTANCE
– TYPE OF PRECIPITATION
– PHYSIOGRAPHIC FACTORS
OHS - 2
HYDROLOGY PROJECTTechnical Assistance
KHEDA CATCHMENT - SABARMATI
OHS - 3
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
REGION A
OHS - 8
HYDROLOGY PROJECTTechnical Assistance
Spatial Correlation - Extended Region
Distance (km)80757065605550454035302520151050
Cor
rela
tion
1.0
0.8
0.6
0.4
0.2
0.0
OHS - 9
HYDROLOGY PROJECTTechnical Assistance
EXTENDED REGION
OHS - 10
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
OHS - 16
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
SPATIAL HOMOGENEITY TESTING
• SPATIAL CORRELATION– CONSISTENCY BETWEEN NEIGHBOURING STATIONS
– COMPARISON OF * OBSERVED VALUE
* VALUE ESTIMATED ON THE BASIS OF NEARBY STATIONS
OHS - 19
HYDROLOGY PROJECTTechnical Assistance
TEST & BASE (NEIGHBOUR) STATIONS
OHS - 20
+
+
+ I
III IV
+ Neighbouring stations
Test station
Selected neighbouringstations
II etc.
Quadrant
II
+++
++
++
+
+
++
+
+
HYDROLOGY PROJECTTechnical Assistance
• 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
HYDROLOGY PROJECTTechnical Assistance
OHS - 22
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
Year mth day hr si P_obs flag P_est Stdv n
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
HYDROLOGY PROJECTTechnical Assistance
Tabulation of series, Year 1988
==========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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
Year mth day hr si P_obs flag P_est Stdv n
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
HYDROLOGY PROJECTTechnical Assistance
Tabulation of series, Year 1995
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
HYDROLOGY PROJECTTechnical Assistance
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
Year mth day hr si P_obs flag P_est Stdv n
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
HYDROLOGY PROJECTTechnical Assistance
Tabulation of series, Year 1997
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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
HYDROLOGY PROJECTTechnical Assistance
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