CORRECTION/COMPLETION OF RAINFALL DATA PRIMARY & SECONDARY VALIDATION –FLAGGING : SUSPECT OR INCORRECT VALUES –MISSING : NON-OBSERVANCE OR LOSS OF DATA ESTIMATE - SAME/NEIGHBOURING STATIONS –WHERE POSSIBLE *INCORRECT DATA TO BE CORRECTED *MISSING DATA TO BE COMPLETED (FILLED-IN) –IF NOT POSSIBLE *SUSPECT DATA WILL BE RETAINED AS FLAGGED *INCORRECT DATA TO BE SET AS MISSING *MISSING VALUES LEFT AS SUCH OHS - 1

CORRECTION/COMPLETION OF RAINFALL DATA PROCEDURE TO BE EMPLOYED –TYPE OF ERROR –AVAILABILITY OF SUPPORTING DATA FOR ESTIMATION DONE AT SDPCs/RDPCs –DATA VALIDATION REPORT FROM DDPCs OHS - 2

CORRECTION/COMPLETION PROCEDURES ARG/SRG DATA AT ONE OR MORE STATIONS CORRECTING TIME SHIFT IN DATA APPORTIONING ACCUMULATIONS ADJUSTING DATA FOR LONG TERM SHIFT *DOUBLE MASS ANALYSIS SPATIAL INTERPOLATION *ARITHMETIC AVERAGE *NORMAL RATIO *NEAREST NEIGHBOUR OHS - 3

SRG SUSPECT/FAULTY - ARG AVAILABLE OHS - 4

ARG MISSING/FAULTY - SRG AVAILABLE ARG RECORD NOT AVAILABLE *FAULT IN EQUIPMENT / RECORDING MECHANISM *CHART/DATA MISSING SRG RECORD AT STATION AVAILABLE HOURLY DISTRIBUTION *SIMILAR TO NEIGHBOURING STATIO(S) OHS - 5

OHS - 6

OHS - 7

CORRECTING TIME SHIFT OHS - 8

APPORTIONING ACCUMULATED RAINFALL DATA VALIDATION –ACCUMULATION INDICATED *AMOUNT OF ACCUMULATION *PERIOD OF ACCUMULATION CORRECTION –ESTIMATE BY SPATIAL INTERPOLATION –APPORTIONING REPORTED ACCUMULATION PROPORTIONATELY OHS - 9

ESTIMATE - SPATIAL INTERPOLATION APPORTIONING ACCUMULATED TOTAL OHS - 10

ACCUMULATION INDENTIFIED OHS - 11

APPORTIONING ACCUMULATION OHS - 12

ADJUSTING LONG TERM SHIFTS - DOUBLE MASS ANALYSIS SLOPE  1 SLOPE  2 ADJUSTED OHS - 13

DATA CORRECTION OHS - 14

RESULTS - DOUBLE MASS ANALYSIS OHS - 15

DATA ADJUSTED OHS - 16

SPATIAL INTERPOLATION ARITHMETIC AVERAGE –ANNUAL AVERAGE WITHIN 10% NORMAL RATIO METHOD OHS - 17

NEAREST NEIGHBOURHOOD METHOD (DISTANCE POWER) I III IV + Neighbouring stations Test station Selected neighbouring stations II etc. Quadrant II OHS - 18

OHS - 19

COMPUTATION OF STATION WEIGHTS OHS - 20

OHS - 21

COMPARISON OF OBSERVED & ESTIMETED OHS - 22

CORRECTION FOR HETEROGENEITY STATION NORMALS –HISTORICAL RECORDS –RELATIONSHIP WITH ELEVATION OHS - 23