PRIMARY VALIDATION OF WATER LEVEL DATA OBSERVED DATA MAY BE SUBJECTED TO ERRORS *RANDOM, SYSTEMATIC AND SPURIOUS *AIM OF VALIDATION IS TO DETECT SYSTEMATIC ERRORS & SPURIOUS VALUES WATER LEVEL DATA *ELEVATION OF WATER SURFACE W.R.T CERTAIN DATUM *BASIC DATA REPRESENTING THE STATE OF A WATER BODY *USED FOR COMPUTATION OF DISCHARGES USING STAGE-DISCHARGE RELATIONSHIPS *QUALITY OF STAGE DATA INFLUENCES RELIABILITY OF DISCHARGE DATA DIRECTLY *OTHER USES - NAVIGATION, INUNDATION, RESERVOIR LEVELS ETC. OHS - 1

PRIMARY VALIDATION - AT SUB-DIV. DPCs –DATA COMPARISON AT SINGLE STATION *INDIVIDUAL OBSERVATION & PRE-SET DATA LIMITS MAXIMUM & MINIMUM UPPER & LOWER WARNING LEVELS MAXIMUM RATE OF RISE AND FALL *TWO MEASUREMENTS OF A VARIABLE MANUAL OBSERVATIONS & AUTOMATICALY RECORDED OHS - 2

EQUIPMENT & OBSERVATION METHODS SOURCES OF ERRORS *METHOD OF MEASUREMENT *TYPICAL ERRORS IN EQUIPMENT OR TECHNIQUE DATA VALIDATION EXERCISE *NOT TO BE PURELY STATISTICAL *FIELD PRACTICES MUST BE CLEARLY UNDERSTOOD *AWARENESS ABOUT THE DISTURBANCES ALONG RIVER SIDES THREE BASIC EQUIPMENT *STAFF GAUGE *AUTOGRAHIC RAINGAUGE *DIGITAL RECORDER OHS - 3

STAFF GAUGE INSTRUMENT & PROCEDURE *PRIMARY MEANS OF MEASUREMENT *ZERO OF GAUGE FORMS THE DATUM AT STATION *OTHER AUTOMATIC GAUGES ARE CALIBRATED & CHECKED AGAINST STAFF GAUGE TYPICAL ERRORS *MISPLACEMENT OF DECIMAL POINTS 0.01, 0.10 *4.12, 4.10, 4.9, 4.6, 4.3, 4.1, , 4.10, 4.09, 4.06, 4.03, 4.01, 3.99 OHS - 4

DATA “ESTIMATED” BY OBERVERS ESTIMATION BY FABRICATION –WITHOUT VISITING THE STATION *MAY SHOW UP AS INCONSISTENT HYDROLOGICAL SEQUENCES ABRUPT FALL OR CHANGE IN SLOPE OF A RECESSION CURVE LARGE PERIODS OF UNIFORM LEVEL FOLLOWED BY DISTINCT FALL UNIFORM MATHEMATICAL SEQUENCES - FALL BY 0.05 TO 0.10 OHS - 5

AUTOMATIC WATER LEVEL RECORDER INSTRUMENT & PROCEDURES –VAST MAJORITY OF AGR *FLOAT & PULLEY WITH STILLING WELL *CHART IS CHANGED - DAILY/ 7-DAILY TYPICAL ERRORS –INSTRUMENT MALFUNCTION *CHART TRACE GOES UP WHEN THE RIVER GOES DOWN *FLOOD HYDROGRAPH TRUNCATED *STAFF GAUGE AND CHART DISAGREE *CHART TIME & CLOCK TIME DISAGREE –PARTIAL BLOCKAGE IN STILLING WELL *SERIOUS SYSTEMATIC ERRORS OHS - 6

DIGITAL WATER LEVEL RECORDER FLOAT TYPE *MECHANICAL LINKAGE REPLACED BY SHAFT ENCODER ELIMINATES MECHANICAL LINKAGE ERRORS PEN TRACE ERRORS *IN STILLING WELLS PRESSURE TRANSDUCER TYPE *WITHOUT STILLING WELL *ERRORS ASSOCIATED WITH STILLING WELL ARE AVOIDED *DATA CORRUPTION IS POSSIBLE DUE TO OTHER ELECTRONIC OR SENSOR’S MALFUNCTIONING STAFF GAUGE DATA IS USED AS BASE OHS - 7

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