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PRIMARY VALIDATION OF WATER LEVEL DATA

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

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PRIMARY VALIDATION OF WATER LEVEL DATA

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  1. 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

  2. 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

  3. 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

  4. 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, 3.99 • 4.12, 4.10, 4.09, 4.06, 4.03, 4.01, 3.99 OHS - 4

  5. 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

  6. 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

  7. 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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