COMPUTATION OF DISCHARGE DATA GENERAL: –DISCHARGE CANNOT BE MEASURED DIRECTLY AND CONTINUOUSLY –STAGE MEASUREMENTS h(t) ARE MADE CONTINUOUSLY OR AT FIXED INTERVALS –h(t) IS CONVERTED INTO DISCHARGE Q(t) BY USING THE Q-h RATING CURVE –COMPUTATION OF Q(t) IS DONE MONTHLY ON THE STAGE DISCHARGE OF THE PREVIOUS MONTH NOTE: –Q(t) REVIEWED ANNUALLY BEFORE TRANSFER TO THE ARCHIVE –TRANSFORMATION DONE AT DDPC AND REVIEWED AT SDPC OHS - 1

STATION REVIEW BEFORE COMPUTING Q(t): – A SUMMARY OF ALL RELEVANT INFORMATION FOR THE STATION SHOULD BE AVAILABLE, INCLUDING: *STAGE RECORD *LISTING OF ALL RATING CURVES WITH VALIDITY PERIOD TO AVOID OVERLAP OF OR GAPS BETWEEN RELATIONS *ANCILLARY INFORMATION FROM THE FIELD RECORD BOOK AND RATING RELATIONS OHS - 2

TRANSFORMATION OF STAGE TO DISCHARGE AVAILABLE PROCEDURES IN HYMOS: –SINGLE CHANNEL RATING CURVE –COMPOUND CHANNEL RATING CURVE –RATING CURVES WITH UNSTEADY FLOW CORRECTION –RATING CURVES WITH CONSTANT FALL CORRECTION –RATING CURVE WITH NORMAL FALL CORRECTION –RATING CURVES FOR HYDRAULIC STRUCTURES OHS - 3

SINGLE CHANNEL RATING CURVE USE: –WHEN A ONE-TO-ONE RELATIONSHIP BETWEEN STAGE AND DISCHARGE EXISTS: *WHEN UNSTEADY FLOW EFFECTS ARE NEGLIGIBLE *WHEN BACKWATER EFFECTS ARE NON-EXISTING *WHEN NO SIGNIFICANT FLOOD PLAINS ARE AVAILABLE OR *NO EXTRA RELATION IS REQUIRED FOR THE FLOOD PLAIN FLOW TYPES: –POWER TYPE EQUATION –PARABOLIC TYPE EQUATION OHS - 4

SINGLE CHANNEL RATING EQUATION POWER TYPE EQUATION –MAXIMUM 5 WATER LEVEL SEGMENTS –CHECK VALIDITY PERIOD –PREFERRED ABOVE PARABOLIC EQUATION PARABOLIC TYPE EQUATION –MAXIMUM 5 WATER LEVEL SEGMENTS –CHECK VALIDITY PERIOD OHS - 5

COMPOUND CHANNEL RATING CURVE MAIN RIVER FLOOD PLAIN TOTAL FLOW OHS - 6

RATING CURVE WITH UNSTEADY FLOW CORRECTION PROCEDURE: –Qst FROM STEADY STATE RATING –COMPUTE THE FACTOR 1/S 0 c –COMPUTE  h/  t FROM THE HYDROGRAPH –COMPUTE Q(t) BY JONES FORMULA OHS - 7

RATING CURVE WITH CONSTANT FALL CORRECTION PROCEDURE: –REFERENCE Qr(t) IS COMPUTED FROM h(t) –WITH SIMULTANEOUS READING AT SECOND STATION FALL Ft IS COMPUTED –Fr AND p ARE READ FROM THE RATING PARAMETER DATABASE –ABOVE EQUATION IS APPLIED OHS - 8

RATING CURVE WITH NORMAL FALL CORRECTION PROCEDURE: –REFERENCE Qr(t) IS COMPUTED FROM h(t) –WITH SIMULTANEOUS READING AT SECOND STATION FALL Ft IS COMPUTED –Fr IS DETERMINED FROM LEFT EQUATION AS FUNCTION OF h(t) AND p ARE READ FROM THE RATING PARAMETER DATABASE –ABOVE EQUATION IS APPLIED OHS - 9