COMPUTATION OF DISCHARGE DATA

1. 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

2. 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

3. 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

4. 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

5. 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 SINGLE CHANNEL RATING EQUATION OHS - 5

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

7. PROCEDURE: Qst FROM STEADY STATE RATING COMPUTE THE FACTOR 1/S0c COMPUTE h/t FROM THE HYDROGRAPH COMPUTE Q(t) BY JONES FORMULA RATING CURVE WITH UNSTEADY FLOW CORRECTION OHS - 7

8. 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 RATING CURVE WITH CONSTANT FALL CORRECTION OHS - 8

9. 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 RATING CURVE WITH NORMAL FALL CORRECTION OHS - 9