WSPC04299 - Laserfiche WebLink

Home Browse Search

00lG82 32.8--6 WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK G. Common Steo 7. Calculate the duration of QLV' The calculated discharge must next be converted to a ratio to determine its duration. The discharge is divided by QR and the resulting ratio is identified as a point on the fl~w- duration curve. The duration (percent of time equaled or exceeded) may then be noted, converted to days and described as an increment as in Common Step 3. (If the ratio of areas approach is used, it is clear, assuming the equality, that the area ratio is the same as the one derived by dividing the calculated flow by QB') The calculated duration must next be adjusted to both the duration and timing of the growing season. This season is the period during which the vegetation encroachment potential is greatest, and the susceptible portions of the channel area identified in Common Step 5 are not inundated. If this season is greater than the calculated duration of inundation, the difference in days is added directly to the discharge requirements described in Common Steps 2 and 3. H. Common Steo 8. Normalize and display the representative station hydrographs. Display the daily mean hydrograph data from the representative gage station and divide the ordinate (cfs) axis by QR for the station. Note: The addition of the station flow-duration hydrograph may be useful to demonstrate the relative magnitude of bankfull discharge and the dampened nature of the daily mean hydrograph. I. Common Step 9. Identify the start of the snowmelt season on the representative gage station long term daily mean hydrograph. From the long term daily mean hydrograph of the representative gage station displayed in Common Step 8, identify the date during the snowmelt season which corresponds to the occurrence, for at least 24-hours, of mean annual discharge (day 1). The beginning of the rising limb of the maintenance flow hydrograph begins after a user defined lapse of time following day 1. This is subject to user discretion. The objective is to identify the average date of occurrence of peak flow and to approximately align the maintenance flow hydrograph peak with this date. J. Common Steo 10. ~sing the representative ~tation normalized flow-duration curve, plot the maintenance flow hydrograph. With the completion of the calculations of the required flow components, their duration, and the determination of the day 1 index point, the scheduling of rising, bankfull, and recession --FSH 4/89 AMEND 3--