5th International Conference on Rain Water Cistern Systems
"Rainwater Catchment for Future Generations"
Keelung, Taiwan, R.O.C. - August 1991

Section 4: Hydrological Data and Analysis

Page 210

Envelope Curves for Extreme Flood Events in SW Iran

Ahang Kowsar, Mohammad Hossein Borhan
Research Institute of Forests and Rangelands, Iran

Mohammad Reza Khooban
Fars Water Authority, Iran

Abstract

Water shortage in dry areas is the most limiting factor in their growth, even in their existence. Many civilization have vanished because their water resources had exhausted. Preparation of the systems which harness and conserve floodwaters in unusual rainfall events is one way to replenish the badly depleted aquifers, as well as to produce and preserve food, feed, fiber and fuel for the lean years. Prediction of the runoff potential of watersheds in extreme events is a rather conservative method for estimation of the size of floodwater spreading systems and artificial recharge facilities. However, long time, continuous hydrological data required to base the pred:.ctions on are lacking for most of the desert watersheds in Iran. Therefore, it is necessary to resort to empiricism for prediction of runoff events. Development of envelope curves for regions with a few gauged watersheds facilitates reasonable estimation of the maximum probable peaks for ungauged basins in the same area.

A total of 36 data points of the deluge of Dec. 1986 were used to derive envelope curves for the Mond, Helleh, Zohreh and Shiraz basins. Euation of the form Q=C+B/A, in which Q is the peak flow in ls-1 km-2, A is the area of the basin in km2 and C and B are constants, best describe the overall performance of the basins. However, other equation farms might better match some individual watersheds in the region.

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