International Conference on Rain Water Cistern Systems
"Rainwater Catchment for Future Generations"
Keelung, Taiwan, R.O.C. - August 1991
4: Hydrological Data and Analysis
Envelope Curves for
Extreme Flood Events in SW Iran
Mohammad Hossein Borhan
Research Institute of Forests and Rangelands, Iran
Fars Water Authority, Iran
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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