EVAPORATION FROM WADI EL-RAYAN LAKES, EGYPT

EVAPORATION FROM WADI EL-RAYAN LAKES, EGYPT
By
MAIYZA, I. A*.; M.M. ABD EL- RAHMAN

AL~ R.G. ABD ELLAH.

*National Institute ofOceanography & Fisheries, Kayet-Bey, Alexandria,EGYPT
Key words: Limnology, Evaporation, Wady EI- Rayan Lakes, Egypt.
ABSTRACT
Evaporation plays a very important role in any ecosystem. The rate
of evaporation is a major factor controlling the heat, water and salt
budgets of Wadi EI-Rayan Lakes. Before the installation of the
Automatic Weather Station, there was no database about the climate
prevailing over Wadi EI-Rayan depression.
Wadi EI-Rayan is a great depression located in Fayoum
Governorate. It was connected with agricultural drainage water system
of Fayoum depression to get a secondary reservoir ofdrainage water
that exceed the capacity of Lake QanJll. Wadi EI-Rayan depression
consists oftwo man-made Lakes. It occupies the area between Latitudes
29° 05’& 29° 18′ N alld Longitudes 30° 21′ & 30° 32′ E.
The air is warmer than the surface water duringfour months (May
& July-September), while it is cooler in the rest mgnths ofthe year. The
difference (Ta-Tw) is a maximum positive value (1.28 °C) in September,
while the maximum negative value (–1.59 °C) is in February. Air
pressure over the Lakes is relatively high. It changes between 1011.8 mb
in July and 1022 mb in December. The wind speed increasesfrom 2.11
m/s in December to 5. -I m/s in June. The relative humidity changes
between 36.82% in June and 57.66% in November.