ESTIMATION OF GROUNDWATER INFLOW TO IRRIGATION DRAINS IN MINIA, UPPEREGYPT, BASED ON A DEUTERIUM AND O-18 EVAPORATION-PAN TECHNIQUE

The possibility of estimating groundwater inflow to irrigation drains in Minia, Egypt, using stable isotopes has been explored. The evaporat ion pan technique described here makes use of small variations in the concentration of naturally occurring stable isotopes (oxygen-18 and de uterium) in irrigation-fed groundwater and surface water as well as ag ricultural drainage water. The agreement between the stable isotope pa n experiments carried out at Minia with others conducted at different locations in Egypt makes it feasible to estimate the inflow of groundw ater to be about 42% of the total drainage water.