CHANGES IN THE STRUCTURE OF EVAPORATION IN THE ARAL SEA BASIN

An analysis of evaporation changes in the Central Asian plain in connection with the drop of the Aral Sea level beginning in 1961 shows that there has been a reduction in evaporation from stream valleys and deltas and an increase in evaporation from irrigated land and newly formed evaporating surfaces. These new entities are primarily the Arnasay depression (west of the Golodnaya Steppe irrigation district) and the Sarykamysh depression (west of the lower reaches of the Amudarya), which have become filled with spent irrigation water draining from the irrigated land. Another new source of evaporation associated with human activity are the lakes and wetlands formed along the Kara Kum Canal as a result of the filtration of canal water. It turns out, furthermore, that irrigation on sloping piedomon plains, such as those watered by the Kara Kum Canal, requires more water than in old irrigated alluvial plains because of the additional water needed to flush salt out of the soil and to fill subsoil cavities and raise the watertable.