ABSTRACT
The basin of the Amu Darya is situated between lat 34°36'N-43°45'N and long 58°15'E-75°07'E. Its length from north to south is 1,230 km and from west to east 1,470 km (Figure 15.1 and General Appendix IV). Its water catchment area, downstream of the confluence of the River Sherabad, is 226,800 km2. Sixty per cent of the catchment area is in the former Soviet Union and approximately 40 per cent in Afghanistan (USSR Surface Waters Resources, 1971). The Amu Darya is formed by the Rivers Pyandzh and Vakhsh and receives important tributaries in the first 180 km. The Amu Darya is the largest river in Central Asia and its natural discharge to the Aral Sea was, until 1961, relatively stable and depended mainly on snow and ice melt. In the 1950s, the actual discharge of the Amu Darya to the Aral (including losses due to evapotranspiration in the delta flood plain) was 39.5 km3 a"1 (Blinov, 1956). From 1961, a rapid growth in irrevocable water abstraction and regulation began which led to a sharp reduction in river discharge to the Aral Sea and at the end of the 1980s (data from 1987-89), the Amu Darya discharge varied between 1.1 and 16 km a (Izrael and Anokhin, 1991). 15.1 River regime A specific feature of the Amu Darya basin is its clear division into an upper basin where the discharge is formed under the influence of predominately natural factors, and a lower part from which water is abstracted (Figure 15.1). The surface water resources of the Amu Darya, in a year of average water discharge measured at Termez sampling station, are 63.6 km3 a"1 comprising discharges from the Pyandzh (51 per cent), Vakhsh (29.8 per cent), Kafirnigan (8.2 per cent), Surkhandarya (5.3 per cent) and Kunduzdarya (5.4 per cent) (Rubinova, 1985).
