Investigation of crop evapotranspiration and irrigation water requirement in the lower Amu Darya River Basin, Central Asia

High water consumption and inefficient irrigation management in the agriculture sector of middle lower reaches Amu Darya River Basin (ADRB) have significantly influenced gradual shrinking Aral Sea its ecosystem. In this study, we investigated crop growing seasons requirement for different types ADRB during 2004–2017. We applied FAO Penman-Monteith method to estimate reference evapotranspiration (ET0) based on daily climatic data collected from four meteorological stations. Crop (ETc) specific was calculated by coefficient. Then, analyzed net (NIR) effective precipitation with requirements. The results indicated that lowest monthly ET0 values were found December (18.2 mm) January (16.0 mm), highest June July, similar 211.6 mm. annual ETc reached 887.2, 1002.1, 492.0 mm cotton, rice, wheat, respectively. average regional NIR ranged 514.9 715.0 10 Irrigation System Management Organizations (UISs) study area, while total required volume whole region 4.2×109 11.6×109 m3 percentages SIW (surface water) 46.4% 65.2% period, exceptions drought years 2008 2011, which there a less runoff River. This provides an overview local authorities achieve optimal allocation area.