WU Jin-kui, DING Yong-jian, SHEN Yong-ping, NIU Li, WANG Gen-xu
The estimation of evapotranspiration of swampy meadow in arid area is significant to ecological and environmental construction, scientific management of pasture and protection of swamp. But so far, there is less observation and research of it. Based on meteorological data, different methods are used to calculate the reference evapotranspiration of swampy meadow in the middle reaches of Heihe River in Hexi Corridor. The analysis results show that the ASCE 1990 Penman-Monteith method, the Penman 1984, and the Hargreaves methods all correlated well with the FAO Penman-Monteith. Priestley Taylor formula shows considerable difference from other methods.ET0 estimated by FAO Penman-Monteith equation shows that in a whole year (2003-09~2004-08), the total ET0 was 1193.9 mm and a daily mean 3.26 mm·d-1 The ET0 varies with growing stage. In non-growing period (NGP), initial growing period (IGP), middle growing period (MGP) and the end-growing period (EGP), the ET0 is 0.92 mm·d-1, 2.13 mm·d-1, 5.33 mm·d-1 and 2.52 mm·d-1 respectively. In the middle and end of February, the ET0 increases rapidly. But in April, the ET0 increases most. After that, it increases gradually and gets the maximal value in July. From then on, the ET0 decreases gradually and in the middle of November it gets a minimal value. Hourly analysis of the ET0 shows that at 8:00 am (during MGP usually at 7:00), the evapotranspiration begins, at 13:00 pm it gets a maximal value and at 18:00 pm (during MGP usually at 19:00), the evapotranspiration stops. The crop coefficients(Kc)are 0.30, 0.40, 0.90 and 0.88 in NGP, IGP, MGP and EGP, respectively. The actual evapotranspiration is determined to be 962.0 mm in a whole year and 2.63 mm·d-1 of a daily mean.
