Influence of "corridor-barrier" function on water demand of paddy irrigation in the Longitudinal Range-Gorge Region

Based on the daily data at the four weather stations of Baoshan, Jinghong, Yuanjiang in the longitudinal range-gorge region, and Kunming nearby from 1970 to 2000, the daily evapotranspiration (ET0) changes at the four stations were analyzed. It was found that: (1) the daily ET0 shows the "delay phenomenon", it means that the daily ET0 change goes up to the maximum point in May and then starts to go down with a wave-like "delay phenomenon" at 80%-85% of ET0max value till Autumn, and the change trend significantly differs from that of other regions in China. Affected by the meteorological factors, the maximum values of paddy water demand and irrigation water consumption do not appear with the peak of paddy growth at the same time, it has a two month's delay. Paddy water requirement intensity is 6.1-8.2 mm/d and its change scale extent is less than that in central China. (2) Under the influence of "corridor-barrier" function on the Longitudinal Range-Gorge Region (LRGR), the paddy irrigation water requirement was related to latitude, longitude, and altitude. In the region of 23.5 degrees N with altitude 1550 m, the correlation coefficient between paddy irrigation water demand and latitude is 0.857, the irrigation quota ranges from 6240 to 8550 m(3)/hm(2); and affected by southwest and southeast monsoons in LRGR, the correlation coefficients between the paddy irrigation water demand and the longitude in the east bank and west bank of Red River great canyon are 0.631 and 0.913 respectively, and the irrigation quotas are 7260 -7440 m(3)/hm(2) and 5970-7740 m(3)/hm(2) respectively; the coefficient between paddy irrigation water demand and altitude at 100 E area is 0.636, the quota is 6240-8550 m(3)/hm(2).