| Utilizing the runoff and precipitation data during 1960—2009 from Xianyang Station of main stream of Weihe River, and adopting the Mathematical Statistic Methods like Kendall's rank correlation coefficient, R/S analysis, and M-K mutation test, has analyzed the change trend and mutation ch
aracteristics of the seasonal runoff in the midstream of Weihe River. Obtained the results as that: (1) The runoff in each season of the midstream of Weihe River all has shown a significant decreasing trend, especially in the fall. And in future, the flow changes will be maintained the same trend that continued decreasing feature; (2) Concentrated period of the average annual flow at the middle re
ach of the Weihe River was mainly distributed around in mid August, the concentrated period of annual precipitation was mainly distributed around the end of July.It was probably needed 32 days from rain after stopping storage, overland flow, flow into the river channel, then convergence to the downstream river, Runoff lag period to precipitation was continued to extend. The runoff coefficient has been shown a decrease trend in the past 50 years at the middle reach of the Weihe River; (3) Adopted the M-K mutation test method and the sliping t test method, has obtained the mutation point time was 1987, the mutation time was more close in Spring and Autumn, but the summer mutation time was more close to the average annual mutation time. |