Abstract: The trends and stages of runoff and precipitation in Zhengshui River watershed, a first-grade tributary of Xiangjiang River, in the past five decades (1961-2012) were analyzed using methods of Mann-Kendall test, accumulated anomaly curve, and double mass curve. The influences of precipitation and human activities on runoff change were also quantified. The data came from observed runoff at Shenshandou hydrometric station and observed daily precipitation at seven adjacent meteorological stations in the Zhengshui River watershed. Research findings demonstrated that the variations of annual runoff and annual precipitation in the Zhengshui River watershed are apparently staged into low-flow period and high-flow period. In general, both annual runoff and annual precipitation were rising, of which the former increased more evidently. Runoff changed abruptly in 1988, while precipitation in 1991. After the abrupt change, runoff climbed obviously under the combined action of precipitation and human activities, of which the former contributed 24.26% of the increment, whereas the latter contributed up to 75.74%. As the major influential factor of runoff change in the Zhengshui River watershed at present, human activity, to be specific, rational human activity, could adjust runoff.

Key words: runoff evolution, precipitation, Mann-kendall testing, variation trend, influential factors, Zhengshui River watershed