JOURNAL OF NATURAL RESOURCES ›› 2016, Vol. 31 ›› Issue (10): 1702-1712.

• Resource Evaluation •

### Complexity Analysis of Low Flow in the Jinghe Watershed

WANG Li-na, LI Xun-gui, WANG Xiao-lei, WANG Nai-ang

1. a. Key Laboratory of Western China’s Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, b. Research Center for Arid and Desert, Lanzhou University, Lanzhou 730000, China
• Received:2015-05-12 Revised:2016-07-30 Online:2016-10-20 Published:2016-10-20
• Supported by:
National Natural Science Foundation of China, No.51679115 and 51109103; Fundamental Research Funds for the Central Universities, No.lzujbky-2016-173

Abstract: As one of the important characteristics of low flow, the complexity of low flow has a significant role in the low flow studies. The time series of monthly runoff at Zhangjiashan (ZJS) station of the Jinghe River Basin during 1933-2010 was studied. The time series of low flow were determined based on the anomalies and the average standard deviation. The measure of approximate entropy (ApEn) was employed to analyze the complexity of low flow. Results show that: 1) The annual average runoff presents significant decreasing trend at the 0.01 level of significance. The low flow occurs more and more since 1997. The upper bound of monthly low flow at the ZJS station was determined to be 9 369.67×104 m3. The occurrences of monthly low flows in January, February and December are much more than those in other months. Therefore, the monthly low flows in these three months were set as the time series of low flow in this study. 2) The value of ApEn of the low flow series was calculated to be 1.059 1, which is close to the value of 1.059 7 calculated from the entire monthly runoff series at the same time. It indicates that the fifteen non-dry months occurring in January, February and December have little impacts on the complexity of low flow series. 3) The complexity of monthly low flow showed increasing trend with fluctuations at the 0.05 level of significance. The complexity of low flow has a significant negative correlation to the monthly runoff, but has no significant relation to the monthly precipitation. The results demonstrate that the precipitation in the watershed is not the major input of the low flow system. The precipitation change does not play a key role in the change of the complexity of low flow. The runoff inertia is probably an important factor resulting in the change of the complexity of low flow.

CLC Number:

• P333.3