Hydrological Variability of Water Level of Dianchi Lake and Its Application

Abstract

The water level is an important indicator for lake operation management, and the variability of lake water level will have an important impact on the ecological suitability of aquatic vegetation. The ecological water level of lakes is the minimum water level for maintaining the structural and functional integrity and biodiversity of lake ecosystems. Therefore, it is very important to determine the ecological water level of lakes is for maintaining the harmony and stability of lake ecosystems. This paper analyzed the characteristics of water level, the lowest and suitable ecological water levels and the guarantee degree, by using the monthly water level data of Dianchi Lake from 1961 to 2016. The main conclusions are as follows: (1) The water level of Dianchi Lake mainly had a change period of about 15 years; (2) The abrupt change point of water level of Dianchi Lake occurred in 1994; (3) The lowest and suitable ecological water levels of Dianchi Lake and its actual water level had a typical unimodal distribution. The ecological water level in spring and winter was high, while that in summer and autumn was low. Thereinto, the lowest and suitable ecological water levels in May were lowest, 1885.86m and 1886.04m respectively, while those in November were highest, 1886.60m and 1886.78m respectively. (4) The guarantee degree of the lowest ecological water level of Dianchi Lake was as high as 93%∼95% within the year, while the guarantee degree of the suitable ecological water level could only reach 46%∼50%. The guarantee rate of the ecological water level during the low water level period was higher than that during the high water level period, and the guarantee degree of the interannual ecological water level varied greatly over the years. The lowest guarantee degree occurred in 1988 and 1989 with 0%, followed by the guarantee degrees of 50% and 8% in 1993, and they had reached 100% since 1994.