Abstract:Understanding the temporal-spatial distribution characteristics of Huangtai algae bloom can provide support decisionmaking for prevention and control of Huangtai algae bloom in Lake Ulansuhai, China. Cloud-free images shot by MODIS sensor from May to September and from 2000 to 2010 were utilized to extract algae bloom area and spatial distribution by means of Normalized Difference Vegetation Index. According to the analysis, conclusions are as below:(1) as for area variation, Lake Ulansuhai had a severe situation of Huangtai algae bloom in 2000, 2001, 2005, 2006, 2008 and 2010, more than the average of the whole period (24 km2). In regard to monthly variation, Huangtai algal areas in May, June, July remained low around 20 km2. Yet Lake Ulansuhai have larger Huangtai algal areas in August and September, around 28 km2 and 40 km2, respectively. (2) As for occurrence frequency, the highest frequency of Huangtai algae bloom occurred in 2001 (0.58), followed by 2005, 2006 and 2010 fluctuating around 0.25 (higher than the average of 11 a, 0.19); occurrence frequency in other years kept a low level around 0.10. In the aspect of monthly variation, occurrence frequency in May, June, July kept a low level around 0.10. The times of Huangtai algal bloom experienced a more rapid increase and a larger scale of outbreak frequency in August and September, 0.27 and 0.52, respectively, higher than the average of 5 months (0.19). (3) Huangtai algae blooms mostly lied in the region called Xidatan, the north coast and middle of the region called Dongdatan, and along the west coast of south Lake Ulansuhai, where local agricultural irrigation drainage water flows into the lake and thus the most striking algal blooms emerge there. (4) Daily average temperature, precipitation and nutrient concentrations (total nitrogen and total phosphorus) in two months ago have a significant correlation relationship with Huangtai algae's occurrence. Additionally, synchronous wind speed has a significant correlation relationship with Huangtai algae's occurrence. The spatial distribution of nutrient (TN, TP) is well consistent with the distribution of Huangtai algae's occurrence. Human activities, especially artificial supplement for water in Lake Ulansuhai, have great impact on the variation of Huangtai algae occurrences.