三峡水库蓄水后洞庭湖区农业水旱灾害的风险性及趋势预测

根据洞庭湖区1950-2017年农业水旱灾情资料和1956-2017年的径流量数据,采用水旱灾害受(成)灾率、熵信息扩散理论模型、标准化径流指数(SRI)和重标极差分析(R/S)等方法,分析三峡水库蓄水后洞庭湖区农业水旱灾害的程度、风险性以及趋势。结果表明:在三峡水库蓄水后,(1)水灾受灾率由6.65%降至1.21%,成灾率由2.97%降至0.71%,旱灾受灾率由5.97%降至2.48%,成灾率由2.98%降至0.99%。(2)水旱灾害成灾率在≥5%,≥10%,≥15%和≥20%时,水灾风险概率分别为0.415,0.192,0.057,0.025,旱灾风险概率依次为0.518,0.359,0.037,0.001,水灾风险等级为中低风险(成灾率≥5%,≥10%)、低风险(成灾率≥15%,≥20%),旱灾风险等级为中风险(成灾率≥5%)、中高风险(成灾率≥10%)、低风险(成灾率≥15%,≥20%)。(3)该区水旱灾害风险趋势为水灾风险将呈现减轻趋势,而旱灾风险将呈现增大趋势。

Agricultural Flood and Drought Risk and Their Trend Analysis in Dongting Lake Area After the Impoundment of Three Gorges Reservoir

Based on the agricultural flood drought data from 1950-2017 and the runoff data from 1956-2017 in Dongting Lake area, the degree and risk of agricultural flood and drought disasters and their trends in Dongting Lake area after impoundment of the Three Gorges Reservoir were analyzed by using the methods of flood and drought disaster acceptance rate, theory model of entropy information diffusion, standardized runoff index (SRI), and re-standard polar difference analysis (R/S). The results showed that:(1) After impoundment of the Three Gorges Reservoir, the rate of flood stricken decreased from 6.65% to 1.21%, the rate of flood disaster decreased from 2.97% to 0.71%, the rate of drought stricken decreased from 5.97% to 2.48%, and the rate of drought disaster decreased from 2.98% to 0.99%. (2) When the disaster rate of agricultural flood and drought disaster was more than 5%, 10%, 15%, and 20%, the probability of flood risk was 0.415, 0.192, 0.057 and 0.025, and the probability of drought risk was 0.518, 0.359, 0.037 and 0.001, respectively. The flood risk level was medium to low risk (disaster rate was more than 5%, 10%) and low risk (disaster rate was more than 15% and 20%). Drought risk level was medium risk (disaster rate was more than 5%), medium to high risk (disaster rate was more than 10%), and low risk (disaster rate was more than 15%, 20%). (3) The trend of flood and drought disasters will be a reducing trend for floods and an increasing trend for drought in studied areas.