基于信息扩散理论的黑河中上游绿洲农业旱灾近20年风险评估

Drought Risk Assessment of Oasis Agriculture in Middle and Upper Heihe River in Recent 20 Years Based on Information Diffusion Theory

基于黑河中上游绿洲各县(区)1991—2010年农业旱灾受灾面积、成灾面积等统计数据,利用信息扩散理论风险分析模型和风险等级划分,对农业旱灾风险进行评估。结果表明:近20年来,研究区农业受旱灾影响的受(成)灾风险估计值随风险指数增加而减小,当受灾风险水平在50%以内时,临泽受灾风险估计值最小,为0.000 29,山丹受灾风险估计值最大,为0.811 12,风险频率达到每1.2年一遇。当成灾风险水平在30%以内时,成灾风险估计值以山丹最大,为0.765 50,达到每1.3年一遇,甘州区最小,为0.118 95,旱灾几乎年年发生。旱灾发生具有高频率和集中性特点,受损度主要集中在15%以内,受损程度在30%以上可能性很小。当旱灾受(成)灾指数为10%时,高台、民乐、山丹的灾损程度最大,而超过50%时灾损程度很小;成灾风险等级空间差异显著,表现为以甘州区、临泽为中心,风险等级水平向外围增加,即山丹、民乐风险等级水平最高,属于高、较高风险等级,甘州区、临泽风险等级水平最低,为低、较低风险等级。

The agricultural drought disaster was analyzed by using risk analysis model and risk hierarchy of information diffusion theory based on the statistical data of oasis agricultural drought stricken area, disaster area in the middle and upper Heihe River each county during 1991-2010. The results showed that the probability of drought risk on agriculture decrease with the increase of risk level in the researched area in recent 20 years. When the drought stricken index was within 50%, the estimated value of the disaster stricken risk reached minimum in Linze （0.000 29） and reached maximum in Shandan （0.811 12）, equivalent to 1.2a occurrence. When the drought forming index was within 30%, the estimated value of the disaster forming risk reached maximum in Shandan （0.765 50）, equivalent to 1.3a occurrence; while it reached minimum in Ganzhou （0.118 95） and drought occurred almost every year. Drought occurred in high concentration and frequency, most of the losses were within 15% but the losses with degree more than 30% are of little possibility. When the drought stricken and forming index was at 10%, the losses with degree reached maximum in Gaotai, Minle and Shandan, but the losses with degree more than 50% are of little possibility. The risk probability of agricultural drought had a significant spatial difference. It showed that Ganzhou and Linze as the center, the drought risk level gradually increases to the periphery. The highest risk level of drought was in Shandan and Minle, with a high and higher risk levels. The lowest risk level of drought was in Ganzhou and Linze, with a low and lower risk ranks levels.