基于地下水埋深的区域干旱频率分析研究

Study on frequency analysis of regional drought based on ground water depth

以地下水埋深为水文干旱指标,在分析研究区实际旱情发生频次的基础上,采用相邻时段地下水埋深变化的累积频率法,识别由地下水干旱历时和干旱烈度组成的干旱特征变量值,并从降水的角度,分析了用相邻时段地下水埋深变化表征干旱的合理性。在采用适线法确定单个干旱特征变量累积分布的基础上,利用Copula函数构建了干旱历时与干旱烈度间的联合分布,并计算了相应的干旱重现期。对淮北平原砀山县的地下水干旱频率分析结果表明:采用基于相邻时段地下水埋深变化的累积频率法所识别的干旱历时和干旱烈度及其对应的干旱重现期与砀山县实际受旱情况相符。该方法概念清晰,可在其它类似的平原区域采用。

Taking ground water depth as a hydrological drought indicator, the drought duration and severity characteristic variables were identified by cumulative frequency approach. The corresponding cumulative frequency of the variation of ground water depth, which suggested the occurrence of drought, was determined based on the statistical analysis of the occurrence of drought in the study region. The reasonability of the drought characteristic variables was illustrated via the relationship of anomalies of the variation of ground water depth and precipitation anomalies. The frequency curve fitting method was adopted to calculate frequency of each drought characteristic variable. Then with GH Copula, the joint distribution of drought duration and severity was constructed and accordingly the drought recurrence periods were estimated. The proposed methods for drought frequency estimation were applied to Dangshan County, Huaibei Plain. The application results show that identified drought events and the corresponding estimated recurrence periods by the GH Copula have high consistency with the actual regional drought circumstances. The presented methods of hydrological drought identified based on the variation of ground water depth of adjacent periods and the recurrence periods calculated by copula, are of clear physical concept. So the methods can be applied to the regions under similar situations.