Regional analysis of groundwater droughts using hydrograph classification
Regional analysis of groundwater droughts using hydrograph classification
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DOI：
10.5194/hess-19-4327-2015
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发表时间：
2015-10
影响因子：
6.3
通讯作者：
J. Bloomfield;B. Marchant;S. Bricker;R. Morgan
中科院分区：
文献类型：
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作者：
J. Bloomfield;B. Marchant;S. Bricker;R. Morgan
地下水干旱是一种时空变化的现象。在这里，我们描述了一种方法的发展，区域分析和量化地下水干旱。该方法使用聚类分析技术（非分层k -均值），以分类标准化地下水位过程线（标准化地下水位指数，SGI）的地下水干旱特征分析之前，并已使用74地下水位时间序列从英国林肯郡进行了测试。使用测试数据集，已确定六组水文。对于每个聚类，可以在平均SGI和平均标准化降水指数（SPI）之间建立相关性，其中每个聚类与不同的SPI累积期相关联。基于SPI时间序列的比较，每个集群和研究区域作为一个整体，它被推断为集群是独立的驱动气象，主要是一个功能的集水区和水文地质因素。这一推论得到以下观察结果的支持：每个组群中的大多数地点都与研究区域的一个主要含水层有关。分析了三个最大的集群的地下水干旱特征，这三个集群构成了约80%的站点。干旱持续时间，幅度和强度的分布的地下水干旱事件之间的三个集群作为每个集群的平均SGI时间序列的自相关函数的差异。此外，各专题组对分析期间发生的三次重大多年干旱的反应也有差异。例如，具有最长SGI自相关性的集群中的站点经历了最严重的干旱，并且从主要干旱中恢复最慢，地下水干旱条件通常比其他集群中的站点持续至少6个月。集群的成员被证明是相关的非饱和区厚度在个别钻孔。这最后一个观察强调的重要性，集水区和含水层的特点（非平凡）控制地下水干旱水文。分析方法灵活，可适用于广泛的水文地质环境，同时能够以一致的方法量化地下水对气象干旱的反应的区域差异。
Groundwater drought is a spatially and temporally variable phenomenon. Here we describe the development of a method to regionally analyse and quantify groundwater drought. The method uses a cluster analysis technique (non-hierarchical k -means) to classify standardised groundwater level hydrographs (the standardised groundwater level index, SGI) prior to analysis of their groundwater drought characteristics, and has been tested using 74 groundwater level time series from Lincolnshire, UK. Using the test data set, six clusters of hydrographs have been identified. For each cluster a correlation can be established between the mean SGI and a mean standardised precipitation index (SPI), where each cluster is associated with a different SPI accumulation period. Based on a comparison of SPI time series for each cluster and for the study area as a whole, it is inferred that the clusters are independent of the driving meteorology and are primarily a function of catchment and hydrogeological factors. This inference is supported by the observation that the majority of sites in each cluster are associated with one of the principal aquifers in the study region. The groundwater drought characteristics of the three largest clusters, which constitute ~ 80 % of the sites, have been analysed. There are differences in the distributions of drought duration, magnitude and intensity of groundwater drought events between the three clusters as a function of autocorrelation of the mean SGI time series for each cluster. In addition, there are differences between the clusters in their response to three major multi-annual droughts that occurred during the analysis period. For example, sites in the cluster with the longest SGI autocorrelation experience the greatest-magnitude droughts and are the slowest to recover from major droughts, with groundwater drought conditions typically persisting at least 6 months longer than at sites in the other clusters. Membership of the clusters is shown to be related to unsaturated zone thickness at individual boreholes. This last observation emphasises the importance of catchment and aquifer characteristics as (non-trivial) controls on groundwater drought hydrographs. The method of analysis is flexible and can be adapted to a wide range of hydrogeological settings while enabling a consistent approach to the quantification of regional differences in response of groundwater to meteorological drought.