An empirical (geo)statistical modelling scheme is developed to address the challenges of modelling the severity and distribution of groundwater droughts given their spatially and temporally heterogeneous nature and given typically highly irregular groundwater level observations in space and time. The scheme is tested using GWL measurements from 948 observation boreholes across the Chalk aquifer (UK) to estimate monthly groundwater drought status from 1960 to 2013. For each borehole, monthly GWLs are simulated using empirical mixed models where the fixed effects are based on applying an impulse response function to the local monthly precipitation. Modelled GWLs are standardised using the Standardised Groundwater Index (SGI) and the monthly SGI values interpolated across the aquifer to produce spatially distributed monthly maps of SGI drought status for 54 years for the Chalk. The mixed models include fewer parameters than comparable lumped parameter groundwater models while explaining a similar proportion (more than 65%) of GWL variation. In addition, the empirical modelling approach enables confidence bounds on the predicted GWLs and SGI values to be estimated without the need for prior information about catchment or aquifer parameters. The results of the modelling scheme are illustrated for three major episodes of multi-annual drought (1975–1976; 1988–1992; 2011–2012). They agree with previous documented analyses of the groundwater droughts while providing for the first time a systematic, spatially coherent characterisation of the events. The scheme is amenable to use in near real time to provide short term forecasts of groundwater drought status if suitable forecasts of the driving meteorology are available.

中文翻译：

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地下水干旱状况的时空模拟

开发了一种经验（地理）统计建模方案，以解决地下水干旱在空间和时间上的异质性以及通常在空间和时间上高度不规则的地下水位观测的情况下对地下水干旱的严重程度和分布进行建模的挑战。该计划使用来自 Chalk 含水层（英国）的 948 个观测钻孔的 GWL 测量值进行测试，以估计 1960 年至 2013 年的每月地下水干旱状况。对于每个钻孔，使用经验混合模型模拟每月 GWL，其中固定效应基于应用当地月降水量的脉冲响应函数。模拟的 GWL 使用标准化地下水指数 (SGI) 和插入整个含水层的每月 SGI 值进行标准化，以生成粉笔的 54 年 SGI 干旱状态的空间分布月度地图。混合模型包含的参数少于可比较的集总参数地下水模型，同时解释了类似比例（超过 65%）的 GWL 变化。此外，经验建模方法可以估计预测的 GWL 和 SGI 值的置信界限，而无需有关集水区或含水层参数的先验信息。模拟方案的结果说明了多年干旱的三个主要事件（1975-1976；1988-1992；2011-2012）。他们同意先前记录的地下水干旱分析，同时首次提供了系统的、事件的空间连贯表征。如果有合适的驱动气象预报，该方案可以近乎实时地用于提供地下水干旱状态的短期预报。