Propagation of drought in a groundwater fed catchment, the Pang in UK

Regional drought characteristics, such as the area covered by drought and the total deficit over that area, are important measures of the severity of a drought event. Gridded, monthly data from the Pang catchment, UK, are analysed here to study the spatial aspects of the drought as it propagates from a meteorological drought, through a drought in the groundwater system and finally appears as a drought in discharge at the catchment outlet. Drought events are derived separately for each grid cell and variable (rainfall, recharge and hydraulic head) using the threshold level method, and combined to yield regional or catchment-specific drought characteristics. The results demonstrate the catchment control in modifying the drought signal from a series of short duration droughts in rainfall covering large parts of the catchment, through fewer and longer droughts in groundwater recharge, head and discharge. The most severe hydrological droughts in the period 1961-1997 occurred in 1975-1977 and 1991-1992. The average area covered by drought is smaller for groundwater recharge than hydraulic head. Hydraulic head and discharge exhibit similar drought behaviour, which can be expected in a groundwater fed catchment