A global evaluation of streamflow drought characteristics

A. K. Fleig (1) , L. M. Tallaksen (1) , H. Hisdal (1, 2) , S. Demuth (3, 4)

1 Department of Geosciences [Oslo]
2 NVE - Norwegian Water Resources and Energy Directorate
3 IHP/HWRP Secretariat
4 Institute of Hydrology

How drought is characterised depends on the region under study, the purpose of the study and the available data. In case of regional applications or global comparison a standardisation of the methodology is preferable. In this study several methods to derive streamflow drought characteristics are evaluated based on their application to daily streamflow series from a wide range of hydrological regimes. Drought deficit characteristics, such as drought duration and deficit volume, are derived with the threshold level method. When it is applied to daily time series an additional pooling procedure is required and three different pooling procedures are evaluated, the moving average procedure (MA-procedure), the inter event time method (IT-method), and the sequent peak algorithm (SPA). The MA-procedure proved to be a flexible approach for the different series, and its parameter, the averaging interval, can easily be optimised for each stream. However, it modifies the discharge series and might introduce dependency between drought events. For the IT-method it is more difficult to find an optimal value for its parameter, the length of the excess period, in particular for flashy streams. The SPA can only be recommended for the selection of annual maximum series of deficit characteristics and for very low threshold levels due to the high degree of pooling. Furthermore, a frequency analysis of deficit volume and duration is conducted based on partial duration series of drought events. According to extreme value theory, excesses over a certain limit are Generalized Pareto (GP) distributed. It was found that this model indeed performed better than or equally to other distribution models. In general, the GP-model could be used for streams in all regime types. However, for intermittent streams, zero-flow periods should be treated as censored data. For catchments with frost during the winter season, summer and winter droughts have to be analysed separately.

Domaines: Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

A. K. Fleig, L. M. Tallaksen, H. Hisdal, S. Demuth. A global evaluation of streamflow drought characteristics. Hydrology and Earth System Sciences Discussions, 2005, 2 (6), pp.2427-2464. ⟨hal-00298786⟩