Low Flow and Drought in a German Low Mountain Range Basin

Paula Farina Grosser,Britta Schmalz

doi:10.3390/w13030316

Abstract

Rising temperatures and changes in precipitation patterns in the last decades have led to an increased awareness on low flow and droughts even in temperate climate zones. The scientific community often considers low flow as a consequence of drought. However, when observing low flow, catchment processes play an important role alongside precipitation shortages. Therefore, it is crucial to not neglect the role of catchment characteristics. This paper seeks to investigate low flow and drought in an integrative catchment approach by observing the historical development of low flows and drought in a typical German low mountain range basin in the federal state of Hesse for the period 1980 to 2018. A trend analysis of drought and low flow indices was conducted and the results were analyzed with respect to the characteristics of the Gersprenz catchment and its subbasin, the Fischbach. It was shown that catchments comprising characteristics that are likely to evoke low flow are probably more likely to experience short-term, seasonal low flow events, while catchments incorporating characteristics that are more robust towards fluctuations of water availability will show long-term sensitivities towards meteorological trends. This study emphasizes the importance of small-scale effects when dealing with low flow events.

Highlights

Insufficient understanding of the relationship between low flows, drought propagation, and catchment processes has been identified as a challenge in the assessment of the effects of influencing factors such as climate and catchment characteristics on the low flow behavior of a stream or river
Droughts may be defined as natural hazards that result from shortfalls in precipitation over a certain period of time [5]
This study showed that low flow is highly sensitive towards regional circumstances and catchment characteristics

Summary

Introduction

Insufficient understanding of the relationship between low flows, drought propagation, and catchment processes has been identified as a challenge in the assessment of the effects of influencing factors such as climate and catchment characteristics on the low flow behavior of a stream or river.Low flow is a hydrological extreme that may severely influence water quantity and quality in streams, affecting the associated environment [1] and the socioeconomic realm [2]. The World Meteorological Organization (WMO) defines low flow as the “flow of water in a stream during prolonged dry weather” [4]. This indicates an inherent relation between the occurrence of low flows and droughts. Not every drought event has a low flow event as a consequence This is the case, e.g., when the existing water resources in a catchment can compensate for the precipitation deficit. Low flow may occur as a seasonal phenomenon and, as an essential element of the flow regime of any river. A seasonal low flow event does not necessarily imply a drought [6]

Objectives

Methods

Results

Discussion

Conclusion