Human influences on streamflow drought characteristics in England and Wales

Abstract

Abstract. Human influences can affect streamflow drought characteristics and propagation. The question is where, when and why? To answer these questions, the impact of different human influences on streamflow droughts were assessed in England and Wales, across a broad range of climate and catchments conditions. We used a dataset consisting of catchments with near-natural flow as well as catchments for which different human influences have been indicated in the metadata ("Factors Affecting Runoff") of the UK National River Flow Archive (NRFA). A screening approach was applied on the streamflow records to identify human-influenced records with drought characteristics that deviated from those found for catchments with near-natural flow. Three different deviations were considered, specifically deviations in (1) the relationship between streamflow drought duration and the base flow index, BFI (specifically, BFIHOST, the BFI predicted from the hydrological properties of soils), (2) the correlation between streamflow and precipitation and (3) the temporal occurrence of streamflow droughts compared to precipitation droughts, i.e. an increase or decrease in streamflow drought months relative to precipitation drought months over the period of record. The identified deviations were then related to the indicated human influences. Results showed that the majority of catchments for which human influences were indicated did not show streamflow drought characteristics that deviated from those expected under near-natural conditions. For the catchments that did show deviating streamflow drought characteristics, prolonged streamflow drought durations were found in some of the catchments affected by groundwater abstractions. Weaker correlations between streamflow and precipitation were found for some of the catchments with reservoirs, water transfers or groundwater augmentation schemes. An increase in streamflow drought occurrence towards the end of their records was found for some of the catchments affected by groundwater abstractions and a decrease in streamflow drought occurrence for some of the catchments with either reservoirs or groundwater abstractions. In conclusion, the proposed screening approaches were sometimes successful in identifying streamflow records with deviating drought characteristics that are likely related to different human influences. However, a quantitative attribution of the impact of human influences on streamflow drought characteristics requires more detailed case-by-case information about the type and degree of all different human influences. Given that, in many countries, such information is often not readily accessible, the approaches adopted here could provide useful in targeting future efforts. In England and Wales specifically, the catchments with deviating streamflow drought characteristics identified in this study could serve as the starting point of detailed case study research.

Natural and Human Influences on the Link Between Meteorological and Hydrological Drought Indices for a Large Set of Catchments in the Contiguous United States

“…Conversely, indices based on hydrological information such as streamflow may not directly or only represent the drought as a natural hazard. As shown and discussed in detail for cases in the UK by Tijdeman et al (), streamflow may show a naturally lagged signal and regulated streamflow may not at all show a drought signal if regulation mitigates the water deficit in the river. Large‐scale maps displaying the drought situation based on or including streamflow observations may therefore be less straightforward to interpret regarding the risk of further drought impacts.…”

“…While it is often possible to generalize the natural controls on streamflow, it can be difficult to generalize the human influences because they can vary in overall impact, timing, and degree. Reservoir operations and groundwater abstractions can both intensify or mitigate the hydrological situation downstream (Tijdeman et al, ). Rangecroft et al () showed a decrease in drought occurrence and severity after the construction of an upstream reservoir used to secure water availability for agriculture downstream.…”

“…López‐Moreno et al (), however, showed an increase in drought occurrence and severity downstream after the construction of a reservoir that stores water during drought. Van Loon and Van Lanen () showed an increase in drought duration and severity compared to the natural situation due to intensive groundwater abstraction whereas Tijdeman et al () showed an example where groundwater abstractions were likely used to augment streamflow during periods of drought. Other human influences such as diversions, instream abstractions, water transfers, or land use change (e.g., urbanization or intensification or changes in agriculture; e.g., Zhang & Schilling, ) also exert a control on streamflow and consequently on the relationship between precipitation and streamflow.…”

A framework for quantifying the impacts of climate change and human activities on hydrological drought in a semiarid basin of Northern China

“…To date, there have been some studies itemized for analysis of the effects of climate change and human activities on hydrological drought, in which the assessments of climate change impacts are mainly based on the drought indices evaluation considering the changes of meteorological conditions (Dai, ; Safavi, Raghibi, Mazdiyasni, & Mortazavi‐Naeini, ; Sheffield et al, ; Trenberth et al, ; Wang et al, ; Yu, Li, Hayes, Svoboda, & Heim, ; Zhu, Wang, Singh, & Liu, ), although the studies of human activities impacts are mainly based on the watersheds comparative analysis and natural runoff reconstruction (Bazrafshan & Hejabi, ; Firoz, Nauditt, Fink, & Ribbe, ; He et al, ; Tijdeman, Hannaford, & Stahl, ; Wan et al, ; Zhang et al, ). For instance, Wang et al () evaluated the spatiotemporal variation of future drought (2016–2100) in the Pearl River Basin in South China and found that climate change enhances the severity and variability of drought in the Pearl River Basin in the 21st century.…”

“…For instance, Wang et al () evaluated the spatiotemporal variation of future drought (2016–2100) in the Pearl River Basin in South China and found that climate change enhances the severity and variability of drought in the Pearl River Basin in the 21st century. Tijdeman et al () quantified the impact of the human activities on the streamflow drought by comparing the data set consisting of catchments with near‐natural flow as well as catchments for which different human influences indicated in the metadata. Compared with the itemized impact assessment, there are only a few investigations comprehensively analysed the effects of climate change and human activities on hydrological drought (Lin et al, ; Liu et al, ; Ren et al, ; Van Loon & Van Lanen, ).…”