Using paired catchments to quantify the human influence on hydrological droughts

Abstract

Abstract. Quantifying the influence of human activities, such as reservoir building, water abstraction, and land use change, on hydrology is crucial for sustainable future water management, especially during drought. Model-based methods are very time-consuming to set up and require a good understanding of human processes and time series of water abstraction, land use change, and water infrastructure and management, which often are not available. Therefore, observation-based methods are being developed that give an indication of the direction and magnitude of the human influence on hydrological drought based on limited data. We suggest adding to those methods a “paired-catchment” approach, based on the classic hydrology approach that was developed in the 1920s for assessing the impact of land cover treatment on water quantity and quality. When applying the paired-catchment approach to long-term pre-existing human influences trying to detect an influence on extreme events such as droughts, a good catchment selection is crucial. The disturbed catchment needs to be paired with a catchment that is similar in all aspects except for the human activity under study, in that way isolating the effect of that specific activity. In this paper, we present a framework for selecting suitable paired catchments for the study of the human influence on hydrological drought. Essential elements in this framework are the availability of qualitative information on the human activity under study (type, timing, and magnitude), and the similarity of climate, geology, and other human influences between the catchments. We show the application of the framework on two contrasting case studies, one impacted by groundwater abstraction and one with a water transfer from another region. Applying the paired-catchment approach showed how the groundwater abstraction aggravated streamflow drought by more than 200 % for some metrics (total drought duration and total drought deficit) and the water transfer alleviated droughts with 25 % to 80 %, dependent on the metric. Benefits of the paired-catchment approach are that climate variability between pre- and post-disturbance periods does not have to be considered as the same time periods are used for analysis, and that it avoids assumptions considered when partly or fully relying on simulation modelling. Limitations of the approach are that finding a suitable catchment pair can be very challenging, often no pre-disturbance records are available to establish the natural difference between the catchments, and long time series of hydrological data are needed to robustly detect the effect of the human activities on hydrological drought. We suggest that the approach can be used for a first estimate of the human influence on hydrological drought, to steer campaigns to collect more data, and to complement and improve other existing methods (e.g. model-based or large-sample approaches).

Remote sensing for drought monitoring & impact assessment: Progress, past challenges and future opportunities

“…With increased research on the effects of climate change and human activities, the role of anthropogenic influences on drought event propagation and termination is now becoming ever more apparent, suggesting that drought is not only a phenomenon induced by solely natural processes (Van Loon & Van Lanen, 2013;Van Loon et al, 2016). Various methods to assess the role of human activity on drought have been proposed (Rangecroft et al, 2019;Van Loon et al, 2019), however no such research has yet considered the role of remote sensing and earth observation in assessing anthropogenic activity and the association with drought propagation/termination.…”

Crossing the rural–urban boundary in hydrological modelling: How do conceptual rainfall–runoff models handle the specificities of urbanized catchments?

“…We collected a sample of 175 urbanized catchments (with a mean TIA above 10% over the period 1997-2017), which is far larger than the samples used in urbanized catchments studies (see the review by Salvadore et al, 2015). Benefiting from a paired-catchment framework (Martin et al, 2012;Van Loon et al, 2019;Zégre, Skaugset, Som, McDonnell, & Ganio, 2010), we compared the average behaviour of the urbanized catchments with geographically close rural catchments. Thus, an additional 175 rural catchments were used, for which mean TIA was less than 5%.…”

Regional Drought Risk in the Contiguous United States

“…The process of translation of deficits in precipitation to deficits in soil moisture, stream flow and water supply is referred to as drought propagation, which is influenced by climate and watershed properties (Apurv, et al., 2017; Haslinger et al., 2014; Konapala & Mishra, 2020; Van Loon & Laaha, 2015; Yang et al., 2017), as well as human activities (Van Loon et al., 2016). Especially, reservoir operations, groundwater pumping, and interbasin water transfer can mitigate the intensity, frequency, and the spatial extents of regions experiencing water shortages (Van Loon & Van Lanen, 2013; Van Loon et al., 2019; Wada et al., 2013; Wan et al, 2017, 2018; Wanders & Wada, 2015; Wu et al., 2017). Therefore, both natural and human factors can influence drought risk via different ways in different regions.…”