Abstract
Abstract. Traditionally, long-term predictions of river discharges and their extremes include constant relationships between landscape properties and model parameters. However, due to the co-evolution of many landscape properties more sophisticated methods are necessary to quantify future landscape–hydrological model relationships. As a first step towards such an approach we use the Brutsaert and Nieber (1977) analysis method to characterize streamflow recession behaviour of ≈ 200 Swedish catchments within the context of global change and landscape co-evolution. Results suggest that the Brutsaert–Nieber parameters are strongly linked to the climate, soil, land use, and their interdependencies. Many catchments show a trend towards more non-linear behaviour, meaning not only faster initial recession but also slower recession towards base flow. This trend has been found to be independent from climate change. Instead, we suggest that land cover change, both natural (restoration of natural soil profiles in forested areas) and anthropogenic (reforestation and optimized water management), is probably responsible. Both change types are characterised by system adaptation and change, towards more optimal ecohydrological conditions, suggesting landscape co-evolution is at play. Given the observed magnitudes of recession changes during the past 50 years, predictions of future river discharge critically need to include the effects of landscape co-evolution. The interconnections between the controls of land cover and climate on river recession behaviour, as we have quantified in this paper, provide first-order handles to do so.
Highlights
River runoff is a key component of the Earth system, performing functions that include energy transfer between the geosphere and the atmosphere, sustaining vegetation growth, transport of sediments and nutrients, and providing drinking water for humanity
Several recent opinion papers in hydrology called for the use of “Darwinian” approaches that try to summarise the effects of co-evolution between soil, vegetation, atmosphere, and humans on the hydrological cycle into general emergent patterns, and use these emergent patterns to explain the origin of the observed variations (Harman and Troch, 2014; Sivapalan et al, 2011; Savenije et al, 2014; Schaefli et al, 2011; Troch et al, 2013b, 2015)
About 50 years of daily streamflow data for 316 gauging stations in Sweden have been analysed in terms of Brutsaert and Nieber (1977) streamflow recession parameters, and trends therein
Summary
River runoff is a key component of the Earth system, performing functions that include energy transfer between the geosphere and the atmosphere, sustaining vegetation growth, transport of sediments and nutrients, and providing drinking water for humanity. Key questions in defining this safe operating space are how terrestrial precipitation is divided between evapotranspiration, storage in biomass, soil and subsurface, and river runoff, and how this division is affected by climate change and human actions. Answering these questions means facing the complexity and multitude of interactions between soil, vegetation, atmosphere, and humans. Sivapalan et al (2012) described three avenues through which this human role in the Published by Copernicus Publications on behalf of the European Geosciences Union
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