Process Controls on Flood Seasonality in Brazil

Chagas, Vinícius B. P.; Chaffe, Pedro Luiz Borges; Blöschl, Günter

doi:10.1029/2021gl096754

Cited by 10 publications

(6 citation statements)

References 59 publications

(82 reference statements)

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“…Similarly, increased RFS is associated with increased precipitation seasonality in S. BR (table S1; r = 0.93) (fig. S6), in agreement with ( 29 ). We noticed that most stations in the Pacific Northwest show increasing monthly river flow in the late spring and summer, contradicting the findings of previous studies (fig.…”

Section: Regional Seasonality Changes and Potential Mechanismssupporting

confidence: 90%

Anthropogenic climate change has influenced global river flow seasonality

Wang,

Liu,

Klaar

et al. 2024

Science

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Riverine ecosystems have adapted to natural discharge variations across seasons. However, evidence suggesting that climate change has already impacted magnitudes of river flow seasonality is limited to local studies, mainly focusing on changes of mean or extreme flows. This study introduces the use of apportionment entropy as a robust measure to assess flow-volume nonuniformity across seasons, enabling a global analysis. We found that ~21% of long-term river gauging stations exhibit significant alterations in seasonal flow distributions, but two-thirds of these are unrelated to trends in annual mean discharge. By combining a data-driven runoff reconstruction with state-of-the-art hydrological simulations, we identified a discernible weakening of river flow seasonality in northern high latitudes (above 50°N), a phenomenon directly linked to anthropogenic climate forcing.

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Section: Regional Seasonality Changes and Potential Mechanismssupporting

confidence: 90%

Anthropogenic climate change has influenced global river flow seasonality

Wang,

Liu,

Klaar

et al. 2024

Science

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“…We analyze only catchments that agree with the following selection criteria: (a) less than 5% of the catchment's area is covered by urban use; (b) total upstream artificial water storage capacity is lower than 10% of the annual river discharge; (c) are larger than 100 km 2 , as smaller catchments are usually close to metropolitan areas. These selection thresholds considerably limit the influence of human interference on the analysis and are similar to those found in other studies (e.g., Beck et al, 2013;Chagas et al, 2022b;Peña-Arancibia et al, 2010). The results are not sensitive to small variations (i.e., ±50%) in these selection thresholds (not shown).…”

Section: Water Table Depthsupporting

confidence: 88%

Regional Low Flow Hydrology: Model Development and Evaluation

Chagas,

Chaffe,

Blöschl

2024

Water Resources Research

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Low flows result from the interplay of climatic variability and catchment storage dynamics, but it is unclear which of these variables is more relevant for explaining low flow spatial patterns. Here, we develop a new conceptual model that integrates process‐based hydrological knowledge with statistics and test it for 1,400 Brazilian catchments. Through comparative hydrology, we isolate the low flow generating mechanisms and estimate their components using linear model trees. The model explains 58% of the spatial variance in 7‐day minimum annual flows (Qmin) based on climate and catchment characteristics. The primary Qmin controls depend on the spatial scale of analysis. Catchment characteristics govern Qmin up to the continental scale (107 km2), where their relative importance matches that of climate. At subcontinental scales, catchment characteristics are twice as important as climate in predicting Qmin, suggesting that low flows are governed by the catchment's capacity to attenuate the climatic variability through water storage. Geological properties are the most important catchment characteristics, particularly bedrock type, lithology and topographic slope, determining streamflow recession rates in the dry season. Soil properties, primarily soil class and depth, are half as important as geology. Climate impacts Qmin mainly through mean annual rainfall minus evaporation, representing the potential groundwater recharge, while dry‐season length has the lowest impact. These results hold mainly for highly seasonal and snow‐free climates. Low flow hydrology that combines statistics with process understanding offers a promising framework for understanding regional low flow generating mechanisms and could support other estimation models than that presented here.

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“…The patterns of flood timing shift (figures 4 and 5) as well as anomalies in the hydrometeorological variables (figure 6) can be contextualized with existing literature. In catchments whose flood-generation mechanisms are controlled by soil moisture and groundwater storage (Dunne and Black 1970a, 1970b, Chagas et al 2022, later floods could be explained by depleted surface and sub-surface water storage due to drought conditions. Those water storages need to be replenished before streamflow responds ( Van Loon and Laaha 2015).…”

Section: Processes Of Drought Effects On Flood Timing and Severitymentioning

confidence: 99%

Compound and consecutive drought-flood events at a global scale

Matanó,

Berghuijs,

Mazzoleni

et al. 2024

Environ. Res. Lett.

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Flooding during or after droughts poses significant challenges to disaster risk management. However, interactions between droughts and floods are often overlooked as studies typically analyse these events in isolation. Here we explore historical occurrences of compound and consecutive drought-flood events and drought effects on flood severity and timing by analysing global datasets of hydrometeorological and biophysical variables for 8255 catchments worldwide. These data show that 24% of floods globally (anomalies above the 85th percentile) are preceded by, or happen during, drought conditions. Flood events occurring during drought conditions are typically of lower magnitude, especially in arid regions, while floods following drought events have a severity distribution comparable to single flood events. For most drought-flood events, flood timing appears relatively unaffected by drought conditions, but almost a quarter of the drought-flood events had flood timings occurring two to three months later than expected. These shifts in flood timing suggest droughts potentially affect flood-generating processes. As both drought and flood occurrences are projected to increase in a warming climate, interactions between them may become more common and need to be accounted for in flood risk assessment and management.

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Process Controls on Flood Seasonality in Brazil

Abstract: One way of exploring the relative importance of these drivers is by analyzing flood seasonality, defined as the day of the year that floods occur. A coincidence in the timing of floods and their drivers can be used as a proxy for the causality of flood generation (

Cited by 10 publications

References 59 publications

Anthropogenic climate change has influenced global river flow seasonality

Anthropogenic climate change has influenced global river flow seasonality

Regional Low Flow Hydrology: Model Development and Evaluation

Compound and consecutive drought-flood events at a global scale

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