Drought‐Rich Periods Are More Likely Than Flood‐Rich Periods in Brazil
Abstract Streamflow exhibits persistent decadal variability; however, it is unclear if the magnitude and spatial extent of these variabilities are symmetric for droughts and floods. Here, we examine drought‐rich and flood‐rich periods in 319 streamflow gauges in Brazil from 1940 to 2020. Drought‐ an...
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Wiley
2024-10-01
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| Series: | Water Resources Research |
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| Online Access: | https://doi.org/10.1029/2023WR035851 |
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| author | Vinícius B. P. Chagas Pedro L. B. Chaffe Günter Blöschl |
| author_facet | Vinícius B. P. Chagas Pedro L. B. Chaffe Günter Blöschl |
| author_sort | Vinícius B. P. Chagas |
| collection | DOAJ |
| description | Abstract Streamflow exhibits persistent decadal variability; however, it is unclear if the magnitude and spatial extent of these variabilities are symmetric for droughts and floods. Here, we examine drought‐rich and flood‐rich periods in 319 streamflow gauges in Brazil from 1940 to 2020. Drought‐ and flood‐rich periods are detected by computing annual streamflow minima and maxima time series and using scan statistics to verify if events exceeding a threshold follow a Bernoulli process. We contrast streamflow time clustering with rainfall, evaporation, water abstraction, the Atlantic Multidecadal Oscillation (AMO), and the Pacific Decadal Oscillation (PDO). We detected a higher spatial frequency of drought‐ than flood‐rich periods. For 5‐year return period thresholds, drought‐rich periods are observed in 81% of the basins, 16.7 times the false positive rate (4.8%) and 4.7 times flood‐rich periods (17%). This asymmetry is linked with sharp increases in water abstractions since the 1990s and a higher prevalence of rainfall‐poor periods (41% of gauges) compared to rainfall‐rich (22% of gauges), which we interpret as being further amplified into drought‐rich periods due to an interannual persistence of water storage deficits. Brazil experienced a dry period until the 1960s, extensive flooding in the 1980s, and record low flows from the 2000s onward. Drought and flood‐rich periods are well aligned with rainfall clustering, water abstractions, the AMO and PDO. Droughts‐rich periods are more frequent in shorter time scales (several years to one decade) and flood‐rich periods in longer time scales (a few decades). Our findings highlight the nonlinearity and asymmetry of drought and flood change at decadal scales. |
| format | Article |
| id | doaj-art-9c75966329474aed854fc87a55075c8d |
| institution | Kabale University |
| issn | 0043-1397 1944-7973 |
| language | English |
| publishDate | 2024-10-01 |
| publisher | Wiley |
| record_format | Article |
| series | Water Resources Research |
| spelling | doaj-art-9c75966329474aed854fc87a55075c8d2025-08-20T03:30:57ZengWileyWater Resources Research0043-13971944-79732024-10-016010n/an/a10.1029/2023WR035851Drought‐Rich Periods Are More Likely Than Flood‐Rich Periods in BrazilVinícius B. P. Chagas0Pedro L. B. Chaffe1Günter Blöschl2Department of Sanitary and Environmental Engineering Federal University of Santa Catarina Florianopolis BrazilDepartment of Sanitary and Environmental Engineering Federal University of Santa Catarina Florianopolis BrazilInstitute of Hydraulic Engineering and Water Resources Management Technische Universität Wien Vienna AustriaAbstract Streamflow exhibits persistent decadal variability; however, it is unclear if the magnitude and spatial extent of these variabilities are symmetric for droughts and floods. Here, we examine drought‐rich and flood‐rich periods in 319 streamflow gauges in Brazil from 1940 to 2020. Drought‐ and flood‐rich periods are detected by computing annual streamflow minima and maxima time series and using scan statistics to verify if events exceeding a threshold follow a Bernoulli process. We contrast streamflow time clustering with rainfall, evaporation, water abstraction, the Atlantic Multidecadal Oscillation (AMO), and the Pacific Decadal Oscillation (PDO). We detected a higher spatial frequency of drought‐ than flood‐rich periods. For 5‐year return period thresholds, drought‐rich periods are observed in 81% of the basins, 16.7 times the false positive rate (4.8%) and 4.7 times flood‐rich periods (17%). This asymmetry is linked with sharp increases in water abstractions since the 1990s and a higher prevalence of rainfall‐poor periods (41% of gauges) compared to rainfall‐rich (22% of gauges), which we interpret as being further amplified into drought‐rich periods due to an interannual persistence of water storage deficits. Brazil experienced a dry period until the 1960s, extensive flooding in the 1980s, and record low flows from the 2000s onward. Drought and flood‐rich periods are well aligned with rainfall clustering, water abstractions, the AMO and PDO. Droughts‐rich periods are more frequent in shorter time scales (several years to one decade) and flood‐rich periods in longer time scales (a few decades). Our findings highlight the nonlinearity and asymmetry of drought and flood change at decadal scales.https://doi.org/10.1029/2023WR035851hazardsSouth Americaextremesdroughtsfloodstime clustering |
| spellingShingle | Vinícius B. P. Chagas Pedro L. B. Chaffe Günter Blöschl Drought‐Rich Periods Are More Likely Than Flood‐Rich Periods in Brazil Water Resources Research hazards South America extremes droughts floods time clustering |
| title | Drought‐Rich Periods Are More Likely Than Flood‐Rich Periods in Brazil |
| title_full | Drought‐Rich Periods Are More Likely Than Flood‐Rich Periods in Brazil |
| title_fullStr | Drought‐Rich Periods Are More Likely Than Flood‐Rich Periods in Brazil |
| title_full_unstemmed | Drought‐Rich Periods Are More Likely Than Flood‐Rich Periods in Brazil |
| title_short | Drought‐Rich Periods Are More Likely Than Flood‐Rich Periods in Brazil |
| title_sort | drought rich periods are more likely than flood rich periods in brazil |
| topic | hazards South America extremes droughts floods time clustering |
| url | https://doi.org/10.1029/2023WR035851 |
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