Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens
This research study was carried out to investigate the characteristics of drought based on the joint distribution of two dependent variables, the duration and severity, in the Eastern Cape Province, South Africa. The drought variables were computed from the Standardized Precipitation Index for 6- an...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2020-07-01
|
| Series: | Water |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4441/12/7/1938 |
| _version_ | 1797563045308792832 |
|---|---|
| author | Christina M. Botai Joel O. Botai Abiodun M. Adeola Jaco P. de Wit Katlego P. Ncongwane Nosipho N. Zwane |
| author_facet | Christina M. Botai Joel O. Botai Abiodun M. Adeola Jaco P. de Wit Katlego P. Ncongwane Nosipho N. Zwane |
| author_sort | Christina M. Botai |
| collection | DOAJ |
| description | This research study was carried out to investigate the characteristics of drought based on the joint distribution of two dependent variables, the duration and severity, in the Eastern Cape Province, South Africa. The drought variables were computed from the Standardized Precipitation Index for 6- and 12-month accumulation period (hereafter SPI-6 and SPI-12) time series calculated from the monthly rainfall data spanning the last five decades. In this context, the characteristics of climatological drought duration and severity were based on multivariate copula analysis. Five copula functions (from the Archimedean and Elliptical families) were selected and fitted to the drought duration and severity series in order to assess the dependency measure of the two variables. In addition, Joe and Gaussian copula functions were considered and fitted to the drought duration and severity to assess the joint return periods for the dual and cooperative cases. The results indicate that the dependency measure of drought duration and severity are best described by Tawn copula families. The dependence structure results suggest that the study area exhibited low probability of drought duration and high probability of drought severity. Furthermore, the multivariate return period for the dual case is found to be always longer across all the selected univariate return periods. Based on multivariate analysis, the study area (particularly Buffalo City, OR Tambo and Alfred Zoo regions) is determined to have higher/lower risks in terms of the conjunctive/cooperative multivariate drought risk (copula) probability index. The results of the present study could contribute towards policy and decision making through e.g., formulation of the forward-looking contingent plans for sustainable management of water resources and the consequent applications in the preparedness for and adaptation to the drought risks in the water-linked sectors of the economy. |
| first_indexed | 2024-03-10T18:37:00Z |
| format | Article |
| id | doaj.art-dcdc645189f94e6eb3b0ff282545a0a1 |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-10T18:37:00Z |
| publishDate | 2020-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Water |
| spelling | doaj.art-dcdc645189f94e6eb3b0ff282545a0a12023-11-20T06:10:21ZengMDPI AGWater2073-44412020-07-01127193810.3390/w12071938Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula LensChristina M. Botai0Joel O. Botai1Abiodun M. Adeola2Jaco P. de Wit3Katlego P. Ncongwane4Nosipho N. Zwane5South African Weather Service, Private Bag X097, Pretoria 0001, South AricaSouth African Weather Service, Private Bag X097, Pretoria 0001, South AricaSouth African Weather Service, Private Bag X097, Pretoria 0001, South AricaSouth African Weather Service, Private Bag X097, Pretoria 0001, South AricaSouth African Weather Service, Private Bag X097, Pretoria 0001, South AricaSouth African Weather Service, Private Bag X097, Pretoria 0001, South AricaThis research study was carried out to investigate the characteristics of drought based on the joint distribution of two dependent variables, the duration and severity, in the Eastern Cape Province, South Africa. The drought variables were computed from the Standardized Precipitation Index for 6- and 12-month accumulation period (hereafter SPI-6 and SPI-12) time series calculated from the monthly rainfall data spanning the last five decades. In this context, the characteristics of climatological drought duration and severity were based on multivariate copula analysis. Five copula functions (from the Archimedean and Elliptical families) were selected and fitted to the drought duration and severity series in order to assess the dependency measure of the two variables. In addition, Joe and Gaussian copula functions were considered and fitted to the drought duration and severity to assess the joint return periods for the dual and cooperative cases. The results indicate that the dependency measure of drought duration and severity are best described by Tawn copula families. The dependence structure results suggest that the study area exhibited low probability of drought duration and high probability of drought severity. Furthermore, the multivariate return period for the dual case is found to be always longer across all the selected univariate return periods. Based on multivariate analysis, the study area (particularly Buffalo City, OR Tambo and Alfred Zoo regions) is determined to have higher/lower risks in terms of the conjunctive/cooperative multivariate drought risk (copula) probability index. The results of the present study could contribute towards policy and decision making through e.g., formulation of the forward-looking contingent plans for sustainable management of water resources and the consequent applications in the preparedness for and adaptation to the drought risks in the water-linked sectors of the economy.https://www.mdpi.com/2073-4441/12/7/1938droughtdependence measureStandardized Precipitation Indexcopulareturn periods |
| spellingShingle | Christina M. Botai Joel O. Botai Abiodun M. Adeola Jaco P. de Wit Katlego P. Ncongwane Nosipho N. Zwane Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens Water drought dependence measure Standardized Precipitation Index copula return periods |
| title | Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens |
| title_full | Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens |
| title_fullStr | Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens |
| title_full_unstemmed | Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens |
| title_short | Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens |
| title_sort | drought risk analysis in the eastern cape province of south africa the copula lens |
| topic | drought dependence measure Standardized Precipitation Index copula return periods |
| url | https://www.mdpi.com/2073-4441/12/7/1938 |
| work_keys_str_mv | AT christinambotai droughtriskanalysisintheeasterncapeprovinceofsouthafricathecopulalens AT joelobotai droughtriskanalysisintheeasterncapeprovinceofsouthafricathecopulalens AT abiodunmadeola droughtriskanalysisintheeasterncapeprovinceofsouthafricathecopulalens AT jacopdewit droughtriskanalysisintheeasterncapeprovinceofsouthafricathecopulalens AT katlegopncongwane droughtriskanalysisintheeasterncapeprovinceofsouthafricathecopulalens AT nosiphonzwane droughtriskanalysisintheeasterncapeprovinceofsouthafricathecopulalens |