Probabilistic assessment of drought plays an important role in providing valuable information for evaluating water resources systems under drought conditions, and bivariate copulas are effective and efficient for the ...Probabilistic assessment of drought plays an important role in providing valuable information for evaluating water resources systems under drought conditions, and bivariate copulas are effective and efficient for the probabilistic assessment of drought based on joint distributions and/or joint return periods of drought characteristics. In this study, hydrological drought events and their characteristics (including duration and severity) in the Tien Yen River Basin of Quang Ninh province are detected using the Standardized Streamflow Index (SSFI). The BB8Copula is selected as the best-fit copula for hydrological drought duration and severity. Joint probabilities and joint return periods of drought duration and severity in the cases “and” and “or” are calculated based on the BB8Copula, which are employed for drought assessment. The results show that the drought events with 1-season or cross-quarter duration were more popular than others;joint probabilities and joint return periods of the detected drought events from 1962 to 2009, ranged from 0.2% to 92.2% and from 0.782 years to 315.414 years, respectively, in the case “and”, and ranged from 3.8% to 99.6% and from 0.724 years to 18.785 years, respectively, in the case “or”.展开更多
The hydrographic eastern Mediterranean Basin of Turkey is a drought sensitive area.The basin is an important agricultural area and it is necessary to determine the extent of extreme regional climatic changes as they o...The hydrographic eastern Mediterranean Basin of Turkey is a drought sensitive area.The basin is an important agricultural area and it is necessary to determine the extent of extreme regional climatic changes as they occur in this basin.Pearson’s correlation coefficient was used to show the correlation between standardized precipitation index(SPI)and standardized streamflow index(SSI)values on different time scales.Data from five meteorological stations and seven stream gauging stations in four sub-basins of the eastern Mediterranean Basin were analyzed over the period from 1967 to 2017.The correlation between SSI and SPI indicated that in response to meteorological drought,hydrological drought experiences a one-year delay then occurs in the following year.This is more evident at all stations from the mid-1990 s.The main factor causing hydrological drought is prolonged low precipitation or the presence of a particularly dry year.Results showed that over a long period(12 months),hydrological drought is longer and more severe in the upper part than the lower part of the sub-basins.According to SPI-12 values,an uninterrupted drought period is observed from 2002–2003 to 2008–2009.Results indicated that among the drought events,moderate drought is the most common on all timescales in all sub-basins during the past 51 years.Long-term dry periods with moderate and severe droughts are observed for up to 10 years or more since the late 1990 s,especially in the upper part of the sub-basins.As precipitation increases in late autumn and early winter,the stream flow also increases and thus the highest and most positive correlation values(0.26–0.54)are found in January.Correlation values(ranging between–0.11 and–0.01)are weaker and negative in summer and autumn due to low rainfall.This is more evident at all stations in September.The relation between hydrological and meteorological droughts is more evident,with the correlation values above 0.50 on longer timescales(12-and 24-months).The results presented in this study allow an understanding of the characteristics of drought events and are instructive for overcoming drought.This will facilitate the development of strategies for the appropriate management of water resources in the eastern Mediterranean Basin,which has a high agricultural potential.展开更多
文摘Probabilistic assessment of drought plays an important role in providing valuable information for evaluating water resources systems under drought conditions, and bivariate copulas are effective and efficient for the probabilistic assessment of drought based on joint distributions and/or joint return periods of drought characteristics. In this study, hydrological drought events and their characteristics (including duration and severity) in the Tien Yen River Basin of Quang Ninh province are detected using the Standardized Streamflow Index (SSFI). The BB8Copula is selected as the best-fit copula for hydrological drought duration and severity. Joint probabilities and joint return periods of drought duration and severity in the cases “and” and “or” are calculated based on the BB8Copula, which are employed for drought assessment. The results show that the drought events with 1-season or cross-quarter duration were more popular than others;joint probabilities and joint return periods of the detected drought events from 1962 to 2009, ranged from 0.2% to 92.2% and from 0.782 years to 315.414 years, respectively, in the case “and”, and ranged from 3.8% to 99.6% and from 0.724 years to 18.785 years, respectively, in the case “or”.
文摘The hydrographic eastern Mediterranean Basin of Turkey is a drought sensitive area.The basin is an important agricultural area and it is necessary to determine the extent of extreme regional climatic changes as they occur in this basin.Pearson’s correlation coefficient was used to show the correlation between standardized precipitation index(SPI)and standardized streamflow index(SSI)values on different time scales.Data from five meteorological stations and seven stream gauging stations in four sub-basins of the eastern Mediterranean Basin were analyzed over the period from 1967 to 2017.The correlation between SSI and SPI indicated that in response to meteorological drought,hydrological drought experiences a one-year delay then occurs in the following year.This is more evident at all stations from the mid-1990 s.The main factor causing hydrological drought is prolonged low precipitation or the presence of a particularly dry year.Results showed that over a long period(12 months),hydrological drought is longer and more severe in the upper part than the lower part of the sub-basins.According to SPI-12 values,an uninterrupted drought period is observed from 2002–2003 to 2008–2009.Results indicated that among the drought events,moderate drought is the most common on all timescales in all sub-basins during the past 51 years.Long-term dry periods with moderate and severe droughts are observed for up to 10 years or more since the late 1990 s,especially in the upper part of the sub-basins.As precipitation increases in late autumn and early winter,the stream flow also increases and thus the highest and most positive correlation values(0.26–0.54)are found in January.Correlation values(ranging between–0.11 and–0.01)are weaker and negative in summer and autumn due to low rainfall.This is more evident at all stations in September.The relation between hydrological and meteorological droughts is more evident,with the correlation values above 0.50 on longer timescales(12-and 24-months).The results presented in this study allow an understanding of the characteristics of drought events and are instructive for overcoming drought.This will facilitate the development of strategies for the appropriate management of water resources in the eastern Mediterranean Basin,which has a high agricultural potential.
