The goal of this study was to identify the possibility of climatic trend for trimester in time serie of rainfall(1975 a 2005), applying non parametric Mann-Kendall test. The data had been gotten by ...National WaterAgency (ANA). The results indicate which the first trimester it presented no significant trend, the second equarter trimesters it presented a negative trend. In relation to third trimester the test it showed negativetrend but is not possible to prove graphically.
The existence of a trend in a hydrological time series is detected by statistical tests. The power of a test is the probability that it will reject a null hypothesis when it is false. In this study, ...the power of the parametric t-test for trend detection is estimated by Monte Carlo simulation for various probability distributions and compared with the power of the non-parametric Mann-Kendall test. The t-test has less power than the non-parametric test when the probability distribution is skewed. However, for moderately skewed distributions the power ratio is close to one. Annual streamflow records in various regions of Turkey are analyzed by the two tests to compare their powers in detecting a trend.
Variability and Trends in the Vișeu River Runoff Regime. The classic hydrological water management dealt with the changing resources by assuming the existence of stationarity. Once stationarity is ...neglected in the design of hydraulic engineering, numerous errors and risk may exist in the operations and management strategies and will lead to unforeseen losses. Thus, one of the most important questions in today’s hydrology are: Did stationarity die? and if it is true How did stationarity die? As we know the climatic change is widely accepted so it is sad that by 2050 the effects of climate change may have a generally larger effect on flow regimes than it is estimated that dams and water withdrawals. If this is so, we must consideration that in this moment one of the most important aspect/moment is the change point identification in a period, from where significant change has occurred in a time series, for this we choose to use the Ms Excel Addinsoft XLStat to assess the homogeneity of the data by the Pettitt’s test, the von Neumann ratio test, the Buishand range test and also the standard normal homogeneity tests (SNHT). For the trend analysis we used the Mann-Kendall test and the classic linear regression test. Based on the results, we conclude that in case of the Vișeu watershed stationarity is questionable if not totally missing. As we see even if the precipitation values do not show significant changes regarding their homogeneity, the runoff series are changing, and in most cases this change is identified in the 20thcentury last decade. These results urge us to rethink and to reevaluate our sustainable water resource management for the future.
Variability and Trends in the Vișeu River Runoff Regime. The classic hydrological water management dealt with the changing resources by assuming the existence of stationarity. Once stationarity is ...neglected in the design of hydraulic engineering, numerous errors and risk may exist in the operations and management strategies and will lead to unforeseen losses. Thus, one of the most important questions in today’s hydrology are: Did stationarity die? and if it is true How did stationarity die? As we know the climatic change is widely accepted so it is sad that by 2050 the effects of climate change may have a generally larger effect on flow regimes than it is estimated that dams and water withdrawals. If this is so, we must consideration that in this moment one of the most important aspect/moment is the change point identification in a period, from where significant change has occurred in a time series, for this we choose to use the Ms Excel Addinsoft XLStat to assess the homogeneity of the data by the Pettitt’s test, the von Neumann ratio test, the Buishand range test and also the standard normal homogeneity tests (SNHT). For the trend analysis we used the Mann-Kendall test and the classic linear regression test. Based on the results, we conclude that in case of the Vișeu watershed stationarity is questionable if not totally missing. As we see even if the precipitation values do not show significant changes regarding their homogeneity, the runoff series are changing, and in most cases this change is identified in the 20thcentury last decade. These results urge us to rethink and to reevaluate our sustainable water resource management for the future.
PDF