科研之友
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摘要
The focus of this research was to determine the extent of spatio-temporal changes in precipitation patterns using methods that can be regionalized and applied to various water resources such as lakes, streams, reservoirs or other water bodies. Many water resources throughout the world have demonstrated changes in historic water levels. As precipitation is the major input to these water bodies, it is important to investigate any changes in rainfall in both time and space. To investigate these patterns regionally, appropriate distributions, either gamma or generalized extreme value (GEV), were fitted to variables at a number of rainfall gauges within 40 kin of a particular lake using maximum likelihood estimation. The variables included total annual rainfall, rainfall days per year, maximum annual event rainfall and maximum annual interevent days. Once the distribution parameters were estimated, an average, representative, distribution for each variable with 99% confidence limits was developed to determine if the fits for all gauges and variables were contained by these limits. To examine the temporal variation, distribution parameters were allowed to vary with time and then compared to constant parameter fits via likelihood ratio tests to determine if the varying parameter model significantly improved the fit. The spatial distribution of rainfall variables was found to be quite homogenous within the given confidence limits with some exceptions at high and low percentiles. Furthermore, the temporal distribution of rainfall variables was found to be stationary with only one gauge showing a significant trend. The average distribution for each precipitation variable developed can be applied at water resources within the region without rainfall gauges in proximity due to the spatial homogeneity and temporal stationarity identified. The methodology can be adapted to water resource management and planning in other regions.
- 出版日期2009-9
