Regional scale spatio‐temporal consistency of precipitation variables related to water resource management and planning

Abstract

ABSTRACT: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 km 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.

Statistical Changes of Lake Stages in Two Rapidly Urbanizing Watersheds

“…Paynter and Nachabe (2009) found that west-central Florida rainfall patterns are spatially homogenous and temporally stationary and no significant shifts that would correlate to trends in lake levels were evidenced. For the present study, the authors selected two lakes undergoing rapid urbanization within the west-central Florida region based on the availability of sufficient data, lack of direct lake withdrawals and lack of proximity to wellfields.…”

“…• Rainfall records were nearly 100% complete for the time periods analyzed, however, none of the lakes had gages located immediately at the lakes themselves but were within 2 to 6 km of the lakes analyzed. This is well within an acceptable range for this analysis (Paynter and Nachabe 2009) but there will be slight variability between gage site and lake rainfall amounts. • Although evaporation is highly correlated with temperature, it is also dependent on wind, humidity and other factors for which data were not available.…”