Variations in High-Intensity Precipitation under Climate Changes in the LMRB and Implications for Drinking Water Supply Security

A systematic temporal and spatial analysis is being conducted at the U.S. EPA on historical precipitation and stream flow in the Lower Mississippi River basin (LMRB) and their relationships with Atlantic hurricanes and flooding events. The objectives are to decipher the periodicity and long-term trends exhibited in the hydroclimatic regime, and to determine their implications on the security of community water supplies in the region and the Gulf Coast, the parts of the continental U.S. prone to the negative impacts of extreme weather events under the current and future climate conditions. Statistical modeling using wavelet functions shows periodicity of continental precipitation and hurricanes with characteristic changes of trends around 1890–1900, 1940–1960, and the 1990s. These long-term decadal and multi-decadal changes were identified in a spatial modeling and wavelet frequency analysis of the 24-hour daily precipitation data obtained from the National Climatic Data Center. Long-term variations are also detected in hurricane and flooding events. Based on these findings, one can incorporate the hydroclimatic periodicity and long-term variations into the emergency water supply management and system designs. Measures such as water intake protection, using decentralized water supply, and planning emergency management are potential options in natural disaster preparedness. The results of the first phase investigation are discussed.