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Climate stationary is often an assumption in water planning, however this assumption has recently been called into question in light of long-term climate variability and climate change. The purpose of this analysis is to evaluate climate trends in the Alabama-Coosa-Tallapoosa (ACT) and Apalachicola-Chattahoochee-Flint (ACF) river basins in Georgia, Alabama, and Florida. Water supply in these river basins is of a particular interest given the disputes regarding equitable management of water between the three states. This work evaluated trends in the United States Historical Climate Network (USHCN) stations using both linear regression and Mann Kendal trend tests for annual, seasonal and monthly time frames for average rainfall, mean temperature, maximum temperature, and minimum temperature. Trend analyses were conducted over the 1895-2009 period for which data was available and also analyzed on the period 1950-2009 to evaluate recent trends. Since station records are not independent, the collective or field significance of trends were evaluated using a Monte Carlo permutation procedure. All trends were evaluated at the (P≤0.05) significance level. For rainfall, field-significant positive trends were only found in the September-November season for the 1895-2009 period of record. Field significant trends for temperature variables were found for both time periods. For temperature means a large number of stations were found to be decreasing in the summer and increasing in the winter. The maximum temperatures were found to be decreasing in the summer and fall and increasing in the spring and summer. The minimum temperatures were found to be mostly decreasing. During the 1950-2009 there were fewer field significant trends and less stations showing significant trends, the exception was for minimum temperatures with a large number of stations showing a significant trend in increasing minimum temperatures. |