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3 Climatic Conditions <br />Local climate is one of the principal controls on groundwater levels in the Stegner Farm area as <br />precipitation recharges the shallow aquifer while temperature, evaporation and plant <br />transpiration ("evapotranspiration") limit recharge and remove water from the shallow <br />subsurface. A review of the precipitation, temperature, and evapotranspiration data between 1995 <br />and 2001 for the Fort Collins, Colorado area was made to determine the variation in climatic <br />conditions prior to and since the slurry wall was installed at the Stegner Farm property. <br />3.1 Precipitation and Temperature <br />Precipitation and temperature (i.e., 90-degree days) data were obtained from the Colorado <br />Climate Center for Station 53005 at Fort Collins, Colorado for the period between January 1995 <br />through December 2001. These data were compiled and analyzed to determine the total annual <br />precipitation and the total number of 90-degree days for each year. A summary of the annual <br />precipitation and temperature data is presented in Figures 2 and 3. Figure 2 is a bar chart <br />showing the total annual precipitation for this station for each year (1995 through 2001). This <br />figure also shows the average annual total precipitation (15.26 inches) for this station for the <br />period between 1900 and 1999. This value is referred to as the "normal" amount of annual <br />precipitation in this report. <br />The results shown on Figure 2 indicate that total precipitation for each year prior to the <br />installation of the Stegner Farm slurry wall was generally near or above normal. The total annual <br />precipitation values for these pre-slurry wall years ranged between near normal and 65 percent <br />above normal. Comparison of these data with precipitation totals for 2000 and 2001 ("the post- <br />slurry wall" period) indicate that the total annual precipitation for these two years is about 21 to <br />26 percent below normal. These data suggest that the Fort Collins area has been experiencing <br />drought conditions since the slurry wall was installed. <br />' Figure 3 shows the total annual number of 90-degree days for 1995 through 2001. Note that 90- <br />degree days normally occur during the summer months. This figure also shows the average <br />' annual number of 90-degree days for the period between 1961 and 1999. A 90-degree day is a <br />day where the maximum temperature equaled or exceeded 90 degrees Fahrenheit (°F). The <br />' results shown on Figure 3 indicate that the number of 90-degree days for each year prior to the <br />installation of the Stegner Fann slurry wall ranged between 18 percent below normal to 65 <br />percent above normal. Comparison of the number of 90-degree days in 2000 and 2001 indicate <br />4 <br /> <br />