Variations in climatic characteristics as related to evapotranspiration in South Park, central Park County, Colorado

Data collected during May through September in 1977, 1978, and 1979 at the towns of Jefferson and Fairplay, and at Antero Reservoir were analyzed to determine variations in climatic characteristics in South Park. An analysis of variance technique was used to determine between-station differences in climatic characteristics. Knowledge of these climatic characteristics will aid State and local agencies in determining the amount of water that may be transferred from agricultural use in South Park to municipal use in the Denver metropolitan area. Results of the analysis of variance of the climatic characteristics can be summarized as follows: 1. Daily maximum temperature was statistically different between the Fairplay and Antero Reservoir stations and between the Jefferson and Antero Reservoir stations at the 1-percent level of significance. Daily maximum air temperature was greater at the Antero Reservoir station than at the Jefferson and Fairplay stations. 2. Daily minimum air temperature was statistically different between the three stations at the 1-percent level of significance. The Antero Reservoir station had the greatest average and the Jefferson station the lowest average daily minimum air temperature. 3. Daily average air temperature from the hygrothermograph records was statistically different between all stations at the 1-percent level of significance. The Antero Reservoir station had the highest and the Fairplay station the lowest daily average air temperature. 4. Daily pan evaporation was statistically different between the Jefferson and Fairplay stations and between the Jefferson and Antero Reservoir stations at the 1-percent level of significance. The Fairplay and Antero Reservoir stations had greater daily pan evaporation than the Jefferson station. 5. Daily cumulative wind was statistically different between the three stations at the 1-percent level of significance. The cumulative wind was greatest at the Fairplay station and lowest at the Jefferson station. 6. Daily relative humidity was statistically different between the three stations at the 1-percent level of significance. The Jefferson station had the highest and the Fairplay station the lowest relative humidity. 7. Daily solar radiation was statistically different between the three stations at the 1-percent level of significance. Solar radiation was greatest at the Jefferson station and least at the Antero Reservoir station. 8. Daily precipitation was not significantly different between the three stations. Estimates of potential evapotranspiration made using the Penman equation were not significantly different between the three stations. The lack of spatial variations in the estimated potential evapotranspi ration indicates that no one climatic characteristic can be used as an indicator of spatial variation of potential evapotranspiration. Variations in solar radiation, as much as 101 langleys per day, between the stations at Jefferson, Fairplay, and Antero Reservoir indicate that solar radiation needs to be measured at sites where evapotranspiration is being determined. With the exception of precipitation during 1977 at the Antero Reservoir station, seasonal precipitation during 1977-78 at all the study stations was less than the 17-year mean seasonal precipitation at Antero Reservoir. In 1979, all stations had greater seasonal precipitation than the 17-year mean seasonal precipitation at Antero Reservoir. During 1977, the seasonal average air temperature at Antero Reservoir was greater than the 17-year mean, during 1978 it was about equal to the 17-year mean, and during 1979 it was slightly below the 17-year mean.