Curve Numbers for Golf Course Watersheds

Abstract

Storm event runoff is a critical component to the environmental and structural design related to hydrology. The curve number (CN) method is a robust and accepted method for determining excess rainfall. Measured CNs for golf course watersheds, and for that matter hydrologic data from golf course watersheds, are limited. Rainfall-runoff data from two golf courses, Morris Williams Municipal Golf Course (MWMGC) located in a semi-arid climate in Texas and Northland Country Club located in a cool-humid climate in Minnesota, were collected for a 5-year period. One hundred twenty-seven events on MWMGC and 86 events on NCC were used to determine CNs. The measured CNs, for normal antecedent moisture (AMC II) conditions were determined to be 63.4 at MWMGC and 78.2 at NCC. Each of the four methods used to calculate CN from the measured data produced CNs that were consistent for each site (standard deviation at MWMGC was 0.7, while standard deviation at NCC was 1.9). Hydrologic soil group, local climate that affects evapotranspiration (ET) and thus antecedent soil moisture, and site characteristics (specifically slope, drainage density, and connectivity) appear to have the most impact on the establishment of CNs for these two golf courses. The findings of this study indicate the importance of understanding local climate and site characteristics that influence hydrology when determining CNs. The CNs developed for these courses provide partial confirmation of CNs previously suggested for plot-scale turfgrass systems but more importantly highlight the significance of having localized measured data. The results from this study suggests that determination of CNs for golf course watersheds should not be based on traditional sources that rely solely on hydrologic soil classifications and land use or vegetative cover type.