SPATIAL AND SEASONAL VARIABILITY OF FIELD MEASURED INFILTRATION RATES ON A RANGELAND SITE IN UTAH

Both spatial and temporal variability of infiltration rates on a rangeland site in west-central Utah were studied. The experiment utilized a grid 20 m long and 18 m wide in both grazed and ungrazed sites with a sample spacing of 2 m within the grid. To investigate the seasonal effect on variability of infiltration rates, data were collected for 3 seasons (summer, fall and spring). Measured infiltration rates at 10 and 30 min during all seasons and under grazed vs. ungrazed conditions were all found to approximate a 2-parameter log normal distribution. Regionalized variable theory was applied to the data through the development of autocorrelograms and semivariograms, revealing a complete lack of variance structure among the infiltration rates. This finding excluded the possibility of using the Kriging technique for interpolation. Seasonal effect was very important in influencing infiltration rates. The difference between the measured infiltration rates at both grazed and ungrazed sites was very significant for the 3 seasons under study.