Field measured infiltration at different sites in the Northern State: 1. Scaling variability
2012
Ahmed, S.H., Agricultural Research Corporation, Land and Water Research Center, Wad Medani, P.O. Box 126, (Sudan)
Infiltration was measured at seventy five sites in the Northern State. Observations were made every 5, 10, 15, 30, 60, 120, and 180 minutes using a double ring infiltrometer. The similar media concept of Miller and Miller was used to scale the Philip infiltration equation. The seventy five cumulative infiltration data for the 180 min. was used to develop a general scaled infiltration equation for the studied area. The rest of the data i.e. observations for time lag periods less than 180 minutes were used to test validity of the developed equation. The equation predicted scaled cumulative infiltration fairly well with a linear regression line slope of 1.03, small positive intercept, 0.011 and a highly significant (P 0.001) coefficient of determination, square R= 0.978. Bonifica (1986) measured infiltration rate during the forth hour at different sites for a total area of 196,723 ha in the Northern state. Their data was used to test the validity of the developed equation as an independent set of data. Again, the equation quite predicted measured infiltration rate with a highly significant (P 0.001) coefficient of determination, square R= 0.999, slope of 1.013 and a small negative intercept (-0.073). Scaling factors ranged between 3.714 and 0.161 and tended to be more log-normally distributed than normal with a mean value of 1.381, median of 1.215 and mode of 0.94. Cumulative and infiltration rate were plotted against time for scaling factors, = 1.015, 1.237 and 1.677 which corresponds to 0.25, 0.50 and 0.75 of the cumulative frequency distribution. At the end of the forth hour infiltration rate for = 1.015, 1.237 and 1.677 were 0.026, 0.031 and 0.042 cm / minute, respectively. Respective cumulative infiltration at the end of the forth hour were 10.8, 12.5 and 16.1 cm
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