Elevation and infiltration in a level basin. I. Characterizing variability

Spatial characterization of soil physical properties could improve the esti mation of surface irrigation performance. The aim of this research was to c haracterize the spatial and time variability of a set of irrigation-related soil properties. The small-scale experimental level-basin (729 m(2)) was l ocated on an alluvial loam soil. A corn crop was established in the basin a nd irrigated five times during the season. A detailed survey of the soil pr operties (generally using a 3 x 3 m network) was performed. Classic statist ical and geostatistical tools were used to characterize the variables and t heir interactions. Semivariograms were validated for the studied variables, except for the clay fraction, the saturated hydraulic conductivity and the infiltration parameters. The resulting geostatistical range was often in t he interval of 6-10 m. For the three surveys of soil surface elevation the range was smaller, about 4 m. No correlation was found between saturated hy draulic conductivity and the other soil physical properties. Soil surface e levation showed a high correlation between surveys. After the first irrigat ion, the standard deviation of elevation increased from an initial 9.6 mm t o 20.8 mm. The soil physical parameters were used to map the soil water man agement allowable depletion. In a companion paper these results are used to explain the spatial variability of corn yield and soil water recharge due to irrigation.