Characterization of Water Movement through the Unsaturated Zone and Groundwater Response Following Flood Irrigation: A field study.

Deep percolation from surface irrigation can be important for groundwater recharge in agricultural zones with shallow aquifers.  The objective of this study was to characterize the continuum of water movement through the unsaturated zone and the shallow groundwater response after flood irrigation in three different soil types of an irrigated valley in northern New Mexico. Two infiltration plots (12 m by 12 m) were installed in each of three predominant local soil types. Plots were instrumented to measure soil moisture, soil temperature, and shallow groundwater level response to different levels of flood irrigation. Data were used to calculate velocity of propagation of the wetting front, water fluxes, and water level response. Water transport was simulated after one flood irrigation using Hydrus-1d. Field-measured results showed relatively low levels of propagation of the wetting front (10 to 80 cm h^-1), water flux (0.1 to 16 cm h^-1), and shallow groundwater response (0 to 10 cm) in Fruitland sandy loam and Werlog clay loam soils. Higher values for wetting front propagation (28 to 380 cm h^-1), water flux (0.5 to 95 cm h^-1), and water level response (0 to 14 cm) were observed in Abiquiu-Peralta complex soil type. In a more uniform soil system, such as that exhibited in the Werlog clay loam, modeling results closely matched measured results. In a more complex layered system such as the Fruitland sandy loam, the model did not fully capture the flux discontinuity across layers.