Field Studies and Modeling of Water Movement through the Shallow Vadose Zone in a Floodplain Irrigated Valley.

Field studies and modeling of water movement through the shallow vadose zone in a floodplain irrigated valley

Deep percolation below the crop root zone is important for groundwater recharge in irrigated lands with shallow aquifers. We conducted several studies to characterize deep percolation and water table response to variable surface irrigation applications on different crop and soil types. Our research studies were conducted at the New Mexico State University Sustainable Agriculture Science Center in Alcalde, NM, which is located in a floodplain irrigated valley along the Rio Grande.  Studies were conducted on alfalfa, apple, and pasture grass, which are common crops in the valley. Crop fields overlie a shallow aquifer with depth ranging from 2.5 to 5.0 m. Soil water content sensors were used to track the wetting front in the upper 1-m soil profile and experimental wells were used to monitor the transient rise of the water table in response to deep percolation. Results showed deep percolation rates ranging from 15% to 62% in alfalfa-grass, 14% to 42% in apple, and 3% to 74% in pasture grass. A transient water table rise observed during most irrigation events with deep percolation ranged from 10 to 380 mm, depending on amount of water applied, soil properties, and depth to water table.