1. Deep Percolation and Groundwater Level Response Following Surface Irrigation Carlos Ochoa, Sam Fernald, Steve Guldan, Manoj Shukla Funding sources: USDA CSREES NRI, New Mexico Agriculture Experiment Station. Rio Grande Irrigation ditch

2. Farm scale Valley scale Basin scale USDA CSREES-funded study to determine seepage effects on Rio Grande flow in an irrigated valley in northern New Mexico (2004-2009). NMSU-Sustainable Agriculture Science Center Deep percolation from irrigation can provide a fair amount of water recharge to shallow aquifers.

3. Water level (m ASL) Previous study findings (2004-2007) – Deep percolation: A 15-62% Dp in an alfalfa field with sandy-loam soil A 14-42% Dp in an apple orchard with sandy-clay and clay soil Rapid water level response and water level rise up to 35 cm Soil moisture sensors Alfalfa field

4. Determine deep percolation following flood irrigation in two crop fields with different soil type. Assess the performance of the Root Zone Water Quality Model in simulating deep percolation. Study objectives: Shallow Aquifer 1 m Deep percolation Characterize groundwater level fluctuations in response to deep percolation inputs.

5. Experimental design: Two 100 m by 100 m fields Two soils: Fruitland sandy-loam and Werlog clay-loam Shallow water table (sandy-loam = 4 m and clay-loam = 2.8 m) Surface (flood) irrigation Cover crop (oats/grass mix) Parameters: Irrigation depth Soil water content Field runoff Water level Sandy-loam Clay-loam NMSU-Sustainable Agriculture Science Center

6. METHODS

7. DP = SWC i + IRR + P - SWC fc – RO – ET Measured and simulated deep percolation A daily water balance method based on field measurements The Root Zone Water Quality Model – Hydrology component Crop type Rainfall data Meteorological data Soil horizons and properties Water applied Deep percolation InputOutput

8. N Soil moisture station 100 m Field runoff Propeller flow meter Flow Water source Driven point well Open channel-flow meter 100 m 1m Slope Field data collection – Schematic of instrumentation

9. Outer well soil moisture station/well N

10. Irrigation applied and field runoff Irrigation applied 12 irrigation events in each field (2008-2009) Variable irrigation depth (4 to 22 cm) Field runoff Open channel S-M flume with pressure transducer Propeller flow meter S-M flow meter

11. Soil water content and groundwater monitoring Vertical nests of soil moisture sensors Driven point wells equipped with water level loggers Instrumentation installed and soil repacked 15 months prior to this experiment 50 cm Soil moisture sensors Clay loam Sandy loam Well

12. RESULTS

13. Date Duration (h) SWCi (cm)IRR (cm)P (cm) SWCfc (cm)RO (cm)ET (cm)DP (cm)DP (%) 6/16/0827.014.026.7028.54.20.97.126.6 7/1/088.822.99.6028.52.20.51.313.3 7/14/0811.523.212.5028.54.00.42.822.4 8/7/088.019.18.7028.53.90.40.0 9/11/087.518.87.4028.51.60.40.0 10/20/087.516.74.10.228.50.00.30.0 5/6/097.116.78.4028.50.80.90.0 6/4/098.814.411.70.3628.52.40.80.0 6/25/097.222.28.5028.50.80.70.89.4 7/20/096.817.48.5028.50.20.80.0 8/10/097.018.08.5028.50.9 0.0 9/1/096.717.310.1028.53.50.40.0 Deep percolation (DP) observed in 4 out of 12 irrigation events DP ranged from 9 to 27 % Fruitland sandy loam soil:

14. Werlog clay loam soil: Date Duration (h) SWCi (cm)IRR (cm)P (cm) SWCfc (cm)RO (cm)ET (cm)DP (cm)DP (%) 6/10/0826.535.021.10.038.21.40.915.674.1 6/24/0823.035.118.70.038.21.70.713.170.1 7/7/0811.535.88.50.038.20.90.44.957.6 8/12/087.023.45.90.038.20.00.40.0 9/9/087.620.88.10.038.21.10.50.0 10/28/087.618.54.20.0338.20.00.40.0 4/29/099.424.812.20.038.20.20.80.0 5/21/098.027.59.70.038.20.50.40.0 6/15/097.727.39.30.038.20.70.80.0 7/13/097.217.48.80.038.20.11.00.0 7/27/097.018.48.50.038.21.60.90.0 9/2/097.314.310.30.038.20.60.40.0 When DP present, high antecedent soil moisture observed DP ranged from 58 to 74 %

15. Field-measured (DWBM) versus simulated (RZWQM) DP: Regardless of soil type, preliminary simulated results with minimum input data show a fair agreement with field-measured based deep percolation.

16. Water level response: Werlog clay-loam field Water level rise of up to 16 cm observed following highest IRR. IRR = 23 cm

17. Water level response: Fruitland sandy-loam field Water level rise of up to 2 cm in the midfield well following highest IRR. IRR = 26.7 cm

18. Water level response: Fruitland sandy-loam field In general, muted water level response (0 to 2 cm) observed following IRR.

19. Conclusions Regardless of soil type, deep percolation was only observed during few irrigation events. Higher antecedent soil moisture and shallower water table contributed to greater deep percolation and higher water table rise in the clay loam soil. Fair agreement between simulated (RZWQM) and field-measurement (DWBM) DP. In general, lower water level rise and longer time of response when compared to previous study results (Alfalfa and Apple fields).

20. Water level rise of up to 8 cm in the midfield well following IRR = 23 cm. Water level response: Werlog clay-loam field