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Submitted to: Irrigation Association Conference Proceedings
Publication Type: Proceedings Publication Acceptance Date: 9/21/2011 Publication Date: 11/5/2011 Citation: King, B.A., Bjorneberg, D.L. 2011. Infiltration Model for Center Pivot Sprinkler Irrigation. Irrigation Association Conference Proceedings, November 6-8, 2011, San Diego, CA. Published on CD only. p.1-17. Interpretive Summary: The marked reduction in infiltration rate caused by formation of a soil surface seal due to water droplet impact on bare soil is a well known phenomenon but is rarely considered in infiltration models, especially under center pivot irrigation. The objective of this study was to develop a soil infiltration model for center pivot sprinkler irrigation that incorporates the transient reduction in soil surface seal hydraulic conductivity as affected by soil and sprinkler characteristics. A sealing soil infiltration model was developed using an explicit finite difference solution scheme with a transient soil seal formation model, which is unique from other studies in that it explicitly uses droplet specific power as the driving factor for formation of a soil surface seal. The model was calibrated to a specific soil using published runoff data from a rainfall simulation study with varying droplet kinetic energies and application rates. The model was then applied to center pivot irrigation for five common sprinklers to evaluate the effect sprinkler selection has on infiltration. Due to the high susceptibility of the soil to surface sealing from water drop impact and low hydraulic conductivity, the sprinkler with the largest wetted diameter was predicted to maximize infiltration. Technical Abstract: The marked reduction in infiltration rate caused by formation of a soil surface seal due to water droplet impact on bare soil is a well known phenomenon but is rarely considered in infiltration models, especially under center pivot irrigation. The objective of this study was to develop a soil infiltration model for center pivot sprinkler irrigation that incorporates the transient reduction in soil surface seal hydraulic conductivity as affected by soil and sprinkler characteristics. A sealing soil infiltration model was developed using an explicit finite difference solution scheme with a transient soil seal formation model, which is unique from other studies in that it explicitly uses droplet specific power as the driving factor for formation of a soil surface seal. The model was calibrated to a specific soil using published runoff data from a rainfall simulation study with varying droplet kinetic energies and application rates. The model was then applied to center pivot irrigation for five common sprinklers to evaluate the effect sprinkler selection has on infiltration. Due to the high susceptibility of the soil to surface sealing from water drop impact and low satiated hydraulic conductivity, the sprinkler with the largest wetted diameter was predicted to maximize infiltration. The infiltration model predicted an average difference of 3.2 mm between protected and bare soil infiltration for a 25.4 mm application depth. Sprinkler kinetic energy had minimal impact on infiltrated depth because all the sprinklers used in this study caused a surface seal. |
