Modeling Infiltration In Constructed Micro-catchments

Authors: FOUNDS, MICHAEL - Desert Research Institute; MCGWIRE, KENNETH - Desert Research Institute; Weltz, Mark; Nouwakpo, Sayjro

Submitted to: Federal Interagency Hydrologic Modeling Conference
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Micro-catchments have successfully been used in arid regions to promote infiltration of rainfall and water availability for plants. In addition to these beneficial outcomes, Micro-catchments also have the ability to reduce soil erosion and sedimentation in arid and semiarid rangelands. The Vallerani System was developed in 1988 to efficiently harvest runoff by creating a series crescent-shaped Micro-catchments with oscillating ripper and plow blades. Like any engineered structure, Micro-catchments need to be sized and spaced adequately for optimal function and cost effectiveness, and better understanding of the infiltration capacity of Micro-catchments would allow better engineering of these structures. The research described here tests the ability of a numerical infiltration model to emulate field measurements for a set of constructed Micro-catchments. A Walnut Gulch Rainfall Simulator was used to simulate two rainfall events over each Micro-catchment. The rainfall simulator applied water with two events of variable intensity and duration, delivering 3-5 cm of water at an intensity of 10-15 cm/hr. A rill simulator then simulated concentrated flow from upslope. Flow from the rill simulator was maintained for at least 15 minutes after water overtopped the Micro-catchment. Three dimensional models of each Micro-catchment were created using handheld photography and Agisoft Photoscan software. The Photoscan software created digital elevation models that were accurate to within 0.5 cm, and these digital elevation modelswere imported to ArcMap GIS software where the surface volume tool was used to capture the 3-D surface area and volume across a range of depths. Polynomial relationships were then developed to relate water stage in each MC to the corresponding wetted surface area (4th order polynomial) and volume (2nd order polynomial) of the pit. Without any direct calibration of the Hydrus model, average error across all Micro-catchments on the hillslope was less than 1% for estimating infiltration rates. Future work could adapt such simulations to represent weather patterns over a seasonal time scale in order to develop a flow budget for the Micro-catchments, including quantification of total water stored in the soil profile or simulation of plant growth. The Hydrus model could also be used in conjunction with physically-based erosion models to simulate how different configurations on the hillslope might reduce erosion and to predict how quickly the Micro-catchments would fill with sediment.

Technical Abstract: Micro-catchments have successfully been used in arid regions to promote infiltration of rainfall and water availability for plants. In addition to these beneficial outcomes, Micro-catchments also have the ability to reduce soil erosion and sedimentation in arid and semiarid rangelands. The Vallerani System was developed in 1988 to efficiently harvest runoff by creating a series crescent-shaped Micro-catchments with oscillating ripper and plow blades. Like any engineered structure, Micro-catchments need to be sized and spaced adequately for optimal function and cost effectiveness, and better understanding of the infiltration capacity of Micro-catchments would allow better engineering of these structures. The research described here tests the ability of a numerical infiltration model to emulate field measurements for a set of constructed Micro-catchments. A Walnut Gulch Rainfall Simulator was used to simulate two rainfall events over each Micro-catchment. The rainfall simulator applied water with two events of variable intensity and duration, delivering 3-5 cm of water at an intensity of 10-15 cm/hr. A rill simulator then simulated concentrated flow from upslope. Flow from the rill simulator was maintained for at least 15 minutes after water overtopped the Micro-catchment. Three dimensional models of each Micro-catchment were created using handheld photography and Agisoft Photoscan software. The Photoscan software created digital elevation models that were accurate to within 0.5 cm, and these digital elevation modelswere imported to ArcMap GIS software where the surface volume tool was used to capture the 3-D surface area and volume across a range of depths. Polynomial relationships were then developed to relate water stage in each MC to the corresponding wetted surface area (4th order polynomial) and volume (2nd order polynomial) of the pit. Without any direct calibration of the Hydrus model, average error across all Micro-catchments on the hillslope was less than 1% for estimating infiltration rates. Future work could adapt such simulations to represent weather patterns over a seasonal time scale in order to develop a flow budget for the Micro-catchments, including quantification of total water stored in the soil profile or simulation of plant growth. The Hydrus model could also be used in conjunction with physically-based erosion models to simulate how different configurations on the hillslope might reduce erosion and to predict how quickly the Micro-catchments would fill with sediment.