Abstract
AbstractVegetative buffers have shown promising results in reducing runoff volume, sediment, nutrients, and manure‐borne contaminants in runoff from agricultural fields. Although these vegetative buffer systems have been extensively tested in field and plot‐scale studies that utilize either natural or simulated rainfall, studies of such systems under highly controlled conditions in the laboratory have been limited. Here, we present the development of a new system for laboratory testing of a full‐scale, sectional, physical model of a new practice under the Continuous Conservation Reserve Program (CRP) Clean Lakes, Estuaries, and Rivers (CLEAR) Initiative, CP‐43 Prairie Strips. This work includes the extraction of prairie strip sections from the field and their integration into an existing laboratory flume facility with specific auxiliary features to facilitate overland flow experimentation. As a proof of concept run, a potassium chloride (KCl) tracer study was conducted to verify system functionality and inform future work. The tracer pulse was injected under saturated conditions and the response was monitored through surface water (upstream and downstream of the prairie strip model) and subsurface water (infiltrated) sampling with continuous flow rate monitoring at the sampling locations. The tracer test provided highly resolved breakthrough curves (BTCs) with 93.5% of the injected tracer mass recovered, and provided useful information on flow partitioning, velocities, and dispersion characteristics along the surface and through the subsurface profile of the model. This model prairie strip system is expected to be useful in optimizing the performance of prairie strips under highly controlled flow and contaminant source conditions.
Highlights
We present the development of a new system for laboratory testing of a full-scale, sectional, physical model of a new practice under the Continuous Conservation Reserve Program (CRP) Clean Lakes, Estuaries, and Rivers (CLEAR) Initiative, CP43 Prairie Strips
In addition to the water quality benefits of Vegetative filter strips (VFS), a recently adopted Continuous Conservation Reserve Program (CRP) practice called CP-43 Prairie Strips, which was developed by the STRIPS (Science-based Trials of Rowcrops Integrated with Prairie Strips) team at Iowa State University (ISU), has demonstrated that integrating strips of prairie within and at the edge of crop fields can yield benefits for soil, water, and biodiversity at levels disproportionately greater than the area diverted from annual crop production. (Schulte et al, 2017)
The installation of prairie strip extractions into the ABE flume is sequentially outlined below with reference to the equipment described previously and the process depicted in Figure 6: Following sample offloading in the laboratory, the lifting beam is attached to built-in threaded posts on the insert tray (Figure 6a); the sample insert is lifted with a jib crane and hoist system and positioned above the ABE flume test section (Figure 6b); the sample insert is lowered into the flume test section (Figure 6c); the process is repeated for the second insert (Figure 6d); the inserts are sealed in place with silicone sealant and guide walls with a flared entrance are installed to prevent short-circuiting of flow around the prairie strip test section (Figure 6e, 6f)
Summary
Vegetative filter strips (VFS) have been integrated with agricultural cropping systems for many years and are a Abbreviations: ABE, agricultural and biosystems engineering; BTC, breakthrough curve; CLEAR, Clean Lakes, Estuaries and Rivers Initiative; CRP, Continuous Conservation Reserve Program; ISU, Iowa State University; STRIPS, Science-based Trials of Rowcrops Integrated with Prairie Strips; VFS, vegetative filter strip. Physical hydraulic modeling is a practical approach to developing effective engineering designs and conducting applied research associated with complex flow systems. ∙ A physical hydraulic modeling approach is utilized to study water quality in prairie strips. Numerical simulations in agricultural water resources applications have evolved to the point that they can resolve the mechanics of many practical flows (e.g., Soil and Water Assessment Tool [SWAT], Agricultural Non-Point Source Pollution Model [AGNPS], Hydrological Simulation Program–FORTRAN [HSPF]). Their ability to include many of the micro-scale pollutant transport processes, such as straining, attachment, entrapment, and adsorption, involved in contaminant mitigation via VFS or prairie strips relies on detailed studies of these processes. The system will be useful to optimize the performance of prairie strips under highly controlled flow and contaminant source conditions
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