Evaluation of a Runoff Monitoring Methodology for Rangelands: UBeTubes

Rangeland degradation is a global concern that is exacerbated by soil loss through water erosion. A deeper understanding of rainfall and runoff dynamics can assist in the development of sustainable management strategies. Current methods to measure surface runoff (e.g., natural runoff plots, rainfall simulation and overland flow experiments, modeling approaches) have many advantages but can be prohibitively expensive, may require considerable maintenance, and/or result in significant disturbance during installation. To address these limitations, we assessed a relatively new and underused method for monitoring runoff, the Upwelling Bernoulli Tube (UBeTube). The UBeTube is a low-cost, passive runoff monitoring method that estimates runoff from the height of water flowing out of a slot machined in the side of a vertical tube. In this study, we evaluated the UBeTube across a range of flow rates with three specific objectives: 1) calibrate the UBeTube measurements using clean water, 2) assess the impacts from varying sediment loads on UBeTube measurement accuracy, and 3) evaluate accuracy under conditions similar to those on undisturbed and disturbed rangelands. We found that properly calibrated UBeTubes could be a relatively accurate runoff monitoring method on rangelands (mean percent error = 7.7% clean water calibration, 34.1% sediment loading, 35.2% undisturbed overland flow, 17.7% disturbed overland flow). UBeTubes provide an alternative method to monitor runoff on rangelands that can augment current methods by providing near real-time measurements of runoff generated during natural precipitation events. Easily and rapidly deployed across the landscape, UBeTubes could allow for the relative measurement of spatially variable hydrologic dynamics and serve as another source of information for management decision-making processes and the creation of sustainable strategies for rangeland development.