Location: Soil Dynamics ResearchTitle: Estimating raindrop kinetic energy: evaluation of a low-cost method Author
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2017
Publication Date: 8/1/2017
Citation: Wang, J., Watts, D.B., Meng, Q., Way, T.R., Zhang, Q. 2017. Estimating raindrop kinetic energy: evaluation of a low-cost method. Applied Engineering in Agriculture. 33(4):551-558. Interpretive Summary: Understanding the influence of rain drop energy on the soil surface is needed for predictive models to improve management practices that reduce soil erosion. Currently, instruments used for measuring rain energy are extremely expensive. Thus, a low cost devices was tested for determining raindrop energy. This device contains two rotating discs combined with filter paper to obtain drop diameter and velocity for determining raindrop kinetic energy of falling raindrops. This devices was measured under natural rainfall in the Loess Plateau region of China and was determined to be useful for providing an estimated of rain energy.
Technical Abstract: The Loess Plateau of China is regarded as the most intensively eroded region in the world and soil erosion caused by raindrop action is a common occurrence on agricultural land within this region. Therefore, understanding the influence of rainfall energy on the soil surface is needed for modeling purposes to improve prescriptions for best management practices aimed at mitigating erosion. Instrumentation for measuring rainfall energy is presently available; however, these apparatuses are extremely expensive and they have limited the scope of determining raindrop action for predictive soil erosion models. To overcome this constraint, a device was tested for evaluating size and velocity of water drops during rainfall events. This device used two rotating discs combined with filter paper to obtain raindrop diameter and velocity for determining the kinetic energy of falling raindrops. Measurements were taken for approximately10 min. under six rainfall events of different intensities over a three month period (from June to August of 2013) to evaluate its effectiveness at estimating raindrop kinetic energy. The smallest raindrop measured was 0.39 mm diameter and the largest was 5.92 mm diameter. The average raindrop diameter increased with increasing rainfall intensity. The minimum raindrop landing speed was is 1.47 m s-1, while the maximum was 9.45 m s-1, with the average terminal velocity increasing as rainfall intensity increased. Estimated raindrop kinetic energy ranged from 0.04 x 10-6 J to 4728.21 x 10-6 J, with mean raindrop kinetic energy ranging from 40.33 x 10-6 J to 276.94 x 10-6 J. The relationship between estimated rainfall kinetic energy and rainfall intensity represented an exponential function. Results from this study show that this low-cost method can be used to estimate rainfall kinetic energy for potential use in predictive models in the Loess Plateau region of Northwest China.