Design and calibration of tipping bucket system for field runoff and sediment quantification

Abstract

This paper describes a low cost tipping bucket system for measuring runoff and soil loss from field plots ranging in size from 25 to 50 m2 (29.89 to 59.79 yd2). It has been designed to minimise errors due to siltation caused by slow flow rates and errors due to instability caused by high flow rates. The resolution of this system for a 50 m2 (59.79 yd2) plot is 0.06 mm (0.0023 in) of runoff and is capable of measuring a maximum rate of 110 mm h?1 (4.33 in h?1). The number of tips can be monitored manually by a magnetic counter or automatically in real time by a datalogger. Soil loss is sampled by either a sediment pipe or a cotton bag. Field calibration indicates the maximum error in estimating flow rate is 2% and is close to the value observed by manual measurements. At a soil loss of 7 t ha?1 (3.125 t ac?1), the sampler pipe overestimated soil loss by 10%, compared to 6% by bag sampler, and 33% by manual measurements. The main advantage of the pipe sampler is the ability to measure high rates of soil loss, with a maximum of 81 t ha?1 (36.16 t ac?1), whereas the bag sampler is more suitable for low soil loss, less than 8 t ha?1 (3.57 t ac?1), and is less laborious than the pipe sampler