Automated microstandpipe system for soil erosion research

The influence of soil water on erosion is well known, but the full effect o f variations in,vater conditions on erosional processes has only recently b een recognized, Micro time domain reflectometer (TDR) probes and microtensi ometers have provided some precise temporal and spatial data necessary for soil erosion models, but data on local water table dynamics are also needed to explain rill incision and network development processes. An automated m ultiprobe microstandpipe system we developed provides continuous water tabl e data at spatial and temporal scales comparable to those from microtensiom eters and TDR microprobes (temporal precision: 1-3 min). The new system use s small probes etched with open-ended conductors to provide incremental inf ormation on water table height with +/-0.25 cm resolution. It has been used in a range of soil erosion experiments, one of which is used to demonstrat e the system by examining drainage of interrill slopes in response to rill incision. This experiment was carried out in a 10 m by 0.8 m bg 0.3 m labor atory flume under simulated rainfall at 43.4 mm h(-1) on a 5 degrees slope, using a composite mixture of Arenic Hapludalf sandy mixed mesic and Aquic Hapludalf clayey mired mesic soils at 4:1 ratio. The microstandpipe system showed sensitive response to a saturated Hedge that progressively extended upflume after initiation at the terminal Heir. Despite separation between i nstruments, agreement between the microstandpipe system, microtensiometers and micro TDR probes was good. Rigorous statistical analysis was not possib le, hut data suggest that temporal agreement of +/-5% is realistic. Despite instrumental precision, the expected interrill drainage response to rill i ncision was not apparent.