Representative Soil Water Benchmarking for Environmental Monitoring

Soil moisture is a key hydrological factor affecting the fate and transport of pollutants in soils as well as greenhouse gas emissions. There is strong spatial variability in field soil water, which requires monitoring many locations to capture the salient features of soil water in the field. The objective of this study was to examine whether there are temporally stable soil moisture patterns in a field and whether a representative moisture benchmark site can be identified from these patterns. The experiments were conducted on a black soil at Alvena, northeast of Saskatoon, SK, Canada. Soil moisture was monitored at 95 measurement sites with a portable Capacitance Probe (CP) along a 612 m rolling transect, from April to September in 2001 and 2002. Temporal stability of spatial patterns in soil moisture for depths of 30, 60, 90, 120 and 160 cm were determined using temporal means and standard deviations of the differences between individual and spatial average values of soil moisture along the transect. The spatial patterns of soil water storage were stable in different locations for each depth. Contrary to reports in the literature, clay content showed the least amount of control of spatial patterns. Coefficient of variation and standard deviation of soil moisture both decreased with increasing soil moisture. Soil moisture benchmark sites identified in this study represent field mean soil moisture and can be used for environmental monitoring and modeling.