Soil water storage benchmarking for environmental monitoring
Soil water, a key hydrological factor, controls the fate and transport of nutrients and pollutants in soil as well as emission of green house gases from soil. Inherent spatial variability of soil water requires multiple monitoring sites for soil water which is expansive in terms of money, time and labour. The objective of this study was to identify the hydrologically time stable location (benchmark point) and spatial pattern of soil water storage in a hummocky landscape in semiarid climate. Soil water was measured in field for consecutive two years (11 measurements) by Neutron Moisture Meter (NMM) along a 128 point transect established at St Denis National Wildlife Area, Saskatchewan, Canada. Soil water measurements were taken at every 20 cm up to the depth of 1.2 m at every 4.5 m on the transect. The NMM was calibrated for this site and the calibration equation was used to calculate the soil water storage at different depths. High Spearman’s rank correlation coefficient between different dates of measurements indicated the spatial similarity of soil water storage pattern over time. Similar environmental events showed more persistent spatial pattern between measurements than different environmental events. The stability or the similarity of the rank of individual observations in the probability distribution functions over time indicated temporal stability of soil water storage pattern. While, 22nd point from the origin of the transect maintained the rank of soil water storage overtime for 0-20 cm with very low measurement variability, 4th point maintained the rank for 0-60 cm and 0-120 cm depth. The similarity or persistency of rank in water storage pattern and the mean water content over field at multiple times helped in identifying representative moisture benchmark site, which can be used for environmental monitoring and modelling, irrigation scheduling, nutrient recommendations and predicting green house gasses.
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