Investigating the Spatio-Temporal dynamics in the soil water storage in Alberta’s Agricultural region

Abstract

Anomalous atmospheric conditions which, for the most part, manifest in the form of heavy precipitation events leading to the generation of pluvial or fluvial flooding in some years, or as extended extreme dry spells resulting in the development of severe drought conditions in other years has significant implications for subsurface moisture budgets in regional and local catchments in the Canadian Prairies. The myriad implications of these frequent and extended dry spells over Alberta’s Agricultural Region can be far reaching economically, socially and otherwise, thereby exerting substantial negative toll on agricultural productivity (crop cultivation, livestock husbandry, and pasture management) within the Province. Soil moisture dynamics both in spatial and temporal scales has critical implications for agricultural water management especially under semi-arid climate conditions that are typical of the local- and regional-scale catchments in southern Alberta. This study is focused on the assessment of the observations of the soil water storage, soil temperature and meteorological variables (precipitation and air temperature) acquired from 39 monitoring stations spanning a 12-year period with the principal objective of examining the spatial and temporal dynamics in the shallow and deep soil water storage processes across the study domain. This study revealed that the moisture anomalies in the deep soil moisture store exhibit the longest hydrologic memory relative to those in the shallow and intermediate soil moisture storages as well as those in the meteorological variables across the study domain. The anomalies computed for the soil moisture measurements undertaken in the deep soil moisture store revealed frequency features that are dominant at seasonal cycle (9-month) and at a higher periodicity of 32-month cycle. This low-frequency feature (32-month cycle) is evidently non-existent in the soil water storage measured at the shallower soil depths nor in the meteorological variables evaluated in this study. This implies that the low-frequency feature of the soil water storage wavelet spectra increases with increasing soil depth across the Agricultural Region; indicating that at deeper soil depths, the largest variances are shifted to lower frequencies. This observed dominant long-memory feature in the deep soil moisture store could have important implications for characterizing the development of temperature extremes as well as for the evaluation of the severity of the recurrent drought outbreaks over regional watersheds in Alberta and potentially for other Canadian Prairie catchments.