Mapping groundwater storage variations with GRACE: a case study in Alberta, Canada

Jianliang Huang,Goran Pavlic,Alfonso Rivera,Dan Palombi,Brian Smerdon

doi:10.1007/s10040-016-1412-0

Abstract

The applicability of the Gravity Recovery and Climate Experiment (GRACE) to adequately represent broad-scale patterns of groundwater storage (GWS) variations and observed trends in groundwater-monitoring well levels (GWWL) is examined in the Canadian province of Alberta. GWS variations are derived over Alberta for the period 2002–2014 using the Release 05 (RL05) monthly GRACE gravity models and the Global Land Data Assimilation System (GLDAS) land-surface models. Twelve mean monthly GWS variation maps are generated from the 139 monthly GWS variation grids to characterize the annual GWS variation pattern. These maps show that, overall, GWS increases from February to June, and decreases from July to October, and slightly increases from November to December. For 2002–2014, the GWS showed a positive trend which increases from west to east with a mean value of 12 mm/year over the province. The resulting GWS variations are validated using GWWLs in the province. For the purpose of validation, a GRACE total water storage (TWS)-based correlation criterion is introduced to identify groundwater wells which adequately represent the regional GWS variations. GWWLs at 36 wells were found to correlate with both the GRACE TWS and GWS variations. A factor f is defined to up-scale the GWWL variations at the identified wells to the GRACE-scale GWS variations. It is concluded that the GWS variations can be mapped by GRACE and the GLDAS models in some situations, thus demonstrating the conditions where GWS variations can be detected by GRACE in Alberta.

Highlights

As the largest freshwater storage component of hydrological systems, groundwater interacts with other land water components in rivers, lakes, soil, snow, ice and plants, and responds to changes in climate at regional and global scales (Green et al 2011; Perez-Valdivia et al 2012; Lambert et al 2013; Watras et al 2014)
The coarse spatial resolution of Gravity Recovery and Climate Experiment (GRACE), which spatially creates the signal from a higher total water storage (TWS) variation region over surroundings, causes the signal leakage from southwest to northeast of the Rocky Mountains; hereafter it is termed as the spatial leakage error
As the objective of this study is to find the connection between the GRACE groundwater storage (GWS) and groundwater-monitoring well level (GWWL) variations directly, the grid gain factors are not applied to the GRACE GWS

Summary

Introduction

As the largest freshwater storage component of hydrological systems, groundwater interacts with other land water components in rivers, lakes, soil, snow, ice and plants, and responds to changes in climate at regional and global scales (Green et al 2011; Perez-Valdivia et al 2012; Lambert et al 2013; Watras et al 2014). Estimates of groundwater storage (GWS) variations remain poorly known (Richey et al 2015b), as does a methodology to link large-scale estimates with groundwater-monitoring well level (GWWL) observations, especially in regions with sparse observation data (Henry et al 2011). In Canada, GWWL observations are made by several government jurisdictions and private industries, and span shallow water-table levels to deep hydraulic heads. The distribution of these observations is spatially variable, with most monitoring wells located in the southern part of the country, and extremely sparse or non-existent data in the northern part; it is challenging if at all possible to have regional and national representation of GWS variation patterns solely from monitoring wells.

Objectives

Methods

Results

Discussion

Conclusion