Christine Rivard

Groundwater recharge trends in CanadaGeological Survey of Canada Contribution 20090009.

Groundwater plays a major role in social and economic development and in human and ecosystem health. However, little is known about the potential impacts of climate change on this resource in Canada, namely if groundwater recharge is increasing or decreasing over time. This paper focuses on trend statistical analysis of historical series of baseflow and groundwater levels and their field significance as indicators of recharge. Monitoring wells are mainly located in the southern half of western Canada, where few gauging stations either are available or provide significant trends. Both data sets are thus complementary. Results show that most available groundwater level series have significant trends (80%), whereas most available baseflow series have not (3%–33%). However, groundwater level series usually show smaller slope magnitudes than baseflow series. Mixed trends are often observed across Canada for a given variable, period, or series length, although some regions can have marked trends. For instance, ...

A watershed-scale study of climate change impacts on groundwater recharge (Annapolis Valley, Nova Scotia, Canada)

Abstract The potential impacts of future climate change on the evolution of groundwater recharge are examined at a local scale for a 546-km2 watershed in eastern Canada. Recharge is estimated using the infiltration model Hydrologic Evaluation of Landfill Performance (HELP), with inputs derived from five climate runs generated by a regional climate model in combination with the A2 greenhouse gas emissions scenario. The model runs project an increase in annual recharge over the 2041–2070 period. On a seasonal basis, however, a marked decrease in recharge during the summer and a marked increase during the winter are observed. The results suggest that increased evapotranspiration resulting from higher temperatures does not offset the large increase in winter infiltration. In terms of individual water budget components, clear differences are obtained for the different climate change scenarios. Monthly recharge values are also found to be quite variable, even for a given climate scenario. These findings are compared with results from two regional-scale studies. Editor D. Koutsoyiannis; Associate editor M. Besbes Citation Rivard, C., Paniconi, C., Vigneault, H., and Chaumont, D., 2014. A watershed-scale study of climate change impacts on groundwater recharge (Annapolis Valley, Nova Scotia, Canada). Hydrological Sciences Journal, 59 (8), 1437–1456. http://dx.doi.org/10.1080/02626667.2014.887203

Can groundwater sampling techniques used in monitoring wells influence methane concentrations and isotopes

Methane concentrations and isotopic composition in groundwater are the focus of a growing number of studies. However, concerns are often expressed regarding the integrity of samples, as methane is very volatile and may partially exsolve during sample lifting in the well and transfer to sampling containers. While issues concerning bottle-filling techniques have already been documented, this paper documents a comparison of methane concentration and isotopic composition obtained with three devices commonly used to retrieve water samples from dedicated observation wells. This work lies within the framework of a larger project carried out in the Saint-Édouard area (southern Québec, Canada), whose objective was to assess the risk to shallow groundwater quality related to potential shale gas exploitation. The selected sampling devices, which were tested on ten wells during three sampling campaigns, consist of an impeller pump, a bladder pump, and disposable sampling bags (HydraSleeve). The sampling bags were used both before and after pumping, to verify the appropriateness of a no-purge approach, compared to the low-flow approach involving pumping until stabilization of field physicochemical parameters. Results show that methane concentrations obtained with the selected sampling techniques are usually similar and that there is no systematic bias related to a specific technique. Nonetheless, concentrations can sometimes vary quite significantly (up to 3.5 times) for a given well and sampling event. Methane isotopic composition obtained with all sampling techniques is very similar, except in some cases where sampling bags were used before pumping (no-purge approach), in wells where multiple groundwater sources enter the borehole.

Conceptual model of regional groundwater flow based on hydrogeochemistry (Montérégie Est, Québec, Canada)

The groundwater geochemistry of the fractured rock aquifer system in the Montérégie Est region, southern Quebec, Canada, was studied as part of a regional groundwater resources assessment. The 9218 km² study area included three major watersheds that were divided into five hydrogeological contexts: Northern St. Lawrence Lowlands, Southern St. Lawrence Lowlands, Appalachian Uplands, Appalachian Piedmont and Monteregian Hills. A large part of this study area was invaded by the Champlain Sea from 13,000 to 11,000 years ago. Study objectives were to identify the mechanisms controlling groundwater composition and to support the understanding of the aquifer hydrodynamics. Groundwater from 206 wells drilled into the rock aquifer was sampled and analyzed for conventional parameters and isotopic analyses were also done on selected samples (δ2H, δ18O and 3H of water; δ13C and 14C of dissolved inorganic carbon). The interpretation of geochemical results was based on a multivariate statistical analysis, which led to the definition of eight water groups. The study allowed the delineation of a 2200-km² zone containing brackish groundwater of marine origin in the northwestern part of the study area. This zone is surrounded by sodic and alkaline groundwater originating from Na+-Ca2+ ionic exchange. Young groundwater and therefore recharge zones were only encountered in the southern part of the Lowlands, in the northern part of the Piedmont and in the Appalachian Uplands. In the southern part of Lowlands, recharge is presumed to be slow and water composition shows the influence of the former presence of the Champlain Sea. Relatively deep groundwater circulation was also inferred to occur from the Appalachian Uplands toward mixing zones mainly located to the west at the Appalachian frontal thrust faults and around the Monteregian Hills. The geochemical interpretation provided indications on regional recharge and discharge zones as well as groundwater flow, which could not have been determined otherwise.