Modeling low-flow bedrock springs providing ecological habitats with climate change scenarios

Abstract

Groundwater discharge areas, including low-flow bedrock aquifer springs, are ecologically important and can be impacted by climate change. The development of and results from a groundwater modeling study simulating fractured bedrock spring flow are presented. This was conducted to produce hydrological data for an ecohydrological study of an endangered species, Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus), in southern Quebec, Canada. The groundwater modeling approach in terms of scale and complexity was strongly driven by the need to produce hydrological data for the related ecohydrological modeling. Flows at four springs at different elevations were simulated for recent past conditions (2006-2010) and for reference (1971-2000) and future (2041-2070) periods using precipitation and temperature data from ten climate scenarios. Statistical analyses of spring flow parameters including activity periods and duration of flow were conducted. Flow rates for the four simulated springs, located at different elevations, are predicted to increase between 2% and 46% and will be active (flowing) 1% to 2% longer in the future. A significant change (predominantly an increase) looking at the seasonality of the number of active days occurs in the winter (2% to 4.9%) and spring seasons (-0.6% to 6.5%). Greatest flow rates were produced from springs at elevations where sub-horizontal fractures intersect the ground surface. These results suggest an intensification of the spring activity at the study site in context of climate change by 2050, which provides a positive habitat outlook for the endangered salamanders residing in the springs for the future.

Modeling cross-scale relationships between climate, hydrology, and individual animals: generating scenarios for stream salamanders

“…Stemming from these changes, net precipitation (i.e., precipitation-potential evapotranspiration) TABLE 1 | Details for the nine climate projections selected for this study out of the group of 25 available for the region: emission scenario, simulated air temperature and precipitation changes, and derived potential evapotranspiration changes (derived from Levison et al, 2014b varies from a 4% decrease (CRCM_CCSM) to a 15% increase (CRCM4.2.3_ECHAM#1). The majority of net precipitation scenarios agree on the sign of change: seven out of nine predict an increase in mean net precipitation.…”

“…The daily flow of groundwater through bedrock fractures to springs on the northeastern face of Covey Hill was simulated by Levison et al (2014b) using HydroGeoSphere software (HGS; Therrien et al, 2012). The numerical integrated surfacegroundwater flow model simulated four springs at elevations of 140, 150, 162, and 177 m. Levison et al (2014b) have shown that for the 1971-2000 reference period, the lower elevation spring (140 m) is the one that flows most often during the year (on average 282 days, more than 75% of the year) (Figure 3).…”

“…The numerical integrated surfacegroundwater flow model simulated four springs at elevations of 140, 150, 162, and 177 m. Levison et al (2014b) have shown that for the 1971-2000 reference period, the lower elevation spring (140 m) is the one that flows most often during the year (on average 282 days, more than 75% of the year) (Figure 3). Spring activity decreases sharply at 150 m and at 162 m and increases slightly at the highest spring located at 177 m. The greater activity at the lowest spring is explained by its position near the base of the hill.…”

“…The greater spring activity period at the highest spring occurs because this spring is located at the intersection of an important sub-horizontal fracture and the ground surface, as opposed to the two middle-elevation springs which discharge from vertical fractures. Applying the net precipitation for the climate change scenarios to the model, Levison et al (2014b) has shown that increases in precipitation predicted by the climate scenarios during the 2041-2070 period has direct consequences on groundwater recharge, and thus on the spring activity time series. In the future, an increase in the length of spring activity periods is expected at all elevations.…”

“…The hydrogeological model requires the use of net precipitation (which is precipitation minus evapotranspiration) as an atmospheric water input. As noted in Levison et al (2014b), the model directs net precipitation to surface flow (runoff) and infiltration (recharge). Predicted net precipitation and evapotranspiration values were derived from the regional climate scenarios described above.…”