Dr. Heather Haig

Quantification of Qu'Appelle valley hydrology using water isotopes - 

Hydrologic processes on the North American Prairies are characterized by high seasonality and interannual variation in runoff.  Often lotic systems are ungauged, despite the need for data to predict occurrence of floods and droughts.  In regions where evaporation is greater than precipitation, analysis of stable isotopes of hydrogen and oxygen may provide an alternate means of quantifying temporal variation in water fluxes in the absence of instrumental records.  We tested this hypothesis in Wascana Creek, Saskatchewan, Canada, where stream hydrology and surface water isotope have been measured May-Sept during 2003-2016.  In each year, deuterium and δ18O values of lake water were enriched 20-88‰ and 4.6-12.7‰, respectively, with greater range of enrichment during years with high river inflow, whereas absolute values reflected the importance of winter snow melt.  Despite a regional precipitation deficit of ~20 cm/year, isotopically-derived estimates of evaporation to inflow ratios were always <0.5, demonstrating regulation of hydrologic balance by inflow.  Application of this approach to other regional lakes suggests that snowmelt runoff is likely the main control of lake persistence in this sub-humid region. 

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Isotopic survey of southern Saskatchewan- 

Aquatic systems in the Northern Great Plaines are known for their sensitivity to changes in regional climate however; the extent that lake and catchment specific characteristics modify the climate signals' effect on water mass balances is not clearly understood.  Lake specific characteristics (e.g. volume, area), and catchment characteristics (e.g. effective drainage, ground cover) influence water availability by modifying evaporation to input (E/I) ratios, source waters isotopes (summer vs winter precipitation vs groundwater), and water yield.  To better understand how prairie lake water mass balances are affected during pluvial periods we used standard isotopic mass balance techniques to assess 105 lakes across a 260,000 km2 area. Lakes fell into three hydrological regimes; open (n = 50, 48%), restricted (n = 39, 37%), or closed (n = 16, 15%), but showed no consistent relationship with climate gradients or geographic position.  Source waters (as and δ18O) ranged from -7.2‰ indicating (rain only) to -29.3‰ (snowpack). Unexpectedly, median values of input waters (-14.5‰) suggest that summer precipitation sustains these systems despite contributing a wide range of water influx (0-1.9 m depth equivalent). These calculations support E/I-based classifications of lake hydrology, with closed basins receiving only minimal catchment input. Overall, the high variability in lake connectivity is suggested by isotopic mass balances suggests that individual lake catchments act as basin-specific filter to modify regional changes in climate.

Comparison of isotopic mass balances across southern Saskatchewan during drought and deluge