Thesis Defence: Evaporation to inflow ratios in palustrine and riparian wetlands in the southern interior of British Columbia
September 18 at 9:00 am - 1:00 pm
Sarah Mavor, supervised by Dr. Edward Hornibrook, will defend their thesis titled “Evaporation to inflow ratios in palustrine and riparian wetlands in the southern interior of British Columbia” in partial fulfillment of the requirements for the degree of Master of Science in Earth and Environmental Sciences.
An abstract for Sarah Mavor’s thesis is included below.
Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.
Abstract
Palustrine wetlands are an uncommon but ecologically important feature of the semi-arid landscape in the southern interior of British Columbia. The wetlands often occur in topographic depressions at a range of elevations, providing critical habitat for flora and fauna, and potential refugia during periods of drought and wildfire. The wetlands exhibit a range of salinities (EC ~200 to 20,000 μS/cm) that reflect differences in geology and evaporation to inflow (E/I) ratios, but which do not provide a reliable means to assess water balance. The stable isotope composition (δ2H and δ18O values) of water was measured from May 2024 to September 2025 in precipitation and 34 wetlands and lakes located near Kelowna, BC. A local meteoric water line (LMWL; δ2H = 6.8 ± 0.19 * δ18O – 17.9 ± 3.42; n = 106, R2 = 0.97) was established from the precipitation data. Surface water stable isotope data defined a local evaporation line (LEL; δ2H = 4.4 ± 0.039 * δ18O – 55.5 ± 0.39; n = 684, R2 =0.99) that intercepts the LMWL at the annual amount-weighted isotopic composition of precipitation. Intersections between individual wetland surface water regression lines and the LMWL were used to estimate E/I ratios. Palustrine wetlands had mean E/I ratios ranging from 0.03 to 2.3. Riparian wetlands Fascieux Creek (E/I = 0.0055) and Mission Creek (E/I = -0.025) showed minimal evaporative losses relative to inflow, consistent with through-flow wetlands that are constantly flushed with new water. Wetlands with E/I ratios >1experience volumetric drawdown, as evidenced by an ephemeral wetland (mean E/I ratio = 2.3), which evaporated to dryness in the summers of 2024 and 2025. Eight wetlands had E/I ratios close to or greater than 1, indicating that they are most at risk to warming and drying trends that cause changes to water balances. This approach provides a means to monitor shifts in water balance in wetlands that may be adversely impacted by interannual changes in precipitation, temperature or land use practices.
