An evaluation of water isotope collection for determining evapotranspiration in seasonal wetlands.

Abstract:

The use of isotope hydrology has become a successful tool for water resource investigations. The complex task of defining interactions between groundwater, surface water, and atmospheric water vapor continue to remain a challenge. Evapotranspiration is still a dominant source of uncertainty for water resources management, especially in the face of climate change. The development of cavity ring-down spectroscopy has provided a valuable tool that makes it possible to quantify evaporation and transpiration using isotopic mass balance techniques. However, these techniques require collection of vapor at both the evaporation and transpiration fronts as well as directly above the canopy. Obtaining these representative samples is difficult. We are unaware of other attempts to use these techniques in seasonal swamps, such as the Florida Everglades, where collection of representative end members is complicated by seasonally inundated conditions. The purpose of the research presented here is to test different methods of collecting the necessary representative samples in variably inundated environments. Our tests are being conducting in a controlled setting to allow us to validate our isotope-derived estimates of evaporation and transpiration against conventional water balances. This paper will present the preliminary results of our first series of tests.