INTEGRATING STABLE ISOTOPES IN PRECIPITATION AND EARTH SYSTEM MODELS TO INTERPRET LOCAL WATER CYCLE DYNAMICS
Here we report the stable isotope values of individual precipitation events in Carbondale, Illinois measured from November 2012 to December 2015. Carbondale is located in Midwestern United States and has an increase in topography in southern Illinois which is thought to increase annual precipitation from ten to fifteen percent than the counterpoints in the maximum low of the basin. The local precipitation patterns are affected by moisture transported from Gulf of Mexico as well as local moisture recycled through transpiration and evaporation of the biosphere.
Our results show that, the average local meteoric water line has a slope of 7.8 and an intercept of 12.4, values similar to those of GMWL. Precipitation isotopic and deuterium excess (d-excess) values show clear seasonality. D-excess parameter can be taken as a measure of recycled water to precipitation. The high-amount precipitation events had enriched isotopic signature and small or negative d-excess values, suggesting the input of moisture originated from Gulf of Mexico. However, the majority of precipitation events were low-amount, had a wide range of isotopic values and d-excess > 5, suggesting that a major component was moisture originating from local recycled water.
Since most of the surface water is stored in soil and vegetation, changes in the amount as well as transfer rates among these reservoirs can have a significant effect on the regional land-atmosphere water fluxes with direct implications on economical activities.