Wyatt Tatge's Qualifying Exam

Wyatt Tatge will stand for the Qualifying Examination for acceptance into candidacy for the Ph.D. degree on Thursday, November 12 at 12:30 PM in Sage 32. All faculty (only faculty) are welcome and invited to attend. Copies of Wyatt’s dissertation prospectus and qualifying exam questions and answers can be obtained from the Doctoral Program Office (contact: elisabeth.barsa@yale.edu). Committee members: • Prof. James Saiers (Chair) • Prof. Peter Raymond • Prof. Ciaran Harman (Johns Hopkins Univ.) Please submit your written responses to your committee and to Elisabeth Barsa by 5:00 PM on October 23, 2026. The use of ChatGPT or other generative AI tools to prepare or assist in writing your responses to the exam questions is not permitted. 1) Trace the evolution of our conceptual understanding of rainfall–runoff processes within temperate headwater catchments over approximately the past 50-60 years. Your discourse should cover, but need not be limited to, infiltration- and saturation-excess overland flow, variable source areas, subsurface storm flow, hydrologic connectivity and threshold behavior, the old-water paradox, and storage-age/travel-time considerations. Describe, where appropriate, how the use of environmental tracers and numerical models have sharpened inferences on these processes and phenomena. Close your discussion by identifying two important, unresolved questions involving rainfall-runoff responses and propose empirical and/or model-based approaches that could improve understanding of them. 2) Chemical weathering shapes the composition of natural waters. Current understanding of this phenomenon has been advanced by development and application of empirical and theoretical frameworks, including mixing models, box models, soil-column reactive-transport models, and watershed reactive-transport models. Describe these modeling approaches, identify key insights they have provided into the controls on chemical weathering, and evaluate how their underlying assumptions affect confidence in these insights. Conclude your discussion by critically evaluating the most significant challenges to improving predictions of chemical weathering at the watershed scale, considering issues such as heterogeneity, process representation, parameter estimation, and disparities between lab and field weathering rates.