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Abstract Developing sustainable urban systems is a fundamental societal challenge for the 21st century, and central Texas faces particularly synergistic challenges of a rapidly growing urban population and a projected increasingly drought-prone climate. To assess the history of urbanization impacts on watersheds here, we analyzed 51 cores from bald cypress trees in paired urban and rural watersheds in Austin, Texas. We find a significant contrast between rural and urbanized watersheds. In the rural watershed, tree-ring-width growth histories (“chronologies”) from 1844–2018 significantly and positively correlate (p < 0.01) with (1) one another, and (2) regional instrumental and proxy records of drought. In the urbanized watershed, by contrast, chronologies weakly correlate with one another, with instrumental records of drought, and with the rural chronologies and regional records. Relatively weak drought limitations to urban tree growth are consistent with the significant present-day transfer of municipal water from urban infrastructure by leakage and irrigation to the natural hydrologic system. We infer a significant, long-term contribution from infrastructure to baseflow in urbanized watersheds. In contrast to the common negative impacts of ‘urban stream syndrome’, such sustained baseflow in watersheds with impaired or failing infrastructure may be an unintended positive consequence for stream ecosystems, as a mitigation against projected extended 21st-century droughts. Additionally, riparian trees may serve as a proxy for past impacts of urbanization on natural streams, which may inform sustainable urban development. 

Stalagmites being prepared for paleoclimate analysis should typically be slabbed along the central growth axis. This is an important first step because it allows for the highest resolution of sampling with minimal over- or under-sampling of the growth layers. Further, stable isotope ratios and trace element concentrations along the central growth axis most closely record climate variability. Choosing how to slab to best expose the central growth axis for geochemical sampling is challenging based on external morphology alone. High-resolution X-ray computed tomography (XRCT) can provide the ability to discern the internal growth morphology of stalagmites non-destructively, inexpensively, and rapidly. These data can inform selection of optimal slabbing plane(s) and can help identify locations for preliminary U-series dating. We develop a conceptual screening model to assess rapidly the internal morphologies of uncut stalagmites. The specifics of screening the internal morphologies through XRCT scans include investigating the internal porosity of the sample, the number and size of voids and hiatuses, and the presence and absence of growth layers and growth axes. We demonstrate that XRCT scans capture the migration of center of growth in uncut stalagmites of both simple and complex internal morphologies. XRCT scanning facilitates the investigation of stalagmites with complex internal growth banding, opening up avenues to work on such samples when stalagmites with simpler internal morphologies are not available. Further, screening stalagmites for paleoclimate reconstructions using XRCT improves the sustainability of speleothem science by helping researchers select which stalagmites should be returned to caves without destructive slabbing, thereby minimizing impact on caves.