Physical controls and ENSO event influence on weathering in the Panama Canal Watershed.

Recent empirical studies have documented the importance of tropical mountainous rivers on global silicate weathering and suspended sediment transport. Such field studies are typically based on limited temporal data, leaving uncertainty in the strength of observed relationships with controlling parameters over the long term. A deficiency of long-term data also prevents determination of the impact that multi-year or decadal climate patterns, such as the El Niño Southern Oscillation (ENSO), might have on weathering fluxes. Here we analyze an 18-year hydrochemical dataset for eight sub-basins of the Panama Canal Watershed of high-temporal frequency collected between 1998 and 2015 to address these knowledge gaps. We identified a strongly positive covariance of both cation (Ca2+, Mg2+, K+, Na+) and suspended sediment yields with precipitation and extent of forest cover, whereas we observed negative relationships with temperature and mosaic landcover. We also confirmed a statistical relationship between seasonality, ENSO, and river discharge, with significantly higher values occurring during La Niña events. These findings emphasize the importance that long-term datasets have on identifying short-term influences on chemical and physical weathering rates, especially, in ENSO-influenced regions.

TanGeoMS: tangible geospatial modeling system.

We present TanGeoMS, a tangible geospatial modeling visualization system that couples a laser scanner, projector, and a flexible physical three-dimensional model with a standard geospatial information system (GIS) to create a tangible user interface for terrain data. TanGeoMS projects an image of real-world data onto a physical terrain model. Users can alter the topography of the model by modifying the clay surface or placing additional objects on the surface. The modified model is captured by an overhead laser scanner then imported into a GIS for analysis and simulation of real-world processes. The results are projected back onto the surface of the model providing feedback on the impact of the modifications on terrain parameters and simulated processes. Interaction with a physical model is highly intuitive, allowing users to base initial design decisions on geospatial data, test the impact of these decisions in GIS simulations, and use the feedback to improve their design. We demonstrate the system on three applications: investigating runoff management within a watershed, assessing the impact of storm surge on barrier islands, and exploring landscape rehabilitation in military training areas.