Hill, Alice FÌý1
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Remote mountain rivers are increasingly under development threat as the low hanging fruit of hydropower dam sites -- ones with easy access and whose rivers have large head potential -- have been picked. Often little is known about the hydrologic regimes of rivers in remote regions due to the impracticality of conducting field work in hard-to-access locations and in challenging climates. Satellite imagery use is the current trend for addressing the data scarcity issue in remote regions but it has shortcomings especially in mountainous terrain (e.g., cloud cover prevents satellites from imaging land surfaces over most frequencies). Even clear remote sensing imagery needs field data for validation. Field work is a necessary component to furthering our understanding of remote mountain and water resources.
The Rio Maranon basin in the Peruvian Andes, the source of the Amazon River by some definitions, is a little known but mostly pristine remote mountain river. It is facing major development pressure from hydropower dams, mining operations and fossil fuel extraction. Well-founded and sustainable river management decisions first require an understanding of the resource itself. While incomplete, the best data available for the Rio Maranon comes from resource developers as part of the regulatory project approval process. In part due to its challenging terrain and whitewater, and in part due to lack of Peruvian funding for science activities, little-to-no science driven data collection projects have been conducted in the corridor. In the case of the Maranon as well as other rivers likely to undergo rapid change, baseline data sets are critical for beginning to discover and characterize these beautiful, flowing resources. Baseline data is also critical as a "pre development" snapshot upon which to use as a comparison to evaluate impacts from change.
Collecting in situ data in headwater basins over small scales is readily achievable, but acquiring field data over hundreds of kilometers and heterogeneous mountain domains is a discipline-wide challenge. Here I use a methodology to survey the hydrologic regime of the Rio Maranon over 620 km from the high alpine headwaters to the lower lying jungle by way of a "Rapid Hydro Assessment" (RHA). Using isotopes, geochemical tracers and rare earth metals, preliminary results of a Lagrangian sampling scheme implemented by way of RHA will be presented that show longitudinal changes in source water composition and water quality. These results provide the first large scale characterization of the snow-to-rain fed transition in a regional mountain river basin in the Peruvian Andes. Results also indicate hot-spot chemical locations along the corridor with implications to point source contamination. These findings bring about questions about the potential for further contamination in the context of mining and fossil fuel development on the Rio Maranon.