Climate Controls on River Chemistry
Abstract
How does long-term river chemistry vary across climate gradients? Existing literature has examined extensively the response of river chemistry to short-term weather conditions from event to monthly scales. Patterns and drivers of long-term river chemistry have remained poorly understood. Here we compile and analyze chemistry data from 506 minimally-impacted rivers (412,801 data points) in the contiguous United States to identify its patterns and drivers (Li et Al., 2022). Despite distinct sources and diverse reaction characteristics, a universal pattern emerges for 16 major solutes at the continental scale. Their long-term mean concentrations (Cm) decrease with mean discharge (Qm), with elevated concentrations in arid climates and lower concentrations in humid climates, indicating overwhelming regulation by climate compared to local Critical Zone characteristics such as lithology. To understand the CmQm pattern, a watershed biogeochemical reactor model was solved by bringing together hydrology (storage-discharge relationship) and biogeochemical reaction theories from traditionally separate disciplines. The derivation of long-term, steady state solutions lead to a power law form of CmQm relationships. The model illuminates competing processes that determine mean solute concentrations: solute addition by external input and production by soil biogeochemical and chemical weathering reactions, and solute export (or removal) by mean discharge, the water flushing capacity dictated by climate and vegetation. In other words, the watersheds mostly function as reactors that accumulate solutes in arid climates, and as transporters that export solutes in humid climates. With space-for-time substitution, these results indicate that in places where river discharge dwindles in a warming climate, solute concentrations will elevate, threatening water quality and aquatic ecosystems even without human perturbation. Water quality deterioration therefore should be considered in the global calculation of future climate risks.
reference: Climate Controls on River Chemistry Li Li, Bryn Stewart, Wei Zhi, Kayalvizhi Sadayappan, Shreya Ramesh, Devon Kerins, Gary Sterle, Adrian Harpold, Julia Perdrial. 2022. Climate controls on river chemistry. Earth's Future. doi.org/10.1029/2021EF002603- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H13G..09L