Recent Trends in Fate, Transport, and Transformation of Inorganic and Organic Carbon in Freshwater Reservoirs

Abstract

Reservoir building is one of mankind's most significant infrastructure undertakings, resulting in the retention of massive volumes of water on continents. The reservoirs slow down the flow of terrestrial carbon through inland water bodies by providing a longer hydraulic retention time, facilitating a hotspot of biogeochemical reactions related to retention and transport of carbon. The major sources of carbon to the reservoirs include terrestrial carbon imports from inflowing rivers, algal production, and plant regeneration along shorelines during drawdown periods. The unique hydrological regime of reservoirs plays a vital role in regulating the deposition and decomposition rate of carbon. Reservoirs are carbon cycling hotspots and critical participants in the global carbon cycle. Recent studies have discovered that the rate of carbon deposition in inland reservoirs is much higher than in the oceans. However, studies also show that oxic and anoxic C decomposition conditions produce substantial fluxes of greenhouse gases (GHGs) at the surface waters and bottom sediments. The estimated GHGs emission from reservoir water surfaces account for ~1.3% of all anthropogenic GHG emissions, with the majority (79%) of this forcing by CH 4 . The carbon dynamics in reservoirs is highly affected by the influx of nutrients, biotic, abiotic, and climatic factors; thus, carbon stocks in reservoir are highly sensitive in response to future climate change. This chapter aims to explore the role of freshwater reservoirs in the global carbon cycle. We will also discuss the processes involved in accumulation, transformation, and transportation of the C in reservoir system.