The Selenga River delta: a geochemical barrier protecting Lake Baikal waters

Abstract

The protection of Lake Baikal and the planning of water management measures in the Selenga River Basin require a comprehensive understanding of the current state and functioning of the delta's ecosystem and hydrogeochemical processes. This is particularly relevant in light of recent and expected future changes involving both the hydrology and water quality in the Lake Baikal basin causing spatiotemporal changes in water flow, morphology, and transport of sediments and metals in the Selenga River delta and thus impacting on delta barrier functions. The central part of the delta had been characterized by sediment storage, especially along the main channels, causing a continuous lift of the delta surface by about 0.75 cm/year-1. Theses morphological changes have a significant impact on hydrological conditions, with historical shifts in the bulk discharge from the left to the right parts of the delta which is distinguished by a relatively high density of wetlands. Regions with a high density of wetlands and small channels, in contrast to main channel regions, show a consistent pattern of considerable contaminant filtering and removal (between 77 and 99 % for key metals), during both high-flow and low-flow conditions. The removal is associated with a significant concentration increase (2-3 times) of these substances in the bottom sediment. In consequence, geomorphological processes, which govern the partitioning of flow between different channel systems, may therefore directly govern the barrier function of the delta.

Environmental change in the Selenga River—Lake Baikal Basin

“…The results of the various international research programs such as the Russian Geographical Society project "Expedition Selenga-Baikal", UNDP-GEF project "Integrated Natural Resource Management in the Baikal Basin Transboundary Ecosystem", and the German BMBF-funded Thematically, the manuscripts consider hydrological changes and their drivers, pollutant and sediment input, transport and deposition and their role for the aquatic ecosystem of the Selenga, its tributaries and its delta. The spatial focus of the manuscripts ranges from basinwide studies (Malsy et al 2016;Frolova et al 2017) to specific subregions such as the Selenga's headwaters (Kopp et al 2016;Kaus et al 2016;Thorslund et al 2012) or its delta (Chalov et al 2016) ( Table 1). These studies provide an important contribution for a better understanding of spatial and temporal processes regarding hydrology, sediment and pollutant fluxes and aquatic ecology in the Selenga River-Lake Baikal Basin, adding novel insights into this unique ecosystem as compared to previous reports in literature (Table 1).…”

“…However, north of the Buryatian capital Ulan Ude, the Selenga River branches into the largest freshwater inland delta in the world (Logachev 2003). The associated wetland constitutes a unique ecosystem (Гармаев and Христофоров 2010) and acts as the final geobiochemical barrier before the Selenga discharges into Lake Baikal (Chalov et al 2016).…”

Modelling suspended sediment distribution in the Selenga River Delta using LandSat data

“…Field measurements of SSC for calibration of the SSC model were undertaken at more than 50 locations within the delta (Chalov et al, 2016) (Fig. 1).…”

“…Since there is no constantly measured discharge data in each channel system, average values for water partitioning between sectors (Chalov et al, 2016) were used. Three possible ratios between sediment input and output were analysed: S 2 >S 1 , S 2 <S 1 and S 2 ≈ S 1 , which correspond to either erosional ( S>0), depositional ( S<0) or equilibrium ( S = 0) states.…”

Speciation and hydrological transport of metals in non-acidic river systems of the Lake Baikal basin: Field data and model predictions

“…Our here estimated mass flows and parallel quantifications Chalov et al 2016) of metal transport in the Tuul River all point to mining activities as the main driver of increasing sediment loads to downstream regions. Coupled to this, geochemical processes (e.g.…”