Drainage Pattern Changes in Southeastern Tibet Inferred from Eocene–Modern Sediment Provenance of the Yanyuan Basin

Lithium isotope compositions of the Yangtze River headwaters: Weathering in high-relief catchments

Simple SummarySchizothorax kozlovi Nikolsky is a unique cold−water fish in the upper reaches of the Yangtze River in China and has high economic value. In our study, genetic diversity and population structure analyses were performed on seven wild populations in the upper reaches of the Yangtze River by GBS. The above results indicate that the populations of S. kozlovi have different degrees of tolerance and selection pressure in response to temperature and altitude. The Wujiang population was genetically differentiated from the Jinsha River and Yalong River populations. The Wujiang intrapopulation has greater genetic diversity and differentiation than the Jinsha River and Yalong River populations, which demonstrates that the Jinsha and Yalong populations require more attention and resources for their protection. The results of this study will increase our understanding of the diversity of S. kozlovi in the upper reaches of the Yangtze River and provide a basis for the conservation and utilization of wild resources.Schizothorax kozlovi Nikolsky is a unique cold−water fish in the upper reaches of the Yangtze River in China and has high economic value. In our study, genetic diversity and population structure analyses were performed on seven wild populations (originating from the Jinsha River, Yalong River, and Wujiang River) in the upper reaches of the Yangtze River by genotyping by sequencing (GBS). The results indicated that a total of 303,970 single−nucleotide polymorphisms (SNPs) were identified from the seven wild populations. Lower genetic diversity was exhibited among the intrapopulations of the three tributaries, and the Wujiang River population had significant genetic differentiation when compared to the Jinsha River and Yalong River populations. Furthermore, the selected SNPs were enriched in cellular processes, environmental adaptation, signal transduction, and related metabolic processes between the Wujiang population and the other two populations. The above results indicate that the populations of S. kozlovi have different degrees of tolerance and selection pressure in response to temperature and altitude. The Wujiang intrapopulation has greater genetic diversity and differentiation than the Jinsha River and Yalong River populations, which demonstrates that the Jinsha and Yalong populations require more attention and resources for their protection. The results of this study will increase our understanding of the diversity of S. kozlovi in the upper reaches of the Yangtze River and provide a basis for the conservation and utilization of wild resources.

The formation and organization of southeastern Tibetan river systems reflect feedbacks between tectonics, climate, and landscape evolution. However, our understanding of these interactions remains unclear. We approach this issue from the view that the river incision histories and their bedload provenance provide complementary evidence for reconstructing the evolution of the ancient river system. Zircon and apatite (U-Th)/He data from the middle Jinsha (upper Yangtze) River gorge reveal two episodes of accelerated river incision at 18-17 Ma and 8-7 Ma. The onset of the former incision event, coeval with other incision events along the upper-middle Jinsha and Lancang Rivers, implies their hydrological connection and formation of a south-flowing river system. Additionally, detrital geochronology and thermochronology data of late Oligocene-Miocene fluvial-alluvial sediments along the Red River valley provide constraints on their ages and provenance, suggesting emergence of a throughgoing paleo-Red River in the early-middle Miocene. This ancient Red River was disconnected from the upper Jinsha River but connected with Yalong River (upper Yangtze tributary), forming another south-flowing river system. Landscape evolution modelling supports the view that these south-flowing rivers were successively captured by the westward-propagating Yangtze River in the middle-late Miocene, giving birth to the modern drainages of southeastern Tibet. The resultant integration of the upper-middle and lower Jinsha River is manifested by the progressively upstream-propagating acceleration in river incision from 13-9 Ma to 6-5 Ma along the gorges. Our findings from southeastern Tibet suggest that orogen-scale topographic change, river reorganization, and a coeval increase in biodiversity were driven by extrusion tectonics.

In 2009, the Chinese government launched a series of policies to stimulate economic development, and the momentum for investments in large-scale development of the western regions increased. Hydropower development on rivers and mineral resource development vigorously moved forward. This trend, together with simplification of the environmental impact assessment (EIA) approval process and supervision, has led to further threats to the environment in western regions. At the beginning of the large-scale development of the western regions, governments on all levels attached great importance to ecological construction and environmental protection. Hydropower development in the Hengduan Mountains of southwest China also poses a threat to local environment and geological conditions. Most of the hydropower stations are built on dangerous sections of the following rivers such as Minjiang River, Dadu River, Yalong River, Jinsha River, Lancang River and Nujiang River. Keywords:Chinese government; Dadu River; environmental impact assessment (EIA); Jinsha River; Lancang River; Minjiang River; Nujiang River; western regions; Yalong River

Dynamics and fluxes of dissolved carbon under short-term climate variabilities in headwaters of the Changjiang River, draining the Qinghai-Tibet Plateau

The unusual drainage pattern of the Jinsha River (upper Yangtze) is closely linked to the uplift of the Tibetan Plateau, but when this pattern became established is controversial. In this study we compare the Pb isotopic composition of detrital K‐feldspars from the modern Jinsha River with those from the Plio‐Pleistocene Xigeda Formation, a sequence of fluvial and lacustrine deposits widely distributed along the major rivers draining the Tibetan Plateau, to investigate their relationship and to constrain the drainage evolution of the region. Our results demonstrate that the Jinsha River had achieved its current sediment‐transport pattern by the late Pliocene, indicating a drainage character similar to that operating at present. Our findings not only suggest an upper age limit for formation of the Jinsha River but also shed new light on the evolution of the whole Yangtze system. K‐feldspar grains from the Jinsha River have less radiogenic Pb than those in the Red, Mekong, and Salween Rivers, providing a key test as to whether the Jinsha River was previously connected to the paleo‐Red River. Comparison with published Pb isotopic data shows that these characteristically unradiogenic feldspars are absent in the onshore Cenozoic archive from the Hanoi Basin, suggesting that there has been no connection between the lower Jinsha River and the Red River since the Eocene.

The response of fluvial nitrate (NO3-) export to climate warming remains poorly constrained in high-elevation basins. Here, we integrate multi-decadal NO3- flux records with multi-year measurements of NO3- concentrations and dual-isotope signatures (δ15N-NO3- and δ18O-NO3-) from two contrasting rivers on the Qinghai-Tibetan Plateau, the permafrost-rich Jinsha River (JSR) and the permafrost-scarce Yalong River (YLR), to evaluate climate-driven shifts in NO3- dynamics. In the JSR, where sustained warming has driven widespread permafrost thaw, NO3- concentrations and fluxes increased by ∼190 and ∼220%, respectively, from 1993 to 2018. In contrast, the NO3- export in the YLR was primarily controlled by hydrological variability rather than temperature. In-soil nitrification is the dominant source of fluvial NO3-, with warming-enhanced nitrification emerging as the primary driver of increased NO3- flux, while runoff plays a minor role. Using the space-for-time substitution method, we infer that ongoing permafrost degradation may shift NO3- export from warming-driven to hydrology-driven controls. This transition is expected to enhance nitrogen leaching under warming and intensified precipitation, contributing to nitrogen limitation in high-elevation vegetation and weakening of CO2 uptake. These findings reveal a previously underappreciated climate-warming nitrogen-carbon feedback with implications for Earth system models in permafrost-affected regions.

To explore the differences in the growth characteristics and population dynamics of Schizothorax wangchiachii populations in the Jinsha River (JSR) and the Yalong River (YLR), samples were collected in the upper reaches of the JSR (n = 230) from 2019 to 2020 and the middle reaches of the YLR (n = 187) from 2017 to 2018. In the JSR and YLR populations, the age range was 11 and 12 years old, respectively, and the best growth equation was the Von Bertalanffy equation. The comparative analysis of the two populations showed that the growth coefficient, initial sexual maturity age and age at first capture of the YLR population were greater than those of the JSR population. Comparing the mortality rates of the two groups, we found that the YLR population had the higher female mortality rate (0.658 years-1) and the lower male mortality rate (0.453 years-1). Our assessment of the three natural mortality rates showed that the Fcur of both male and female populations was greater than F25%, indicating that both populations were in an overexploited state. Therefore, we suggest considering the two groups as separate protection units and implementing management measures such as ecological regulation, restoration of tributary habitat and strengthening of fishing ban monitoring to protect their resources.

Fish diversity is essential for maintaining the balance of aquatic ecosystems, particularly in rivers impacted by overfishing and hydropower projects, such as the Jinsha river, the upstream segment of the Yangtze river. During initial phases (August and November, 2023) of the 10-year fishing ban in the Yangtze river basin, we investigated fish diversity, seasonal variations, and their correlation with environmental factors in the Jinsha river using environmental DNA (eDNA) metabarcoding. Utilizing two pairs of 12S rRNA primers, MiFish-U and AcMDB07, we identified 61 fish species across 5 orders, 17 families, and 52 genera, including 4 national protected and 7 invasive alien fish. Among them, Cypriniformes constituted the predominant group within the fish community, accounting for 65.6%. This finding aligns with the results from a recent fish catch study, which recorded 68 species of fish belonging to 4 orders, 15 families, and 48 genera, including 4 national protected species and 8 invasive alien fish. The alpha diversity analysis revealed compositional differences in the fish community across various regions and seasons. Furthermore, key environmental factors, such as water temperature, dissolved oxygen, nitrate nitrogen, total suspended solids, and conductivity, were found to be highly correlated with fish diversity in the Jinsha river. Consequently, we provided detailed seasonal data on fish diversity and its correlations with environmental factors, which will aid in the systematic management and restoration of fisheries and the assessment of the 10-year fishing ban in the Jinsha river.

The Central Yangtze ecoregion in China includes a number of lakes, but these have been greatly affected by human activities over the past several decades, resulting in severe loss of biodiversity. In this paper, we document the present distribution of the major lakes and the changes in size that have taken place over the past 50 years, using remote sensing data and historical observations of land cover in the region. We also provide an overview of the changes in species richness, community composition, population size and age structure, and individual body size of aquatic plants, fishes, and waterfowl in these lakes. The overall species richness of aquatic plants found in eight major lakes has decreased substantially during the study period. Community composition has also been greatly altered, as have population size and age and individual body size in some species. These changes are largely attributed to the integrated effects of lake degradation, the construction of large hydroelectric dams, the establishment of nature reserves, and lake restoration practices.

The main tributaries of the upper reaches of the Yangtze River are not only the strategic base for China’s water resources, but also an important hydropower base for the “West-East Power Transmission Strategy”. With the completion of these reservoir groups, a large-scale mixed reservoir system across the different basins has been formed, which makes the requirements for joint optimization and scheduling of large-scale hydropower system getting higher and higher. This paper focuses on the key problems faced by the joint optimization of large-scale hydropower system in the basin. Taking the Yalong River and the middle and downstream of the Jinsha River as the research area, the hybrid optimization method is introduced herein to solve the joint optimal scheduling model. The results reveal that the power generation by joint optimal scheduling is much more than separately scheduling, and the total power generation increased by 2.84% on average. As Mid-Jinsha cascade and Yalong River cascade has a 690 million kW·h and 190 million kW·h decrease in power generation respectively, the downstream Jinsha River cascade has a power generation increase of 4.31 billion kW·h.

The Indo-Asia collision significantly changed the topography and drainage network of rivers around the Tibetan Plateau. Debate continues as to when and how the current drainage system of the Yangtze River was formed. Here we use 40 Ar/ 39 Ar dating of detrital micas (muscovite and biotite) to constrain provenances of the Pliocene sediments from the Jianchuan and Yuanmou basins in SE Tibet. Muscovite and biotite data of the same Pliocene samples from the Jianchuan Basin suggest contrasting distal v. local sources, respectively. Similarly, muscovite data of the Yuanmou Basin suggest a derivation of sediments from the Yalong River, but the characteristics of the Pliocene cobbles (palaeocurrent and subrounded cobbles) suggest that these sediments are locally sourced. Sediment reworking is proposed as an explanation for the different sediment provenance signals in the Jianchuan and Yuanmou basins that have led to the controversy of an either Pleistocene or pre-Miocene age of formation of the current Yangtze. Based on sediment provenance constraints, the evolution of the Jinsha River is reconstructed. The upper Jinsha River lost its connection with the southward flowing Red River upstream from the Jianchuan basin at least before the Pliocene. At the same time a parallel site in the Yuanmou Basin shows that the Yalong River stopped flowing southward into this basin. Detrital mica from early Pleistocene sediments at the Panzhihua site between the Jianchuan and Yuanmou basins is sourced from the current Jinsha and Yalong rivers. These results would suggest that the current upper Yangtze drainage system should have been established before the Pliocene. Supplementary material: Muscovite 40 Ar/ 39 Ar data, biotite 40 Ar/ 39 Ar data and muscovite geochemistry are available at https://doi.org/10.6084/m9.figshare.c.4821573

A general framework of design flood estimation for cascade reservoirs in operation period

Rutile and zircon U-Pb dating as a constraint on sedimentary provenance of the Jianchuan Basin: Implications for paleo-drainage evolution

High-elevation mountains have experienced disproportionately rapid warming, yet the effect of warming on the lateral export of terrestrial carbon to rivers remains poorly explored and understood in these regions. Here, we present a long-term data set of dissolved inorganic carbon (DIC) and a more detailed, short-term data set of DIC, δ13CDIC, and organic carbon from two major rivers of the Qinghai-Tibetan Plateau, the Jinsha River (JSR) and the Yalong River (YLR). In the higher-elevation JSR with ∼51% continuous permafrost coverage, warming (>3 °C) and increasing precipitation coincided with substantially increased DIC concentrations by 35% and fluxes by 110%. In the lower-elevation YLR with ∼14% continuous permafrost, such increases did not occur despite a comparable extent of warming. Riverine concentrations of dissolved and particulate organic carbon increased with discharge (mobilization) in both rivers. In the JSR, DIC concentrations transitioned from dilution (decreasing concentration with discharge) in earlier, colder years to chemostasis (relatively constant concentration) in later, warmer years. This changing pattern, together with lighter δ13CDIC under high discharge, suggests that permafrost thawing boosts DIC production and export via enhancing soil respiration and weathering. These findings reveal the predominant role of warming in altering carbon lateral export by escalating concentrations and fluxes and modifying export patterns.