Despite the increasing Siberian river discharge, the sensitivity of streamflow to climate forcing/permafrost thawing is poorly quantified. Based on the Budyko framework and superposition principles, we detected and attributed the changes in streamflow regimes for the three great Siberian rivers (Ob, Yenisei, and Lena) during 1936–2019. Over the past 84 years, streamflow of Ob, Yenisei and Lena has increased by ∼7.7%, 7.4% and 22.0%, respectively. Intensified precipitation induced by a warming climate is a major contributor to increased annual streamflow. However, winter streamflow appears to be particularly sensitive to temperature. Whilst rising temperature can reduce streamflow via evapotranspiration, it can enhance groundwater discharge to rivers due to permafrost thawing. Currently, every 1 °C rise in temperature likely leads to 6.1%–10.5% increase in groundwater discharge, depending on the permafrost condition. For permafrost-developed basins, the contribution to increased streamflow from thawing permafrost will continue to increase in the context of global warming.

The northern mid-high latitudes experience climate warming much faster than the global average. However, the difference in the temperature change rates between permafrost and non-permafrost zones remains unclear. In this study, we investigated the temporal changes in temperature means and extremes across the Siberian lowlands (<500 m) over the past six decades (1960–2019) using in situ observations and reanalysis data. The results show that permafrost zones (0.39 °C/decade) have warmed faster than non-permafrost zones (0.31 °C/decade). The minimum values of the daily maximum (TXn) and minimum (TNn) temperatures changed faster than their maximum values (TXx, TNx), suggesting that low minimum temperatures increase faster, as evidenced by the considerably higher warming rate in the cool season (October–April, 0.43 ± 0.10 °C/decade, n= 126) than that in the warm season (May–September, 0.25 ± 0.08 °C/decade, n= 119). The change rates of TXx and TNx in permafrost areas were 2–3 times greater than those in non-permafrost areas; however, over the last ten years, TXx and TNx in non-permafrost areas showed decreasing trends. Moreover, faster-warming permafrost regions do not exhibit a faster increase in surface net solar radiation than slower-warming non-permafrost regions. While our findings suggest that carbon emissions from thawing soils are likely a potential driver of rapid warming in permafrost-dominated regions, the potential feedback between ground thawing and climate warming in permafrost regions remains uncertain.

Fresh water scarcity is considered a significant component, and potentially one of the most critical, of global climate change. With the rapid development of industry, there is an increasing risk of freshwater contamination by heavy metals (HMs). The danger of HM pollution is also attributed to their accumulation, which can subsequently become a source of secondary pollution in aquatic environments. In the Lake Gusinoe basin, located in Russia, concentrations of HMs were measured in both water and bottom sediments within the lake area, as well as in inflowing and outflowing watercourses. Ecological risk indices were also calculated for the Gusinoe basin. Our results showed that the average concentrations of Fe, Zn, Cr, Ni, Cd, and Pb in the water did not exceed the maximum allowable concentrations (MACs) set by Russian national standards and WHO standards, while the concentrations of Mn and Cu exceeded the corresponding MACs during winter, spring, and autumn possibly due to decomposition of aquatic vegetation and influx from groundwater sources. The average concentrations of the investigated HMs in the BSs did not exceed the background values. The water hazard index indicated a low risk for all samples in the lake water area. For all BS samples, the geoaccumulation index (Igeo) and the Pollution Load Index (PLI) indicated low pollution levels, while the values of the Enrichment Factor (EF) and the Contamination Factor (CF) indicated moderate pollution in the central part of the lake. The Ecological Risk Factor (Er) for Cu in BSs at points near major settlements and in the Tel River indicated moderate pollution. The Potential Ecological Risk Index (RI) in all investigated BS samples indicated a low risk of contamination.

The geochemical processes of groundwater in arid regions are generally influenced by both natural hydrological processes and human activities. However, impacts of water-rock interactions on groundwater recharge via hydrological processes, controlled by both intermittent river water flow and groundwater withdrawals, is still poorly understood. In this study, 327 groundwater chemistry datasets collected from the upper, middle (including Gobi and riparian zones), and lower regions of the Ejina Delta in Northwest China from 2001 to 2023 were analyzed. Our results revealed that the total dissolved solids (TDS) concentration of groundwater in Ejina Delta ranged from approximately 881.5 ± 331.6 mg/L in the upper regions to 1,953.6 ± 1,208.5 mg/L in the lower regions, with an increasing trend observed. Ecological water conveyance (EWC), recharging aquifer through intermittent river water flow, resulted in a decrease in TDS concentrations from 2001 to 2023 mainly in the upper region. While irrigation notably affected groundwater chemistry in the lower region, resulting in a substantial increase in groundwater salinity. Groundwater chemistry in the Middle Gobi region remained relatively stable over the study period. Generally, the hydrochemical composition shifted from the Na-Mg-SO₄-HCO₃ and Na-Mg-Ca-SO₄-HCO₃ types in the upper region to Na-Mg-SO₄-HCO₃ and Na-Mg-SO₄-Cl types in the lower region, with Na-SO₄-Cl predominant in the Middle Gobi. These shifts were likely be attributed to the interplay of water-rock interactions, coupled with evaporation-crystallization processes. Inverse modeling using PHREEQC revealed that in the upper-middle region, primary water-rock interactions involved calcite dissolution and the precipitation of dolomite, gypsum, halite, and sylvite salts, as well as cation exchange reactions (2NaX+Ca²⁺→CaX₂+2Na⁺). In contrast, the hydrogeological system in the middle-lower region exhibited an opposite pattern of water-rock interactions. Overall, ecological water conveyance partially facilitated water-rock interactions during lateral groundwater flow, while irrigation disrupted the natural hydrogeochemical equilibrium, involving halite dissolution and opposite cation exchange reactions compared to other regions.