Syr Darya Basin Research Articles

Precipitation in the mountains of Central Asia: isotopic composition and source regions

Abstract. Over 900 event-based precipitation samples were collected in 2019–2021 in the Tien Shan and its foothills and analysed using cavity ring-down spectroscopy. δD and δ18O values were highest in summer and lowest in winter, and annual cycles of deuterium excess (d-excess) varied between sites, reflecting local conditions. The δ18O and δD values increased from north to south in all seasons except autumn, and latitude was a statistically significant predictor of δ18O and δD in the overall data set, along with elevation in winter and elevation and longitude in autumn. Elevation was a significant predictor of d-excess in all seasons, and local air temperature was a more important control over δ18O and δD than precipitation depth. Local meteoric water lines were derived using seven regression methods applied to non-weighted and weighted precipitation. Non-weighted ordinary least squares regression and reduced major axis regression methods are recommended overall, except for summer when the precipitation-weighted least squares regression should be used, particularly in the south. Atmospheric back-trajectory and mixing-model analyses were applied in combination to identify air mass source regions and their relative contribution to precipitation. Recycled moisture from irrigated land in the Amu Darya and Syr Darya basins and from the study catchments accounted for 29 %–71 % of precipitation, depending on the site and season. In the Chon Kyzyl-Suu catchment, local re-evaporation from Issyk-Kul accounted for up to 85 % of precipitation. These findings highlight the importance of moisture from terrestrial sources, especially irrigated land, for the formation of precipitation in the Tien Shan.

What drives the distinct evolution of the Aral Sea and Lake Balkhash? Insights from a novel CD-RF-FA method

Study RegionThe Aral Sea and Lake Balkhash. Study FocusThis study explores the impacts of climate change and human activities on the inflow of the Aral Sea and Lake Balkhash, revealing the different driving factors behind the evolution of inland lakes in arid environments. To achieve this, we propose a novel approach that combines classical seasonal decomposition with Random Forest and Factor Analysis (CD-RF-FA) to quantitatively assess the influences of climate change and human activities on lake inflow. New Hydrological Insights for the RegionDuring the period from 1960 to 1990, anthropogenic factors predominantly influenced the inflow to the lakes, contributing 89.9 %, 91.8 %, and 91.6 % to the Lake Balkhash Basin (BAK), the Syr Darya Basin (SYR), and the Amu Darya Basin (AMU), respectively. However, from 1991 to 2020, the influence of human activities diminished, and climate variables gradually dominated the changes in inflow, contributing 52.2 % and 47.2 % to BAK and SYR, respectively, with upstream inflow being the main driving factor. Additionally, reservoir construction and political factors also played significant roles in the variation of inflow, exerting direct or indirect effects. This study provides crucial insights into the complex interplay of factors affecting inland lakes in arid regions and informs strategies to mitigate the Aral Sea Syndrome.

Water Tales from Turkistan: Challenges and Opportunities for the Badam-Sayram Water System under a Changing Climate

The Badam River, a tributary to the Arys River located in the Syr Darya basin, is a crucial natural resource for ecological, social, and economic activities in the semi-arid region of southern Kazakhstan. The river basin is heavily influenced by manmade water infrastructure and faces water scarcity, particularly during summer, highlighting the importance of understanding its hydrological processes for effective water resource management. In this study, a semi-distributed conceptual hydrological model of the Badam River was implemented using the RS MINERVE hydrological software to evaluate the impacts of climate change on hydrology and to test the resilience of the water system. Connected HBV models were implemented for each of the hydrological response units that were defined as altitudinal zones. The hydrological model was calibrated using daily time steps between 1979 and 2011, and the resulting flow exceedance curves and hydrographs were used to assess the potential impacts of climate change on the basin, using CMIP6 precipitation and temperature scenarios. Future climate scenarios for the 2054 – 2064 period demonstrate that the peak discharge will be shifted to spring/late spring compared to the current early summer with no significant decrease in average discharge per day of the year. The insights gained from this hydrological-hydraulic model can be used to effectively manage the water system and inform future hydropower design decisions and serve as a blueprint for similar studies in the region and elsewhere.

Northward shift of Indian summer monsoon and intensifying winter westerlies cause stronger precipitation seasonality over Pamirs and its downstream basins in the 21st century

Hydroclimate will change over Pamirs and its downstream basins (PDB), including Indus River, Tarim River, Amu Darya and Syr Darya Basins, in response to the variation of Indian summer monsoon (ISM) and mid-latitude westerlies. However, the precipitation variation and its mechanism over PDB in the 21st century are yet not fully understood. Here, the best models ensemble selected from 25 CMIP6 models under SSP2–4.5 and SSP5–8.5 scenarios is applied to detect the precipitation variations over PDB in the 21st century. A remarkable dipolar pattern is found in both summer and winter precipitation over PDB, particularly in the central Indus River Basin and upper Amu and Syr Darya Basins. The central Indus River Basin (upper Amu and Syr Darya Basins) will experience an increasingly wet (dry) summer in response to northward ISM and a dry (wet) winter driven by mid-latitude westerlies. The amplifying dipolar pattern of seasonal precipitation thus increases the water resource vulnerability over PDB and emphasizes the role of Pamirs in modulating the water resources over surrounding basins, especially the Amu Darya and Syr Darya Basins in the future. The findings underscore the need for prioritizing policies by considering the impacts of precipitation seasonality on social planning.

Prediction of groundwater drawdown and quality at Kyzylzharma well field in the arid Syr Darya Basin, Kazakhstan

Prediction of groundwater drawdown and quality at Kyzylzharma well field in the arid Syr Darya Basin, Kazakhstan

Long-Term Dynamics of Persistent Organic Pollutants in Water Bodies of the Aral Sea–Syrdarya Basin

The huge decrease in water volume in the Aral Sea, which was caused predominately by enormous water withdrawals from the Aral Sea tributaries, has changed the former world’s fourth-biggest inland lake into a new desert called Aralkum. Due to its long-term use in agriculture, persistent organic pollutants (POPs), including organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) play a special role in the pollution of the Aral Sea tributaries and in the Aral Sea itself. For the first time, POPs, OCPs, and PCBs were studied in the Large Aral Sea, Small Aral Sea, and the Syrdarya River. PCBs and OCPs in the collected water samples were analyzed using gas chromatography. The results of long-term and inter-annual analyses of POPs in water resources of the Kazakh part of the Aral Sea–Syrdarya Basin are presented. The analyses covered the Large and Small Aral Seas, the Syrdarya River, reservoirs, lakes of the river delta, and drainage water of the collectors from irrigation areas. The inflow to the Syrdarya River that came from the collector–drainage water was the main cause of water pollution. The pollution levels of toxic compounds, including the trends of temporal and spatial changes in pollutant concentrations, were analyzed and assessed. The latest studies from 2021 and 2022 show a decrease in pesticide concentrations by tens and hundreds of times.

Current State of Rare and Endangered Barbels of the Genus Luciobarbus Heckel, 1843 in the Aral-Syrdarya Basin (Kazakhstan) and Prospects for Their Conservation (A Review).

The current status of the barbels inhabiting the Kazakhstan section of the Syrdarya River needs special study, as has been noted since the second half of the 20th century. Stocks of commercial fish valuable in the past as barbels in the Aral-Syrdarya basin are now catastrophically reduced as a result of anthropogenic impact on the ichthyofauna and natural environment of the Aral Sea region. The study of the condition; abundance and distribution range is necessary to determine measures for their restoration in natural habitats and their breeding in fish farms. Research on the biotechnology of barbel breeding with subsequent acclimatization and reacclimatization of these fish species will not only improve the composition of the ichthyofauna of the Aral-Syrdarya basin, but also preserve the genetic potential of natural populations. At present, the only way to restore the population of the Aral barbel is stocking hatchery reared juveniles in natural environments. Under the current situation, a way forward is seen in the creation of domesticated replacement-broodstocks of barbels. As a result of the influence of anthropogenic factors, the populations of this species have come to almost complete degradation and depletion and require the development and adoption of urgent measures for their conservation and restoration through reintroduction, which is a priority and urgent task for the fisheries of the republic.

Assessment and forecast of water resources use in Uzbekistan

The article examines the assessment of the state and problems of irrigation water use in the republic in the past and in the near future. A comparative analysis of the state of water resources use for the period of the last 30 years from 1989 to 2019 was carried out. According to the estimates, own water withdrawal for 5 years (2014 / 15-2018/19) shows that an average of 53.2 billion m3 were used for irrigation, including 50.5 billion m3 from rivers. At present (2018-2019), an average of 57.06 billion m3 of water is taken for irrigation of 4.289 million hectares of land, against 63.02 billion m3 approved in 1989. At the same time, the actual water consumption amounted to 48.9 billion m3. Specific water consumption (in the years of average water content) in the Amudarya river basin is 12.5 thousand m3/ha, in the Syrdarya basin - 10.4 thousand m3/ha. Forecast calculations show that there is a tendency to reduce water from rivers to agriculture by an average of 0.104 billion m3/year, with an increase in other sectors from 11.53% (communal and household sector) to 100% (fisheries). The volume of discharges into CDS is decreasing due to the use of collector-drainage waters throughout the region, while specific water consumption has increased to 11.50 thousand m3/ha, i.e. by 450 m3/ha or 28.1%. The reasons for the lack of water for irrigating agricultural crops during the period of vegetative irrigation are stated. The issues of water saving and ways of transition to modern technologies for the use of surface and ground waters, redistribution of water and solutions for the interstate use of river resources are touched upon.

Paleodemography of the Altyn-Asar burial grounds (concerning migrations in the Lower Syrdarya Basin)

Jetyasar archaeological culture was discovered and studied by the Khorezm expedition of the Institute of Ethnography of USSR. According to archeological data, this culture experienced many times transformations due to the influx of new population groups. This article presents for the first time complete data on paleodemography of samples from nineteen burial grounds of Altyn-Asar 4a–t, Kosasar 2 and Tompakasar, taking into account frac-tional chronological differentiation. We examined anthropological materials from over 600 burials in the storage of the Institute of Archeology RAS. In total samples from Altyn-Asar 4 of the 2nd c. BC. — 4th century was mentioned to the weak numerical predominance of females. The sex ratio in favor of males changed in the 4th–6th centuries. The average age at death of the adult population decreased by the 6th century, primarily among men. Data on separate cemeteries allow a more differentiated assessment of the chronological dynamics of demographic indi-cators. The numerical predominance of male burials was found: in the 2nd c. BC. — 4th c. AD in burial grounds Kosa-sar 2, Altyn-Asar 4 m; in the 4th–6th c. in the Altyn-Asar necropolises 4a, b, o, v. In opposite to the most groups, the Kosasar 2 sample stands out with its demographic profile and increased average age of death for males and fe-males. According to archeological data, it may be associated with Xiongnu migration. In 2nd–4th centuries the number of this group was falling, it showed a decrease in life expectancy for men, however, for this period, it seems to be comparable the maximal one. Their antagonists during this period were representatives of other group of incomers, buried in necropolis AA4m, with a low life expectancy for males and females. Despite the supposed influx of new-comers, it is obvious that the genetic continuity of a part of the Jetyasar population, which probably belonged to in-fluential local clans (the necropolises of Altyn-Asar4l and later Altyn-Asar4r), might be evident.

Evaluation of dissolved and acid-leachable trace element concentrations in relation to practical water quality standards in the Syr Darya, Aral Sea Basin, South Kazakhstan

The Syr Darya is one of the major rivers supplying the Aral Sea with freshwater. Soviet programs aimed at maximizing agricultural productivity in the Syr Darya basin increased diversion of water drastically affecting its water quality with significant consequences to its suitability for irrigation, fisheries and other uses. While water quality standards for trace elements are typically measured in the dissolved phase, there is evidence that adsorbed phases may also be relevant. Here we report potentially available heavy metals and metalloid concentrations in the Syr Darya water through the treatment of unfiltered waters samples with dilute nitric acid. Significant differences were found for most studied elements (Mann-Whitney U Test, p < 0.05) between their dissolved and acid-leachable concentrations. For Sr and Se in both sampling campaigns, no significant differences were found between their dissolved and acid-leachable concentrations, indicating their low geochemical reactivity. Dissolved V concentrations and acid-leachable Ni and Zn were found to exceed Kazakhstan Maximum Permissible Concentrations (MPC) values for the protection of fishery water quality. Our study evaluates the importance of considering regulatory issues of measuring trace metal concentrations to assess the water suitability for fisheries and irrigation.

Relieving water stress by optimizing crop structure is a practicable approach in arid transboundary rivers of Central Asia

With the challenges of arid transboundary river water management among Central Asian countries, it is important to evaluate the water stress and propose practicable climate adaptation strategies. This study used the Syr Darya Basin (SDB) in a Central Asia data scarce region as the study area and, conducted the first quantified analysis of the spatiotemporal characteristics of water supply and requirements at the basin and irrigation district scale; identified its driving mechanisms based on systematic monitoring data concerning reservoir regulation and complex crop structure from 2000 to 2018; and a climate change scenario combined with a crop restructuring scenario was applied to evaluate water conservation effects and propose a climate adaptation strategy from 2019 to 2030. The results showed that runoff increased by 7.45 billion m3 but the water withdrawal decreased by 3.42 billion m3 after reservoir regulation in the basin during 2000–2018. Due to the unified water allocation, it was challenging to conduct and usually exceeded the plan by 0.4–8.5 %. The total crop water requirement (TCWR) mainly derived from cotton (61.5 %), winter wheat (12.1 %) and rice (13.9 %) increased by 3.15 billion m3 (+30.7 %) and the influence of crop area (380 million m3/a) was greater than that of climate (130 million m3/a). The wind speed (27.5 %) and rice area (19.2 %) also significantly contributed to the TCWR variation. The contradiction between water supply and requirement resulted in water scarcity in the basin. From 2019–2030, the water conservation effect of winter wheat (+20 %) under the restructuring scenarios reached 28.7 mm, which helped relieve water stress under the scenario of a 0.51–0.91 °C increase. Thus, priority planting of a winter wheat rotation and low water consuming crops is a practicable approach for coping with water scarcity and adapting to climate change in arid transboundary rivers of Centra Asia.

Predicted aquatic and human health risks associated with the presence of metals in the Syr Darya and Shardara Reservoir, Kazakhstan

Due to the decline of the Aral Sea fishery and recent efforts to expand the fisheries sector in Kazakhstan for both local consumption and global export, there is a need to sustain other fisheries in the area, including the Shardara Reservoir, which lies in the Syr Darya basin. Metals are present in the Syr Darya; yet, their impacts on fishery and consumer health remain unclear. Thus, the objectives of this study were to evaluate: 1) the potential impacts of metals on Syr Darya basin fish and 2) the human health risks posed by consumption of Shardara Reservoir fish. The health of the fishery was assessed by comparing surface water metal concentrations to maximum permissible concentrations (MPCs), calculating water quality index (WQI) and degree of contamination (Cd) values, and evaluating gene expression biomarker responses in wild-caught roach (Rutilus rutilus). To assess the risk to consumers, metal concentrations in roach were used to calculate hazard quotients (HQs) and hazard indices (HIs). Water concentrations of Cu, Fe, Mn, Se, Sr and V exceeded MPCs and all sites were classified as highly polluted based upon WQI and Cd values. This, along with site-specific differences in the expression of genes associated with xenobiotic metabolism and oxidative stress in roach, indicates potential risks to the fishery. Though all HQs and HIs were below 1 indicating a lack of significant risk to consumers, Pb levels in roach exceeded MPCs for safe consumption indicating a potential risk. Given the potential risks to the fishery and consumers, the development of pollution monitoring and management programs are warranted. The work presented here provides initial monitoring data that can be used to aid such efforts and also underscores the need to identify environmental stressors that may thwart the anticipated growth of fisheries in this region.

Effects of Vegetation Change on Soil Erosion by Water in Major Basins, Central Asia

The uncertainties in soil erosion (SE) are further intensified by various factors, such as global warming, regional warming and humidification, and vegetation cover changes. Moreover, quantitative evaluations of SE in major basins of Central Asia (CA) under changing environments have rarely been conducted. This study conducted quantitative evaluation of SE in four major basins (Syr Darya Basin (SDB), Amu Darya Basin (ADB), Ili River Basin (IRB) and Tarim River Basin (TRB) using the Revised Universal Soil Loss Equation (RUSLE) and analyzed the main driving factors. SE quantities in the basins presented relatively consistent upward fluctuating trends from 1982 to 2017. Vegetation cover variation fluctuated significantly from 1982 to 2017. Specifically, vegetation cover decreased continuously in SDB, ADB, and IRB, but increased gradually in TRB. Pixels with positive spatial variation of vegetation mainly occurred around lakes and oases near rivers. The Normalized Difference Vegetation Index (NDVI) showed higher correlation with precipitation (80.5%) than with temperature (48.3%). During the study period, the area of arable land (AL) exhibited the largest change among all land use types in CA. Under long-term human activities, the proportion of NDVI of other land types converting to AL was the highest. In the structural equation model (SEM), precipitation, temperature, Shannon Diversity Index (SHDI), and NDVI strongly influenced SE. Overall, the major basins in CA were jointly affected by climate, human activities, and vegetation. Specifically, climatic factors exerted the strongest influence, followed by SHDI (human activities). SE was found to be relatively serious in ADB, SDB, and IRB, with SE in SDB even approaching that in the Loess Plateau. Under the background of global changes, appropriate water and land resource management and optimization configurations should be implemented in CA with reference to TRB in order to relieve local SE problems.

Triplophysadaryoae, a new nemacheilid loach species (Teleostei, Nemacheilidae) from the Syr Darya River basin, Central Asia.

Triplophysadaryoae, new species, is described from the Sokh River, a former tributary of Syr Darya that today fails to reach the river, in the Sokh District, an exclave of Uzbekistan, surrounded by Kyrgyzstan. Triplophysadaryoae is distinguished from other species of Triplophysa in Central Asia by a truncate caudal fin with 13 or 14 branched rays, body without obvious mottling, dorsal-fin origin opposite to pelvic-fin insertion, and absence of the posterior chamber of the air bladder. Molecular data suggest that Triplophysadaryoae is closely related to T.ferganaensis from the Shakhimardan stream, a small tributary of Syr Darya in the Yordon village, another exclave of Uzbekistan in Kyrgyzstan. The two species were separated by a Kimura 2-parameter genetic distance of 2.8% in the mitochondrial DNA cytochrome c oxidase subunit I barcode region; they are also distinguished morphologically. A key to the species of Triplophysa in the Syr Darya basin and adjacent regions is provided.

A review of the genus Psammocrуptus (Coleoptera: Tenebrionidae: Tentyriini)

A taxonomic review of the tenebrionid genus Psammocryptus Kraatz, 1865 (Coleoptera: Tenebrionidae: Pimeliinae: Tentyriini) is given. Species of this genus are distributed in the south of Russia (Caspian depression), Transcaucasia, Kazakhstan and Central Asia, Afghanistan and Pakistan, occurring in areas with salty soil, often in tugay forests of river basins. Two new species and one new subspecies are described: P. bogatchevi Nabozhenko, Chigray &amp; Bekchanov, sp. nov. (Kazakhstan: Syrdarya basin, Kyzylkum desert; Uzbekistan: Amudarya lower reaches and delta, Syrdarya basin, Kyzylkum desert); P. kompantsevae Nabozhenko &amp; Chigray, sp. nov. (Uzbekistan and Tajikistan: Amudarya, upper river basin); P. bayeri vachshianus Nabozhenko &amp; Chigray, subsp. nov. (Tajikistan: Vakhsh River valley). The nominotypical subspecies P. bayeri bayeri Koch, 1943 occurs in Turkmenistan (Tejen valley and Amudarya valley middle river course) and Tajikistan (a new record for the country: Kafirnigan River valley). Psammocryptus minutus (Tauscher, 1812) is recorded for Armenia for the first time, but the population from Yerevan has become extinct due to urbanization. The following synonymy is restituted: Psammocryptus minutus (Tauscher, 1812) = P. bergi Kuzin 1934, syn. restit.

Contrasting Fate of Western Third Pole's Water Resources Under 21st Century Climate Change

AbstractSeasonal melting of glaciers and snow from the western Third Pole (TP) plays important role in sustaining water supplies downstream. However, the future water availability of the region, and even today's runoff regime, are both hotly debated and inadequately quantified. Here, we characterize the contemporary flow regimes and systematically assess the future evolution of total water availability, seasonal shifts, and dry and wet discharge extremes in four most meltwater‐dominated basins in the western TP, by using a process‐based, well‐established glacier‐hydrology model, well‐constrained historical reference climate data, and the ensemble of 22 global climate models with an advanced statistical downscaling and bias correction technique. We show that these basins face sharply diverging water futures under 21st century climate change. In RCP scenarios 4.5 and 8.5, increased precipitation and glacier runoff in the Upper Indus and Yarkant basins more than compensate for decreased winter snow accumulation, boosting annual and summer water availability through the end of the century. In contrast, the Amu and Syr Darya basins will become more reliant on rainfall runoff as glacier ice and seasonal snow decline. Syr Darya summer river‐flows, already low, will fall by 16%–30% by end‐of‐century, and striking increases in peak flood discharge (by &gt;60%), drought duration (by &gt;1 month) and drought intensity (by factor 4.6) will compound the considerable water‐sharing challenges on this major transboundary river.

Evaluation and Application of MSWEP in Drought Monitoring in Central Asia

Thanks to the large scope, high spatial resolution, and increasing data records, satellite-based precipitation products are playing an increasingly important role in drought monitoring. First, based on the data from ground sites, the long-term Multi-Source Weighted-Ensemble Precipitation (MSWEP) precipitation product was evaluated in respect to drought monitoring. Then, based on the MSWEP product, the drought trends and the spatiotemporal characteristics of the drought events in four major basins (Amu Darya Basin, Syr Darya Basin, Chu-Talas River Basin, and Ili River Basin) in Central Asia, which have relatively dense gauge sites, were studied. The Standardized Precipitation Index (SPI) and the run theory were used to identify drought events and describe their characteristics. The results showed that MSWEP can effectively capture drought events and their basic characteristics. In the past 40 years, the study area experienced 27 drought events, among which the severest one (DS = 15.66) occurred from June 2007 to September 2008. The drought event that occurred from June 1984 to October 1984 had a drought peak value of 3.39, with the largest drought area (99.2%). Since 1881, there appeared a drying trend and a wetting trend in the Amu Darya River basin and the Ili River basin, respectively. No obvious wetting or drying trend was found in both the Chu-Talas River basin and the Syr Darya basin. Since 2016, the drought area has been on the increase.

Rival Eco-Anxieties: Legacy of Soviet Water Management in the Syr Darya Basin

Abstract This article focuses on the security and human rights implications of the water infrastructure legacy bequeathed to the Syr Darya river basin in the border area of the Ferghana Valley, by the Soviet period. Taking an environmental history approach, I consider the complex legacy of the system of ageing dams, irrigation canals, and reservoirs which for the most part were set in place between the 1950s and 1980s. Correcting the prevailing narrative that post-Soviet water tensions are often caused by the Soviet habit of disregarding borders and republican-level interests in designing water infrastructure, I show how Soviet water policy in the region fanned and exacerbated inter-republican tensions even while the national territorial divisions were ongoing. Current tensions are therefore not a response to a sudden and unexpected hardening of borders, but the fruit of much longer processes.

Adaptive estimation of multi-regional soil salinization using extreme gradient boosting with Bayesian TPE optimization

ABSTRACT Soil salinization endangers the development of ecological agriculture. As soil salinization is often heavily affected by regional environments, difficulties arise when constructing an adaptive multi-regional soil salinity estimation model. In this study, we proposed an extreme gradient boosting (XGBoost) model based on the Tree-structure Parzen Estimator (TPE) optimization algorithm to apply to four study areas with different environments (TPE-XGBoost). The four areas are the Weigan-Kuqa Oasis (Weiku), the Sangong River Basin (Sgr) and the Qitai Oasis in Xinjiang, China, and the middle and lower reaches of the Syr Darya Basin in Kazakhstan. Most previous soil salinity studies did not pay much attention to the impact of feature selection and hyper-parameter tuning on the performance of machine learning models, and the complex dependence and interaction between input features and hyper-parameters. In order to improve the performance of XGBoost model in estimating soil salinity, we proposed for the first time to use TPE algorithm to jointly optimize feature selection and hyper-parameter tuning, and verified it in four areas. Coefficient of determination (R2) and Root Mean Square Error (RMSE) were used to evaluate the model performance. First, we calculated 55 environmental features from Landsat and terrain data. Then, in order to reduce the computational complexity of the TPE-XGBoost model, we used Pearson correlation analysis between surface soil salinity content (SSC) and features to initially filter out the features that were not significantly related (P > 0.05). Finally, the TPE algorithm was used to jointly optimize the parameter space composed of features and hyper-parameters. The results showed that (1) TPE joint optimization algorithm significantly improved the performance of the XGBoost model, achieving high accuracy in the four areas, and had powerful generalization. R2 values of test sets for Weiku Oasis, Qitai Oasis, Sgr Basin, and the Syr Basin were 0.95, 0.95, 0.80, and 0.81, respectively. (2) There is no universal feature can be applied to soil salinity inversion in different environments. TPE algorithm adaptively selected different types and numbers of features for four areas, 19, 11, 25, and 15 features were selected in Weiku Oasis, Qitai Oasis, Sgr Basin, and the Syr Basin, respectively. This showed that the optimal model parameters should not be fixed parameters, but should be re-determined locally according to different environmental conditions. The TPE algorithm can capture the features that reflect environmental differences. (3) The XGBoost model can provide feature importance ranking, which improves the interpretability of machine learning model. The importance analysis results showed that the features had different contributions in different areas. The TPE-XGBoost model proposed in this study has great potential in multi-regional soil salt estimation research.

Some Medieval and Post-Golden Horde’s Towns of the Itil (Volga) and Syr-Darya Basins According to the Arabic and Chinese Maps

Research objectives: The earliest depictions of the towns of the Itil (Volga) and Syr-Darya Basins in medieval cartography are found on the Idrisi map (1154). The post-Golden Horde towns in these areas are found in the Jenkinson map and the Kunyu wanguo quan tu (Map of the Ten Thousand Countries of the Earth, 1602) by Matteo Ricci. In 1772, the Qianlong neifu yutu 乾隆内府舆圖 (Terrestrial Map of the Imperial Repository of Qianlong), which used modern cartographic techniques, enriched the geographic information of Central Asian countries and filled the gaps in contemporary European maps. Research materials: Influenced by the map of Al-Idrīsī’, the geographic gaps and blind spots on the European maps were filled, reconstructed, and connected with the new world geographic knowledge, forming a relatively complete world map. At the end of the Ming and early Qing dynasties, a large amount of overseas geographic knowledge was introduced by Western missionaries who entered China. Results and novelty of the research: The analysis of Arab, European, and Chinese maps made it possible to assess the degree of accuracy of their information about the post-Golden Horde cities of the Itil (Volga) and Syr-Darya basins. The authors managed to determine the geographical ideas of Arab, European, and Chinese geographers about Central Asia. Specifically, this article examined the place names of the Itil Basin (including Western Siberia) and the Qazaq Steppe (including adjacent regions) in the European-Russian imperial maps and in the Qing Chinese maps. Historical maps provide rich resources of knowledge that graphically encode information about the state of a fraction of the real world at a certain point in time.