Groundwater is a vital component of the hydrological cycle and essential for the sustainable development of ecosystems. Numerical simulation methods are key tools for addressing scientific challenges in groundwater research. This study uses bibliometric visualization analysis to examine the progress and trends in groundwater numerical simulation methods. By analyzing literature indexed in the Web of Science database from January 1990 to February 2023, and employing tools such as Citespace and VOSviewer, we assessed publication volume, research institutions and their collaborations, prolific scholars, keyword clustering, and emerging trends. The findings indicate an overall upward trend in both the number of publications and citations concerning groundwater numerical simulations. Since 2010, the number of publications has tripled compared to the total before 2010, underscoring the increasing significance and potential of numerical simulation methods in groundwater science. China, in particular, has shown remarkable growth in this field over the past decade, surpassing the United States, Canada, and Germany. This progress is closely linked to strong national support and active participation from research institutions, especially the contributions from teams at Hohai University, China University of Geosciences, and the University of Science and Technology of China. Collaboration between research teams is primarily seen between China and the United States, with less noticeable cooperation among other countries, resulting in a diverse and dispersed development pattern. Keyword analysis highlights that international research hotspots include groundwater recharge, karst water, geothermal water migration, seawater intrusion, variable density flow, contaminant and solute transport, pollution remediation, and land subsidence. Looking ahead, groundwater numerical simulations are expected to play a more prominent role in areas such as climate change, surface water-groundwater interactions, the impact of groundwater nitrates on the environment and health, submarine groundwater discharge, ecological water use, groundwater management, and risk prevention.

Asia stands out as the most populous and geographically diverse region globally. The pressing issues of water resource development and the resulting ecological impacts are exacerbated by the region's rapid population growth and economic expansion. Groundwater, a vital source of water in Asia, faces significant disparities in distribution and suffers from unsustainable exploitation practices. This study applies groundwater system theory and categorizes Asia into 11 primary groundwater systems and 36 secondary ones, based on intercontinental geological structures, climate, terrain, and hydrogeological characteristics. As of the end of 2010, Asia's assessed groundwater resources totalled 4.677×10⁹ m³/a, with exploitable resources amounting to 3.274×10⁹ m³/a. By considering the geological environmental impacts of groundwater development and the distinctive characteristics of terrain and landforms, six categories of effect zones with varying distribution patterns are identified. The current research on Asia's groundwater resources, environmental dynamics, and human impacts aims to provide a theoretical foundation for sustainable groundwater management and environmental conservation in the region.

Groundwater, as a critical component of the hydrological cycle, is essential for sustainable ecosystem development. To clarify the current status of domestic and overseas research, and to identify hotspots, frontier and future trends of groundwater and ecology research, this study utilizes bibliometric methods and CiteSpace software to examine relevant published articles in the Web of Science (WOS) and CNKI databases from 1978 to 2022. Specifically, this study analyzes (1) the annual number of published papers; (2) research institutions; (3) keywords; and (4) evolution of research hotspots. The findings reveal that the United States, China, and Germany are the top three countries in groundwater and ecology research. International research hotspots mainly focus on microbial ecology, climate change, groundwater-surface water interactions in the hyporheic zone, biodiversity, and submarine groundwater discharge, while domestic research hotspots mainly focus on ecological water conveyance, ecological flow, groundwater development and utilization, groundwater pollution, and groundwater and ecological protection. Both domestic and international research hotspots exhibit interdisciplinary features with diverse research objects and assessment methods. Future research in this area is expected to focus on topics such as contamination, groundwater quality, framework, mechanism, spatial distribution, and dissolved organic matter. Additionally, the study of ecological recharge, ecological flow, ecological protection, water intake and use will continue to be the hot topics domestically.

The natural groundwater recharge in Asia is estimated to be 4 677.74×10⁹ m³/a. However, it features extremely uneven spatial-temporal distribution. Groundwater is distributed in various natural and geological environments, and it is liable to be affected by numerous factors and possesses different properties. Moreover, groundwater faces complex ecological problems. This paper gains a complete understanding of groundwater in Asia in terms of the structure of aquifer systems, the processes of groundwater cycle, and the spatial variation laws of surface ecosystems. Based on this, it proposes the ecological function zoning scheme of groundwater in Asia, aiming to provide guidance for the utilization of regional water resources and the planning for economic and social development, coordinate the relationship between social and economic development and water resource protection, and improve the ecological functions of groundwater. Furthermore, this paper analyzes the problems with regional groundwater management in Asia and puts forward countermeasures and suggestions, thus providing a theoretical basis for the sustainable development and utilization of regional groundwater and environmental protection.

Hydrogeological map is one of the important carriers of groundwater related information. It directly reflects the hydrogeological conditions and previous investigation and research results of a mapping area. The hydrogeological map of China is a map reflecting the characteristics of hydrogeology and groundwater dynamics on a national scale. On the basis of the hydrogeological map of China (1: 4 000000) compiled in 1988, this map compilation attempted to update and enhance the existing map, with the latest survey results from the project of National Investigation and Evaluation of Groundwater Resources and Environmental Problems led by China Geological Survey. Task of the mapping program included redefining groundwater types, quantifying the classification standard of the groundwater and adding the pore-fissure water in laterite layer of hilly basin. The multilayer structures for porous, karst and porous-fractured groundwater and their water-rich grades are reflected on the map. Based on the comprehensive summary of the latest hydrogeological data of China, this research conducts an in-depth analysis of the regional distribution characteristics of groundwater in China, utilizes a digital mapping process and establishes a cartographic database for the purpose of further use. With the enrichment of the content and the continuous improvement of cognitive level, mapping content can be updated quickly, which has practical significance for the concept of surveying and mapping and scientific popularization.

In compilation of 1: 50000 hydrogeological map, Some principles which are suitable for hydrogeological characteristics in China have been defined. Groundwater development and protection have been regarded as equally important. Some key problems such as classification of water-bearing formation, water yield property, color system and color scale of water yield property of water-bearing formation, expression of groundwater system, expression of hydrogeological parameters have been solved. This standardizing work can lay solid foundation for integration of 1: 50000 synthetic hydrogeological map achievement and data, so as to broaden the service areas of hydrogeological survey.

Lake Balkhash is the third largest inland lake in Central Asia after the Caspian Sea and the Aral Sea. The Ili River-Balkash Lake Basin resides in the southeastern part of the Republic of Kazakhstan and the western part of China’s Ili Prefecture, which belongs to the arid and semi-arid region. In the middle to late 20^th century, the Ili River-Balkash Lake Basin was affected by climate change and human activities, and the problems of water ecology and water resources became increasingly prominent, which became the focus of attention for China and Kazakhstan. In this study, the water level derived from radar altimeter data, the water surface area extracted from Landsat data, and the temperature and precipitation data in the basin were comprehensively utilised. Data analysis of the time course and correlation of hydrological, meteorological elements in the lake basin, water dynamic changes, and influencing factors of Lake Balkhash was studied. The results show that the cyclical change of regional climate is the main factor affecting the change of lake water, and human activities in the short term can regulate the change of water volume in Lake Balkhash. The research results in this paper can provide a scientific basis for the solution of water disputes in cross-border rivers between China and Kazakhstan.

Based on landform, climate, river system, geological structure and hydrogeological structure and from the perspective of systematology, the groundwater system of Asia can be divided into 36 secondary groundwater systems under 11 primary ones by the intercontinental scale. A scientific evaluation of groundwater resources in Asia can be secured using water balance method and runoff modulus method through water circulating analysis and feature study of groundwater system on the basis of groundwater system division of Asia. With natural recharge (runoff) modulus (10⁴m³/km²·a), the total amount of water resources and those available for exploitation of primary groundwater system can be evaluated-continuous aquifers in plains and basins contain 242.465×10⁹ m³/a of water, 169.725×10⁹ m³/a of which is recoverable; discrete aquifers contain 186.695×10⁹m³/a, 130.686×10⁹m³/a of which is available for exploitation; other scattered aquifers contain 38.614×10⁹m³/a, 27.029×10⁹m³/a of which could be exploited. In total, there is 467.774×10⁹m³/a of groundwater with 327.440×10⁹ m³/a recoverable. The groundwater map of Asia is compiled according to groundwater system division, evaluation of the total amount and aquifer types to reflect the macro features of groundwater resources in Asia, laying a scientific foundation for exploitation and management of water resources here and for avoiding disputes over groundwater resources and environment among Asian countries.

With the ever-accelerating economic and social growth in Asia, the sustainable development of environment, economy and society of Asia and beyond, is severely constrained by a series of grave issues, such as global climate change, population explosion, resource shortage, and rampant disasters. The need for study on groundwater resources and environment in Asia as part of the efforts to tackle global climate change looms even larger. In analyzing how global changes of modern times and human activities are related to primary geo-environment, the groundwater environment serial maps of Asia introduces a new concept for mapping geo-environment of Asia that connects the geological background to groundwater environment. The serial maps reveal the geographic environment that is closely related to groundwater, the special-temporal features of the geo-environment and how it is distributed. The study is vital not only to the harmonious development among environment, economy and society as well as ecological progress in Asia, but also to the strategic requirements posed by the “One Belt One Road”.

Based on the Virtual Water Theory, the research analyzed the spatial and temporal distribution characteristics of major crops in China. Analysis results indicate that the unit virtual water content varies with the type of crop obviously as well as the distribution region. We also found irrational water utilization in some regions, which means that the renewable water sources could not meet the water demand for crop growth. With a view solving these problems found in the research, discussions on agricultural water-saving technology, comprehensive allocation of crops, selection of rational cropping pattern, full use of green water and trade of virtual water were carried out, which may result in some theoretical basis for the sustainable utilization of agricultural water resources in China.