Regional Water Resources Research Articles

Water resources of the Podilia region and their use

Purpose. To analyze the state of water resources of the Podilsk region and the territorial features of water use in order to optimize their use. Methods. Methods of system-structural analysis, statistical, cartographic, modeling. Rresults. The current state and peculiarities of the use of water resources in the territory of the administrative districts of the Podilsk region were analyzed according to the indicators of total water intake from natural water bodies, the use of fresh water in general and the sectoral structure of water use. The main consumers of water resources in the region are industrial enterprises and housing and communal services. The largest share of underground water intake is in Ternopil Oblast, and the smallest in Vinnytsia, which is related to natural reserves of underground water. The largest volumes of water intake from natural water bodies and the use of fresh water are observed in the Khmelnytskyi region, and the smallest - in the Ternopil region. The analysis of the dynamics of water use indicators over the period 2020-2022 determined a decrease in the volume of water intake, especially in 2022, in all regions of the region. The largest share of water is used in the regions of the region for production needs. Conclusions. The dynamics of water consumption in all regions of the region has a tendency to decrease the volume of water intake. There are certain differences in the amount of surface and underground water intake. For many administrative districts and territorial communities, the problem of rational use of water resources is relevant.

The "sponge city" program as a system of adaptation methods to climate changes in reforming and forming the architectural environment

This article analyzes the implementation of the «Sponge city» concept in the formation and reform of the urban and architectural environment, as a comprehensive method of adaptation to the problems caused by climate change, which was caused by the global warming of our planet. In this concept, the emphasis is on the regulation of all types of water resources in the aspects of floods, swamps and inundations. One of the main reasons for accelerating the pace of global warming is rapid industrial development and urbanization. This led to increased use of resources, including water, which created major environmental risks. The problems of climate change have worsened not only due to the growth of gas emissions into the atmosphere, but also due to the rapid and unplanned urbanization of the urban environment, which was formed in the post-industrial period and reflects the greedy approach of society to the limited resources of the planet. Due to this, large-scale post-industrial processes took place in many countries of the world, which led to significant environmental problems. The urban population grew at a rapid rate, with the simultaneous construction of the necessary infrastructure, including housing, factories and roads. Such processes also took place in the People's Republic of China, due to which the issue of regulating water resources was raised in the country, and the concept of "Sponge city" was applied as an answer. On the example of several Chinese cities of Wuhan, Pingxiang and Haikou, where this concept was successfully applied, adaptation methods and complex approaches for reforming the existing urban and forming a new architectural environment were systematized. Based on them, an action algorithm for the implementation of these methods and technologies was developed as a program of communication of all large-scale levels among themselves. Applying this program, at the levels from the region to an individual building and vice versa. A self-regenerating system is formed - a "sponge city-region-ecosystem" as a complex of innovative methods of combating floods, inundation, wetlands, excess precipitation, which promotes adaptation to climate changes and ensures sustainability , safety and harmony of the environment.

Government‐industrial‐research cooperation in virtual water strategy: A multi‐agent evolutionary game analysis

AbstractThe virtual water strategy (VWS) is an effective tool to balance regional water resource endowments and guarantee water supply security. However, because of self‐interested games around VWS (human decision bias), there is a need for methods to maintain reliable cooperation between governments, virtual water (VW) enterprises and research institutions. This study builds a multi‐agent evolutionary game model to analyse the relationship of players and their impacts on VWS through changing decision mechanisms and the paths to enhance their confidence in cooperation. Considering differences in initial willingness to cooperate and changing factors affecting payoffs, an evolutionary game can produce changing stable equilibriums or stable cooperations, even if some players are reluctant to cooperate. Therefore, to promote the development of VWS, a multistep support mechanism can be built for the VW industry, which fosters model enterprises and optimizes the cooperation framework to stimulate research innovations at scientific institutions.

The Impact of Land Use on Water Resources in the Gulf Cooperation Council Region

The Gulf Cooperation Council (GCC) countries experience a harsh environment with low precipitation and high evaporation rates. This presents a significant challenge of water scarcity and water quality degradation which is exacerbated by land use practices. Agriculture, urbanization, and industrialization are impacting the management of water resources. This paper examines the state of water resources in the GCC countries and presents the impact of land use practices. A detailed analysis of the relationship between land use and groundwater is conducted with a focus on the Kingdom of Saudi Arabia (KSA), the Sultanate of Oman, and the United Arab Emirates (UAE). The results indicate a drop in agricultural activities, an increase in bare land and urban areas, depletion of groundwater, and water quality degradation. These changes were attributed to excessive agricultural and industrial uses, climate change, and rapid urbanization. The findings show the need for sustainable land use practices and water resources management. Further research addressing the impact of land use on water in Kuwait, Qatar, and Bahrain, and evaluating the effectiveness of policy, is essential.

Diagnosis of the physicochemical quality of groundwater in the Zaouiet Kounta Region

The water resources of the Adrar region are essentially represented by the water table, which supplies all the oases with water through ancient techniques called “foggaras.” This study aims to determine the state of the quality of the waters of the Adrar region, essentially based on the water’sphysicochemical parameters assessment, which allows us to have an idea of its quality and availability for drinking water supply and irrigation. Thirteen parameters were analyzed: pH, conductivity, turbidity, pollution elements such as nitrates, nitrites, ammonium, phosphates, and organic matter, and mineralization elements: calcium, magnesium, sodium, chlorides, and sulfates.The physicochemical characterizations of the waters of this region will be based on the interpretation of different parameters of the data during a campaign of sampling and analysis of samples and comparing them with the WHO.The results showed that the measurements of the physicochemical parameters of the waters analyzed conformedwith the WHO, such as pH, turbidity, ammonium, and phosphate. At the same time, sulfate, sodium, Chloride, and nitrate presented high values. It proved abnormal in the three points of foggara, while the rest of the analyses showed values varying between F1, F2, and F3.

Appraising water resources for irrigation and spatial analysis based on fuzzy logic model in the tribal-prone areas of Bangladesh.

The lack of quality water resources for irrigation is one of the main threats for sustainable farming. This pioneering study focused on finding the best area for farming by looking at irrigation water quality and analyzing its location using a fuzzy logic model on a Geographic Information System platform. In the tribal-prone areas of Khagrachhari Sadar Upazila, Bangladesh, 28 surface water and 39 groundwater samples were taken from shallow tube wells, rivers, canals, ponds, lakes, and waterfalls. The samples were then analyzed for irrigation water quality parameters like electrical conductivity (EC), total dissolved solids (TDS), sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium bicarbonate (RSBC), magnesium hazard ratio (MHR), Kelley's ratio (KR), and permeability index (PI). Fuzzy Irrigation Water Quality Index (FIWQI) was employed to determine the irrigation suitability of water resources. Spatial maps for parameters like EC, KR, MH, Na%, PI, SAR, and RSBC were developed using fuzzy membership values for groundwater and surface water. The FIWQI results indicate that 100% of the groundwater and 75% of the surface water samples range in the categories of excellent to good for irrigation uses. A new irrigation suitability map constructed by overlaying all parameters showed that surface water (75%) and some groundwater (100%) in the northern and southwestern portions are fit for agriculture. The western and central parts are unfit for irrigation due to higher bicarbonate and magnesium contents. The Piper and Gibbs diagram also indicated that the water in the study area is magnesium-bicarbonate type and the primary mechanism of water chemistry is controlled by the weathering of rocks, respectively. This research pinpoints the irrigation spatial pattern for regional water resource practices, identifies novel suitable areas, and improves sustainable agricultural uses in tribal-prone areas.

Evaluation of water resources carrying capacity in China based on entropy weight TOPSIS model

Water resources carrying capacity refers to the ability of the water resources ecosystem to continuously carry the coordination relationship between human society and economy in the normal development process of a country or a region. Its self-sustaining ability, self-regulation and self-development potential often hinder sustainable development in water shortage areas. Research on water resources’ carrying capacity is a meaningful way to support regional water resources security and realize harmonious development of society, economy, and ecological environment. Correct assessment of water carrying capacity and response to government policies will contribute to improved water use and sustainable economic and social development. This study first sorts out the relevant questionnaires of water resources carrying capacity level evaluation, proposes the evaluation indicators of water resources carrying capacity level, collects and standardizes the required data, and calculates the weight of each evaluation index by entropy weight method. Then, it calculates the comprehensive evaluation value of China’s water resources carrying capacity from 2012 to 2022 in the TOPSIS model. The results show that the total afforestation area, total investment in environmental pollution control, and total industrial wastewater discharge are the third most important factors in improving the carrying capacity of water resources. From 2003 to 2010, China’s water resources carrying capacity improved year by year. From 2011 to 2021, China’s water resources carrying capacity remained stable year by year. The continuous adjustment of China’s industrial structure and strengthening environmental pollution control are inevitable measures to improve the carrying capacity of China’s water resources. This study provides a scientific basis for exploring the changing trend of China’s water resources carrying capacity and formulating reasonable optimal allocation of water resources. It also has great significance for promoting China’s water resources’ carrying capacity and sustainable development of the social economy and ecological environment.

GIS-based multi-criteria decision analysis for groundwater dam site selection in an arid and semi-arid region of Algeria

Securing reliable water resources in arid and semi-arid regions poses a significant challenge for decision-makers, especially under recent droughts and projected climate change. This need is particularly acute in the M'zi Wadi basin, located in the north-central part of Algeria, where its surface water projects are challenged by low and erratic rainfall coupled with high water evaporation, adversely impacting its water resources sustainability. Implementing water harvesting techniques in such arid regions, specifically groundwater dams, can be regarded as an effective water scarcity adaptation strategy, and their effectiveness is dependent on the optimal site selection which must consider many complex criteria. The paper aims to identify potential sites for groundwater dams in the M'zi Wadi basin using a multi-criteria decision-making approach in a GIS environment based on seven socio-economic and natural factors such as rainfall, stream order, land use/land cover (LULC), geology, Topographic wetness index (TWI), and distances from faults and villages. The results showed that approximately 1.27% of the M'zi Wadi basin area is highly suitable for groundwater dam siting. Four candidate sites were identified as having favourable conditions for installing new groundwater dams based on field and geophysical survey data conducted along the alluvial aquifer of the M'zi Wadi basin, and the remaining areas were deemed unsuitable due to specific constraints. The suitability of the selected sites was validated through a comparative analysis with existing groundwater dams. The results of the present study could offer valuable insights for decision-makers at all levels, facilitating informed judgments during the initial planning of groundwater dam construction. Furthermore, the methodology can be replicated in other data-scarce regions under similar arid climate conditions.

Joint optimal allocation of regional water and land resources considering their mutual feed relationship

Water and land resources are indispensable prerequisites for the sustenance and advancement of human civilization. In recent decades, China has faced significant challenges in managing its water and land resources due to the intensifying competition resulting from rapid urbanization, industrialization, and population growth. The joint optimal allocation of water and land resources can effectively address these issues. However, there have been limited accomplishments in investigating the integrated water and land resources allocation system’s interaction with social, economic, and environmental development. This paper develops a novel joint optimal allocation model of regional water and land resources (JOAMRWLS). The model integrates water and land resources for integrated allocation, taking into account the mutual feed relationship between them, and thereby achieving comprehensive utilization and coordination of water and land resources within the region. Then a two-layer nesting algorithm based on successive approximation and nonlinear programming (SA-NLP) is proposed to solve the model, obtaining the regional optimal land use pattern and optimal water allocation scheme. Subsequently, this paper uses Luoyang City in Henan Province, China, as a case study to verify the proposed JOAMRWLS. The results indicate that the water volume and area of each land use type tend to stabilize after the fifth iteration of the calculation with a consistent water volume of 18.65 × 108 m3. Compared with the conventional optimization model of water resources (COMWR), the JOAMRWLS encompasses five cities experiencing water scarcity, whereas the latter includes twelve such cities. Furthermore, the economic benefit of the JOAMRWLS is 2.65 × 1011 CNY, surpassing that of the former at 2.56 × 1011 CNY, highlighting its superiority.

Horticultural Irrigation Systems and Aquacultural Water Usage: A Perspective for the Use of Aquaponics to Generate a Sustainable Water Footprint

The expansion of food production is becoming more important due to a rising world population, which is relying on food security on regional and local scales. Intensive food production systems exert a negative impact on the regional ecosystem because of agrochemical pollution and nutrient-rich water discharging into nearby rivers. Furthermore, these systems highly depend on regional water resources, causing water scarcity and soil erosion due to the overexploitation of natural resources in general. The objective of this article is to review the water usage in the two most water-intensive food production systems, agriculture and aquaculture, showing lacking areas like system management and climate change, which must be considered in the implementation of a sustainable water footprint. In addition, the review includes an analysis of the combination of both production systems in aquaponic food production and the possibilities of water saving. There are a variety of analyses related to water usage for crop and aquatic animal production, but in these analyses, there is a lack of information about system management in general, which includes cleaning processes, water substitution, pond removal, water evaporation, and, especially in aquaculture, the water usage required for industrially elaborated fish feed.

Research on low-energy consumption automatic real-time regulation of cascade gates and pumps in open-canal based on reinforcement learning

ABSTRACT Cascade gates and pumps are common hydraulic structures in the open-canal section of water transfer projects, characterized by high energy consumption and substantial costs, making it challenging to regulate. By implementing cascade gates regulation to control the hydraulic process, lift distribution of pump stations can be optimized, thus enhancing operational efficiency and reducing energy consumption. However, the selection of control models and parameter optimization is difficult because hydraulic processes are nonlinear, high-dimensional, large hysteresis, strong coupling, and time-varying. This study considers minimum energy consumption of pump stations as the regulation objective and employs the reinforcement learning (RL) algorithm for optimization regulation (OR) within a typical canal section of the Jiaodong Water Transfer Project. Our results demonstrate that after regulating, OR can precisely control the water level to achieve the high efficiency lift interval of pump station, enhancing efficiency by 4.12–6.02% compared to previous operation. Moreover, using optimized hyperparameters group, the RL model proves robust under different work conditions. The proposed method is suitable for complex hydraulic processes, highlighting its potential to support more effective decision-making in water resources regulation.

Harnessing SMAP satellite soil moisture product to optimize soil properties to improve water resource management for agriculture

Estimation of accurate soil physical and hydraulic properties are of prime importance for the management of water resources in agriculture-dominant regions. This study introduces a simplified framework for estimating soil physical and hydraulic properties crucial for managing agricultural water resources. The developed framework optimizes soil properties for the Regional Hydrological Extremes Assessment System (RHEAS) to enhance the performance of its core hydrological model, Variable Infiltration Capacity (VIC). These soil properties were optimized using six years (2015–2021) of satellite soil moisture observations from NASA’s Soil Moisture Active Passive (SMAP) mission with a modified Shuffled Complex Evolution (SCE-UA) optimization algorithm. A total of three most sensitive soil properties that control model soil moisture simulations, such as Ksat (Saturated hydraulic conductivity), expt (exponent parameter in Campbell’s equation for hydraulic conductivity), and bd (Bulk density) were optimized for the Lower Mekong River (LMR) basin. To better assess the impact of optimized soil properties, streamflow simulation as well as agricultural drought severity assessment, were estimated using the RHEAS framework’s VIC Routing module and Soil Moisture Deficit Index (SMDI) module, respectively. The streamflow simulation involved four approaches: an initial open-loop setup, one optimized with SMAP soil moisture data (SMAP), another optimized with actual streamflow data (Runoff), and a final one combining the previous two datasets (SMAP_Runoff). Switching from the initial setup to the SMAP-optimized model increased the Nash-Sutcliffe Efficiency (NSE) by 56.4 % and upgrading from the streamflow-optimized to the combined data model raised the NSE by 21.9 %. This showcases the benefits of optimizing soil properties for more accurate simulations. Furthermore, the optimized model accurately represented the severity and extent of historical agricultural droughts, aligning with regional drought reports of LMR basin. This framework offers a valuable tool for hydrological modeling and drought management, particularly in data-scarce and agriculture-intensive regions, informing agricultural water resource management, irrigation decision-making, and food security initiatives within the LMR basin and beyond.

Analysis of Changes in Water Body Area in Southwest, China Based on GEE

It is of great significance for policymakers to develop management strategies for water resource regulation, habitat protection and wetland restoration. Based on the Google Earth Engine platform, this study extracted remote sensing data of water quality change in Southwest China in the past 20 years, combined with ArcGIS for spatial analysis, and used M-K trend test and mutation test to analyze the long-term temporal variation of water bodies in Southwest China. The analysis shows that the water area in Southwest China increased every five years from 2000 to 2020, but the growth rate changed, while the growth rate slowed down from 2010 to 2020, and the increase mainly occurred in the central and western regions. The results show that in the past 20 years, the water surface area in Southwest China has shown a statistically significant increasing trend, especially after 2020, this trend is more statistically significant. This study can provide a theoretical basis for the protection of water environment in Southwest China.

Study on adaptive regulation based on water supply-demand system structure and water use desirability under extreme drought

The frequent occurrence of drought events has changed the structure of the water supply-demand system, seriously hindering the sustainable development of society. This study aims to address the challenges of unclear impact of the system structure changes on water use desirability (WUD), as well as the regional water resources adaptive regulation. First, the structure of the water supply-demand system was analyzed based on the system theory. Then water supply priority (WSP) and water use compression (WUC) were considered to set combined regulation scenarios, which respectively characterize the structure of the water supply and demand systems. The MIKE BASIN/NAM water resources regulation coupling model was constructed to simulate the water use process under different scenarios. The desirability function approach was introduced to quantify the impact of system structure changes on WUD, and ultimately the adaptive regulation strategies were proposed with the goal of the highest WUD. Taking Chuxiong Prefecture in Yunnan, China as the study area, the validity of the model was verified, and the main results show that (1) t he optimal WSP in Chuxiong Prefecture was: urban domestic > rural domestic > industry > agriculture; (2) agriculture was identified as the most appropriate water user for compressing; (3) it was recommended that the adaptive regulation measure was to adjust the WSP in Dayao, Mouding and Wuding; and change the WUC in Yongren and Yao'an. In Nanhua, Chuxiong, Shuangbai and Lufeng, the adaptive regulation measure was to joint adjustment of WSP and WUC. These results clarify the impact of the system structure changes on WUD in Chuxiong Prefecture, identifying the optimal WSP and optimal WUC user under extreme drought, and propose water resources adaptive regulation suggestions for each county. In addition, the water resources adaptive regulation technology proposed in this study can provide scientific basis for water resources allocation under future climate change.

Overestimation of water pressure by traditional water footprint: Method revision and application

The water footprint (WF) is an essential indicator for assessing the pressure of human activities on freshwater resource utilization. The traditional WF model assumes that human water resource occupation comprises a green, blue, and grey WF, which can be linearly summed to the total WF. However, since there are two kinds of human demand for water resources, consumptive occupation and functional occupation, the relationship between them is not exclusive and does not have simple linear addition characteristics. The overlapping relationship between blue and grey WF has long been overlooked in the traditional WF calculation, resulting in a duplicate calculation of water requirement and exaggerating actual water resource demand. This study introduced a new index of blue-grey WF that deducted the overlapping portions of blue and grey WF, thereby calculating a region’s actual freshwater resource utilization. Northern Anhui, an arid region short of water resources with water pollution, was selected as a case study. The traditional WF calculation showed that the multi-year average WF of Northern Anhui was 3.44 × 1010 m3 from 2011 to 2020, with the grey, green, and blue WF accounting for 52.59 %, 27.63 %, and 19.78 %, respectively. The blue and grey WF overlapped each other and the blue WF can be fully covered by grey WF, resulting in a total blue-grey WF of 1.81 × 1010 m3, much lower than the sum of blue and grey WF. Based on the revised WF calculation model, the multi-year average WF of Northern Anhui was 2.76 × 1010 m3, decreased by 19.78 %, indicating a severe issue of duplicate calculation of blue and grey WF. The revised WF model could avoid the repeated calculation issues of water resources used by different functions. It provides a more reliable and accurate research method for regional water resources accounting and management decision-making.

Historical reconstruction of glacier mass balance and its contribution to water resources in the Sawir Mountains from 2000 to 2020

Glacial changes are crucial to regional water resources and ecosystems in the Sawir Mountains. However, glacial changes, including the mass balance and glacial meltwater of the Sawir Mountains, have sparsely been reported. Three model calibration strategies were constructed including a regression model based on albedo and in-situ mass balance of Muz Taw Glacier (A-Ms), regression model based on albedo and geodetic mass balance of valley, cirque, and hanging glaciers (A-Mr), and degree-day model (DDM) to obtain a reliable glacier mass balance in the Sawir Mountains and provide the latest understanding in the contribution of glacial meltwater runoff to regional water resources. The results indicated that the glacial albedo reduction was significant from 2000 to 2020 for the entire Sawir Mountains, with a rate of 0.015 (10a)−1, and the spatial pattern was higher in the east compared to the west. Second, the three strategies all indicated that the glacier mass balance has been continuously negative during the past 20 periods, and the average annual glacier mass balance was −1.01 m w.e. Third, the average annual glacial meltwater runoff in the Sawir Mountains from 2000 to 2020 was 22 × 106 m3, and its contribution to streamflow was 25.81 % from 2000 to 2018. The glacier contribution rates in the Ulkun- Ulastu, Lhaster, and Kendall River basins were 31.37 %, 22.51 %, and 19.27 %, respectively.

Model-based prediction of water levels for the Great Lakes: a comparative analysis

This comprehensive study addresses the correlation between water levels and meteorological features, including air temperature, evaporation, and precipitation, to accurately predict water levels in lakes within the Great Lakes basin. Various models, namely multiple linear regression (MLR), nonlinear autoregressive network with exogenous inputs (NARX), Facebook Prophet (FB-Prophet), and long short-term memory (LSTM), are employed to enhance predictions of lake water levels. Results indicate that all models, except for FB-Prophet, perform well, particularly for Lakes Erie, Huron-Michigan, and Superior. However, MLR and LSTM show reduced performance for Lakes Ontario and St. Clair. NARX emerges as the top performer across all lakes, with Lakes Erie and Superior exhibiting the lowest error metrics—root mean square error (RMSE: 0.048 and 0.034), mean absolute error (MAE: 0.036 and 0.026), mean absolute percent error (MAPE: 0.021% and 0.014%), and alongside the highest R-squared value (R2: 0.977 and 0.968), respectively. Similarly, for Lake Huron-Michigan, NARX demonstrates exceptional predictive precision with an RMSE (0.029), MAE (0.022), MAPE (0.013%), and an outstanding R2 value of 0.995. Despite slightly higher error metrics, NARX consistently performs well for Lake Ontario. However, Lake St. Clair presents challenges for predictive performance across all models, with NARX maintaining relatively strong metrics with an RMSE (0.076), MAE (0.050), MAPE (0.029%), and R2 (0.953), reaffirming its position as the leading model for water level prediction in the Great Lakes basin. The findings of this study suggest that the NARX model accurately predicts water levels, providing insights for managing water resources in the Great Lakes region.

Multi-criteria analysis for sustainable and cost-effective development of desalination plants in Chile

In Chile, there is an increasing demand for freshwater supply for human consumption, agriculture, and industrial activities. In this sense, the country is highly threatened by climate change, which is drastically affecting the availability of water resources in the north-central region due to desertification processes. Therefore, seawater reverse osmosis (SWRO) desalination is becoming one of the most feasible alternatives to address current and future challenges regarding water scarcity in the country. This investigation aims to evaluate potential locations for a sustainable and cost-effective installation of desalination projects; the latter, under a multi-criteria and geographic information system (GIS)-model. The model was tested in the highly water scarcity-threatened Valparaiso Region, Chile, as a case study. The model was developed integrating economic and socio-environmental criteria involved in the development and/or construction of desalination projects. The results of the multi-criteria analysis show that the Valparaıso Region presents optimal areas for developing SWRO projects. Both the northern and central areas of the Region show appropriate locations for installing SWRO plants and their freshwater distribution lines, ensuring short- and long-term water supply, especially for agriculture and population consumption. The results obtained in this study could be extrapolated as a tool to assess the desalination projects development in other world regions to make future desalination projects more viable and sustainable for addressing global water demands.

Effects of climate change on dry-wet and its driving factors in the Palu watershed, Indonesia

Abstract Assessing dry-wet climate change is very important in the context of global climate change to ensure regional water resources, stabilize ecosystems, and develop socio-economic development. This study aims to investigate the temporal variations in aridity index (AI), precipitation (P), reference evapotranspiration (ET0), and the underlying driving climatic factors. The methodology used includes the aridity index (AI), trend analysis, sensitivity, and contributors. Daily temperature and rainfall data were collected from 5 meteorological stations in the Palu Watershed (Bora, Kalawara, Kulawi, Palolo, Wuasa) from 2002 - 2022. The results show that 84.58% of the Palu watershed experienced wetting while only 15.42% experienced drought during the last two decades. AI changes are mainly determined by changes in the ET0 trend. During observations (2002-2021), ET0 experienced a significant decrease at a rate of 4.08mm/day. The trend of ET0 is negatively affected by a decrease in wind speed and duration of sunlight and is positively affected by a decrease in relative humidity and an increase in air temperature. Air temperature (T) and relative humidity (RH) contribute to increasing ET0 while wind speed (V) and sunshine duration (S) contribute to decreasing ET0.

Evapotranspiration increment was underestimated in China due to underrepresented land cover changes

Numerous evapotranspiration (ET) products have been produced using various approaches and diverse forcing data even as the magnitude and trends of ET show divergence. We simulated ET using updated land use and cover change (LUCC) data in China from 1900 to 2020. We found that China’s ET increased slightly from 1900 to 1980, but it increased rapidly after 1980 due to LUCC characterized by forest expansion (2.05 mm yr−1, P < 0.01). We also found that the ET trends derived from our simulation were significantly higher than other ET products (−0.70–1.47 mm yr−1, P < 0.01), implying that existing, long-term ET products might have underestimated ET trends in China during the post-1980 period because of underrepresented LUCC. These underestimated ET trends could introduce biases in the regional water budget and water resources management. We advocate for future studies to take into account the impacts of LUCC in global ET simulations.