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The Grain for Green project (GGP), initialized by the Chinese government in 1999, has achieved substantial achievements accompanied by a decrease in surface runoff on the Loess Plateau, but the impacts of large-scale afforestation on regional water resources are uncertain. Hence, the objective of this study was to explore the impact of land use change on generalized water resources and ecological water stress using the blue and green water concepts, taking the Yanhe River Basin as the case study. The Soil and Water Assessment Tool (SWAT) was applied to quantify the green water and blue water, which are defined as generalized water resources. The ecological water requirement of vegetation (forest and grass), agricultural water footprint and virtual water flow are considered regional water requirements. The land use types of 1980 (Scenario I) and 2017 (Scenario II) were entered into the SWAT model while keeping the other parameters constant to isolate the influence of land use changes. The results show that the average annual differences in blue, green and generalized water resources were -72.08 million m3, 24.34 million m3, and -47.74 million m3, respectively, when the simulation results of Scenario II were subtracted from those of Scenario I, which shows that land use change caused by the GGP led to a decrease in blue and generalized water resources and an increase in green water resources. Surface runoff in Scenario I was more than that in Scenario II in all of the years of the study period from 1980-2017, and green water storage in Scenario I was more than that in Scenario II in all of the years of the study period except in 1998; although lateral flow in Scenario I was less than that in Scenario II except in 2000 and 2015, as was groundwater runoff in 1992, 2000 and 2015, and green water flow in 1998. Blue water flow, green water storage and green water flow in Scenario II were less than those in Scenario I in the whole basin, 12.89 percent of the basin and 99.21 percent of the basin, respectively. The total water footprint increased from 1995 to 2010 because the forest water footprint increased significantly in this period, although the agricultural water footprint and grass water footprint decreased. The ecological water stress index values had no obvious temporal change trends in either land use scenario, but the ecological water stress index in Scenario II was greater than that in Scenario I, which illustrates that the GGP led to an increase in ecological water stress from the perspective of generalized water resources., Competing Interests: The authors have declared that no competing interests exist.

It is vital for analyzing groundwater chemical characteristics to develop, manage and protect groundwater resources. Hydrogeochemistry simulation, graphic method, and other methods are applied to analyze 22 pieces of groundwater chemical data in the urban area of Zhumadian City. The results show that shallow groundwater is mainly of HCO3-Ca type. Besides, from northeast to southwest, salinity and hardness increase gradually, the hydrodynamic condition becomes worse, and groundwater is significantly affected by human activities. This study is of important significance to scientifically using and managing groundwater resources in the urban area of Zhumadian City. Características químicas y distribución espacial de las aguas freáticas en el área urbana de Zhumadian (China) Resumen El análisis de las características químicas de las aguas freáticas o subterráneas es determinante para desarrollar, administrar y proteger los recursos hídricos. Este trabajo se basó en la simulación hidrogeoquímica, el método gráfico y otros procedimientos para analizar la información química de 22 muestras de aguas freáticas en el área urbana de Zhumadian, en el este de China. Los resultados muestran que las aguas freáticas poco profundas son principalmente del tipo HCO3-Ca. Además, del noreste al suroeste, la salinidad y la rigidez aumentan gradualmente, las condiciones hidrodinámicas empeoran y las aguas freáticas son afectadas por las actividades humanas. Este estudio es de una importancia significativa para el manejo científico y la administración de los recursos de aguas subterráneas en el área urbana de Zhumadian.

The over-exploitation of shallow groundwater in the People's Victory Canal irrigation area has led to the continuous decline in the groundwater level. The formation of a groundwater drawdown cone has changed the original runoff conditions and hydrochemical environment. Based on the groundwater data in the irrigated area from 1996 to 2022, multivariate statistical analysis, traditional hydrochemical methods, and inverse geochemical modeling were used to reveal the impact of the formation of the groundwater depression cone on hydrochemical evolution. The results show that the formation of the groundwater depression cone near the central area in 2003 changed the direction of the canal head flowing to the northwest area, making the groundwater flow from the canal head and the northwest area to the central area. The change in the hydrodynamic fields also caused the groundwater with high salinity in the northwest region to flow to the funnel area, and the ion concentration of groundwater along the pathway area to increase. The groundwater type in the runoff area changes, gradually evolving from Group 1 to Group 2 groundwater. Analysis of the hydrochemical characteristics of groundwater in the runoff area for many years shows that after the formation of the central funnel area in 2003, the groundwater with high SO 4 2 − ion in the northwest area flows to the funnel area, and the correlation between total dissolved solids and S O 4 2 − ions in the groundwater along the way is significantly enhanced. The inverse geochemical modeling shows that the main water–rock action along the runoff direction is the dissolution of halite and gypsum. In addition, the study area has a strong cation exchange reaction. [ABSTRACT FROM AUTHOR]

This study first analysed the crucial function of agricultural activities on groundwater system in Shijiazhuang Plain. Then the influence indexes of agricultural activities on regional groundwater are discussed. The Projection pursuit evaluation model and MapGIS technique have been used to evaluate the degree of such effect and its spatial difference. Finally, according to effect degree of agricultural activities on groundwater, Shijiazhuang Plain is divided into four types of regions. [ABSTRACT FROM AUTHOR]

• Analysis of long-term evolution of groundwater hydrochemistry by SOM algorithm. • Finding out the main period of the Yellow River's influence on hydrochemistry. • The change of hydrodynamic fields results in the change of hydrochemistry field. The primary water source for agricultural irrigation in the People's Victory Canal irrigation area was the Yellow River water in the early stage, and the Yellow River water diversion volume decreased in the later stage. Hence, the groundwater became the primary water source for the irrigation area. It is significant for the rational utilization of groundwater resources to explore groundwater hydrochemistry's evolution characteristics and formation mechanism. Based on the hydrochemical data of groundwater and Yellow River in the irrigation area from 1987 to 2022. The spatiotemporal evolution of chemical components of groundwater and the main influencing factors were revealed using traditional hydrochemistry research methods, self-organizing map, and stable isotopes. The results show that the classification results of groundwater and Yellow River water samples by the self-organizing map show regional and phased characteristics. Regionally, the self-organizing map classifies groundwater into five clusters, and Cluster Ⅰ–III of groundwater are mainly distributed in the head, middle and northeast areas. Cluster Ⅳ and V of groundwater are mainly distributed in the northwest region. In terms of time, from 1987 to 2001, the Yellow River water diversion volume was higher, and the ion concentration of groundwater showed a decreasing trend. The ion concentration was close to the Yellow River water ion concentration except in the northwest area. Accordingly, the classification results of the self-organizing map change from Cluster Ⅰ of groundwater to Cluster Ⅱ of groundwater. After 2001, the amount of water diverted from the Yellow River decreased, and the concentration of each ion in the groundwater at the head of the canal and the central area showed an overall increasing trend from 2001 to 2022. The classification results of the self-organizing map change to Cluster Ⅰ of groundwater. Due to the change in runoff conditions and the influence of domestic sewage, the classification results of the self-organizing map in the funnel area in the middle of the irrigation district changed to Cluster III of groundwater after 2013. [ABSTRACT FROM AUTHOR]