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Review: Safe and sustainable groundwater supply in China
Exploitation of groundwater has greatly increased since the 1970s to meet the increased water demand due to fast economic development in China. Correspondingly, the regional groundwater level has declined substantially in many areas of China. Water sources are scarce in northern and northwestern China, and the anthropogenic pollution of groundwater has worsened the situation. Groundwater containing high concentrations of geogenic arsenic, fluoride, iodine, and salinity is widely distributed across China, which has negatively affected safe supply of water for drinking and other purposes. In addition to anthropogenic contamination, the interactions between surface water and groundwater, including seawater intrusion, have caused deterioration of groundwater quality. The ecosystem and geo-environment have been severely affected by the depletion of groundwater resources. Land subsidence due to excessive groundwater withdrawal has been observed in more than 50 cities in China, with a maximum accumulated subsidence of 2–3 m. Groundwater-dependent ecosystems are being degraded due to changes in the water table or poor groundwater quality. This paper reviews these changes in China, which have occurred under the impact of rapid economic development. The effects of economic growth on groundwater systems should be monitored, understood and predicted to better protect and manage groundwater resources for the future.
Journal Article
Non-renewable groundwater use and groundwater depletion: a review
Population growth, economic development, and dietary changes have drastically increased the demand for food and water. The resulting expansion of irrigated agriculture into semi-arid areas with limited precipitation and surface water has greatly increased the dependence of irrigated crops on groundwater withdrawal. Also, the increasing number of people living in mega-cities without access to clean surface water or piped drinking water has drastically increased urban groundwater use. The result of these trends has been the steady increase of the use of non-renewable groundwater resources and associated high rates of aquifer depletion around the globe. We present a comprehensive review of the state-of-the-art in research on non-renewable groundwater use and groundwater depletion. We start with a section defining the concepts of non-renewable groundwater, fossil groundwater and groundwater depletion and place these concepts in a hydrogeological perspective. We pay particular attention to the interaction between groundwater withdrawal, recharge and surface water which is critical to understanding sustainable groundwater withdrawal. We provide an overview of methods that have been used to estimate groundwater depletion, followed by an extensive review of global and regional depletion estimates, the adverse impacts of groundwater depletion and the hydroeconomics of groundwater use. We end this review with an outlook for future research based on main research gaps and challenges identified. This review shows that both the estimates of current depletion rates and the future availability of non-renewable groundwater are highly uncertain and that considerable data and research challenges need to be overcome if we hope to reduce this uncertainty in the near future.
Journal Article
Sustainability of groundwater resources of weathered and fractured schists in the rural areas of Galicia (Spain)
Water supply deficits in droughts, groundwater pollution and climate change are the main challenges for the sustainability of groundwater resources from hard-rock aquifers in rural areas of Galicia (Spain). Here, we address the sustainability of groundwater resources of weathered and fractured schists in the rural areas of the Abegondo municipality. The conceptualization of the hydrogeology of the study area includes: (1) The weathered schist (regolith), (2) The decompressed highly fractured schist layer; and (3) An underlying slightly fractured schist. Groundwater flows mostly through the regolith and the highly fractured rock. Rainfall infiltration is the source of aquifer recharge. Groundwater discharges in seepage areas, springs and along creeks and valleys. The water table is generally shallow and shows seasonal oscillations of up to 4 m. The equivalent transmissivity of the regolith and the highly fractured schist ranges from 15 to 35 m
2
/days. The electrical resistivity tomography identifies a shallow water table and attests that the contact of the highly fractured schist and the slightly fractured schist is highly heterogeneous. Groundwater resources were quantified with a hydrological water balance model. The mean annual recharge is about 185 mm. Groundwater recharge at the end of the twenty-first century could decrease from 6 to 10% due to climate change. The decline in groundwater table could aggravate the shortages during droughts. Groundwater quality data show bacteriological and nitrate contamination due to the poor management of the manure in the fields and occasional discharges of slurry from pig and mink farms. Groundwater management and protection actions are proposed to prevent groundwater pollution and achieve a sustainable groundwater supply in the study area.
Journal Article
Aquifer characterization and hydrogeological modeling for devising groundwater management strategies for the Chennai aquifer system, southern India
The Chennai aquifer system, which occupies an area of 6629 km
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, is one of the most stressed aquifer systems in southern India and is under severe threat of over exploitation and quality deterioration. This is due to the increasing groundwater abstraction for irrigation, domestic, industrial purposes and for drinking water supply to the ever-expanding Chennai city. To offset the effect of this heavy extraction a paradigm shift towards groundwater management was imperative. A multidisciplinary integrated approach was used to map the aquifers, delineate their geometry, to determine the hydraulic behavior of the aquifer system, and to formulate an aquifer management plan through the development of a groundwater flow model. The main aquifers in the area include weathered and fractured crystalline rocks and recent alluvial formation. Alluvium is the most significant aquifer system in the study area, and this aquifer contains potable quality groundwater except in the eastern part of the study area that has been affected by seawater intrusion. A two-layered groundwater flow model was developed using Visual MODFLOW classic version 4.6 with a 1 km
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grid pattern to simulate groundwater flow for a period of 9 years. The model was calibrated under steady and transient state conditions and allowed components of the water balance of the system to be determined at a regional scale. The simulated results indicate that this aquifer system is under tremendous stress at the prevailing groundwater withdrawal rate of 899 million cubic meter (mcm)/year and would become unstable with the predicted 25% increase in groundwater withdrawal by 2025. However, the interventions to recharge an additional 54 mcm of water could help mitigate the current decline in potentiometric heads and could partially help to arrest the further advancement of seawater intrusion. A scenario of maintaining flow in rivers for a period of 120 days each year coupled with the construction of an unlined canal shows increase in groundwater head and development of the groundwater mounds, which are positive signs for arresting the decline of the water table and pushing saline groundwater in a seaward direction. As a result of the high rate of groundwater depletion in the area, management strategies need to be implemented urgently in the region. These strategies should include the regulation of groundwater abstraction and maintaining an extended flow period in the rivers. These measures are required to improve the sustainability of the available groundwater resources of the region.
Journal Article
Karst hydrogeological characteristics of Jindong large coal basin, northern China
Jindong coal basin is one of the 14 large coal basins planned and constructed by the state, and groundwater resources play an important role in supporting the sustainable development of the coal basin. To improve the understanding of deep karst hydrogeological characteristics of the coal basin, the combination of techniques (i.e., 1:50,000 and 1:100,000 surveys, geophysical prospecting, drilling, dynamic monitoring, hydrochemistry and isotopes, etc.) was used to characterize the hydrogeological structures of deep-buried aquifers and analyze the evolution characteristics of groundwater systems under the conditions of long-term and large-scale coal mining. Deep Cambrian Zhangxia formation oolitic limestone water-rich aquifer was newly discovered in this survey, which characterized by the development of karstic fissures and strong water-richness in the effective structural zone. The dissolubility of the Cambrian Zhangxia formation oolitic limestone is weaker than that of the Ordovician Majiagou formation and Carboniferous Taiyuan formation limestone, but stronger than that of the Ordovician and Cambrian dolomite. Controlled by Jinhuo fault zone, there are many large karst groundwater-bearing basins distributed on both sides, such as Jincheng basin, Yangcheng basin, Changzhi basin, etc., and water yield in the center of the basins can reach more than 10,000 m
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/days. Main types of karst groundwater storage structures in study area are syncline basin type, fault fracture zone type and permeable-impermeable contact zone type. Affected by coal mining, the dynamic conditions of karst groundwater have changed significantly, mainly manifested in the movement of the boundary of the karst groundwater system, the decline of the groundwater level, the attenuation of karst springs flow, and the complex conversion of multi-source water. The variation characteristics of the spring flow can be subdivided into three stages, namely relatively stable stage, rapid decline stage and slow decline stage. The main controlling factors of these three stages are atmospheric precipitation, coal mining and karst water exploitation, respectively. The regional groundwater circulation pattern under coal mining can be divided into shallow groundwater flow system, deep groundwater flow system and local groundwater flow system. The local groundwater flow system was mainly affected by coal mining, which was manifested as the concentrated discharge of groundwater to goaf. The results of this study will provide scientific basis for groundwater exploration and exploitation and sustainable development of coal basins.
Journal Article