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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.

Using publicly-available average monthly groundwater level data in 478 sub-basins and 30 basins in Iran, we quantify country-wide groundwater depletion in Iran. Natural and anthropogenic elements affecting the dynamics of groundwater storage are taken into account and quantified during the period of 2002–2015. We estimate that the total groundwater depletion in Iran to be ~ 74 km 3 during this period with highly localized and variable rates of change at basin and sub-basin scales. The impact of depletion in Iran’s groundwater reserves is already manifested by extreme overdrafts in ~ 77% of Iran’s land area, a growing soil salinity across the entire country, and increasing frequency and extent of land subsidence in Iran’s planes. While meteorological/hydrological droughts act as triggers and intensify the rate of depletion in country-wide groundwater storage, basin-scale groundwater depletions in Iran are mainly caused by extensive human water withdrawals. We warn that continuation of unsustainable groundwater management in Iran can lead to potentially irreversible impacts on land and environment, threatening country’s water, food, socio-economic security.

Effective assessment of any region's groundwater resources depends greatly on the levels of the sub-surface water. Since groundwater resources are being overused, the availability of groundwater is in a critical scenario. Quality of the groundwater is deteriorating in numerous regions as a result of the worrisome rate of groundwater table depletion. Depending on how frequently the aquifer under the earth surface is recharged by surface water supplies, groundwater can be kept underground for days, weeks, months, years, centuries, or even millennia. Currently, the utility is increased as compared to availability. The current water demand exceeds the surface water supply. As a result, for the effective management and usage of the priceless natural resources, groundwater potential zones’ systematic evaluation is now essential. The understanding about monitoring and a suitable sustainable development strategy for water resources is provided by groundwater potential zoning. The delineation of groundwater potential zoning is influenced by various factors, including rainfall, land-use cover, geological formations, geomorphology, drainage features, slope, etc. To ensure the sustainable groundwater management in the basin, it is essential to locate groundwater potential zones, so that series of recharge structures may be built there to manage aquifer recharge. Remote sensing and GIS are recent techniques that become very crucial tools in accessing, monitoring, and conserving groundwater resources because of their advantages of spatial, spectral, and temporal availability and interpolation of data covering big and inaccessible areas in short amount of time.

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 m2/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.

Groundwater pumping from wells, together with water uses such as agricultural irrigation have been converting formerly open groundwater basins into closed systems that accumulate total dissolved solids (TDS). This process of anthropogenic basin closure and salinization (ABCSal) would appear to pose a threat to groundwater sustainability that is at least as formidable as groundwater overdraft and contamination from the surface, yet has been little explored. Models of groundwater flow and solute transport herein show that groundwater basin openness itself should be considered a primary determinant of sustainability. Results show that groundwater basin closure is a threshold condition that sets the aquifer system on a path of increasing salinity that can only be halted by opening the basin. Further, the magnitude of groundwater pumping and degree of basin closure significantly influence the spatial distribution of salinity. In open basins, salinity approaches dynamic equilibrium over long‐term conditions. Stratification of higher‐TDS groundwater overlying lower‐TDS groundwater occurs below farmlands whose irrigation‐supplying wells are impacted by irrigation return flow from upstream farmlands, and act to redistribute relatively saline groundwater to the land surface. More intensive pumping leads to groundwater basin closure and more vertically‐oriented groundwater flow toward pumping wells. TDS retainment in the basin and repeated well capture, re‐distribution as irrigation water, and evapoconcentration lead to progressive salinization. Regardless of basin closure status, fresh recharge protects nearby downstream portions of the basin from salinization, indicating that managing or limiting the spread of contaminated groundwater may be achieved via managed aquifer recharge of good quality water. Plain Language Summary This paper presents hydrologic basin openness, the degree to which inflow of groundwater is balanced by non‐evaporative outflow, as a new criteria for groundwater sustainability. Water use practices such as irrigation and groundwater pumping have in many cases been reducing groundwater basin openness, promoting accumulation of dissolved intrabasin salts. State‐of‐the‐art but simple groundwater models demonstrate the spatiotemporal dynamics of this Anthropogenic Basin Closure and groundwater Salinization (ABCSal) process. Simulations show that significant salinization with total dissolved solids concentration exceeding 1,000 to 6,000 mg/L can occur in large portions of a basin within two to six centuries. Strength of pumping and the degree of basin closure significantly influence spatial extent and organization of zones with different salinities. Structured salinization zones and relatively low salinity levels downstream of fresh recharge areas indicate viable water management strategies (e.g., managed aquifer recharge of good quality water) for coping with ABCSal consequences. However, maintaining sufficient groundwater basin openness is required to avoid ABCSal, necessitating a different paradigm of integrated water resources management with much greater emphasis on subsurface storage of water and more modern and intensive monitoring of the groundwater system state to ensure a sustainable evolution trajectory of both groundwater quantity and quality. Key Points Groundwater pumping and irrigation cause progressive groundwater salinization that can be halted only by maintaining enough basin openness Groundwater development strength influences groundwater flow pattern and salt load, and ultimately, the salinization pattern and intensity Distinct zones of different salinity levels establish under open and closed basin status