Groundwater Level Recovery Research Articles

The influence of withdrawal-recharging pattern on the deformation characteristics of sand in confined aquifer

Land subsidence caused by excessive groundwater withdrawal has become a global hazard, which demands further researches and the potential measures to control. Using the FlowTrac Ⅱ consolidation test system, six compression tests were designed to investigate the stress state and stress paths of sand within confined aquifers under conditions of withdrawal and recharging. The deformation characteristics of aquifer sand were studied under different withdrawal-recharging patterns. During pumping and recharge processes, sand deformation responses were observed to lag behind changes in applied stress. The characteristics of this hysteresis effect on deformation were summarized. The alternating phenomenon of rebound and compression of sand deformation under the recharging process is analyzed. When the recharging effect was relatively small than withdrawing effect under the stable withdrawal-recharging pattern, the compression deformation was observed in the recharging process. The research results provide a rational explanation for the continuous compression deformation of the aquifer during groundwater level recovery and offer experimental evidence for the rational design of artificial groundwater recharge in engineering construction.

Sources and transformation of nitrogen in shallow aquifers with progressive water table recovery using geochemical and isotopic approaches.

Groundwater level recovery has a significant effect on the sources and transformation of nitrogen in groundwater, but there are still few studies on the influences of the water table on the sources and transformation of nitrogen in groundwater using field data. In this study, the changes in groundwater level, geochemical composition, and isotopic signatures of NO3- and NH4+ during a period of groundwater level recovery at a pilot site were analyzed in detail. The water table underwent progressive recovery of almost 1.6 m in 16 months. At a depth of 5.5 m below the surface, both low NH4+ and high NO3- appeared in the groundwater, whereas below that depth, both high NH4+ and low NO3- simultaneously appeared in the groundwater. The main sources of NO3- were manure and septic waste, and NH4+ fertilizers. The main sources of NH4+ were mineral fertilizers. The main transformation process were nitrification and denitrification at a depth of 5.5 m below the surface; below that depth, the main transformation processes were denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This study provides a theoretical understanding of the relationship between the changing water table and nitrogen in groundwater level recovery areas.

Effective groundwater level recovery from mining reduction: Case study of Baoding and Shijiazhuang Plain area

Effective groundwater level recovery from mining reduction: Case study of Baoding and Shijiazhuang Plain area

Simulation of groundwater dynamic conditions in the Baiquan spring region under optimal groundwater resource allocation

Abstract Xingtai, once been famous city for its spring groups in history, has become one of the regions in the country where water resources are in high demand due to long-term over-exploitation in groundwater resource. In the region where the springs in the area have dried up and been cutting-off over the years, including Baiquan and Dahuo. In order to allocate the amount of water diverted from the Middle Section of South-North Water Diversion Project reasonably, to effectively make the springs re-rushing and restore the groundwater level, this research established a numerical groundwater model based on the hydrogeological conditions of the study area. The calculate model is used to discuss the hydrodynamical patterns changes and predict the flowrate of spring groups under different allocation of supplement diversion schemes quantifiably. It was found that the scheme of using the amount of river diversion to rehabilitate the Xingtai urban funnel was most conducive to the recovery of groundwater levels in the spring groups, which is due to the reduction in groundwater extraction has reduced the influence range of the urban funnel and improved the hydrodynamic conditions in the northern preferential runoff zone. The results have demonstrated the feasibility of re-rushing the spring groups.

関東平野内陸部における水位回復期以降の浅層地下水について −水理水頭と地下水流動の一時的変化−

関東平野内陸部における水位回復期以降の浅層地下水について −水理水頭と地下水流動の一時的変化−

Using Simple LSTM Models to Evaluate Effects of a River Restoration on Groundwater in Kushiro Wetland, Hokkaido, Japan

Wetland ecosystems with proper functioning provide various ecosystem services. Therefore, their conservation and restoration are of fundamental importance for sustainable development. This study used a deep learning model for groundwater level prediction to evaluate a wetland restoration project implemented in the Kushiro Wetland in Japan. The Kushiro Wetland had been degraded due to river improvement work. However, in 2010, a wetland restoration project was carried out to restore the meandering river channel, and a decade has passed since its completion. In this study, the wetland restoration project was evaluated by comparing the response of the groundwater level using a model that reproduced physical conditions with different characteristics before and after the restoration. At first, a deep learning model was created to predict groundwater levels pre- and post-restoration of a meandering river channel using observation data. Long short-term memory (LSTM) was used as the deep learning model. The most important aspect of this study was that LSTM was trained for each of the pre- and post-restoration periods when the hydrological and geological characteristics changed due to the river channel’s restoration. The trained LSTM model achieved high performance with a prediction error of the groundwater levels within 0.162 m at all observation points. Next, the LSTM models trained with the observation data of the post-restoration period were applied to evaluate the effectiveness of the meandering channel restoration. The results indicated that the meandering channel restoration improved hydrological processes in groundwater levels, i.e., their rainfall response and average groundwater water levels. Furthermore, the variable importance analysis of the explanatory variables in the LSTM model showed that river discharge and precipitation significantly contributed to groundwater level recovery in the Kushiro Wetland. These results indicated that the LSTM model could learn the differences in hydrological and geological characteristics’ changes due to channel restoration to groundwater levels. Furthermore, LSTM is a data-driven deep learning model, and by learning hydrological and geological conditions to identify factors that may affect groundwater levels, LSTM has the potential to become a powerful analysis method that can be used for environmental management and conservation issues.

Quantify the effects of groundwater level recovery on groundwater nitrate dynamics through a quasi-3D integrated model for the vadose zone-groundwater coupled system

Groundwater level (GWL) recovery in some semiarid regions, attributed to mitigation countermeasures for groundwater depletion, potentially causes nitrate accumulated in the vadose zone to be introduced into the aquifer. However, the extent to which GWL recovery affects interactions between the vadose zone and saturated aquifers, migration pathways of soil nitrogen and groundwater nitrate dynamics have not been explicitly determined. This study established a quasi-3D feedback model for the vadose zone-groundwater coupled system in a typical GWL recovery area and quantitatively evaluated the effects of GWL recovery on nitrate-N leaching fluxes via the vadose zone and groundwater nitrate-N dynamics. Within the framework of the integrated model, both the water/contaminant leaching fluxes and the depth to groundwater were exchanged at each flow time step. The obtained results reveal that the temporal changes in nitrate-N leaching fluxes depended on the behaviors of precipitation, farmland irrigation and lithology of the vadose zone, while its spatial patterns were determined by both the GWL undulation and the vertical profiles of nitrate-N content. Furthermore, the GWL recovery caused the magnitude of the nitrate-N leaching fluxes into the aquifer to increase by 44.4%. Along with the GWL recovery, the phreatic aquifer volume increased by 7.47%, and the nitrate-N mass herein increased by 40.06%, which was largely driven by the nitrate-N leaching flux. Consequently, the average groundwater nitrate-N concentration in the GWL recovery region increased by approximately 2.4 mg/L, apart from the artificial recharge route. This finding suggests that the intensified leaching of soil contaminants, given the circumstances of GWL recovery, has a negative effect on groundwater quality. An appropriate groundwater management scheme is therefore urgently required to achieve an optimal balance between GWL recovery and groundwater environment.

Evaluation of Land Subsidence during Groundwater Recovery

The Chao Phraya River basin is located in the central area of Thailand, which experiences many land subsidence issues due to groundwater pumping. The Department of Groundwater Resources (DGR) has been recording data on the changes in the groundwater level due to water pumping since 1960 until the present time. In 1997, the DGR issued a law regulating the use of groundwater due to its effect on the changes in the groundwater level. The changing of the groundwater level was separated into two periods. The first period is the high groundwater pumping ratio that led to a rapid decrease in the groundwater level of about 27 m from the ground surface. After the DGR issued the new law in the second period, the pumping ratio decreased and the groundwater level increased. The groundwater level tends to reach the ground surface. In the past, the groundwater level decrease was affected by the land subsidence. Therefore, this study focused on calculating and learning the behavior of the soil surface displacement during groundwater level recovery to the ground surface in Bangkok, Thailand. We obtained the 3D soil profiles adopted from eight boreholes from the Department of Public Works and Town & Country Planning. The soil profile data were verified by monitoring the data from the Department of Groundwater Resources (DGR) in the same area. The soil layers of the 3D soil profile were analyzed to calculate the soil surface displacement based on the consolidation theory of Terzaghi. We also examined the displacement behavior of the clay layers during the groundwater level recovery to the ground surface by assuming that the soil layers below the groundwater level do not settle or rebound. The surface displacement results showed that the surface ends to move upward or rebound, which is a similar trend to that reported in previous research. All the considered locations showed similar soil surface displacement trends. The soil displacement ratio is 0.21 to 0.53 cm/year during the groundwater recovery.

Combining river replenishment and restrictions on groundwater pumping to achieve groundwater balance in the Juma River Plain, North China Plain

In recent years, to alleviate the decline in groundwater levels, extensive restrictions on groundwater pumping have been implemented in the North China Plain (NCP). In September 2018, a large-scale ecological water replenishment project was executed involving 22 rivers and lakes. How to adjust the layout of reduction on groundwater pumping within the context of ecological water replenishment is a key issue to be addressed in the study of groundwater level recovery in the NCP. This study adopted the Juma River Plain in Baoding city as a case study, established a numerical model of river replenishment of groundwater, predicted groundwater level changes over the next 15 years (2021–2035) and quantitatively calculated the impact of river replenishment on groundwater levels. To achieve the goal of an overall groundwater balance by 2035, a suitable groundwater pumping restriction scenario was defined based on the impact of river replenishment on groundwater levels. The results indicated that by 2035, the relative rise in groundwater levels attributed to river replenishment and restrictions on groundwater pumping could reach 3.51 and 2.28 m, respectively. River replenishment significantly impacts groundwater levels, especially those near the river. Under the current groundwater exploitation conditions, river replenishment could ensure groundwater level recovery near the river, which accounts for 15% of the total study area. The goal of an overall groundwater balance by 2035 could be achieved if restrictions on groundwater pumping were superimposed, with an average annual reduction of 56 million m3. This study provides valuable insights into groundwater management across the NCP. The proposed methods are useful for the management of other depleted aquifers recharged via ecological water replenishment.

Groundwater-level recovery following closure of open-pit mines

Open-pit mining has increased substantially over the past two decades. Many currently operating open-pit mines are facing the end of mine-life over the next few decades and, increasingly, focus is shifting towards mine-closure planning that provides evidence on available closure options under the given geological, hydro(geo)logical and climatic conditions. This study uses synthetic groundwater modelling to build basic process understanding of closure options and how these will determine the formation of pit lakes. This governs the long-term pit lake water quality and how postmining landscapes may be utilised. Simulations show that the recovery time of postmining groundwater levels increases with decreasing aquifer transmissivity. Final postmining water tables are predominantly controlled by the implemented mine closure options and climatic conditions. The most important decision is, thereby, whether to backfill the pit to above the water table or allow a pit lake to develop. Under moderately transmissive aquifer settings, backfilling of pits leads to rapidly rising groundwater levels within the first decade after mining, with water-table recoveries of above 70%. If mine voids remain unfilled, evaporation from the pit lake surface becomes a governing factor in determining whether the unfilled mine pit becomes a terminal sink for groundwater. Lake levels may remain subdued by several 10s of metres in arid to semiarid climates. If surplus surface water can be diverted into open pits, rapid filling can accelerate groundwater recovery of open pits in regions of low permeability. This is a less successful management option in transmissive aquifers.

ԱՐԱՐԱՏՅԱՆ ԴԱՇՏԻ ԳՐՈՒՆՏԱՅԻՆ ՋՐԵՐԻ ՄԱԿԱՐԴԱԿԻ ԴԻՆԱՄԻԿԱՆ ԵՎ ՈՌՈԳԵԼԻ ՀՈՂԵՐԻ ՄԵԼԻՈՐԱՏԻՎ ՎԻՃԱԿԸ

The current article presents the dynamics of groundwater level in the Armavir, Edjmiatsin, Masis, Artashat and Ararat provinces of the Ararat valley. The groundwater levels have been mapped in ArcGIS environment per years and months (2015-2018). Discrepancy between the rising and falling rates of groundwater level has been recorded. Meanwhile, groundwater level recovery has been observed which is related to the uncontrolled exploitation of groundwater basin in the recent decades

Restoring groundwater levels after tunneling: a numerical simulation approach to tunnel sealing decision-making

Tunneling is often unpopular with local residents and environmentalists, and can cause aquifer damage. Tunnel sealing is sometimes used to avoid groundwater leakage into the tunnel, thereby mitigating the damage. Due to the high cost of sealing operations, a detailed hydrogeological investigation should be conducted as part of the tunneling project to determine the impact of sealing, and groundwater modeling is an accurate method that can aid decision-making. Groundwater-level drawdown induced by the construction of the Headrace water-conveyance tunnel in Sri Lanka dried up 456 wells. Due to resulting socio-environmental problems, tunnel sealing was decided as a remedy solution. However, due to the expectation of significant delays and high costs of sealing, and because the water pressure in the tunnel may prevent groundwater seepage into the tunnel during operation, there was another (counter) decision that the tunnel could remain unsealed. This paper describes groundwater modeling carried out using MODFLOW to determine which option—sealed or unsealed tunnel—is more effective in groundwater level recovery. The Horizontal Flow Barrier and River packages of MODFLOW were used to simulate sealed and unsealed tunnels, respectively. The simulation results showed that only through tunnel sealing can the groundwater level be raised to preexisting levels after 18 years throughout the study area. If the tunnel remains unsealed, about 1 million m3/year of water conveyed by the tunnel will seep into the aquifer, reducing the operational capacity of the tunnel as a transport scheme. In conclusion, partial tunnel sealing in high-impact sections is recommended.

Coupling model of groundwater and land subsidence and simulation of emergency water supply in Ningbo urban Area, China

Groundwater withdrawal has caused severe land subsidence in Ningbo since 1964. The land subsidence rate slowed down by the prohibition of groundwater exploitation. However, water supply crisis prompted a new task of how to satisfy the emergency demands of water supply. This study tries to provide insights into the prediction of groundwater level and land subsidence and formulate reasonable exploitation plans for emergency water supply in Ningbo urban area. A coupling model of groundwater and land subsidence was developed to quantify the subsidence caused by water withdrawal. The proposed model is recognized for the period 1989–1992 and is verified for the period 1992–1993 using observed groundwater and land subsidence records in Ningbo urban area. Based on the calibrated and evaluated model, six reasonable exploitation plans for emergency water supply in Ningbo urban area are formulated, and the dynamic prediction of groundwater level and land subsidence changes in each plan are made. Numerical results show that the pore confined water in Ningbo urban area has good supply conditions and strong water level recovery ability, which can meet the demand of short-term centralized water supply. A longer time of emergency water supply and a lower controlling depth of water level leads to larger subsidence. After the completion of water supply, areas near exploited well may appear subsidence rebound due to the recovery of groundwater level, but subsidence continues to increase in areas far away from the exploited well due to the delayed settlement of the lagging interbeds.

Evaluation of Groundwater Overdraft Governance Measures in Hengshui City, China

Groundwater overdraft is a worldwide phenomenon, resulting in environmental issues, such as water contamination, land subsidence, seawater intrusion, streamflow reduction, and deterioration of the ecological environment. Located in the central North China Plain, Hengshui City has experienced a regional groundwater depression cone due to excessive pumping of groundwater, resulting in the largest overdraft area in the North China Plain. Since 2014, Hebei Province has adopted measures to realize the comprehensive governance of groundwater overdraft in partial areas of Hengshui City, including adjusting planting structures, promoting agronomic water-saving techniques, strengthening hydraulic engineering construction, and innovative management systems. These measures have been in effect for two years, such that their effectiveness must be assessed for the beneficial recovery of groundwater levels to determine the means for their continuation and extension. However, the change in regional groundwater levels is not gradual, but reflects a process of sudden increase due to the intervention of government behavior, and many existing groundwater recharge models are difficult to apply. Therefore, establishing a reasonable, scientific evaluation system of the measures is a key problem that requires a solution. Using field surveys and experiments, this study establishes a quantitative analysis evaluation method to assess the performance of governance measures adopted by Hengshui City in 2015, with full consideration of the crop water demand process and rainfall frequency. The results show that governance measures had a significant positive outcome on reducing groundwater overdraft in pilot areas. Approximately 98.4% of the agricultural governance target was achieved, with confined groundwater rebounding by approximately 4.92 m as compared to 2015. According to the analysis, the three most efficient measures (the top three largest amounts of groundwater-saved per mu) adopted by the government were (1) non-agricultural crops replacement (forestry), (2) planting pattern adjustments, and (3) integration of water and fertilizer-vegetable, which can be promoted in future measures. However, considering the size of the implementation area and total governance capacity, water-saving during spring irrigation of wheat and replacement by surface water are the two most important conservation measures, which are required to further strengthen the management and implementation effect.

Justificationof options of ecological protection of mine field areas in conditions of groundwater level recovery

Justificationof options of ecological protection of mine field areas in conditions of groundwater level recovery

The Effect of Undetected Barriers on Groundwater Drawdown and Recovery.

In large-scale pumping projects, such as mine dewatering, predictions are often made about the rate of groundwater level recovery after pumping has ceased. However, these predictions may be impacted by geological uncertainty-including the presence of undetected impermeable barriers. During pumping, an impermeable barrier may be undetected if it is located beyond the maximum extent of the cone of depression; yet it may still control drawdown during the recovery phase. This has implications for regional-scale modeling and monitoring of groundwater level recovery. In this article, non-dimensional solutions are developed to show the conditions under which a barrier may be undetected during pumping but still significantly impact groundwater level recovery. The magnitude of the impact from an undetected barrier will increase as the ratio of pumping rate to aquifer transmissivity increases. The results are exemplified for a hypothetical aquifer with an unknown barrier 3km from a pumping well. The difference in drawdown between a model with and without a barrier may be <1m in the 10 years while pumping is occurring, but up to 50 m after pumping has ceased.

Mechanism of sinkhole formation during groundwater-level recovery in karst mining area, Dachengqiao, Hunan province, China

The Meitanba Coal Mine area in Hunan province, China, had been impacted by severe cover collapse sinkholes since 1982 due to mine dewatering. After the coal mine was closed in February 2015, the groundwater level has increased significantly. A series of sinkholes were recorded in the study area during groundwater-level recovery. Analysis of monitoring results and in-situ investigation indicated that 13 sinkhole collapses were more likely induced by abrupt change of groundwater–air pressure in response to heavy rainfall from March 2015 to July 2016 when the groundwater level increased by as much as 76 m. When the karst conduit was flooded, a relatively sealed environment was formed between saturated sediments and flooded karst conduit. Implosion of entrapped air might have caused the cave roof to collapse followed by surface collapses in a short time. On the other hand, four sinkholes occurred in November 2016 when the groundwater levels were near the soil–bedrock interface at elevations between 52.5 and 58.9 m amsl and the groundwater-level increase was at slower paces. Field measurements indicate that the groundwater-level fluctuation at the soil–bedrock interface could enlarge the soil cavity and accelerate the subsoil erosion process.

Long‐term effects of aquifer overdraft and recovery on groundwater quality in a Ramsar wetland: Las Tablas de Daimiel National Park, Spain

AbstractLas Tablas de Daimiel National Park is one of Spain's most representative groundwater‐dependent ecosystems. Under natural conditions, water inflows combined brackish surface water from River Gigüela with freshwater inputs from River Guadiana and the underlying aquifer. Since the mid‐1970s, aquifer overexploitation caused the desiccation of the wetlands and neighbouring springs. The National Park remained in precarious hydrological conditions for three decades, with the only exception of rapid floods due to extreme rainfall events and sporadic water transfers from other basins. In the late 2000s, a decrease in groundwater abstraction and an extraordinarily wet period reversed the trend. The aquifer experienced an unexpected recovery of groundwater levels (over 20 m in some areas), thus restoring groundwater discharge to springs and wetlands. The complex historical evolution of the water balance in this site has resulted in substantial changes in surface and groundwater quality. This becomes evident when comparing the pre‐1980 groundwater quality and the hydrochemical status in the wetland in two different periods, under “dry” and “wet” conditions. Although the system is close to full recovery from the groundwater‐level viewpoint, bouncing back in the major hydrochemical constituents has not yet been obtained. These still appear to evolve in response to the previous overexploitation state. Moreover, in some sectors, there are groundwater‐dependent ecosystems that remain different to those found in preoverexploitation times. The experience of Las Tablas de Damiel provides an observatory of long‐term changes in wetland water quality, demonstrating that the effects of aquifer overexploitation on aquatic ecosystems are more than a mere alteration of the water balance and that groundwater quality is the key to aquifer and aquatic ecosystem sustainability.

Groundwater and surface water connectivity within the recharge area of Guarani aquifer system during El Niño 2014–2016

AbstractRecharge areas of the Guarani Aquifer System (GAS) are particularly sensitive and vulnerable to climate variability; therefore, the understanding of infiltration mechanisms for aquifer recharge and surface run‐off generation represent a relevant issue for water resources management in the southeastern portion of the Brazilian territory, particularly in the Jacaré‐Pepira River watershed. The main purpose of this study is to understand the interactions between precipitation, surface water, and groundwater using stable isotopes during the strong 2014–2016 El Niño Southern Oscillation event. The large variation in the isotopic composition of precipitation (from −9.26‰ to +0.02‰ for δ18O and from −63.3‰ to +17.6‰ for δ2H), mainly associated with regional climatic features, was not reflected in the isotopic composition of surface water (from −7.84‰ to −5.83‰ for δ18O and from −49.7‰ to +33.6‰ for δ2H), mainly due to the monthly sampling frequency, and groundwater (from −7.04‰ to −7.76‰ for δ18O and from −49.5‰ to −44.7‰ for δ2H), which exhibited less variation throughout the year. However, variations in deuterium excess (d‐excess) in groundwater and surface water suggest the occurrence of strong secondary evaporation during the infiltration process, corresponding with groundwater level recovery. Similar isotopic composition in groundwater and surface water, as well as the same temporal variations in d‐excess and line‐conditioned excess denote the strong connectivity between these two reservoirs during baseflow recession periods. Isotopic mass balance modelling and hydrograph separation estimate that the groundwater contribution varied between 70% and 80%, however, during peak flows, the isotopic mass balance tends to overestimate the groundwater contribution when compared with the other hydrograph separation methods. Our findings indicate that the application of isotopic mass balance methods for ungauged rivers draining large groundwater reservoirs, such as the GAS outcrop, could provide a powerful tool for hydrological studies in the future, helping in the identification of flow contributions to river discharge draining these areas.

Demonstrating the utility of a drought termination framework: prospects for groundwater level recovery in England and Wales in 2018 or beyond

During prolonged droughts, information is needed about when and how the extreme event is likely to terminate. A drought termination framework based on historical data comprising current rate and historical ensemble approaches is presented here for assessing the prospects of groundwater level recovery. The current rate approach is evaluated across all initialisation months in the historical record and provides reasonable estimates for the duration of recovery from relatively severe groundwater level deficiencies in some slowly responding boreholes. The utility of the framework is demonstrated through a near-real-time application to 30 groundwater boreholes in England and Wales from October 2017 onwards. Recovery during winter 2017/18 was considered unlikely, as some aquifers required increases in groundwater levels that have occurred seldom, if ever before, in long historical records. Data to February 2018 confirmed the success of these pre-winter outlooks. Recovery by mid- to late-2018 or beyond was more likely; slow rates of recovery by October 2017 and increasing return periods of effective rainfall required for recovery over timeframes in the summer half-year underlined the importance of winter rainfall and suggested that the historical ensemble may underestimate the duration of recovery. There was moderate confidence for a delay in recovery beyond the end of 2018 in some slowly responding Chalk boreholes in south-central and eastern England. There is considerable potential for the transferability of the drought termination framework beyond the UK wherever there are sufficient historical data. The two approaches provide limited information in distinctly different circumstances and their relevance and value may differ in space and time, suggesting their complimentary use as the most robust way to incorporate information on the prospects for groundwater level recovery into existing seasonal forecasting services, supporting decision-making by water managers during prolonged droughts.