Spatio-temporal variation of depth to groundwater level and its driving factors in arid and semi-arid regions of India

Climate change and increasing anthropogenic activities,such as over-exploitation of groundwater,are exerting unavoidable stress on groundwater resources.This study investigated the spatio-temporal variation of depth to groundwater level(DGWL)and the impacts of climatic(precipitation,maximum temperature,and minimum temperature)and anthropogenic(gross district product(GDP),population,and net irrigated area(NIA))variables on DGWL during 1994-2020.The study considered DGWL in 113 observation wells and piezometers located in arid western plains(Barmer and Jodhpur districts)and semi-arid eastern plains(Jaipur,Ajmer,Dausa,and Tonk districts)of Rajasthan State,India.Statistical methods were employed to examine the annual and seasonal patterns of DGWL,and the generalized additive model(GAM)was used to determine the impacts of climatic and anthropogenic variables on DGWL.During 1994-2020,except for Barmer District,where the mean annual DGWL was almost constant(around 26.50 m),all other districts exhibited increase in DGWL,with Ajmer District experiencing the most increase.The results also revealed that 36 observation wells and piezometers showed a statistically significant annual increasing trend in DGWL and 34 observation wells and piezometers exhibited a statistically significant decreasing trend in DGWL.Similarly,32 observation wells and piezometers showed an statistically significant increasing trend and 37 observation wells and piezometers showed a statistically significant decreasing trend in winter;33 observation wells and piezometers indicated a statistically significant increasing trend and 34 had a statistically significant decreasing trend in post-monsoon;35 observation wells and piezometers exhibited a statistically significant increasing trend and 32 observation wells and piezometers showed a statistically significant decreasing trend in pre-monsoon;and 36 observation wells and piezometers reflected a statistically significant increasing trend and 30 observation wells and piezometers reflected a statistically significant decreasing trend in monsoon.Interestingly,most of the observation wells and piezometers with increasing trends of DGWL were located in Dausa and Jaipur districts.Furthermore,the GAM analysis revealed that climatic variables,such as precipitation,significantly affected DGWL in Barmer District,and DGWL in all other districts was influenced by anthropogenic variables,including GDP,NIA,and population.As a result,stringent regulations should be implemented to curb excessive groundwater extraction,manage agricultural water demand,initiate proactive aquifer recharge programs,and strengthen sustainable management in these water-scarce regions.

Determining safe yield and mapping water level zoning in groundwater resources of the Neishabour Plain

Groundwater is a crucial sources of water supply,especially in arid and semi-arid areas around the world.With uncontrolled withdrawals and limited availability of these resources,it is essential to determine the safe yield of these valuable resources.The Hill method approach was used in this study to determine the safe yield the Neishabour aquifer in Khorasan Razvi province in Iran.The results showed that the safe yield in the Neishabour aquifer is 60%lower than the current pumping amounts during the study period,indicating that further overdrafts could result in the destruction of this aquifer.This highlights the importance of using the Hill method to estimate the permitted exploitation from other aquifers,thus preventing problems caused by over-extraction and maintaining stability of global groundwater levels.

Using the concept of ecological groundwater level to evaluate shallow groundwater resources in hyperarid desert regions

This paper, based on the analysis and calculation of the groundwater resources in an arid region from 1980 to 2001, put forward the concept of ecological groundwater level threshold for either salinity control or the determination of ecological warning. The surveys suggest that soil moisture and soil salinity are the most important environmental factors in determining the distribution and changes in vegetation. The groundwater level threshold of ecological warning can be determined by using a network of groundwater depth observation sites that monitor the environmental moisture gradient as reflected by plant physiological characteristics. According to long-term field observations within the Ejin oases, the groundwater level threshold for salinity control varied between 0.5 m and 1.5 m, and the ecological warning threshold varied between 3.5 m and 4.0 m. The quantity of groundwater re- sources （renewable water resources, ecological water resources, and exploitable water resources） in arid areas can be calculated from regional groundwater level information, without localized hydrogeological data. The concept of groundwater level threshold of ecological warning was established according to water development and water re- sources supply, and available groundwater resources were calculated. The concept not only enriches and broadens the content of groundwater studies, but also helps in predicting the prospects for water resources development.

Dynamic Variations and Influencing Factors of Groundwater Levels in Lhasa City

This paper focuses on the dynamic variation of groundwater level in Lhasacity. According to the data, the obvious characteristic of the groundwater level of the city is thatit is changing seasonally. Lhasa is divided into three districts according to hydrogeologicalconditions: the alluvial plain of the Lhasa-river, the alluvial plain of the Doilung-river, and thealluvial fan of inter mountain, which presents a downward trend, a slight upward trend and basicallystabilizing trend over the years individually. The analysis indicates that meteorological andhydrological factors lead to the obvious dynamic change of the groundwater level. However, more andmore human activities and over-exploitation of the groundwater cause the downward trend inthegroundwater level.

Groundwater level prediction of landslide based on classification and regression tree

According to groundwater level monitoring data of Shuping landslide in the Three Gorges Reservoir area, based on the response relationship between influential factors such as rainfall and reservoir level and the change of groundwater level, the influential factors of groundwater level were selected. Then the classification and regression tree（CART） model was constructed by the subset and used to predict the groundwater level. Through the verification, the predictive results of the test sample were consistent with the actually measured values, and the mean absolute error and relative error is 0.28 m and 1.15%respectively. To compare the support vector machine（SVM） model constructed using the same set of factors, the mean absolute error and relative error of predicted results is 1.53 m and 6.11% respectively. It is indicated that CART model has not only better fitting and generalization ability, but also strong advantages in the analysis of landslide groundwater dynamic characteristics and the screening of important variables. It is an effective method for prediction of ground water level in landslides.

Groundwater Level Prediction Using Artificial Neural Networks: A Case Study in Tra Noc Industrial Zone, Can Tho City, Vietnam

The objective of this study is to predict groundwater levels (GWLs) under different impact factors using Artificial Neural Network (ANN) for a case study in Tra Noc Industrial Zone, Can Tho City, Vietnam. This can be achieved by evaluating the current state of groundwater resources (GWR) exploitation, use and dynamics;setting-up, calibrating and validating the ANN;and then predicting GWLs at different lead times. The results show that GWLs in the study area have been found to reduce rapidly from 2000 to 2015, especially in the Middle-upper Pleistocene (qp2-3) and upper Pleistocene (qp3) due to the over-withdrawals from the enterprises for production purposes. Concerning this problem, an Official Letter of the People’s Committee of Can Tho City was issued and taken into enforcement in 2012 resulting in the reduction of exploitation. The calibrated ANN structures have successfully demonstrated that the GWLs can be predicted considering different impact factors. The predicted results will help to raise awareness and to draw an attention of the local/central government for a clear GWR management policy for the Mekong delta, especially the industrial zones in the urban areas such as Can Tho city.

Effects of groundwater level on vegetation in the arid area of western China

At present,investigation about the relationship between the change of groundwater level and vegetation mostly focuses on specific watersheds,i.e.limited in river catchment scale.Understanding the change of groundwater level on vegetation in the basin or large scale,be urgently needed.To fill this gap,two typical arid areas in the west of China(Tarim Basin and Qaidam Basin)were chosen the a typical research area.The vegetation status was evaluated via normalization difference vegetation index(NDVI)from 2000 to 2016,sourced from MODN1F dataset.The data used to reflect climate change were download from CMDSC(http://data.cma.cn).Groundwater level data was collected from monitor wells.Then,the relationship of vegetation and climate change was established with univariate linear regression and correlation analysis approach.Results show that:Generally,NDVI value in the study area decreased before 2004 then increased in the research period.Severe degradation was observed in the center of the basin.The area with an NDVI value>0.5 decreased from 12%to 6%between 2000 and 2004.From 2004 to 2014,the vegetation in the study area was gradually restored.The whole coverage of Qaidam Basin was low.And the NDVI around East Taigener salt-lake degraded significantly,from 0.596 to 0.005,2014 and 2016,respectively.The fluctuation of groundwater level is the main reason for the change of surface vegetation coverage during the vegetation degradation in the basin.However,the average annual precipitation in the study area is low,which is not enough to have a significant impact on vegetation growth.The annual average precipitation showed an increase trend during the vegetation restoration in the basin,which alleviates the water shortage of vegetation growth in the region.Meanwhile,the dependence of surface vegetation on groundwater is obviously weakened with the correlation index is−0.248.The research results are of some significance to eco-environment protection in the arid area of western China.

Effects of urbanization on groundwater level in aquifers of Binh Duong Province,Vietnam

The purpose of this paper was to assess the impact of urbanization on the groundwater level(GWL)in aquifers of Binh Duong(BD)Province.The research method is to analyze the trend of GWL,the recharge capacity of surface over time and the relationship between them.The data of the GWL used in the study are the average values in the dry and rainy seasons of 35 observation wells from 2011 to 2018,which are in Pleistocene and Pliocene aquifers.The ability to recharge groundwater from the surface in this study was represented by the curve number(CN),a parameter used in hydrology for calculating direct runoff or infiltration from rainfall.The land use data to identify the CN was analyzed from the Landsat images.The results show that besides over-exploitation,the change of surface characteristic due to the urbanization development process is also the cause of the GWL decline.The analysis of seasonal GWL data shows that the increase in impervious surface area is the cause of GWL decline in the Pleistocene aquifer,which is more evident in the rainy season than in the dry season.The statistical results also show that in the rainy season and in shallow aquifers,a higher CN change can be found with the wells that had a remarkable GWL decline compared to the remaining wells.

Assessment of water level threshold for groundwater restoration and over-exploitation remediation the Beijing-Tianjin-Hebei Plain

The Beijing-Tianjin-Hebei Plain(BTHP)is the political,economic and cultural center of China,where groundwater is the main source of water supply to support social and economic development.Continuous overdraft of the resources has caused a persistent decline of groundwater level and formed a huge cone of depression at a regional scale.This paper addresses current groundwater situation over the BTHP area.The paper also delineates the groundwater flow field,using groundwater level data,in order to provide an effective method for the restoration of groundwater level and associated water resources management.Based on the analysis of multiple factors,such as groundwater level,soil salinization,ground subsidence,groundwater recharge and storage,urban underground space security,formation of fractures,and seawater intrusion,the threshold for groundwater level restoration is defined,and some measures for groundwater over-exploitation management are accordingly proposed.The study shows that:(i)Since the 1980s to 2020,shallow groundwater level in the western part of the BTHP area has dropped by 25 m to 60m,while the cumulative decline of deep groundwater in the central and eastern regions is in the range of 40–80 m;(ii)The water table of the shallow groundwater within the depression zone over the Western Piedmont Plain should be controlled in the range of 15–30 m below ground level(mbgl),while the depth of groundwater level in large and medium-sized urban areas should be controlled within 20–30 mbgl.The groundwater level in the resource preservation area should be controlled within 10–15 mbgl,and the groundwater level in the area with identified soil salinization in the central and eastern plain should be controlled within 3–10 mbgl.However,for the deep groundwater in the central and eastern plainwater,the main focus of the resources management is to control the land subsidence.The water level in the severe land subsidence area should be controlled within 45–60 mbgl,and in the general subsidence area should be controlled within 30–45 mbgl;(iii)Based on the water level recovery threshold and proposed groundwater overdraft management program,if the balance of abstraction and recharge is reached in 2025,the shallow groundwater abstraction needs to be gradually reduced by about 2×10^(8) m^(3).Meanwhile,the ecological water replenishment of rivers through the South-to-North Water Transfer Project should be increased to 28.58×10^(8) m^(3)/a,and the deep groundwater abstraction needs to be gradually reduced by 2.24×10^(8) m^(3).To reach the target of shallow groundwater level in 2040,surface water replacement is recommended with a rate of 25.77×10^(8) m^(3)/a and the ecological water replenishment of rivers in the South-to-North Water Diversion Project should reach 33.51×10^(8) m^(3)/a.For deep groundwater recovery,it is recommended to replace the deep freshwater extraction with the utilization of shallow salt water by 2.82×10^(8) m^(3),in addition to the amount of 7.86×10^(8) m^(3) by water diversion.The results are of great significance to the remediation of groundwater over-exploitation,the regulation of water resources development and utilization,and ecological protection in Beijing-Tianjin-Hebei plain.

Dynamic Characteristics and Influencing Factors of Groundwater Level in Qianyang County

The dynamic characteristics and influencing factors of groundwater level in Qianyang County were analyzed.The results showed that in the south bank of the Qianhe River,the change of groundwater level was mainly affected by precipitation,and the response of the groundwater level to the change of precipitation was one year later.The groundwater level presented a downward trend on the whole.In the north bank of the Qianhe River,the supply source of the groundwater level included precipitation and hydrology,and the groundwater level showed a rising trend on the whole.In the plain area,there was a sudden change in the groundwater level under the control of human activities.In a word,the main factors influencing the groundwater level in various geological conditions were different,so there were great differences between various regions in the dynamic characteristics of the groundwater level in Qianyang County.

Simulation of groundwater level recovery in abandoned mines, Fengfeng coalfield, China

Abandoned mines are of high potential risk as they could be a large underground storage of pollutants(heavy metals and organic wastes, etc.). Various physical, chemical and biological reactions would take place when groundwater flows into underground spaces, which makes abandoned mine a huge potential hazard to groundwater environment. The recovery of groundwater level is one of the key elements controlling the reactions and causing such hazards. This paper simulated groundwater level recovery processes in the abandoned mines, Fengfeng coalfield by using the computer program FEFLOW. The paper integrated the pipe flow model, "three zones" model and groundwater inrush(discharge) model in the simulation of groundwater in the complex laneway-aquifer system. Groundwater flow in the laneway systems was considered pipe flow and described in Bernoulli equation. The water-bearing medium(coal seam roof) overlying the laneway systems was divided into "three zones" composed of the caving zone, fissure zone and bending zone based on the disruption degrees of previous mining. Groundwater in the Ordovician limestone aquifer(bottom of coal seam) flowing into laneway systems was considered a major inrush/recharge source, and its flow rate was calculated by an inrush(discharge) model which was newly developed in this study and incorporated into FEFLOW. The results showed that it would take approximately 95 days for groundwater in abandoned mines to recover to regional groundwater level elevation, and the total amount of water filling up would be about 1.41195×10~7 m^3, which is consistent with the actual data. The study could be of theoretical and practical significance to mitigate abandoned mines' hazards and improve mine groundwater utilization.

Cause Analysis and Prediction of the Groundwater Level in Jinghuiqu Irrigation District

Groundwater environment evolution can comprehensively reflect groundwater dynamics. Based on the relationship between the groundwater system and the external environment in Jinghuiqu irrigation district, adopting the Principal Component Analysis method, variation characteristics of environmental factors including climate and human activity and their impact on groundwater were systematically analyzed. The results show that groundwater level in Jinghuiqu irrigation district has been significantly dropped in nearly 34 years;the reduction of surface water irrigation use, which reduced the amounts of groundwater recharge and destroyed the water balance, is considered as the most direct cause for falling of regional groundwater level. Besides, reduction in precipitation, increase of evaporation also accelerated the declining of the groundwater level at some extent. Finally, a predicting method of groundwater depth based on BP neural network is developed. The experimental results show that the predicting model can reasonablely predict the groundwater level in Jinghuiqu irrigation district with a high precision.

Assessment of prediction performances of stochastic models:Monthly groundwater level prediction in Southern Italy

Stochastic modelling of hydrological time series with insufficient length and data gaps is a serious challenge since these problems significantly affect the reliability of statistical models predicting and forecasting skills.In this paper,we proposed a method for searching the seasonal autoregressive integrated moving average(SARIMA)model parameters to predict the behavior of groundwater time series affected by the issues mentioned.Based on the analysis of statistical indices,8 stations among 44 available within the Campania region(Italy)have been selected as the highest quality measurements.Different SARIMA models,with different autoregressive,moving average and differentiation orders had been used.By reviewing the criteria used to determine the consistency and goodness-of-fit of the model,it is revealed that the model with specific combination of parameters,SARIMA(0,1,3)(0,1,2)_(12),has a high R^(2) value,larger than 92%,for each of the 8 selected stations.The same model has also good performances for what concern the forecasting skills,with an average NSE of about 96%.Therefore,this study has the potential to provide a new horizon for the simulation and reconstruction of groundwater time series within the investigated area.

Inclusive Multiple Models(IMM)for predicting groundwater levels and treating heterogeneity

An explicit model management framework is introduced for predictive Groundwater Levels(GWL),particularly suitable to Observation Wells(OWs)with sparse and possibly heterogeneous data.The framework implements Multiple Models(MM)under the architecture of organising them at levels,as follows:(i)Level 0:treat heterogeneity in the data,e.g.Self-Organised Mapping(SOM)to classify the OWs;and decide on model structure,e.g.formulate a grey box model to predict GWLs.(ii)Level 1:construct MMs,e.g.two Fuzzy Logic(FL)and one Neurofuzzy(NF)models.(iii)Level 2:formulate strategies to combine the MM at Level 1,for which the paper uses Artificial Neural Networks(Strategy 1)and simple averaging(Strategy 2).Whilst the above model management strategy is novel,a critical view is presented,according to which modelling practices are:Inclusive Multiple Modelling(IMM)practices contrasted with existing practices,branded by the paper as Exclusionary Multiple Modelling(EMM).Scientific thinking over IMMs is captured as a framework with four dimensions:Model Reuse(MR),Hierarchical Recursion(HR),Elastic Learning Environment(ELE)and Goal Orientation(GO)and these together make the acronym of RHEO.Therefore,IMM-RHEO is piloted in the aquifer of Tabriz Plain with sparse and possibly heterogeneous data.The results provide some evidence that(i)IMM at two levels improves on the accuracy of individual models;and(ii)model combinations in IMM practices bring‘model-learning’into fashion for learning with the goal to explain baseline conditions and impacts of subsequent management changes.

Effect of Sea Level Rise and Groundwater Withdrawal on Seawater Intrusion in the Gulf Coast Aquifer: Implications for Agriculture

The two main factors contributing to depletion of freshwater resources are climate change and anthropological variables. This study presents statistical analyses that are local in its specifics yet global in its relevance. The decline in Gulf Coast aquifer water quality and quantity has been alarming especially with the increased demand on fresh water in neighboring non-coastal communities. This study used seawater levels, groundwater use, and well data to investigate the association of these factors on the salinity of water indicated by chloride levels. Statistical analyses were conducted pointing to the high significance of both sea water level and groundwater withdrawals to chloride concentrations. However, groundwater withdrawal had higher significance which points to the need of water management systems in order to limit groundwater use. The findings also point to the great impact of increased groundwater salinity in the Gulf Coast aquifer on agriculture and socioeconomic status of coastal communities. The high costs of desalinization point to the increased signification of water rerouting and groundwater management systems. Further investigation and actions are in dire need to manage these vulnerabilities of the coastal communities.

NARX neural network approach for the monthly prediction of groundwater levels in Sylhet Sadar, Bangladesh

Groundwater is important for managing the water supply in agricultural countries like Bangladesh. Therefore, the ability to predict the changes of groundwater level is necessary for jointly planning the uses of groundwater resources. In this study, a new nonlinear autoregressive with exogenous inputs(NARX) network has been applied to simulate monthly groundwater levels in a well of Sylhet Sadar at a local scale. The Levenberg-Marquardt(LM) and Bayesian Regularization(BR) algorithms were used to train the NARX network, and the results were compared to determine the best architecture for predicting monthly groundwater levels over time. The comparison between LM and BR showed that NARX-BR has advantages over predicting monthly levels based on the Mean Squared Error(MSE), coefficient of determination(R^2), and Nash-Sutcliffe coefficient of efficiency(NSE). The results show that BR is the most accurate method for predicting groundwater levels with an error of ± 0.35 m. This method is applied to the management of irrigation water source, which provides important information for the prediction of local groundwater fluctuation at local level during a short period.

Land subsidence induced by groundwater extraction and building damage level assessment—a case study of Datun, China

As in many parts of the world, long-term excessive extraction of groundwater has caused significant land-surface sub- sidence in the residential areas of Datun coal mining district in East China. The recorded maximum level of subsidence in the area since 1976 to 2006 is 863 mm, and the area with an accumulative subsidence more than 200 mm has reached 33.1 km2 by the end of 2006. Over ten cases of building crack due to ground subsidence have already been observed. Spatial variation in ground subsi- dence often leads to a corresponding pattern of ground deformation. Buildings and underground infrastructures have been under a higher risk of damage in locations with greater differential ground deformation. Governmental guideline in China classifies build- ing damages into four different levels, based on the observable measures such as the width of wall crack, the degree of door and window deformation, the degree of wall inclination and the degree of structural destruction. Building damage level (BDL) is esti- mated by means of ground deformation analysis in terms of variations in slope gradient and curvature. Ground deformation analysis in terms of variations in slope gradient has shown that the areas of BDL III and BDL II sites account for about 0.013 km2 and 0.284 km2 respectively in 2006, and the predicted areas of BDL (define this first) III and II sites will be about 0.029 km2 and 0.423 km2 respectively by 2010. The situation is getting worse as subsidence continues. That calls for effective strategies for subsidence miti- gation and damage reduction, in terms of sustainable groundwater extraction, enhanced monitoring and the establishment of early warning systems.

MAR Technique to Reverse the Declining Trend of Groundwater Level in Barind Area, NW, Bangladesh

The study was carried out in the drought prone water stressed Barind area to know the state of rainfall, trend of groundwater level and groundwater management options including Managed Aquifer Recharge (MAR) techniques. Rainfall and groundwater level data have been used and shown a decreasing trend in Godagari and Mohonpur Upazila. But in Niamatpur Upazila rainfall is in reverse condition of rising trend. Decreasing trend of groundwater level (GWL) has been found in the entire study area. The decreasing trend of GWL demands judicious management of groundwater for the area. For recovery of GWL as well as groundwater management, a recharge well as MAR structure has been installed and observed that the situation is better than the before and increasing GWL. More research and study are necessary to know about the trend of groundwater level for the whole Barind area and to introduce proper designed and modified MAR techniques to reverse the declining situation of GWL.

Co-seismic groundwater-level and temperature changes of the 2011 Mw9. 0 Japan earthquake in Chinese mainland

Co-seismic groundwater-level and temperature changes caused by the Mw9. 0 Japan earthquake in Chinese mainland are described. The recorded water-level changes were mostly oscillations, with some step decreases mostly in the coastal area of Southeast China and step increases mostly in Northeast China and the North-South Seismic Belt. The water-temperature changes were mainly decrease with slow recovery in Sichuan- Yunnan, South China, and lower reaches of Jiangzhong, and sharp increase followed by sharp decrease, or vice versa, in North China and Northeast China. For wells that showed step changes in both water level and temperature, more showed them in the same direction than in the opposite direction.