scholarly journals Regression Analysis and Risk Assessment of Groundwater Levels

Proceedings ◽  
2018 ◽  
Vol 2 (11) ◽  
pp. 641
Author(s):  
Panagiota Theodoridou ◽  
Emmanouil Varouchakis ◽  
George Karatzas
Keyword(s):  
Groundwater Level ◽  
Research Work ◽  
Ground Surface ◽  
Threshold Value ◽  
Auxiliary Variable ◽  
Indicator Kriging ◽  
Trend Function ◽  
Groundwater Levels ◽  
Trend Model ◽  
Residual Kriging

The present research work uses Residual Kriging to estimate the groundwater level of an unconfined alluvial aquifer, as well as the trend function. The ground surface elevation is used as auxiliary variable in the trend model. Indicator Kriging is applied to detect potential vulnerable locations. Classical variogram functions are applied to determine the spatial correlation of the measurements. The risk of hydraulic head to lie below a threshold value is significant, mainly at the South and North parts of the aquifer, where the lower values of groundwater level are estimated, indicating that these areas require intense monitoring to ensure the water resources availability.

Detecting land deformation due to groundwater changes with InSAR observations - the case of the island of Gotland, Sweden

2021 ◽  
Author(s):  
Mehdi Darvishi ◽  
Fernando Jaramillo
Keyword(s):  
Land Subsidence ◽  
Groundwater Level ◽  
Ground Deformation ◽  
Soil Depth ◽  
Ground Surface ◽  
Groundwater Depletion ◽  
Groundwater Levels ◽  
Small Baseline Subset ◽  
Small Baseline ◽  
The Baltic

<p>In the recent years, southern Sweden has experienced drought conditions during the summer with potential risks of groundwater shortages. One of the main physical effects of groundwater depletion is land subsidence, a geohazard that potentially damages urban infrastructure, natural resources and can generate casualties. We here investigate land subsidence induced by groundwater depletion and/or seasonal variations in Gotland, an agricultural island in the Baltic Sea experiencing recent hydrological droughts in the summer. Taking advantage of the multiple monitoring groundwater wells active on the island, we explore the existence of a relationship between groundwater fluctuations and ground deformation, as obtained from Interferometric Synthetic Aperture Radar (InSAR). The aim in the long-term is to develop a high-accuracy map of land subsidence with an appropriate temporal and spatial resolution to understand groundwater changes in the area are recognize hydroclimatic and anthropogenic drivers of change.</p><p>We processed Sentinel-1 (S1) data, covering the time span of 2016-2019, by using the Small BAseline Subset (SBAS) to process 119 S1-A/B data (descending mode). The groundwater level of Nineteen wells distributed over the Gotland island were used to assess the relationship between groundwater depletion and the detected InSAR displacement. In addition to that, the roles of other geological key factors such as soil depth, ground capacity in bed rock, karstification, structure of bedrock and soil type in occurring land subsidence also investigated. The findings showed that the groundwater level in thirteen wells with soil depths of less than 5 meters correlated well with InSAR displacements. The closeness of bedrock to ground surface (small soil depth) was responsible for high coherence values near the wells, and enabled the detection land subsidence. The results demonstrated that InSAR could use as an effective monitoring system for groundwater management and can assist in predicting or estimating low groundwater levels during summer conditions.</p>

Transpiration of Acacia plantation under managed tropical peatland in Riau, Sumatra

2021 ◽  
Author(s):  
Yogi Suardiwerianto ◽  
Sofyan Kurnianto ◽  
Adibtya Asyhari ◽  
Tubagus Muhamad Risky ◽  
Muhammad Fikky Hidayat ◽  
...  
Keyword(s):  
Transpiration Rate ◽  
Groundwater Level ◽  
Large Scale ◽  
Hydrological Modeling ◽  
Ground Surface ◽  
Terrestrial Ecosystems ◽  
Ratio Method ◽  
Flow Measurements ◽  
Groundwater Levels ◽  
Relative Contribution

<p>Transpiration is a key process in the terrestrial ecosystems linking water, carbon, and energy exchanges between the vegetation and the atmosphere. However, the understanding of transpiration rate, its spatiotemporal dynamics, and the controlling factors in tropical peatlands are still constrained by limited measurements. This study aims to investigate the transpiration rates at the stand level of Acacia plantation under different groundwater levels. The measurements were performed at two large-scale lysimeter plots with groundwater level of 40 and 80 cm below the ground surface. The transpiration rate was quantified based on sap flow measurements from 16 trees with different diameters at breast height using heat ratio method. The initial results indicate that the transpiration rate was closely correlated to the meteorological parameters, including atmospheric vapor pressure deficit and solar radiation. The two plots with different groundwater level regimes exhibit the same diurnal pattern of transpiration rate yet shows differences in their magnitude. The findings from this study will improve the understanding about relative contribution of transpiration to the total water balance under different groundwater levels. Further, an ongoing measurement of above and below-ground biomass growth and hydrological modeling work will advance the knowledge on plant-water interaction from this ecosystem.</p>

A new deterministic method for groundwater mapping using a digital elevation model

2013 ◽  
Vol 13 (4) ◽  
pp. 1146-1153 ◽  
Author(s):  
Tamás Ács ◽  
Zoltán Simonffy
Keyword(s):  
Digital Elevation Model ◽  
Groundwater Level ◽  
Ground Surface ◽  
Terrestrial Ecosystems ◽  
Groundwater Depth ◽  
Deterministic Method ◽  
Groundwater Levels ◽  
Geostatistical Methods ◽  
Digital Elevation ◽  
Elevation Model

Accurate knowledge of groundwater levels and flow conditions in the vicinity of groundwater-dependent terrestrial ecosystems (GWDTE-s) is required for identifying groundwater dependency and comparing the present situation with the optimal one, as part of the status assessment of groundwaters according to the EU Water Framework Directive. Geostatistical methods (like kriging or cokriging) may result in an unrealistic groundwater level map if only a few measured data are available. In this paper a new, grid-based, deterministic method (GSGW-model) is introduced. The aim of the model is to calculate groundwater depth within the required accuracy from sparse data of monitoring wells. The basic principle of the GSGW-model is that the groundwater table is a smoothed replica of the ground surface. Hence, changes in the groundwater level between two grid points are calculated as a function of the digital elevation model (DEM) and soil properties. The GSGW-model was tested in the Nyírség region (Hungary). Results were compared with those gained by ordinary kriging and cokriging. It has been concluded that kriging overestimates the groundwater level in the low part of the test area, where wetlands are located, while the maps produced by the GSGW-model are a better fit of the real variability, providing more reliable estimates of groundwater depth in GWDTE-s as well.

scholarly journals Measuring the unseen: mobilizing citizen scientists to monitor groundwater in Nepal

2021 ◽  
Vol 193 (9) ◽  
Author(s):  
Rajaram Prajapati ◽  
Rocky Talchabhadel ◽  
Bhesh Raj Thapa ◽  
Surabhi Upadhyay ◽  
Amber Bahadur Thapa ◽  
...  
Keyword(s):  
Groundwater Level ◽  
Groundwater Monitoring ◽  
Monsoon Season ◽  
Land Use Changes ◽  
Ground Surface ◽  
Shallow Groundwater ◽  
Monitoring Network ◽  
Essential Information ◽  
Groundwater Levels ◽  
Personal Connections

AbstractGroundwater-level monitoring provides crucial information on the nature and status of aquifers and their response to stressors like climate change, groundwater extraction, and land use changes. Therefore, the development of a spatially distributed long-term monitoring network is indispensable for sustainable groundwater resource management. Despite being one of our greatest unseen resources, groundwater systems are too often poorly understood, ineffectively managed, and unsustainably used. This study investigates the feasibility of establishing a groundwater monitoring network mobilizing citizen scientists. We established a network of 45 shallow monitoring wells in the Kathmandu Valley using existing wells. We recruited 75% of the citizen scientists through personal connections and the rest through outreach programs at academic institutes and site visits. We used various methods to encourage citizen scientists to complete regular measurements and solicited feedback from them based on their experiences. Citizen scientists were more consistent during the monsoon season (June through September) than non-monsoon seasons. The depth-to-water below the ground surface varied from − 0.11 m (negative sign represents a groundwater level higher than the ground surface) to 11.5 m, with a mean of 4.07 m and standard deviation of 2.63 m. Groundwater levels began to rise abruptly with the onset of monsoon season and the shallowest and the deepest groundwater levels were recorded in peak rainfall months and dry months respectively. Citizen science-based groundwater monitoring using existing wells would be an economic and sustainable approach for groundwater monitoring. Improved groundwater-level data will provide essential information for understanding the shallow groundwater system of the valley, which will assist concerned authorities in planning and formulating evidence-based policy on sustainable groundwater management.

The Identification of Hydrological Threshold Variables

2020 ◽  
Author(s):  
Arturs Veinbergs ◽  
Ainis Lagzdins
Keyword(s):  
Groundwater Level ◽  
Ground Surface ◽  
Base Flow ◽  
Specific Yield ◽  
Groundwater Levels ◽  
Groundwater Level Fluctuations ◽  
Below Ground ◽  
Runoff Hydrographs ◽  
Basin Area ◽  
Runoff Component

<p>The threshold groundwater levels limiting the drainage depth and tile drain runoff as well as runoff recession and runoff partitioning are case-specific.  These are the characteristics that are usually necessary for setting up and calibration processes for such models as HYPE (Lindström et al. 2010) and SWAT (Neitsch et al. 2002).  </p><p>The objective of the present study is to identify the thresholds of groundwater levels and runoff rates that limit the formations of such runoff components as base flow and tile drain runoff. This study utilizes the data that represents the daily runoff measurements in open ditch with such characteristics as total length 2.4 km, basin area 368 ha, loamy soils, agricultural lands with subsurface drainage systems installed in 98% of the area, average tile depth 1.2m below ground surface.</p><p>The runoff components were partly separated from the daily runoff hydrographs through the analysis of storm runoff recession gradients (eq.1) and groundwater level fluctuations during the period from 2006. to 2015. Baseflow and tile drain runoff ware calculated as beeing linearly dependent on daily groundwater level fluctuations (eq.2).</p><p>  R<sub>ci</sub>=Q<sub>i+1</sub>/Q<sub>i</sub>,     (1)</p><p>Q<sub>x</sub>=f<sub>x</sub>(GWT)=a<sub>x</sub>*GWT+b<sub>x</sub> ,      (2)</p><p>Where: R<sub>ci</sub> – recession gradient; Q<sub>i </sub>and Q<sub>i+1</sub>– runoff of day i and i+1 respectively;  Q<sub>x</sub> – runoff component; GWT– groundwater level; a<sub>x </sub>and b<sub>x</sub>– slope and intercept of a linear function.</p><p>Nash-Sutcliffe efficiency (NSE) and percent bias (PBIAS) were used for comparison of calculated and separated runoff components.</p><p>The results indicate a decrease in drainage intensity and reduction in specific yield during the study period. The groundwater level of 1.18m below ground surface limit the existence of the tile drain runoff, that, furthermore,  is similar for rising and falling groundwater level. The results reveal that runoff could be contributed by 35%, 57% and 8% of baseflow, tile drain runoff and surface runoff respectively.</p>

scholarly journals CROSS-SPECTRUM ANALYSIS OF GROUNDWATER LEVELS IN AN ESKER

1970 ◽  
Vol 1 (4) ◽  
pp. 245-259 ◽  
Author(s):  
ERIK ERIKSSON
Keyword(s):  
Phase Shift ◽  
Water Level ◽  
River Water ◽  
Spectrum Analysis ◽  
Groundwater Level ◽  
Ground Surface ◽  
Groundwater Levels ◽  
Cross Spectrum ◽  
Water Stage ◽  
Surface And Groundwater

A study is made on 30-year records of precipitation, river water stage, and groundwater levels in the esker area south of Uppsala, Sweden, using cross-spectrum analysis. The results are summarized as coherence graphs for frequencies up to 18 cycles/year and tables of phase shifts for selected frequencies. The coherence between precipitation and the other variables is extremely weak or absent. The river water level and groundwater levels show appreciable coherence relatively independent of frequency, suggesting that variation in groundwater levels runs parallel to variations in river water stage. The coherence between groundwater levels, however, is such that interaction is suggested. The phase shift between river water level and groundwater level is approximately 10–30 days with the groundwater levels lagging. The magnitude of phase shift seems to depend on the distance between ground surface and groundwater level.

scholarly journals Investigating Groundwater Condition and Seawater Intrusion Status in Coastal Aquifer Systems of Eastern India

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1952
Author(s):  
Subrata Halder ◽  
Lingaraj Dhal ◽  
Madan K. Jha
Keyword(s):  
Groundwater Quality ◽  
Seawater Intrusion ◽  
Groundwater Level ◽  
Coastal Aquifer ◽  
Quality Data ◽  
Confined Aquifer ◽  
Groundwater Levels ◽  
Post Monsoon ◽  
Aquifer Systems ◽  
Sustainable Water Supply

Providing sustainable water supply for domestic needs and irrigated agriculture is one of the most significant challenges for the current century. This challenge is more daunting in coastal regions. Groundwater plays a pivotal role in addressing this challenge and hence, it is under growing stress in several parts of the world. To address this challenge, a proper understanding of groundwater characteristics in an area is essential. In this study, spatio-temporal analyses of pre-monsoon and post-monsoon groundwater-levels of two coastal aquifer systems (upper leaky confined and underlying confined) were carried out in Purba Medinipur District, West Bengal, India. Trend analysis of seasonal groundwater-levels of the two aquifers systems was also performed using Mann-Kendall test, Linear Regression test, and Innovative Trend test. Finally, the status of seawater intrusion in the two aquifers was evaluated using available groundwater-quality data of Chloride (Cl−) and Total Dissolve Solids (TDS). Considerable spatial and temporal variability was found in the seasonal groundwater-levels of the two aquifers. Further, decreasing trends were spotted in the pre-monsoon and post-monsoon groundwater-level time series of the leaky confined and confined aquifers, except pre-monsoon groundwater-levels in Contai-I and Deshpran blocks, and the post-monsoon groundwater-level in Ramnagar-I block for the leaky confined aquifer. The leaky confined aquifer in Contai-I, Contai-III, and Deshpran blocks and the confined aquifer in Nandigram-I and Nandigram-II blocks are vulnerable to seawater intrusion. There is an urgent need for the real-time monitoring of groundwater-levels and groundwater quality in both the aquifer systems, which can ensure efficient management of coastal groundwater reserves.

scholarly journals Evaluation of Seasonal Groundwater Quality Changes Associated with Groundwater Pumping and Level Fluctuations in an Agricultural Area, Korea

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 51
Author(s):  
Kyoochul Ha ◽  
Eunhee Lee ◽  
Hyowon An ◽  
Sunghyun Kim ◽  
Changhui Park ◽  
...  
Keyword(s):  
Water Quality ◽  
Groundwater Quality ◽  
Groundwater Level ◽  
Irrigation Water ◽  
Agricultural Area ◽  
Water Type ◽  
Quality Changes ◽  
Groundwater Pumping ◽  
Rice Paddies ◽  
Groundwater Levels

This study was conducted to evaluate seasonal groundwater quality due to groundwater pumping and hydrochemical characteristics with groundwater level fluctuations in an agricultural area in Korea. Groundwater levels were observed for about one year using automatic monitoring sensors, and groundwater uses were estimated based on the monitoring data. Groundwater use in the area is closely related to irrigation for rice farming, and rising groundwater levels occur during the pumping, which may be caused by the irrigation water of rice paddies. Hydrochemical analysis results for two separate times (17 July and 1 October 2019) show that the dissolved components in groundwater decreased overall due to dilution, especially at wells in the alluvial aquifer and shallow depth. More than 50% of the samples were classified as CaHCO3 water type, and changes in water type occurred depending on the well location. Water quality changes were small at most wells, but changes at some wells were evident. In addition, the groundwater quality was confirmed to have the effect of saltwater supplied during the 2018 drought by comparison with seawater. According to principal component analysis (PCA), the water quality from July to October was confirmed to have changed due to dilution, and the effect was strong at shallow wells. In the study areas where rice paddy farming is active in summer, irrigation water may be one of the important factors changing the groundwater quality. These results provide a qualitative and quantitative basis for groundwater quality change in agricultural areas, particularly rice paddies areas, along with groundwater level and usage.

scholarly journals Seismically induced changes in groundwater levels and temperatures following the ML5.8 (ML5.1) Gyeongju earthquake in South Korea

2021 ◽  
Author(s):  
Soo-Hyoung Lee ◽  
Jae Min Lee ◽  
Sang-Ho Moon ◽  
Kyoochul Ha ◽  
Yongcheol Kim ◽  
...  
Keyword(s):  
South Korea ◽  
Groundwater Level ◽  
Seismic Waves ◽  
Groundwater Resources ◽  
Fluid Pressure ◽  
Water Levels ◽  
Aquifer System ◽  
Groundwater Levels ◽  
Monitoring Wells ◽  
Gyeongju Earthquake

AbstractHydrogeological responses to earthquakes such as changes in groundwater level, temperature, and chemistry, have been observed for several decades. This study examines behavior associated with ML 5.8 and ML 5.1 earthquakes that occurred on 12 September 2016 near Gyeongju, a city located on the southeast coast of the Korean peninsula. The ML 5.8 event stands as the largest recorded earthquake in South Korea since the advent of modern recording systems. There was considerable damage associated with the earthquakes and many aftershocks. Records from monitoring wells located about 135 km west of the epicenter displayed various patterns of change in both water level and temperature. There were transient-type, step-like-type (up and down), and persistent-type (rise and fall) changes in water levels. The water temperature changes were of transient, shift-change, and tendency-change types. Transient changes in the groundwater level and temperature were particularly well developed in monitoring wells installed along a major boundary fault that bisected the study area. These changes were interpreted as representing an aquifer system deformed by seismic waves. The various patterns in groundwater level and temperature, therefore, suggested that seismic waves impacted the fractured units through the reactivation of fractures, joints, and microcracks, which resulted from a pulse in fluid pressure. This study points to the value of long-term monitoring efforts, which in this case were able to provide detailed information needed to manage the groundwater resources in areas potentially affected by further earthquakes.

scholarly journals Hydraulic Tomography for Estimating the Diffusivity of Heterogeneous Aquifers Based on Groundwater Response to Tidal Fluctuation in an Artificial Island in Taiwan

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Jet-Chau Wen ◽  
Hong-Ru Lin ◽  
Tian-Chyi Jim Yeh ◽  
Yu-Li Wang ◽  
Keng-Li Lin ◽  
...  
Keyword(s):  
Groundwater Level ◽  
Hydraulic Properties ◽  
Tidal Fluctuation ◽  
Heterogeneous Aquifers ◽  
Hydraulic Diffusivity ◽  
The Real ◽  
Groundwater Levels ◽  
Hydraulic Tomography ◽  
Groundwater Response ◽  
Spectrum Ratio

This study investigated the hydraulic properties of the heterogeneous aquifers of an artificial island (Yunlin Offshore Industrial Park) in Taiwan. The research was based on the groundwater level response affected by tidal fluctuation using the hydraulic tomography (HT) to analyze the hydraulic diffusivity (α). Specifically, the power spectrum ratio of groundwater and tidal fluctuations derived from the Gelhar solution was used to estimate α in homogeneous aquifers; this, however, could not be applied in the artificial island. Next, the spatial distribution of the groundwater level response affected by tidal fluctuation was analyzed and found to be irregular, proving the existence of hydrogeological heterogeneity in the artificial island. Furthermore, the results of the estimated α using the HT showed low error and high correlation, 0.41 m2/hr and 0.83, respectively, between the optimal estimated heterogeneous and reference α fields in the synthetic aquifer. Last, the HT was used in the real tested scenario. By comparing the predicted groundwater levels of the optimal estimated heterogeneous α field and the observed groundwater levels of the real aquifer, it was found that the correlation was higher than 0.99. Therefore, the HT can be used to obtain the optimal estimated heterogeneous α field in the artificial island.

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