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.

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>

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.

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 Characterising hillslope–stream connectivity with a joint event analysis of stream and groundwater levels

2020 ◽  
Vol 24 (12) ◽  
pp. 5713-5744
Author(s):  
Daniel Beiter ◽  
Markus Weiler ◽  
Theresa Blume
Keyword(s):  
Time Series ◽  
Water Level ◽  
Groundwater Level ◽  
Stream Water ◽  
Water Levels ◽  
Joint Analysis ◽  
Strong Increase ◽  
Groundwater Levels ◽  
The Relationship ◽  
Insight Into

Abstract. Hillslope–stream connectivity controls runoff generation, during events and during baseflow conditions. However, assessing subsurface connectivity is a challenging task, as it occurs in the hidden subsurface domain where water flow can not be easily observed. We therefore investigated if the results of a joint analysis of rainfall event responses of near-stream groundwater levels and stream water levels could serve as a viable proxy for hillslope–stream connectivity. The analysis focuses on the extent of response, correlations, lag times and synchronicity. As a first step, a new data analysis scheme was developed, separating the aspects of (a) response timing and (b) extent of water level change. This provides new perspectives on the relationship between groundwater and stream responses. In a second step we investigated if this analysis can give an indication of hillslope–stream connectivity at the catchment scale. Stream water levels and groundwater levels were measured at five different hillslopes over 5 to 6 years. Using a new detection algorithm, we extracted 706 rainfall response events for subsequent analysis. Carrying out this analysis in two different geological regions (schist and marls) allowed us to test the usefulness of the proxy under different hydrological settings while also providing insight into the geologically driven differences in response behaviour. For rainfall events with low initial groundwater level, groundwater level responses often lag behind the stream with respect to the start of rise and the time of peak. This lag disappears at high antecedent groundwater levels. At low groundwater levels the relationship between groundwater and stream water level responses to rainfall are highly variable, while at high groundwater levels, above a certain threshold, this relationship tends to become more uniform. The same threshold was able to predict increased likelihood for high runoff coefficients, indicating a strong increase in connectivity once the groundwater level threshold was surpassed. The joint analysis of shallow near-stream groundwater and stream water levels provided information on the presence or absence and to a certain extent also on the degree of subsurface hillslope–stream connectivity. The underlying threshold processes were interpreted as transmissivity feedback in the marls and fill-and-spill in the schist. The value of these measurements is high; however, time series of several years and a large number of events are necessary to produce representative results. We also find that locally measured thresholds in groundwater levels can provide insight into the connectivity and event response of the corresponding headwater catchments. If the location of the well is chosen wisely, a single time series of shallow groundwater can indicate if the catchment is in a state of high or low connectivity.

scholarly journals Study on compaction mechanism of overconsolidated soil and critical groundwater level in Cangzhou

2019 ◽  
Vol 79 ◽  
pp. 02010
Author(s):  
Yunlong Wang ◽  
Ye Chen ◽  
Haipeng Guo ◽  
Xisheng Zang
Keyword(s):  
Stress Analysis ◽  
Water Level ◽  
Water Resource ◽  
Land Subsidence ◽  
Groundwater Level ◽  
Groundwater Exploitation ◽  
Groundwater Levels ◽  
Good Consistency ◽  
Long Time ◽  
Groundwater Overexploitation

Cangzhou area is facing increasingly serious land subsidence problem caused by groundwater overexploitation during a long time. In order to make effectively use of water resource and to limit the development of subsidence, it is necessary to establish the warning critical water level, that is, the subsidence rate will increase significantly as the water level depths exceeds the critical groundwater levels. In this paper, the 3rd aquifer group, the main groundwater exploitation layer, has been taken as a research object. The critical water level is calculated by stress analysis, and then determined by the correlation between the monitoring data of groundwater levels and subsidence. The calculated results indicate good consistency.

scholarly journals Characterizing hillslope-stream connectivity with a joint event analysis of stream and groundwater levels

2020 ◽  
Author(s):  
Daniel Beiter ◽  
Markus Weiler ◽  
Theresa Blume
Keyword(s):  
Time Series ◽  
Water Level ◽  
Groundwater Level ◽  
Stream Water ◽  
Water Levels ◽  
Joint Analysis ◽  
Catchment Scale ◽  
Groundwater Levels ◽  
The Relationship ◽  
Insight Into

Abstract. Hillslope-stream connectivity controls runoff generation, both during events and baseflow conditions. However, assessing subsurface connectivity is a challenging task, as it occurs in the hidden subsurface domain where water flow cannot be easily observed. We therefore investigated if the results of a joint analysis of rainfall event responses of near-stream groundwater levels and stream water levels could serve as a viable proxy for hillslope-stream connectivity. The analysis focuses on the extent of response, correlations, lag times and synchronicity. A newly developed data analysis scheme of separating the aspects of (a) response timing and (b) extent of water level change provides new perspectives on the relationship between groundwater and stream responses. In a second step we investigated if this analysis can give an indication of hillslope-stream connectivity at the catchment scale. Stream- and groundwater levels were measured at five different hillslopes over 5 to 6 years. Using a new detection algorithm we extracted 706 rainfall response events for subsequent analysis. Carrying out this analysis in two different geological regions (schist and marls) allowed us to test the usefulness of the proxy under different hydrological settings while also providing insight into the geologically-driven differences in response behaviour. For rainfall events with low initial groundwater level, groundwater level responses often lag behind the stream with respect to the start of rise and the time of peak. This lag disappears at high antecedent groundwater levels. At low groundwater levels the relationship between groundwater and stream water level responses to rainfall are highly variable, while at high groundwater levels, above a certain threshold, this relationship tends to become more uniform. The same threshold was able to predict increased likelihood for high runoff coefficients, indicating a strong increase in connectivity once the groundwater level threshold was surpassed. The joint analysis of shallow near-stream groundwater and stream water levels provided information on the presence or absence and to a certain extent also on the degree of subsurface hillslope-stream connectivity. The underlying threshold processes were interpreted as transmissivity feedback in the marls and fill-and-spill in the schist. The value of these measurements is high, however, time series of several years and a large number of events are necessary to produce representative results. We also find that locally measured thresholds in groundwater levels can provide insight into catchment-scale connectivity and event response. If the location of the well is chosen wisely, a single time series of shallow groundwater can indicate if the catchment is in a state of high or low connectivity.

scholarly journals Analysis of groundwater levels in piezometers in the Vipava Valley

2020 ◽  
pp. 61-78
Author(s):  
Mateja Jelovčan ◽  
Mojca Šraj
Keyword(s):  
Surface Water ◽  
Water Level ◽  
Groundwater Level ◽  
Tectonic Structure ◽  
Unique Region ◽  
Groundwater Levels ◽  
Groundwater Level Fluctuations ◽  
The Third ◽  
Autumn And Winter ◽  
The Impact

The Vipava Valley is a unique region in south-western Slovenia. In addition to surface water, groundwater is also important, although it is hidden from the eye. The paper presents an analysis of groundwater levels in piezometers in the Vipava Valley. The analysis was performed on 10 piezometers, which are still operating today, and includes a display of levels and basic statistics, correlations, the impact of distance from the Vipava riverbed, trends, and seasonality. According to the groundwater level, piezometers in the Vipava Valley can be divided into three groups. The first group with the highest levels includes piezometers Gradišče, Vipavski Križ, and Ajdovščina, the second group piezometers Prvačina, Šempeter, Volčja Draga, Renče, and Vrtojba, and the third group with the lowest groundwater levels includes the piezometers Miren and Orehovlje. The results of the analyses showed good or bad connections between groundwater levels in piezometers, as well as between groundwater levels and the Vipava River water level at various gauging stations. The fluctuation of the groundwater level is conditioned by the distance from the Vipava riverbed and the area’s geological or tectonic structure. An unambiguous trend of groundwater levels cannot be determined. The seasonality of groundwater level fluctuations is not pronounced, but the highest values of groundwater levels occur in autumn and winter, and the lowest in summer.

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.

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