scholarly journals Estimating specific yield and storage change in an unconfined aquifer using temporal gravity surveys

2009 ◽  
Vol 45 (4) ◽  
Author(s):  
Carter L. Gehman ◽  
Dennis L. Harry ◽  
William E. Sanford ◽  
John D. Stednick ◽  
Nathaniel A. Beckman
Keyword(s):  
Unconfined Aquifer ◽  
Specific Yield ◽  
And Storage ◽  
Temporal Gravity ◽  
Storage Change

Gravimetric Determination of Storage Coefficient and Storage Change of Groundwater in an Uncontrolled and Unconfined Aquifer

2021 ◽  
Author(s):  
Rosa Isabel Hernández-Sánchez ◽  
Francisco Castellanos ◽  
Jaime Herrera-Barrientos ◽  
Salvador Isidro Belmonte-Jiménez
Keyword(s):  
Unconfined Aquifer ◽  
Storage Coefficient ◽  
Gravimetric Determination ◽  
And Storage ◽  
Storage Change

Using groundwater levels and Specific Yield to Estimate the Recharge, South of Erbil, Kurdistan Region, Iraq

2018 ◽  
Vol 7 (4) ◽  
pp. 191
Author(s):  
Sherwan Sh. Qurtas
Keyword(s):  
Unconfined Aquifer ◽  
Middle Part ◽  
Water Levels ◽  
Specific Yield ◽  
Aquifer System ◽  
Groundwater Levels ◽  
Monitoring Wells ◽  
Water Table Fluctuation Method ◽  
Recharge Estimation ◽  
Fluctuation Method

Recharge estimation accurately is crucial to proper groundwater resource management, for the groundwater is dynamic and replenished natural resource. Usually recharge estimation depends on the; the water balance, water levels, and precipitation. This paper is studying the south-middle part of Erbil basin, with the majority of Quaternary sediments, the unconfined aquifer system is dominant, and the unsaturated zone is ranging from 15 to 50 meters, which groundwater levels response is moderate. The purpose of this study is quantification the natural recharge from precipitation. The water table fluctuation method is applied; using groundwater levels data of selected monitoring wells, neighboring meteorological station of the wells, and the specific yield of the aquifers. This method is widely used for its simplicity, scientific, realistic, and direct measurement. The accuracy depends on the how much the determination of specific yield is accurate, accuracy of the data, and the extrapolations of recession of groundwater levels curves of no rain periods. The normal annual precipitation there is 420 mm, the average recharge is 89 mm, and the average specific yield is around 0.03. The data of one water year of 2009 and 2010 has taken for some technical and accuracy reasons.

scholarly journals Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

2016 ◽  
Vol 20 (1) ◽  
pp. 55-71 ◽  
Author(s):  
C.-S. Huang ◽  
J.-J. Chen ◽  
H.-D. Yeh
Keyword(s):  
Groundwater Flow ◽  
Integral Transform ◽  
Three Dimensional ◽  
Vertical Component ◽  
Hydraulic Head ◽  
Unconfined Aquifer ◽  
Specific Yield ◽  
Specific Storage ◽  
Sink Term ◽  
Radial Collector Well

Abstract. This study develops a three-dimensional (3-D) mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The streams with low-permeability streambeds fully penetrate the aquifer. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. Robin boundary conditions are adopted to describe fluxes across the streambeds. The head solution for the point sink is derived by applying the methods of finite integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length, and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow for the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.

scholarly journals Analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

2015 ◽  
Vol 12 (8) ◽  
pp. 7503-7540 ◽  
Author(s):  
C.-S. Huang ◽  
J.-J. Chen ◽  
H.-D. Yeh
Keyword(s):  
Groundwater Flow ◽  
Integral Transform ◽  
Three Dimensional ◽  
Vertical Component ◽  
Hydraulic Head ◽  
Unconfined Aquifer ◽  
Specific Yield ◽  
Specific Storage ◽  
Sink Term ◽  
Radial Collector Well

Abstract. This study develops a three-dimensional mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. The head solution for the point sink is derived by applying the methods of double-integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.

scholarly journals Sequential hydraulic tests for transient and highly permeable unconfined aquifer systems – model development and field-scale implementation

2015 ◽  
Vol 12 (12) ◽  
pp. 12567-12613 ◽  
Author(s):  
C.-F. Ni ◽  
Y.-J. Huang ◽  
J.-J. Dong ◽  
T.-C. J. Yeh
Keyword(s):  
Boundary Conditions ◽  
Joint Inversion ◽  
Model Development ◽  
Unconfined Aquifer ◽  
Inverse Model ◽  
Hole Injection ◽  
Specific Yield ◽  
Field Scale ◽  
Systems Model ◽  
Aquifer Systems

Abstract. The transient hydraulic tomography survey (THTS) is a conceptually improved technique that efficiently estimates detailed variations in aquifer parameters. Based on the concept of the THTS, we developed a geostatistical inverse model to characterize saturated hydraulic conductivity (K) and the specific yield (Sy) in transient and unconfined aquifer systems. In this study, a synthetic example was first used to assess the accuracy of the developed inverse model. Multiple random K and Sy realizations with different variances of natural logarithm of K (lnK) were generated and systematically compared to evaluate the effects of joint inversion on K estimations. The model was implemented in field-scale, cross-hole injection tests in a shallow and highly permeable unconfined aquifer near the middle reaches of the Wu River in central Taiwan. To assess the effect of constant head boundary conditions on the estimation results, two additional modeling domains were evaluated on the basis of the same field data from the injection tests. The results of the synthetic example showed that the proposed inverse model can effectively reproduce the predefined K patterns and magnitudes. However, slightly less detail was obtained for the Sy field based on the sampling data from sequential transient hydraulic stresses. The joint inversion by using transient head observations could slightly decrease the accuracy of K estimations. The model implementation for field-scale injection tests showed that the model can estimate K and Sy fields with detailed spatial variations. Estimation results showed a relatively homogeneous aquifer for the tested well field. Results based on the three modeling domains showed similar patterns and magnitudes of K and Sy near the well locations. These results indicated that the THTS is relatively insensitive to artificially drawn boundary conditions even under transient conditions.

scholarly journals Evaluating the effect of partial contributing storage on the storage–discharge function from recession analysis

2013 ◽  
Vol 17 (10) ◽  
pp. 4283-4296 ◽  
Author(s):  
X. Chen ◽  
D. Wang
Keyword(s):  
Remote Sensing ◽  
Water Storage ◽  
Hydrologic Connectivity ◽  
Storage Effect ◽  
Streamflow Data ◽  
Recession Analysis ◽  
Daily Evaporation ◽  
And Storage ◽  
Storage Change ◽  
Possible Cause

Abstract. Hydrograph recession during dry periods has been used to construct water storage–discharge relationships and to quantify storage dynamics and evaporation when streamflow data is available. However, variable hydrologic connectivity among hillslope–riparian–stream zones may affect the lumped storage–discharge relationship, and as a result, affect the estimation of evaporation and storage change. Given observations of rainfall and runoff, and remote-sensing-based observations of evaporation, the ratio (α) between estimated daily evaporation from recession analysis and observed evaporation, and the ratio (β) between estimated contributing storage and total watershed storage are computed for 9 watersheds located in different climate regions. Both evaporation and storage change estimation from recession analysis are underestimated due to the effect of partial contributing storage, particularly when the discharge is low. It was found that the values of α decrease significantly during individual recession events, while the values of β are relatively stable during a recession event. The values of β are negatively correlated with the water table depth and vary significantly among recession events. The partial contributing storage effect is one possible cause for the multi-valued storage–discharge relationship.

scholarly journals Groundwater Parameter Inversion Using Topographic Constraints and a Zonal Adaptive Multiscale Procedure: A Case Study of an Alluvial Aquifer

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1899 ◽  
Author(s):  
Dimitri Rambourg ◽  
Philippe Ackerer ◽  
Olivier Bildstein
Keyword(s):  
Parameter Estimation ◽  
Groundwater Flow ◽  
Unconfined Aquifer ◽  
Water Levels ◽  
Specific Yield ◽  
Local Minima ◽  
Diffusion Type ◽  
Aquifer Parameters ◽  
Water Head ◽  
Verification Period

The identification of aquifer parameters (i.e., specific yield and hydraulic conductivity) and forcing terms (recharge) is crucial for the process of modeling groundwater flow and contamination. Inversion techniques allow the unravelling of complex systems’ heterogeneity with more ease than manual calibration by computing parameter fields through an automated minimization between simulated and measured data (i.e., water head or measured aquifer parameters). It also allows the iterative search of multiple, equally plausible solutions, depending on system complexity (e.g., aquifer heterogeneity and variability of the forcing terms such as recharge). A Zoned Adaptive Multiscale Triangulation (ZAMT) is used for parameter estimation. ZAMT is the extension of an adaptive multiscale parameter estimation procedure already applied on different field cases. This extension consists of adding constraints varying over the domain. The ZAMT dissociates the parameter grid from the calculation mesh and allows local parameter grid refinement depending on local criteria, addressing the ill-posedness of inversion problems, decreasing computation time by reducing the amount of possible solutions and local minima, and ensuring flexibility in the parameter’s distribution. Each parameter is defined per vertex of the parameter grid; it can be set with a different range of values in order to integrate more pedo-geological information and help the optimization process by reducing the number of local minima. For the same purpose, a plausibility term based on topological characteristics of the aquifer or minimal and maximal water levels is added to the objective function. Groundwater flow is described by a classical nonlinear diffusion-type equation (unconfined aquifer), which is discretized with a two-dimensional nonconforming finite element method because water head data is unsuitable to invert three-dimensional parameter fields. Therefore, flow is considered mainly horizontal, and the parameters are obtained as average values on the saturated thickness. The study area is an alluvial (unconfined) aquifer of 6.64 km², situated in the southern, Mediterranean part of France. The simulation runs with a chronicle of 191 piezometers over 7 years (2012–2019), using a calibration period of 5 years (2012–2016). The optimization threshold is set to ensure a mean absolute error below 40 cm. The ZAMT and the additional plausibility criterion were found to produce an ensemble of realistic parameter sets with low parameter standard deviation. The model is considered robust as the water head error remains at the same level during the verification period, which includes an exceptionally dry year (2017). Overall, the calibration is best near the rivers (Dirichlet boundaries), while the terraced portion of the site challenges the limits of the 2D approach and the inversion procedure.

scholarly journals High-temporal-resolution water level and storage change data sets for lakes on the Tibetan Plateau during 2000–2017 using multiple altimetric missions and Landsat-derived lake shoreline positions

2019 ◽  
Vol 11 (4) ◽  
pp. 1603-1627 ◽  
Author(s):  
Xingdong Li ◽  
Di Long ◽  
Qi Huang ◽  
Pengfei Han ◽  
Fanyu Zhao ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Water Level ◽  
Lake Water ◽  
Water Levels ◽  
High Temporal Resolution ◽  
Data Sets ◽  
The Tibetan Plateau ◽  
Altimetry Data ◽  
And Storage ◽  
Storage Change

Abstract. The Tibetan Plateau (TP), known as Asia's water tower, is quite sensitive to climate change, which is reflected by changes in hydrologic state variables such as lake water storage. Given the extremely limited ground observations on the TP due to the harsh environment and complex terrain, we exploited multiple altimetric missions and Landsat satellite data to create high-temporal-resolution lake water level and storage change time series at weekly to monthly timescales for 52 large lakes (50 lakes larger than 150 km2 and 2 lakes larger than 100 km2) on the TP during 2000–2017. The data sets are available online at https://doi.org/10.1594/PANGAEA.898411 (Li et al., 2019). With Landsat archives and altimetry data, we developed water levels from lake shoreline positions (i.e., Landsat-derived water levels) that cover the study period and serve as an ideal reference for merging multisource lake water levels with systematic biases being removed. To validate the Landsat-derived water levels, field experiments were carried out in two typical lakes, and theoretical uncertainty analysis was performed based on high-resolution optical images (0.8 m) as well. The RMSE of the Landsat-derived water levels is 0.11 m compared with the in situ measurements, consistent with the magnitude from theoretical analysis (0.1–0.2 m). The accuracy of the Landsat-derived water levels that can be derived in relatively small lakes is comparable with most altimetry data. The resulting merged Landsat-derived and altimetric lake water levels can provide accurate information on multiyear and short-term monitoring of lake water levels and storage changes on the TP, and critical information on lake overflow flood monitoring and prediction as the expansion of some TP lakes becomes a serious threat to surrounding residents and infrastructure.

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