Understanding the importance of hydraulic head timeseries for calibrating a flow model: application to the real case of the Bacchiglione Basin

2020 ◽  
Author(s):  
Mara Meggiorin ◽  
Giulia Passadore ◽  
Andrea Sottani ◽  
Andrea Rinaldo
Keyword(s):  
Missing Values ◽  
Flow Model ◽  
Hydraulic Head ◽  
Parameters Estimation ◽  
Real Case ◽  
Time Interval ◽  
Specific Storage ◽  
Monthly Data ◽  
Calibration Process ◽  
Daily Data

<p>Hydrogeological timeseries of hydraulic head contain important information for modelling the groundwater resource. Calibrating in transient conditions allows to define both conductivity and specific storage fields plus, in case, other flow boundary conditions (BCs) that fit at best the observations. Moreover, by having at least one year of records, different hydrological conditions are considered and fitted.</p><p>The major problem encountered by hydrogeologists is that hydrological records often have missing values. Then, different choices on observation sampling time are possible: for example, using daily data with missing values or monthly data that fastens also the model. These choices can alter the calibration process and affect the parameters estimation.</p><p>This study aims at understanding if and how optimal estimated parameter sets are different and, therefore, if the different choice on the time interval can preclude a proper calibration of the groundwater model. This analysis was performed by calibrating: (i) with all daily data, (ii) with different percentages of missing values on daily data, (iii) with weekly data, (iv) with monthly data and (v) with stationary conditions.</p><p>The estimated parameter sets of the different models obtained by using part of the data available (to simulate the loss of information) are compared to a base model, which is the best fit achieved by using all available daily observations. The flow model and calibration setup are constant for all models, only timeseries‘ observation vary.</p><p>The analysis is carried out on a real case of study: a flow model is built using the software FEFLOW for an area of the Bacchiglione Basin (Veneto, Italy). This area has been selected in a way to facilitate the calibration process. It is located on the plain close to the Leogra river where the aquifer is unconfined. The domain has both upstream and downstream borders roughly perpendicular to the regional groundwater flow direction and passing by sensors recording continuously the hydraulic head. In this way, the following BCs can be assigned: the Dirichlet BCs with transient values of the corresponding recording sensor for the boarders upstream and downstream and no-flow conditions for the lateral borders. Furthermore, inside the study area, there are sensors monitoring the hydraulic head, i.e. transient observations. Two borderline and four central sensors are recording daily values of hydraulic head. The year 2016 was chosen as calibration period, since no data is missing.</p><p>The comparison of resulting conductivity and specific storage fields is carried out by visual inspection of fields heterogeneity and statistical distributions. Moreover, models’ uncertainty is quantified with a calibration-constrained Monte-Carlo analysis.</p><p>The main understanding of this analysis is the anomalous result estimated by the monthly data model respect to other models: both conductivity and specific storage field are different in their heterogeneity and magnitude, reaching unlikely values.</p><p>This comprehension is important because the choice of monthly data is usually done for data scarcity or model fastening, but the effects on estimated fields are evident and important to consider. The analysis shows how different observations types, meaning daily to monthly data, affect the calibration process.</p>

Quantitative investigations of the hydraulic connection between a large reservoir and a buried valley aquifer in southern Alberta

2005 ◽  
Vol 42 (5) ◽  
pp. 1461-1473 ◽  
Author(s):  
B D Smerdon ◽  
C A Mendoza ◽  
A M McCann
Keyword(s):  
Groundwater Flow ◽  
Flow Model ◽  
Hydraulic Head ◽  
Water Levels ◽  
Groundwater Flow Model ◽  
Reservoir Level ◽  
Hydraulic Connection ◽  
Southern Alberta ◽  
Approximate Location ◽  
Pumping Rates

Quantitative investigations, including two aquifer tests and development of a three-dimensional (3D) groundwater flow model, were required to determine the hydraulic connection between an irrigation reservoir and a buried valley aquifer in southern Alberta. Evidence of seepage was detected in the buried valley aquifer 10 km east of the Pine Coulee reservoir at the onset of filling in 1999, when the reservoir level exceeded an elevation of 1035 m above sea level (a.s.l.). Concern for an increase in the local water table and the creation of artesian conditions in the aquifer prompted this study to determine the approximate location of a seepage window that appeared to be connecting the reservoir and aquifer. Observations of hydraulic head in the aquifer during the pumping tests revealed a barrier boundary when the reservoir level was at an elevation of 1035 m a.s.l. and a recharge boundary condition when the elevation exceeded 1039 m a.s.l. These data were used to calibrate a 3D groundwater flow model, which was needed to determine the hydraulic properties and approximate location of the leakage zone. The quantitative investigation showed that seepage likely occurred through the sideslopes of the flooded coulee, rather than through the low-permeability coulee floor sediments or the embankment dam. Further simulations illustrated the expected seepage rates at various reservoir supply levels and the pumping rates required for relief wells installed in the buried valley aquifer to maintain historic aquifer hydraulic head. A brief postanalysis indicated that the forecasted pumping rates were only 15% lower than have been required to maintain preconstruction water levels in the buried valley aquifer.Key words: dams, seepage analysis, groundwater modelling, buried valley aquifer, pumping test.

scholarly journals Leakage Calibration in Water Distribution Networks with Pressure-Driven Analysis: A Real Case Study

2020 ◽  
Vol 2 (1) ◽  
pp. 59
Author(s):  
Joaquim Sousa ◽  
Nuno Martinho ◽  
João Muranho ◽  
Alfeu Sá Marques
Keyword(s):  
Water Distribution ◽  
Simulated Annealing Algorithm ◽  
Distribution Networks ◽  
Water Distribution Networks ◽  
Real Case ◽  
Calibration Process ◽  
Pressure Step ◽  
Water Companies ◽  
Pressure Driven

Leakage in water distribution networks (WDN) is still a major concern for water companies. In recent years, the scientific community has dedicated some effort to the leakage calibration issue to obtain accurate models. But leakage modelling implies the use of a pressure-driven approach as well as specific data to define the pressure/leakage relationship. This paper presents the calibration process of a real case study WDN model. The process started with pressure step tests, the model was built in WaterNetGen and the leakage calibration process was performed by a simulated annealing algorithm. As illustrated, after calibration the model was able to produce accurate results.

scholarly journals Accumulation patterns around Dome C, East Antarctica, in the last 73 kyr

2018 ◽  
Vol 12 (4) ◽  
pp. 1401-1414 ◽  
Author(s):  
Marie G. P. Cavitte ◽  
Frédéric Parrenin ◽  
Catherine Ritz ◽  
Duncan A. Young ◽  
Brice Van Liefferinge ◽  
...  
Keyword(s):  
Large Scale ◽  
Flow Model ◽  
East Antarctica ◽  
Small Scale ◽  
Time Interval ◽  
Accumulation Rates ◽  
Ice Flow ◽  
Last Glacial ◽  
Prevailing Wind Direction ◽  
The Last Glacial

Abstract. We reconstruct the pattern of surface accumulation in the region around Dome C, East Antarctica, since the last glacial. We use a set of 18 isochrones spanning all observable depths of the ice column, interpreted from various ice-penetrating radar surveys and a 1-D ice flow model to invert for accumulation rates in the region. The shallowest four isochrones are then used to calculate paleoaccumulation rates between isochrone pairs using a 1-D assumption where horizontal advection is negligible in the time interval of each layer. We observe that the large-scale (100s km) surface accumulation gradient is spatially stable through the last 73 kyr, which reflects current modeled and observed precipitation gradients in the region. We also observe small-scale (10 s km) accumulation variations linked to snow redistribution at the surface, due to changes in its slope and curvature in the prevailing wind direction that remain spatially stationary since the last glacial.

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.

Hydraulic head in a clayey sand till over multiple timescales

2004 ◽  
Vol 41 (1) ◽  
pp. 89-105 ◽  
Author(s):  
David W Ostendorf ◽  
Don J DeGroot ◽  
Wayne M Shelburne ◽  
Travis J Mitchell
Keyword(s):  
Leading Edge ◽  
Hydraulic Head ◽  
Unconfined Aquifer ◽  
Analytical Models ◽  
Storm Events ◽  
Finite Radius ◽  
Clayey Sand ◽  
Monthly Data ◽  
Pressure Transducers ◽  
Lower Permeability

This paper presents an analysis of hydraulic head data measured every 2 h for 2 years in the leading edge of a drumlin that consists of weathered, brown clayey sand till and underlying unweathered gray clayey sand till. The brown till responds as an unconfined aquifer and acts as a boundary condition for the confined gray till aquifer. Analytical models are presented for interpretation of the hydraulic head data using annual, monthly, and daily timescales, for estimation of drumlin (landform) hydraulics and till (formation) properties. The annual average head data from open-standpipe piezometers calibrate drumlin hydraulics that feature steady radial flow in the brown till, because of its higher permeability (1.1 × 10–13 m2) and the finite radius of the drumlin. The lower permeability (1.4 × 10–15 m2) gray till has steady cylindrical flow with an appreciable downward gradient. Open-standpipe piezometer data are modeled at the monthly timescale to confirm the landform hydraulics and calibrate a brown till macroporosity of 0.016. The amplitude of periodic monthly head fluctuations increases towards the edge of the drumlin. Hydraulic head response to aperiodic storm events is significantly magnified by this macroporosity as measured by precipitation gages and buried pressure transducers. The storm data are modeled on a daily timescale to confirm the brown till macroporosity value estimated from the monthly data and to further elucidate gray till hydraulics. Compressibility delays and attenuates the groundwater mound, with a calibrated gray till compressibility of 3 × 10–9 Pa–1. The calibrated models accurately recover drumlin flow fields with plausible property values of the clayey sand till, and accordingly should describe other sites with similar landforms and deposits.Key words: drumlins, till, hydraulics, compressibility, permeability, macroporosity, piezometer.

Traffic Overflow Modeling and Numerical Simulation

2012 ◽  
Vol 241-244 ◽  
pp. 2072-2075
Author(s):  
Jing Shan Pan ◽  
Li Dong Zhang
Keyword(s):  
Numerical Simulation ◽  
Traffic Flow ◽  
Queue Length ◽  
Flow Model ◽  
Negative Impact ◽  
Intrinsic Factor ◽  
Time Interval ◽  
Effective Solution ◽  
Traffic Flow Model ◽  
Simulation Results

Traffic overflow has great negative impact on normal traffic flow. Improper time setting and offset, even more right turn input traffic flow can cause this extreme phenomenon. In order to discover the intrinsic factor and relationship between overflow and signal setting, traffic flow incoming, we build the traffic flow model. This model takes two adjacent crosses as example, and to count the remained traffic flow queue length in given time interval. The simulation results prove our model’s feasibility. Our model well helps us to understand the overflow characteristics and to find the effective solution to conquer it in the future.

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.

Development of an Inverse Method to Estimate Overall Building and Ventilation Parameters of Large Commercial Buildings

1999 ◽  
Vol 121 (1) ◽  
pp. 40-46 ◽  
Author(s):  
T. A. Reddy ◽  
S. Deng ◽  
D. E. Claridge
Keyword(s):  
Linear Regression ◽  
Parameter Identification ◽  
Inverse Method ◽  
Commercial Buildings ◽  
Physical Parameters ◽  
Monthly Data ◽  
Heating And Cooling ◽  
Daily Data ◽  
Regression Approach ◽  
Data Points

We propose an inverse method to estimate building and ventilation parameters from non-intrusive monitoring of heating and cooling thermal energy use of large commercial buildings. The procedure involves first deducing the loads of an ideal one-zone building from the monitored data, and then in the framework of a mechanistic macro-model, using a multistep linear regression approach to determine the regression coefficients (along with their standard errors) which can be finally translated into estimates of the physical parameters (along with the associated errors). Several different identification schemes have been evaluated using heating and cooling data generated from a detailed building simulation program for two different building geometries and building mass at two different climatic locations. A multistep identification scheme has been found to yield very accurate results, and an explanation as to why it should be so is also given. This approach has been shown to remove much of the bias introduced in multiple linear regression approach with correlated regressor variables. We have found that the parameter identification process is very accurate when daily data over an entire year are used. Parameter identification accuracy using twelve monthly data points and daily data over three months of the year was also investigated. Identification with twelve monthly data points seems to be fairly accurate while that using daily data over a season does not yield very good results. This latter issue needs to be investigated further because of its practical relevance.

scholarly journals Non-Parametric and Parametric Analysis of Runoff in Satluj River Basin, Himachal Pradesh, India

2015 ◽  
Vol 54 ◽  
pp. 15-36
Author(s):  
Sandeep Kumar ◽  
Santosh
Keyword(s):  
River Basin ◽  
Missing Values ◽  
Monsoon Season ◽  
Linear Regression Analysis ◽  
Kendall Test ◽  
Data Series ◽  
Annual Series ◽  
Daily Data ◽  
Satluj River ◽  
Non Parametric

Testing the significance of observed trends in hydrological time series has received a great attention recently, especially in connection with climate change. The changing pattern of runoff deserves urgent and systematic attention over a basin for planning, development, utilisation and management of water resources. Therefore, one large catchment i.e. Indian part of Satluj River Basin is selected for the present study. The daily data of runoff were converted to monthly and then computed to seasonal and annual series. The missing values in the data were computed by using average method. For better understanding of the observed trends, data were computed into standardised runoff indices (SDI). These standardised data series were plotted against time and the linear trends observed were represented graphically. The records of runoff were subjected to trend analysis by using both non-parametric (Mann-Kendall test) and parametric (linear regression analysis) procedures.Trend analysis results of runoff show that out of 8 annual trends 2 (25%) are statistically insignificant increasing and 6 (75%) are decreasing in nature where 2 (25%) are statistically significant at 95% confidence level. Apart from annual, the changes were investigated for the four seasons: winter (December-March), pre-monsoon (April-June), monsoon (July-September) and post-monsoon (October-November). The analysis of annual as well as seasonal runoff for the Satluj River Basin indicates significant changes from 1984 to 2010. There is a clear contrast in the runoff pattern of river between the high altitude mountainous region and the lower reaches where it changes as a result of contribution from rainfall, especially during monsoon season. Although the runoff at majority of stations showed decreasing trend, but very few are statistically significant. Such studies help us to resolve potential issues associated with availability of water for agriculture, industry, hydropower, domestic use etc.

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