Explicit algebraic influence coefficients: a one-dimensional transient aquifer model

Saffi, Mohamed; Cheddadi, Abdesselam

doi:10.1623/hysj.52.4.763

Cited by 8 publications

(6 citation statements)

References 8 publications

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“…Again LMA performs well within the observation period [s min , s max ] but it poorly identifies the pumping rates lying outside of it. Moreover, a similar test to that carried out by Saffi & Cheddadi (2007) in which data are perturbed to 2.5%, 5% and 7.5%, shows that the regularized pumping rates are not obscured by the added noise though the quality of the results slightly deteriorates.…”

Section: Numerical Experiments Under Regularized δP (K)mentioning

confidence: 81%

“…This work attempts to contribute to addressing this issue by combining calibrated numerical models and observations. It extends the problem formulated and solved for a one-dimensional semi-confined aquifer by Saffi & Cheddadi (2007). So, given a reliable calibrated direct code and a record of observed heads, the point is to arrive at the well configuration (locations and magnitudes) which gives the best possible reproduction of the monitored hydraulic head.…”

Section: Introductionmentioning

confidence: 98%

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Identification of illegal groundwater pumping in semi-confined aquifers

Saffi¹,

Cheddadi

2010

Hydrological Sciences Journal

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Illegal pumping from underground reservoirs is approached as an inverse problem. The procedure seeks among a set of suspected potential areas the ones from which water is effectively pumped out (or in) and at what rate does this take place? Influence coefficient and finite element are combined in order to simulate the aquifer response to hypothetical pumping scenarios. Then the optimal scenario which makes of simulated head distribution the best fit to the observed headset is retained as solution to the foregoing question. This optimal scenario is derived by minimizing the classical least squares error using the Levenberg-Marquardt Algorithm (LMA). Under the conditions of the treated aquifer example it is observed that LMA is non-convergent unless a regularizing measure is taken during the calculation of the correction applied to the parameter-vector between two successive iterations. The procedure is tested with uniform and non-uniform pumping. In both cases, it yields good identified pumping rates within the observation period, but its performance deteriorates markedly for the rates corresponding to the days when no monitoring well is yet active.Key words illegal pumping; identification; semi-confined aquifer; inverse problem; finite elements; singular value decomposition (SVD)Identification des pompages souterrains illégaux Résumé L'identification des pompages illégaux à partir des réservoirs souterrains est approchée comme un problème inverse. La procédure consiste à chercher parmi une série de positions potentielles suspectes, celles d'où l'eau est effectivement pompée (ou injectée) et avec quel débit cela a-t-il lieu? Les coefficients d'influence et la méthode des éléments finis sont combinés pour simuler la réponse de l'aquifère à des scénarios de pompage hypothétique. Ensuite, le scénario optimal qui rend la distribution du potentiel hydraulique simulé la meilleure approximation de celle observée est retenu comme réponse à la question soulevée. Ce scénario optimal est obtenu indirectement en minimisant l'erreur au sens des moindres carrés en utilisant l'Algorithme de Levenberg-Marquardt (ALM). Sous les conditions de l'exemple considéré il est remarqué que l'ALM ne converge pas à moins qu'une mesure régularisante est prise lors du calcul de la correction appliquée au vecteur des paramètres entre deux itérations successives. La procédure est testée sur des scénarios de pompage uniforme et non uniforme. Dans les deux cas elle identifie correctement le débit pompé pour les jours d'observation, mais ses performances se détériorent nettement vis-à-vis des débits correspondants aux jours où les observations n'ont pas encore été commencées.Mots clefs pompage illégal; identification; aquifère semi-confiné; problème inverse; éléments finis; décomposition en valeurs singulières (DVS)

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Section: Numerical Experiments Under Regularized δP (K)mentioning

confidence: 81%

Section: Introductionmentioning

confidence: 98%

Identification of illegal groundwater pumping in semi-confined aquifers

Saffi¹,

Cheddadi

2010

Hydrological Sciences Journal

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“…Saffi and Cheddadi (2007) developed an algebraic expression which gave the matrix of transient influence coefficients for one-dimensional semi-confined aquifer model and solved the governing equation by using a mixed compartment model. Tung and Chou (2004) integrated pattern classification and tabu search to optimize the average zonal groundwater pumping for an aquifer.…”

Section: Introductionmentioning

confidence: 99%

Optimal Well Locations using Genetic Algorithm for Tushki Project, Western Desert, Egypt

Khalaf¹,

Gad²

2017

Engineering Journal

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“…Unfortunately, the groundwater change due to individual sources cannot be known. Consequently, source identification in the past can only give a rough sketch of large-scale hydrology (Wittenberg and Sivapalan 1999, Ruud et al 2004, Wang et al 2005, Misstear et al 2009, or can evaluate a few suspicious sources and related pumping or recharging rates using a large number of observed data in time and space (Aral et al 2001, Tung and Chou 2004, Mahinthakumar and Sayeed 2005, Saffi and Cheddadi 2007, Ayvaz and Karahan 2008, Lin and Yeh 2008, Cheng et al 2009, Saffi and Cheddadi 2010.…”

Section: Introductionmentioning

confidence: 99%

Novel information for source identification of local pumping and recharging in a groundwater system

Liu

2015

Hydrological Sciences Journal

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The aim of this paper is to solve the local pumping and recharging source identification problem by introducing a statistical technique, independent component analysis (ICA), into groundwater modelling. Such a problem suffers from limited observations in the field and is ill-posed. With the help of ICA, the observed head at monitoring wells is decomposed into a linear combination of head fluctuations caused by each source. The ill-posed problem is transferred into several independent well-posed ones. Moreover, the decomposed hourly head fluctuation, specially referred to as 'characteristic pattern', provides novel information on the type and distance of local sources. A hypothetical case to identify two local sources using two observation wells is presented, and the results show the accuracy and efficiency of the proposed method. The identified results are stable as long as the observation error is within a reasonable range. The characteristic pattern provides novel information, which can be widely used for source identification in the future.

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Explicit algebraic influence coefficients: a one-dimensional transient aquifer model

Cited by 8 publications

References 8 publications

Identification of illegal groundwater pumping in semi-confined aquifers

Identification of illegal groundwater pumping in semi-confined aquifers

Optimal Well Locations using Genetic Algorithm for Tushki Project, Western Desert, Egypt

Novel information for source identification of local pumping and recharging in a groundwater system

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