NDLI: Effects of model layer simplification using composite hydraulic properties

Content Provider	Springer Nature Link
Author	Sepúlveda, Nicasio Kuniansky, Eve L.
Copyright Year	2009
Abstract	The effects of simplifying hydraulic property layering within an unconfined aquifer and the underlying confining unit were assessed. The hydraulic properties of lithologic units within the unconfined aquifer and confining unit were computed by analyzing the aquifer-test data using radial, axisymmetric two-dimensional (2D) flow. Time-varying recharge to the unconfined aquifer and pumping from the confined Upper Floridan aquifer (USA) were simulated using 3D flow. Conceptual flow models were developed by gradually reducing the number of lithologic units in the unconfined aquifer and confining unit by calculating composite hydraulic properties for the simplified lithologic units. Composite hydraulic properties were calculated using either thickness-weighted averages or inverse modeling using regression-based parameter estimation. No significant residuals were simulated when all lithologic units comprising the unconfined aquifer were simulated as one layer. The largest residuals occurred when the unconfined aquifer and confining unit were aggregated into a single layer (quasi-3D), with residuals over 100% for the leakage rates to the confined aquifer and the heads in the confining unit. Residuals increased with contrasts in vertical hydraulic conductivity between the unconfined aquifer and confining unit. Residuals increased when the constant-head boundary at the bottom of the Upper Floridan aquifer was replaced with a no-flow boundary.Les effets de simplifier les propriétés hydrauliques de couches dans un rejéteau aquifer et l’unité de confinant sous-tendante ont été évalués. Les propriétés hydrauliques pour les couches distinctes dans le rejéteau aquifer et l’unité de confinant ont été calculées des analyses de données aquifer-d’essai en utilisant le 2D écoulement radial, axi-symétrique. Le taux recharge au rejéteau aquifer et pompant d’aquifer Supérieur de Floride a été simulé en utilisant le 3D écoulement. Les modèles d’écoulement conceptuels ont été développés en en réduisant progressivement le nombre de couches dans le rejéteau aquifer et l’unité de confinant en calculant des propriétés hydrauliques composites pour le nombre simplifié de couches. Les propriétés hydrauliques composites ont été calculées en utilisant des moyennes basées sur les épaisseurs de couche ou une estimation de paramètre basée sur les techniques de régression. Aucuns residuals significatifs n’ont été simulés quand toutes les couches comprenant le rejéteau aquifer ont été simulées comme une couche. Les plus grandes erreurs ont été simulées quand le rejéteau aquifer et l’unité de confinant a été agrégé dans une couche simple (quasi-3D), avec les erreurs plus de 100% pour les taux de fuite à aquifer confiné et les niveaux d’eau dans l’unité de confinant. Les erreurs d’écoulement simulées ont augmenté avec les contrastes dans la conductivité hydraulique verticale entre le rejéteau aquifer et l’unité de confinant. Les erreurs d’écoulement simulées ont augmenté quand la condition de niveaux constants d’eau à la base d’aquifer Supérieur de Floride a été remplacée avec une condition d’aucun écoulement.Los efectos de simplificar las propiedades hidráulicas de varias capas litológicas en un acuífero de nivel freático y en la capa confinante subyacente fueron investigados. Las propiedades hidráulicas de las capas litológicas en el acuífero de nivel freático y en la capa confinante fueron obtenidas del análisis de los niveles de agua de las pruebas de bombeo mediante la simulación de flujo radial bidimensional (2D) con simetría axial. La recarga transitoria al acuífero de nivel freático y el bombeo en el acuífero confinado Superior de Florida fueron simulados utilizando flujo en 3D. Varios modelos conceptuales de flujo fueron desarrollados reduciendo gradualmente el número de capas litológicas en el acuífero de nivel freático y en la capa confinante mediante el computo de propiedades hidráulicas compuestas para el número reducido de capas. Las propiedades hidráulicas compuestas fueron calculadas utilizando un promedio basado en el espesor de las capas litológicas ó utilizando la optimización de parámetros basada en regresiones. No se simularon cambios significativos cuando todas las capas litológicas del acuífero de nivel freático fueron simulados como una sola capa. La simulación de flujo de agua produjo los errores residuales mayores cuando el acuífero de nivel freático y la capa confinante fueron agrupadas en una sola capa (cuasi-3D), con errores residuales de más de 100% en el flujo de infiltración simulado al acuífero confinado y en los niveles de agua simulados en la capa confinante. Los errores residuales de simulación de flujo aumentaron con el aumento en contraste en conductividad hidráulica vertical entre el acuífero de nivel freático y la capa confinante. Los errores residuales de simulación de flujo aumentaron cuando la condición de niveles constantes de agua en la base del acuífero Superior de Florida fue sustituída por una condición de cero flujo ó base impermeable.本文评估了简化潜水和下伏承压含水层组的水力特性的效应。首先分析潜水和承压含水层单元组的含水层测试数据, 而后利用呈放射状轴向对称的二维流对单元岩层的水力学特性进行计算。用三维流模拟潜水层不同时期的补给和上弗罗里达含水层 (美国) 的抽水。通过计算合成水力特性从而单一化岩石单元, 以达到逐步减少潜水和承压含水层单元组的岩石单元的数目这一目的来发展概念模型。水力特性合成计算通过厚度平均或基于回归的参数估计反演模拟完成。将承压含水层所有的岩石单元合为一层时未形成明显残差。将潜水和承压含水层单元简化成单一岩性 (准三维) 时生成了最大残差, 此时承压含水层的渗透速率和潜水层的水头的残差都查过了100%。当对比潜水和承压含水层的垂向水力传导率时, 残差增加。将上弗罗里达含水层的底部的定水头边界用零流通量边界取代时, 残差增加Efectuou-se uma avaliação dos efeitos da simplificação das propriedades hidráulicas das camadas de um aquífero livre e da unidade confinante subjacente. As propriedades hidráulicas das unidades litológicas do aquífero livre e da unidade confinante foram calculadas através da análise de ensaios de caudal, considerando fluxo radial, com simetria em relação ao eixo (2D). A recarga transitória e a captação de água do aquífero livre Upper Floridan (EUA) foram simuladas recorrendo a fluxo 3D. Foram desenvolvidos modelos conceptuais de fluxo, reduzindo progressivamente o número de unidades litológicas no aquífero livre e na unidade confinante, através do cálculo de propriedades hidráulicas compósitas para as unidades litológicas simplificadas. As propriedades hidráulicas compósitas foram calculadas utilizando médias ponderadas das espessuras, ou modelação inversa, com estimativas de parâmetros baseados em regressão. Não se registaram valores residuais significativos quando todas as unidades litológicas que compõem o aquífero livre foram simuladas como uma única camada. Os valores residuais mais elevados foram observados quando o aquífero livre e a unidade confinante inferior foram agregados numa única camada (quasi-3D), com valores residuais acima dos 100% para a taxa de drenância em relação ao aquífero confinado, e para o potencial hidráulico na unidade confinante. Os valores residuais aumentaram com o contraste na condutividade hidráulica vertical entre o aquífero e a unidade confinante, e quando a fronteira de fluxo constante na base do aquífero Upper Floridan foi substituída por uma fronteira impermeável.
Starting Page	405
Ending Page	416
Page Count	12
File Format	PDF
ISSN	14312174
Journal	Hydrogeology Journal
Volume Number	18
Issue Number	2
e-ISSN	14350157
Language	Portuguese
Publisher	Springer-Verlag
Publisher Date	2009-09-04
Publisher Institution	International Association of Hydrogeologists
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Conceptual models Groundwater flow Hydraulic properties Hydraulic testing USA Waste Water Technology Water Pollution Control Water Management Aquatic Pollution Geology Hydrogeology
Content Type	Text
Resource Type	Article
Subject	Earth and Planetary Sciences Water Science and Technology

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