Estimation of hdraulic conductivity using geoelectrical data for assessing of scale effect in a karst aquifer

The Salman Farsi Dam was constructed on the Ghareh-Aghaj river in the catchment of the Asmari limestone aquifer, Changal Anticline, Zagros region, Iran. In order to estimate the hydraulic conductivity of the aquifer, combination of geoelectrical (i.e., bulk resistivity of the aquifer) and hydrophysical (i.e., electrical conductivity of groundwater) data are used as an alternative approach. Porosity of the aquifer is estimated based on the modified form of Archie’s empirical law assuming well-cemented carbonate rocks. Formation resistivity factor and critical pore size of the Asmari limestone aquifer are used for estimating the hydraulic conductivity on the small scale based on the Thompson Equation. The results suggest an average porosity and hydraulic conductivity of 14.4 % and 0.016 m/day, respectively. The estimated value for hydraulic conductivity is smaller than values previously determined for the aquifer, based on tracer, pumping and Lugeon tests. Comparison of the hydraulic conductivity obtained by different methods revealed scale effect of hydraulic conductivity measurements in the Asmari limestone aquifer. As a result, application of the geoelectrical and hydrophysical data can provide a cost-effective and efficient alternative to estimate hydraulic conductivity in karst aquifers on the small scale.Keywords: hydraulic conductivity, Karst, Scale effect, Vertical electrical sounding, Iran.Uporaba geoelektričnih podatkov za oceno hidravlične prevodnosti in učinka merila v kraškem vodonosnikaJez Salman Farsi je postavljen na reku Ghareh-Aghaj v območju kraškega vodonosnika Asmari, ki pripada antiklinali Changal v gorovju Zagros, Iran. Hidravlično prevodnost vodonosnika smo ocenili z kombinacijo meritev celokupne električne upornosti vodonosnika in električne prevodnosti podzemne vode. Ocena poroznosti je temeljila na prilagojeni obliki Archiejevega empiričnega zakona, pri čemer smo predpostavili dobro cementirane karbonate. Iz upornosti formacije in kritične velikosti por smo s Thompsonovo enačbo izračunali hidravlično prevodnost v majhnem merilu. Dobljena povprečna poroznost tako znaša 14,4 %, povprečna prevodnost pa 0.016 m/dan. Vrednosti hidravlične prevodnosti so precej manjše of prej dobljenih vrednosti iz sledilnih, črpalnih in Lugeonovih poskusov, kar kaže na pomemben učinek merila v obravnavanem vodonosniku. Raziskava med drugim kaže na primernost geoelektričnih in hidrofizikalnih podatkov za stroškovno ugodno oceno hidravlične prevodnosti v majhnem merilu.Ključne besede: Hidravlična prevodnost, kras, učinek merila, vertikalno električno sondiranje, Iran

Optimization of the hydrodynamic characteristics of a karst conduit with CFPv2 coupled to OSTRICH

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.jhydrol.2018.10.050 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/In order to better define the characteristics of a karst conduit, an integrated hydrogeological study including numerical modeling using CFPv2 is conducted at a karst aquifer in the Zagros Mountain Region of Iran. The Sarvak limestone aquifer in the Nil Anticline is the main karst aquifer of the study area with major groundwater discharge taking place at Sarkur spring. An annual water balance and a dye tracing test confirmed that the karst system is mainly recharged through rainfall and the Maroon River. Several depressions are observed along the banks of the river with a major one classified as a sinkhole used for dye injection. A groundwater flow model was developed based on the available hydrogeological information. A probable direct conduit flow path with an estimated groundwater flow velocity of 96 m/h is estimated between the injection point and the Sarkur spring. Four scenarios are assumed to simulate the probable conduit flow path using the CFPv2 code. As one of the first attempts in regional groundwater flow modeling of a karst aquifer, CFPv2 is automatically calibrated with field measurements of spring discharge and a dye breakthrough curve through a parameter estimation code OSTRICH to optimize the characteristics of the conduit through the minimization of the weighted sum of square error. Simulated results reveal that a conduit with a diameter of 2.9 m is required to adequately simulate spring discharge and dye tracer migration between the injection and discharge points. Our new approach (linking of CFPv2 and OSTRICH) provides a deeper understanding of groundwater flow and solute transport in karst terrains even when available data are limited and the approach should be applicable to other areas.Shiraz UniversityUniversity of Waterlo

Comparative study of figurative statues of Evan Penny and Ron Mueck

Throughout the history of art, human has been a creature that always has created and has been created. How human body is viewed in different periods carries an especial concept. By assessing the history of art and artworks, it can be understood that human body is presented and taken into account by artists in different ways. Comparing the artworks of one period clarifies the hidden features in the works and diversity of views of artists to one single subject. Meanwhile, though there is diversity in different artistic expressions, commonalities and similarities can be seen among artworks.The present research is a comparative study of figurative statues of two contemporary sculptors i.e., Evan Penny and Ron Mueck. by using the subject of human body with a new vision, these two artists expand meaning that is the concern of the modern art in their works. The present study aims at finding out the methods and indicators that the two artists used to create their figurative works and the similarities and differences in the method of them. In this study along with introducing these two artists, their sculpture indicators and thesimilarities and differences in their method of working are studied and compared. At the end, it seems that in order to achieve the intended meaning, both artists created their works by omitting, adding and changing the identified features for the viewer

Analysis of Flow Dimension from a Pumping Test in a Karst Aquifer

Pumping test is a well-known method for determining hydraulic characteristics of an aquifer. Diagnostic plot technique is applied to facilitate the identification of an appropriate groundwater flow conceptual model, and for interpretation of the pumping test data. The diagnostic plots of six observation wells around a pumping well at the Salman Farsi Dam Site showed simultaneous presence of integer and non-integer flow dimensions of pumping test around the pumping well. Type of flow pattern on two observation wells shows two-dimensional flow and that on four observation wells follows one-and-a-half-dimensional flow. The results revealed that flow pattern around the pumping well in the karst study area changes from two-dimensional within a distance of less than about 100 m from the pumping well to one-and-a-half dimensional at a distance from the pumping well larger than about 100 m. The change of flow dimensions with increasing distance from the pumping well is due to radial flow around the observation wells within a distance of less than about 100 m from the pumping well, and bilinear flow around the observation wells with a distance of more than about 100 m from the pumping well. Radial and bilinear flows are related to cone of depression and preferential flow paths, respectively

Assessing flow paths in a karst aquifer based on multiple dye tracing tests using stochastic simulation and the MODFLOW-CFP code

Karst systems show high spatial variability of hydraulic parameters over small distances and this makes their modeling a difficult task with several uncertainties. Interconnections of fractures have a major role on the transport of groundwater, but many of the stochastic methods in use do not have the capability to reproduce these complex structures. A methodology is presented for the quantification of tortuosity using the single normal equation simulation (SNESIM) algorithm and a groundwater flow model. A training image was produced based on the statistical parameters of fractures and then used in the simulation process. The SNESIM algorithm was used to generate 75 realizations of the four classes of fractures in a karst aquifer in Iran. The results from six dye tracing tests were used to assign hydraulic conductivity values ​​to each class of fractures. In the next step, the MODFLOW-CFP and MODPATH codes were consecutively implemented to compute the groundwater flow paths. The 9,000 flow paths obtained from the MODPATH code were further analyzed to calculate the tortuosity factor. Finally, the hydraulic conductivity values ​​calculated from the dye tracing experiments were refined using the actual flow paths of groundwater. The key outcomes of this research are: (1) a methodology for the quantification of tortuosity; (2) hydraulic conductivities, that are incorrectly estimated (biased low) with empirical equations that assume Darcian (laminar) flow with parallel rather than tortuous streamlines

Assessing the Effect of Conduit Pattern and Type of Recharge on the Karst Spring Hydrograph: A Synthetic Modeling Approach

It is widely accepted that spring hydrographs are an effective tool for evaluating the internal structure of karst aquifers because they depict the response of the whole aquifer to recharge events. The spring hydrograph is affected by various factors such as flow regime, geometry, type of recharge, and hydraulic properties of conduit. However, the effect of conduit network geometry received less attention and required more comprehensive research studies. The present study attempted to highlight the impact of the two most frequent patterns of karst conduits (i.e., branchwork and network maze) on the characteristic of the spring hydrograph. Therefore, two conduit patterns, branchwork and network maze, were randomly generated with MATLAB codes. Then, MODFLOW-CFP was used to quantify the effect of conduit pattern, conduit density, and diffuse or concentrated recharge on the spring hydrograph. Results reveal that peak discharge, fast-flow recession coefficient, and the return time to baseflow are mainly affected by conduit network pattern, conduit network density, and recharge, respectively. In contrast, the time to reach peak flow only reacts to recharge conditions. Large variations in conduit density produce tangible changes in the baseflow recession coefficient

A dye-tracing test as an aid to studying karst development at an artesian limestone sub-aquifer: Zagros Zone, Iran

A dye-tracing test is employed to study the karst development and flow regime at an artesian limestone sub-aquifer, the Khersan3 Dam site, Zagros Zone, Iran. Tracer breakthrough curves showed an early dominant peak followed by a pronounced tailing effect. The peak concentration was a response to induced pressure during dye injection. The results suggest that the dye was pushed into the small pores and fissures around the injection point during dye injection. Hence, the dye moved out as a result of matrix and fissure diffusive processes and created a long pronounced tailing. The maximum flow velocity in the upper artesian sub-aquifer ranged from 0.97 to 2.9 m/h. However, the mean tracer velocity ranged from 0.19 to 0.51 m/h based on the mean residence tracer time; consequently, the flow regime in the artesian sub-aquifer was determined to be mainly diffusive. The results reveal (1) a low hydraulic gradient from upstream of the dam axis to downstream; consequently, there is no considerable flow; (2) poor karst development and diffuse flow at the tracing test area; (3) a discharge zone at a location downstream of the dam axis which is the main terminal of general flow direction at the dam site

Determining the source and mechanism of river salinity: An integrated regional study

Study region: Zohreh River Basin, Southwest Iran Study focus: The salinity of Zohreh River sharply increases in three salinity zones (SZs) along the river named SZ1, SZ2 (the focus of this study), and SZ3. Determining the salinity sources and salinization mechanism using an integrated approach including geological, hydrochemical, isotopic, geophysical, river sinuosity and hydrocarbon analysis are the main objectives of this study. The study focuses on the combination of evidence of regional-scale (i.e., river sinuosity and seismic data) and small-scale (i.e., drilling core analysis). New hydrologic insights for the region: Among several known sources of river salinity, it was found that the water quality of the Zohreh River is mainly threatened by the salt-bearing Gachsaran Formation and oil-field brine. It is concluded that halite brine and oil-field brine simultaneously cause the salinization in SZ2, and their contributions were delineated to be 95% and 5%, respectively. The lack of reliable geological evidence to support halite dissolution in surficial layers by circulating waters suggests the possibility of a deep source of halite brine in SZ2. The results revealed that deep halite brine of the salt layers of Gachsaran Formation is mainly responsible for the salinization of SZ2. The mechanism of deep brine penetration to the river through the hidden fault failures detected by the combination of river sinuosity analysis and geophysical data for the first time