Numerical Modelling of Water Flow (Seepage) in the Karun 4 Dam and Abutments (Steady State)

Numerical Modelling of Water Flow (Seepage) in the Karun 4 Dam and Abutments (Steady State) Mohammad Hosseiny Sohi 03 November 2015

Contents: Objectives Karun River & Karun 4 Dam in Iran Geology of dam site Softwares Nummerical Modelling 2 Scenarios 2

Objectives: Water seepage could be a problem in the foundation and abutments of a big reservoir located in a karstic limestone formation A case study: modelling Karun 4 dam & abutments Using the groundwater softwares for modelling: Current situation of dam site and; Projecting the future probable scenarios. 3

Karun river is: the largest river of Iran the only navigable waterway in Iran. It originates in the Zagros mountains, And joins the Shatt al-arab, and Persian Gulf. 4

The Karun 4 Dam is: located on the Karun River in the southwest Iran The highest dam of Iran : 230 m from foundation Constructed over a karst limestone. Water leakage is one of it s important problems. 6

Some technical specifications of Karun 4 dam: 8

Geology of dam site: Location: in the tectonically folded belt of the Zagros Mountains Geological era of the reservoir : Cretaceous to Miocene limestone and marly limestone geological formations: carbonate layers of the Asmari formation (As) including: lower (As1), middle (As2) and upper (As3) units and marlstone and marly limestone of impervious Pabdeh formation (Pd) on upstream of dam site 10

Geological cross-section of dam site

Softwares: MODFLOW: The USGS's (The U.S. Geological Survey) production by McDonald and Harbaugh, A three-dimensional (3D) finite-difference groundwater model First published in 1984 The program is free and open-source software Is written in FORTRAN language 12

Softwares: PMWIN: Processing Modflow: A Simulation System for Modeling Groundwater Flow and Pollution. PMWIN was originally developed for a remediation project of a disposal site in the coastal region of Northern Germany in 1998 by Wen-Hsing Chiang (Hamburg) and Wolfgang Kinzelbach (Zürich). A friendly package in windows operating system. PMWIN (version 5.3) is one of the most complete groundwater simulation systems in the world which supports these models: MODFLOW, MT3D, MT3DMS, MOC3D, PMPATH for Windows, PEST2000, and UCODE. 13

Softwares: CFP: The conduit flow process for MODFLOW-2005 (CFP) has the ability to simulate turbulent or laminar groundwater flow conditions (unsteady state): Conduit flow pipes (CFPM1) represent: large dissolution features, such as submerged caves in carbonate aquifers or large voids from dissolution of burrowed carbonate rock; voids in fractured rock; lava tubes in basaltic aquifers. Preferential flow layers (CFPM2) represent: a porous media where turbulent flow is suspected to occur under the observed hydraulic gradients; a single secondary porosity subsurface feature, such as a well-defined laterally extensive underground cave. 14

Numerical Modelling of Water Flow (Seepage) in the Karun 4 Dam and Abutments (Steady State) using PMWIN 5.3 File Grid Parameters Models Tools Help 15

Grid: Mesh Size Layer Type Boundry conditions Top of Layer (TOP) Bottom of Layers(BOT) 16

Grid: Mesh Size: 10 X 10 [m^2] => Area: 1500 X 1000 [m^2] or 150X100 Cells Layer Type: 3 Confined/Unconfined(Tranmissivity varies) Boundry conditions: IBOUND(modflow) Top of Layer (TOP): from Topography with Arc-GIS software from exiting surveyed maps (AutoCAD files) from dam site would be produced the Raster file for PMWIN 17

Raster file of topography (Top of Layer in PMWIN) 18

Modelling Area based on the exiciting topography 19

Top of Layer(TOP) 20

Grid: Mesh Size: 10 * 10 m^2 Layer Type:?? Boundry conditions: IBOUND(modflow) Top of Layer (TOP): from Topography Bottom of Layers(BOT):? 21

Bottom of Layers(BOT): Exisiting data: Geological cross-section along the dam axes Geological plan view of dam site (Topography) Geological horizental section (each 25meter) from topographical level of dam site to the founndation level Lugeon values in the excaveted boreholes in the exiting galleries General geological information of the geological formations and sub-units of the dam site (Asmary and Pabdeh formations) 22

Bottom of Layers(BOT): Exisiting data: Geological cross-section along the dam axes Geological plan view of dam site (Topography) Geological horizental section (each 25meter) from topographical level of dam site to the founndation level Lugeon values in the excaveted boreholes in the exiting galleries General geological information of the geological formations and sub-formations of the dam site (Asmary and Pabdeh formations) 23

Geological plan of dam site

Horizental geological section at elevation of +805.0 27

Definition of Lugeon test: The loss of water in liters per minute and per meter of borehole at an over-pressure of 1 MPa 31

Lugeon Test results example: Excel Table 32

3D view of dam site galleries 33

Hydraulic Conductivity associated with different Lugeon values Lugeon Range Classification Hydraulic Conductivity Range(cm/sec) <1 Very Low < 1 x 10-5 1-5 Low 1 x 10-5 - 6 x 10-5 5-15 Moderate 6 x 10-5 - 2 x 10-4 15-50 Medium 2 x 10-4 - 6 x 10-4 50-100 High 6 x 10-4 - 1 x 10-3 >100 Very High > 1 x 10-3 34

Bottom of Layers(BOT): Exisiting data: Geological cross-section along the dam axes Geological plan view of dam site (Topography) Geological horizental section (each 25meter) from topographical level of dam site to the founndation level Lugeon values in the excaveted boreholes in the exiting galleries General geological information of the geological formations and subformations of the dam site (Asmary and Pabdeh formations) 35

lithological description of subunits of AS1 Name AS1-A AS1-B AS1-C AS1-D AS1-E AS1-F Description Limestone (about 90%) gray to brownish gray, thick to very thick, strength to very strength, with no considerable karstic phenomena. There is some surficial erosion which is related to marly limestone (about10%) Limy marlstone mostly covered by colluviums and slopewash. This rock is gray to dark green in natural colour, weak to relatively strength and with no karstic features Limestone, thick to very thick bed, gray to light brown with no particular karstic phenomena. More or less similar to AS1-B Limestone with some (in unweathered locations)gray to blue outcrops (marly limestone) very thick layers and without considerable karstic phenomena This unit commences from As1-E and continues to the first porous key bed. Composed mostly with limestone having slight to medium karstic features (vug). There are some (10%) porous limestones. AS1-G Porous limestone which are solution vugs gray to light brownish gray in natural colour. At the right abutment the fresh outcrop is gray. Regarding with porous characteristics, it is considered as key bed. AS1-H AS1-I AS1-J Limestone with some grey to blue outcrops (probably marly limestone very thickbed. There are more or less karstic vugs at the top of this sub-unit This sub-unit is more or less similar to AS1-G so it is considered as key bed. There is a cave with approximate size(3*4*5)min this sub-unit Lime stone with marly limestone. the Marl limestone is frequent in he lower part, thick to very thick, no important karstic features is seen in this sub-unit 38

Bottom of Layers(BOT): 2 Scenarios based of existing data: The number of layer: 1 Layer => 2D modelling (virtual 3D modelling) more than 1 Layer based on the geological data => 3D Modelling The geometrical and hydraulical properties of each layer: 1 Layer => Equivalent K (Hydraulics Conductivity) => Calibration Process More than 1 Layer => Relevant K for each Layer based on measuerd data and engineering judgment... 39

Thank you for your attention! 40