Territory Stories

Development of a Groundwater Flow Model - Berry Springs

Details:

Title

Development of a Groundwater Flow Model - Berry Springs

Creator

Knapton, Anthony

Collection

E-Publications; E-Books; PublicationNT; 17/2016

Date

2016

Location

Berry Springs

Description

Made available via the Publications (Legal Deposit) Act 2004 (NT).

Table of contents

Table of Contents -- List of Figures -- List of Tables -- Acknowledgements -- Glossary of Terms -- Executive Summary -- 1 Introduction -- 1.1 Background -- 1.1 Aim of the study -- 2 Site Description -- 2.1 Study area location -- 2.2 Climate -- 2.2.1 Rainfall data -- 2.2.2 Evaporation data -- 2.3 Hydrology -- 2.4 Land use -- 2.5 Groundwater extraction -- 2.6 Water quality -- 3 Hydrogeology -- 3.1 Geological formations -- 3.1.1 Mount Bonnie Formation (Pso) -- 3.1.2 Unnamed Dolostone Unit (Psd): Berry Springs Dolostone -- 3.1.3 Burrell Creek Formation (Pfb) -- 3.1.4 Depot Creek Formation (Ptd) -- 3.1.5 Petrel Formation (JKp) -- 3.1.6 Darwin Member (Kld) -- 3.2 Geological structure -- 3.3 Aquifer characteristics -- 3.3.1 Hydraulic conductivity -- 3.3.2 Storage coefficient -- 4 Groundwater hydrology -- 4.1 Groundwater flow -- 4.2 Recharge -- 4.2.1 Water balance method -- 4.2.2 Water table fluctuation method -- 4.2.3 Spring discharge -- 4.2.4 Evapotranspiration -- 4.3 Rainfall-runoff modelling -- 4.4 Predicted natural conditions compared to recent observed flows -- 4.5 Groundwater chemistry -- 5 Available data -- 5.1 Climate data -- 5.2 SRTM digital terrain model -- 5.3 Geological data -- 5.4 Groundwater level data -- 5.4.1 Steady state groundwater levels -- Berry Springs Groundwater Flow Model -- 5.4.2 Time series groundwater levels -- 5.5 River discharge data -- 5.5.1 Manual gauging data -- 5.5.2 Continuous recorder data -- 5.6 Pumping data -- 5.7 Data gaps -- 6 Groundwater flow model development -- 6.1 What is a groundwater flow model? -- 6.2 Conceptual model -- 6.3 Modelling approach -- 6.4 Model package -- 6.5 Model mesh geometry -- 6.5.1 Mesh design -- 6.5.2 Mesh generation -- 6.6 Material properties -- 6.7 Fracture flow -- 6.8 Boundary conditions -- 6.8.1 Recharge and Areal ET Flux -- 6.8.2 Constant head BC values -- 6.9 Pumping data -- 6.10 FEFLOW settings -- 6.10.1 Problem class -- 6.10.2 Temporal and control data -- 7 Calibration -- 7.1 Steady state finite element model -- 7.1.1 Steady state model results -- 7.2 Transient finite element model -- 8 Scenarios -- 8.1 Water balance assessment -- 8.2 Scenario A – Historic climate without pumping -- 8.2.1 Water balance under historic climate -- 8.3 Scenario B – Historic climate with current pumping estimates -- 8.3.1 Pumping estimate methodology -- 8.3.2 Water balance under historic climate and current pumping -- 8.3.3 Impacts of pumping on groundwater discharge at Berry Springs -- 8.3.4 Flow duration -- 9 Results and discussion -- 9.1 Measurable impacts -- 9.1.1 Reduced dry season flows -- 9.1.2 Recession slope of dry season flows -- 9.1.3 Groundwater levels -- 9.2 Rainfall, recharge & minimum flows analysis -- 9.3 Impacts of pumping based on zones -- 10 Conclusions -- 10.1 Key performance indicators -- 11 References -- Appendix A - Groundwater level hydrographs -- Appendix B - Calibrated transient model results

Language

English

Subject

Berry Springs Dolostone; Berry Springs aquifer System; Groundwater Flow Model

Publisher name

Department of Land Resource Management

Place of publication

Darwin

Series

17/2016

Format

72 pages : colour illustration and maps ; 30 cm.

File type

application/pdf.

ISBN

9781743501092

Copyright owner

Check within Publication or with content Publisher.

Parent handle

https://hdl.handle.net/10070/272355

Citation address

https://hdl.handle.net/10070/428025

Page content

Berry Springs Groundwater Flow Model Page 72 of 72 Appendix E Formulation of discrete feature fracture flow Fracture flow is a major component of karstic aquifers. The discrete fracture approach is typically applied to fractured media with low primary permeability. Flow through a single fracture may be idealised as occuring between two parallel plates with a uniform separation equivalent to the fracture aperture. It is evident that substituting for Kfrac that Qfrac is proportional to the cube of the fracture aperture. These results for tubes and cracks are known as the Hagen-Poisseuille Law after two separate discovers. These formulae are only valid for laminar flow so always calculate the Reynolds Number in any particular numerical case. Implementing the Hagen-Poiseuille cubic law the hydraulic conductivity of the fracture elements is related to the hydraulic radius (rhydr) of the fracture which is determined from the aperture (). = 2 = = 12 = 6.3 10& where: 0 = 1000 [kg m-3] 0 = 1.3 [Pa s] g = 9.81 [m2 s-1] w is the fracture width [metres] is the fracture aperture [metres] rhydr = /2 = 3 for a planar geometry FEFLOW provides 1D and 2D discrete feature elements which can be mixed with the porous matrix elements in two and three dimensions. Different laws of fluid motion can be defined within such discrete features, e.g., Darcy, Hagen-Poiseuille or Manning-Strickler laws. Both the geometric and physical characteristics of the discrete feature elements provide a large flexibility in modeling complex situations. Although the overall water balance remains relatively consistent, the discharge response at the spring shows an improved match with the observed record.


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