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 38 of 72 6.7 Fracture flow The karstic aquifer system conceptually is dual permeability. To simulate this discrete features were employed. It has been assumed that the flow through the karsts and fractures may be idealised as occurring between two parallel plates with a uniform separation equivalent to the fracture aperture. Formulation of the discrete feature fracture flow employed in FEFLOW is presented in Appendix E. 6.8 Boundary conditions Boundary conditions used in the model were: recharge applied to the upper surface of the model using time series areal fluxes generated using a 1D MIKE SHE soil model; seepage face condition at nodes on the upper surface of the model to remove water as it intersects the surface; spring features as constant head boundary conditions with a constraint of 0 m/d flux into the model domain (ie only flow out of the model domain, no flow into the model domain); Pumping bores for stock and domestic and horticultural use were implemented using Well BCs. The Well BC describes the injection or withdrawal of water at a single node in kL/d (m 3 /d). 6.8.1 Recharge and Areal ET Flux The MIKESHE recharge power function (refer to Appendix C) was imported into the model using the Timevarying power function editor dialog as a constant curve type. Evapotranspiration and rejected recharge were estimated using the seepage face condition applied to the upper slice of the model. It was assumed that when the groundwater level intersects the ground surface the water is removed from the model as evaporation or overland flow. Evapotranspiration was estimated using a ramp function similar to that used in the ModFlow package EVT and is based on the following conditions: When the water table is at or above the ground surface (Slice 1), evapotranspiration loss from the water table occurs at the maximum rate specified. When the elevation of the water table is below the extinction depth evapotranspiration from the water table is 0. Between these limits, evapotranspiration from the water table varies linearly with water table elevation. The resulting recharge / evapotranspirational function is presented in Equation 1. Term A= 0.003 if Head REFDSTR.GndSurface0.003 1 - REFDSTR.GndSurface - Head 2 if REFDSTR.GndSurface - Head < 2 0 otherwise Qp=0.00161*POWER.SILORech - Term A Equation 1 Recharge / evapotranspiration function Qp is in m/d.


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