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 43 of 72 8 Scenarios Two scenarios have been considered here based on available data: Scenario A Historic climate under natural conditions Scenario B Historic climate with current estimate of pumping 8.1 Water balance assessment Essential a water balance describes the inflows and outflows from a groundwater system and the resulting changes in groundwater storage in the system; Inflows - Outflows = Change in storage If the change in storage is positive then inflows are greater than outflows and the system is gaining water; groundwater levels will be seen to trend upwards. If the change in storage is negative then inflows are less than outflows and water is being lost from the system and groundwater levels will be seen to trend downwards. 8.2 Scenario A Historic climate without pumping 8.2.1 Water balance under historic climate The FEFLOW budget analyser was used to determine the applied recharge to the model from 01/01/1900 - 01/03/2012 a total of 5631 GL was applied to the model domain during this period or an average annual volume 51.3 GL/yr. The area of the groundwater model is 87,911,271 m 2 , this means that equivalent to 584 mm/yr. Evapotranspiration and runoff in areas where the water table was at the surface is calculated at 1461 GL or 13312 mm for the same period, which is equivalent to 151 mm/yr. This value is expected to represent the rejected recharge from the system, therefore the actual amount of rainfall recharging the groundwater system is 4170 GL this is equivalent to 432 mm/yr. The total groundwater discharge to springs and rivers is estimated at 38.1 GL/yr which equates to an equivalent height of 433 mm/yr. Discharge to Berry Springs for the period 1/1/1900 - 1/9/2009 is estimated at 13.8 GL/yr this is equivalent to 157 mm/yr. Table 9 summarises the water balance information expressed in gigalitres (GL). Median discharge from the Berry Springs spring complex is 0.4 m 3 /s. The water balance for the Berry Springs system over 109.75 years indicates that it is in dynamic equilibrium, with inputs very close to outputs 38.0 GL/yr cf 38.1 GL/yr with a difference of approximately 0.3% between recharge and discharge. The model also identifies that there are significant discharges to the Darwin River in the vicinity of the Parsons and Twin River Farm Springs.


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