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 22 of 72 4.2 Recharge Groundwater recharge or deep drainage is a hydrologic process where water moves downward from surface water to groundwater. This process usually occurs in the vadose (unsaturated) zone below plant roots and is often expressed as a flux (the flow per unit area per unit time) to the water table surface. Groundwater levels in the Berry Springs aquifer respond strongly to rainfall events and the lag between initial rainfall and the corresponding increase in groundwater levels is relatively short. Similarly groundwater levels begin to decline just before or soon after rainfall ceases. Figure 9 shows the groundwater hydrograph for RN029016 in relation to daily rainfall for the period 2005 - 2011. Figure 10 shows the mass residual rainfall curve compared to the groundwater hydrograph for RN029016. The direct correlation in the timings between rainfall and groundwater levels is evident. Approximately 240 mm of rain was required prior to the groundwater levels rising in 2009/10. It should be noted that the increase in groundwater levels also coincides with an event in excess of 310 mm over 2 days. Groundwater levels show considerable seasonal range with approximately 15-20 metres between the highest levels at the end of the wet season to the lowest levels at the end of the dry season. An example of the variation in groundwater level is seen in Figure 10, which shows manually collected water levels for RN029016, continuous logger data are also available at this site from late 2009 to early 2010. The logger data demonstrates the rapid rise in groundwater levels in response to rainfall. 4.2.1 Water balance method Verma (1995) assumed a recharge of ~480 mm which is approximately 30% of mean annual rainfall (1600 mm). Cook et al (1998), in a study of Howard East approximately 35 km away in a similar climatic and hydrogeological setting, using water balance methods, identified that recharge was approximately 200 mm/yr which is 11-12% of the rainfall (1720 mm average annual). They did note however that: 'The uncertainty on the estimated recharge rate is believed to be approximately 50%. Also, the figure represents a spatial average, and it is likely that groundwater recharge will be higher than this in some areas and lower in others.' Figure 9 Comparison of daily rainfall manual groundwater levels and logger data for RN029016 from 2005 - 2010.


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