Territory Stories

Development of a Groundwater Model for the Western Davenport Plains



Development of a Groundwater Model for the Western Davenport Plains


Knapton, Anthony; CloudGMS Pty Ltd

Commissioned by

Northern Territory. Department of Environment, Parks and Water Security


E-Publications; E-Books; PublicationNT; WRD Technical Report 27/2017




Western Davenport Water Control District


CloudGMS has been commissioned by DENR to develop a numerical groundwater model of the aquifers within the central area of the WDWCD to improve confidence in the sustainability of the groundwater resources, as this is the area within the WCD with greatest potential for intensive development.


Made available by via Publications (Legal Deposit) Act 2004 (NT); Prepared for Dept Environment and Natural resources

Table of contents

Executive summary -- 1 Background -- 2 Physical -- 3 Available data -- 4 Conceptual model -- 5 Model design & construction -- 6 Parameter estimation -- 7 Water balances -- 8 Sensitivity analysis -- 9 Predictive scenarios -- 10 Conclusions -- 11 Reference -- 12 Document history and version control -- Appendix A - Groundwater level hydrographs - Appendix B - Alek range horticultural farm sub-regional modelling




Groundwater; Northern Territory; Western Davenport Water Control District; Conceptual mode

Publisher name

Northern Territory Governmnet

Place of publication



version 2.0


WRD Technical Report 27/2017


ix, 127 pages : colour illustration and maps ; 30 cm

File type





Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government



Related links

https://hdl.handle.net/10070/842058 [LANT E-Publications: Development of a Groundwater Model for the Western Davenport Plains, version 1.1]

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Citation address


Page content

Western Davenport WCD Groundwater Model (v2.0) Sensitivity Analysis CloudGMS 98 8 Sensitivity analysis 8.1. Transient sensitivity analysis Sensitivity is the variation in the value of one of more output variables (such as hydraulic heads) due to changes in the value of one or more inputs to a groundwater flow model (such as hydraulic properties or boundary conditions). Sensitivity analysis is a procedure for quantifying the response of a models output to an incremental variation in the model input parameters, stresses, and boundary conditions where applicable. This section discusses sensitivity in the historic groundwater modelling, through a systematic variation of model input values to: Identify those model input elements that cause the most significant variations in model output; and to Quantitatively evaluate the impact of parameter variability (sometimes referred to as parameter uncertainty) in model input on the degree of calibration and on the model's predictive capability. The sensitivity of the objective function to the adjustable parameters is calculated by PEST as a Jacobian matrix (Doherty, PEST Model-Indepedent Parameter Estimation User Manual Part I: PEST Software, 2016). To obtain sensitivity information, the Jacobian matrix was calculated after the completion of the parameter estimation process using PEST with each parameter adjusted by 1% of the final estimated value. The results of this analysis are presented graphically below in Figure 8-1. It should be noted that the sensitivities are normalised to the number of observations in each observation group. The relative composite sensitivity of a parameter is obtained by multiplying its composite sensitivity by the magnitude of the value of the parameter. It is thus a measure of the composite changes in model outputs that are incurred by a fractional change in the value of the parameter. The parameters adjusted during the sensitivity analysis are listed below in Table 33. Table 33 Parameters included in the sensitivity analysis. Process module Parameter Relative change OL Manning n 0.01 Global Storage detention 0.01 Global UZ Root depth 0.10 All vegetation zones pFfc (specific yield) 0.05 All soils pFw (soil moisture store) 0.024 All soils Saturated hydraulic conductivity (infiltration) 0.01 All soils SZ Hydraulic conductivity 0.01 All hydrostrat. units Specific storage 0.01 All hydrostrat. units