Territory Stories

Development of a Groundwater Model for the Western Davenport Plains

Details:

Title

Development of a Groundwater Model for the Western Davenport Plains

Creator

Knapton, Anthony; CloudGMS Pty Ltd

Commissioned by

Northern Territory. Department of Environment, Parks and Water Security

Collection

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

Date

2018-03

Location

Western Davenport Water Control District

Abstract

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.

Notes

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

Language

English

Subject

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

Publisher name

Northern Territory Governmnet

Place of publication

Palmerston

Edition

version 2.0

Series

WRD Technical Report 27/2017

Format

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

File type

application/pdf

ISBN

9781743502976

Use

Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government

License

https://creativecommons.org/licenses/by/4.0/

Related links

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

Parent handle

https://hdl.handle.net/10070/858845

Citation address

https://hdl.handle.net/10070/858846

Page content

Western Davenport WCD Groundwater Model (v2.0) Parameter Estimation CloudGMS 83 Jolly, 1990) at 24700m3/d. Greater throughflow requires either increasing hydraulic conductivity to values outside the documented range (refer to section 3.8). 6.4.6. Steady state 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 model parameters, stresses, and boundary conditions. During parameter estimation the sensitivity of the objective function to the adjustable parameters is calculated by PEST as a Jacobian matrix (Doherty, 2010). 6.5. Transient parameter estimation 6.5.1. Transient parameter estimation strategy The transient model parameters estimation process was completed in accordance with the guiding principles outlined by Barnett et al, (2012). Like the steady state optimisation analysis, the transient parameter estimation process was initially conducted using trial-and-error to gain an understanding of the model sensitivity to parameter changes and to inform the automated parameter optimisation design. The PEST code was initially used to optimise the large parameter set associated with the unsaturated zone modules. 6.5.2. PEST settings The PEST input file defines the adjustable parameters, parameter transformations, parameter bounds and observations used in the objective function. 6.5.3. Simulation period for parameter estimation The simulation period from 1970 to 2015 was selected for the parameter estimation process. The reason for using the full period of available observations is due to experience gained from previous modelling in similar conditions, where attempts to reduce run times by using a shorter simulation period between the years 1970 1995 resulted in an overestimate of the recharge for the subsequent recharge events in 2001 and 2010 when the model was run from 1970 - 2015. In addition, measured evaporation data is available from the BOM SILO database from 1/1/1970, before this date only average evaporation data is available. 6.5.4. Evapotranspiration parameters The root depth was adjustable during the optimisation process. Each of the zones identified in section 5.2.7 were updated and the corresponding PEST identifiers for root depth were rootdep1 rootdep6. 6.5.5. Unsaturated zone parameters The saturated hydraulic conductivity (ks1 ks9) and the van Genuchten retention curve parameters a and n were adjusted, primarily to change the specific yield and the moisture content at wilting point which determine the overall capacity of the soil to store water.