the development of a catchment management modelling system for the googong reservoir catchment

©2006 Ecowise Environmental Pty Ltd

The Development of a Catchment The Development of a Catchment Management Modelling System for the Management Modelling System for the

Googong Reservoir CatchmentGoogong Reservoir CatchmentGavan Thomas, Ian Musto and Tony SparksEcowise Environmental Pty Ltd, Fyshwick, ACT Ph: 02 6270 7650


Contents

ACTEW Corporation (ACTEW) hold responsibility for providing safe drinking water to the residents of Canberra.

Central to this responsibility is the appropriate management of source water supply catchments.

Although ACTEW does not hold regulatory control over the

catchments it has, in response to catchment risk assessment, chosen a pro-active approach to stakeholder engagement and ongoing management


Catchment Management for the ACT

ACTEW Corporation (ACTEW) hold responsibility for providing safe drinking water to the residents of Canberra.

Central to this responsibility is the appropriate management of source water supply catchments.

Although ACTEW does not hold regulatory control over the

catchments it has, in response to catchment risk assessment, chosen a pro-active approach to stakeholder engagement and ongoing management


The Study

Googong Reservoir provides an important role in the delivery of Canberra and Queanbeyan’s drinking water.

The catchment for this reservoir, some 89,400ha is wholly in New South Wales and is termed a mixed land use catchment of parks and reserves, forestry, agriculture and rural residential developments.

Following an extensive analysis of risk, ACTEW has commissioned Ecowise Environmental to develop an integrated management model for the catchment.


Outcomes

What are we trying to achieve? A common understanding of the nature of the catchment and

its functioning Actions to reduce impact of sediment movement within the

catchment Actions to substantially reduce the risk of contamination of the

catchment

Through: A series of individual models addressing the areas of concern A scenario assessment model to assist the end-user in

determining priorities for a series of agreed management prescriptions that can be enacted through controls on existing landuse


Why use modelling?

Modelling of the Googong catchment will enable a number of outcomes: a quantitative understanding of the drivers for the

catchment such as climate, soils, land use and settlement;

provide a consistent set of management alternatives for comparison (include measures of uncertainty);

facilitate the active participation of stakeholders in the discussion of future options for management of the catchment; and

enable us to identify critical gaps in the extent and accuracy of our data.


The existing state of play There have been many excellent catchment inventory

studies, stored in GISs, that provide a good description of the pattern of the environment – what’s out there.

Issues: a lot of analysis and interpretation required to provide

information required for management – tends to reinforce the divisions between the hydrographers, hydrologists and biologists and the end user

there tends to be a widening divide between the researchers and the day-to-day managers

has not changed the efficacy of our management actions – we do link our monitoring activities to the system components


Change…

Concentrate on a higher level of information output rather (GIS) than simply storing data

Move from a description of pattern to include those processes basic to catchment functioning

Establish a common understanding of the processes and the factors that affect the required outcomes

Provide a mechanism for the sharing of information and knowledge

web portal for all stakeholders system usable by all provides benefits to all

Move all aspects of our thinking and system from reactive to proactive.

Implement an ArcHydro information template GISWR (GIS in Water Resources Consortium) Dr. David Maidment – Director, Centre for Research in Water

Resources, University of Texas at Austin


Streams

Drainage Areas

Hydrography

Channels

Terrain Surfaces

Rainfall Response

Digital Orthophotos

ArcHydro Basic idea: Transition from …Basic idea: Transition from …

Data Model Based on Inventory


… and …

Data Model Based on Behaviour

Follow a drop of water from where it falls on the land, to the stream, and all the way to the ocean.


… to Arc Hydro Data Model

Integrate Data Inventory using a Behavioral ModelRelationships betweenobjects linked by tracing pathof water movement


Groundwater integration ArcHydro groundwater geodatabase design is integrated with the

surface water data model to provide a better representation of hydrologic systems within a geodatabase.

Four initial goals were set for the geodatabase design: The data model should support representation of both regional and

site-scale groundwater systems. The data model should enable the integration of surface and

groundwater information. The data model should facilitate the extraction of archived

groundwater data for use with groundwater modelling software. The data model should support the storage and display of solutions

computed by external groundwater models. The groundwater data model consists of three main components:

Hydrogeology (including a hydrogeologic unit table) Modelling (for posting model results) Surfaces (rasters and TINs)


Pattern and process… DEM

mixture of ALS and topographic data, fine scale around reservoir and in areas of low relief, medium scale in remainder of catchment

High level of drainage enforcement – DEM constructed with ANUDEM 5.2 (CRES, ANU) using 1:25,000 drainage lines corrected for flow

Flow corrected – all local sinks filled to lowest surrounding pixel ArcHydro

DEM processed using ArcHydro Tools 1.3 Flow direction → flow accumulation → streamlines →

catchments → drainage points → flow paths →drainage area characterisation → drainage boundary characterisation → drainage connectivity characterisation → watershed delineation → flow path analysis (verification)


Pattern and process…

→→

→ →


Modelling Critical areas:

Rainfall-runoff model Sediment movement & amelioration Pathogen movement – Cryptosporidium sp., Giardia sp.,

E. coli

Platform: E2 – developed by eWater CRC, direct liaison with

CSIRO Water TIME – coding framework (.NET) – we will modify E2

code to ‘talk’ directly to data in GIS as appropriateHydsys Hydsys → ArcSDE time series → E2→ ArcSDE time series → E2

Hydsys Hydsys → ArcSDE time series → DHI’s Temporal Analyst→ ArcSDE time series → DHI’s Temporal Analyst


Modelling Example Burra Creek

The Problem:


Modelling… Riparian Particulate Model (RPM) Riparian buffers are vegetated strips of land separating runoff and pollutant

contributing areas from surface waters Riparian buffers play an important environmental role by:

reducing pollutant inputs to streams creating in-stream habitat improving local landscape aesthetics

Overland flow carries sediment and associated pollutants - typically highly intermittent and spatially heterogeneous.

Riparian buffers can be placed in a flow path and can act to change the overland flow by:

creating a physical barrier to slow the overland flow and promote particulate deposition.

spreading concentrated overland flow so that the slowing of overland flow is enhanced.

infiltrating a portion of the overland flow into storage within the buffer - an effect enhanced by soil macropores frequently found in riparian buffers - negated by zones of soil saturation that are frequently found in convergent parts of the landscape.


Riparian Particulate Model During a surface flow event particulate matter from the hill slope is

carried into the riparian buffer. The incoming particulate load comprises different size fractions and material of different chemical composition.

Particle size distribution and chemical composition affect the proportion of material trapped, its behaviour in the riparian buffer

re-entrainment, breakdown release of solutes etc.

and its potential impact on the receiving stream.

The three main processes that operate to trap particulates in a riparian buffer are:

settling, infiltration and adhesion.


RPM… The Riparian Particulate Model (RPM) quantifies the

particulate trapping capacity of riparian buffers through simulation of the processes of settling, infiltration and adhesion.

RPM subdivides the total particulate load into two size classes: coarse - which is trapped principally by settling and fine - which is trapped by infiltration and adhesion.

The RPM and uses simplified descriptions of these three trapping mechanisms. It captures important features of experimental findings and enables investigation of the anticipated effects of changes to a range of important buffer characteristics.


RPM… The RPM consists of three components which simulate

particulate trapping: coarse particulates by settling, fine particulates by adhesion, and fine particulates by infiltration.

SettlingCoarse particulate input (t/day)

Coarse particulate output (t/day)

Adhesion

Infiltration

Fine particulate output (t/day)

Fine particulate input (t/day)


RPM – data input The RPM relies on E2 for the generation of time series of

overland flow and particulate (suspended sediment inputs) inputs.

Temporal data inputs from the E2 model are provided at a daily time step and are required to be continuous.

The spatial pre-processor requires that the E2 network be defined using a DEM and that the functional units (FU) are assigned using a land use map. A buffer map is also required by the pre-processor to enable automatic generation of parameters.

The spatial data required for the RPM is generally widely available, particularly DEM data and land use mapping. Mapping of riparian buffer areas is much less commonly available but may be generated using standard techniques.

A final requirement for the use of the RPM is to describe characteristics of the soil and vegetation of the riparian zones being simulated. All soil and vegetation characteristics are theoretically measurable. Standard techniques generally exist for their measurement in the field.


RPM… Outputs

Systematic evaluation of riparian buffer sizes

Variable depending on stream order and flow

Defendable method

One layer into management matrix


Pathogen model Based on:

Development of a process-based model to predict pathogen budgets for the Sydney drinking water catchment (PCB)

Christobel Ferguson, Barry Croke, Peter Beatson, Nicholas Ashbol and Daniel Deere

To assist with evaluation of management options, a process-based mathematical model (pathogen catchment budgets - PCB) developed to predict Cryptosporidium, Giardia and E. coli loads generated within and exported from drinking water catchments.

The model quantifies the key processes affecting the generation and transport of micro-organisms from humans and animals using land use and flow data, and catchment specific information including point sources such as sewage treatment plants and onsite systems.

The resultant pathogen catchment budgets (PCB) can be used to prioritize the implementation of control measures for the reduction of pathogen risks to drinking water.


Model I/O The model predicts for each micro-organism a local generated source budget (input)

and the routed downstream (export) budget.

The PCB model consists of 5 components: a hydrologic module, a land budget module, an on-site systems module, a sewage treatment plant (STP) module and an in-stream transport module.

The model is coded using the Interactive Component Modelling System (ICMS) software freely available from the CSIRO.

Inputs to the model include land use and hydrologic flow data and catchment specific

information to predict pathogen loads. The hydrologic module uses the non-linear loss module of the IHACRES rainfall-runoff

model. This model assumes an initial catchment moisture deficit and using the distribution of

surface rainfall (GIS layer) an amount of rainfall is converted into a depth of effective rainfall (rainfall that ends up as stream flow) for each sub-catchment.

The effective rainfall is used to estimate the wet weather mobilisation of faeces that

have been deposited on the land - the depth of effective rainfall depends only on the amount of rainfall and the soil moisture. The antecedent dry period is adjustable (30 days used in this study).


Model Integration Output of model runs are a series of rasters with values

giving individual suitabilities high values from RPM good suitability for riparian buffer… high values from agricultural suitability model… best mix of landuse to maximise quality runoff

What managers are looking for is a series of outcomes that can be encoded as optimal management - If we put in high level of riparian buffers, how does that impact

on existing landuse What regime of forestry practice (clearfelling) is consistent with

maintaining water quality and maximum water yield What are the important riverine systems and what level of

environmental flows are required to maintain community values


Management models Obvious that not all outcomes from models are

complementary and how do we best to provide integration that takes account of opposing uses and the inherent uncertainties associated with our models and model outcomes

Research project (just beginning) – National ICT Australia Looking at a range of non-boolean logic mechanisms including

Bayesian networks (recent European experience) A Bayesian network is a graphical way to represent a particular

factorization of a joint distribution. Each variable is represented by a node in the network.


‘Community’ Interaction ACTEW is supporting the development of a web interface that

provides secure access by all stakeholders to all activities within the catchment

Catchment managers Researchers NSW & ACT government agencies

Stores: any activities studies engineering works findings and references personnel and contacts

Provides access to: GIS visualisation and query model outcomes model integration all measurement stations through WRON widgets (uses ACTEW portal

through GIS to online data stored in Hydsys database)

the development of a catchment management modelling system for the googong reservoir catchment

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