Reports and Papers
GIS and simulation models for Water Resources Management:
Published in: GIS Development, August 2002, Vol.6/8, 39-43.
A case study of the Kelantan River, Malaysia
The Kelantan river drains the province of Kelantan in north-eastern
peninsular Malaysia. A catchment of about 12,000 km2 (upstream of
Guillemard bridge) and an altitude difference of more than 2100 m generates
an average runoff of about 500 m3/sec, with the variations of the local
Monsoon climate. The variability of rainfall with extreme monthly values
between 0 and 1750 mm in dry and wet months, respectively, already suggest
the main problem: reliability of water resources for the rice paddies that supply
about 12 % of national production. Droughts and floods that affect the
efficiency of the irrigation system, continuing changes in land use, and the
potential of water pollution from intensive agriculture pose a range of
problems that require innovative tools for their solution.
WaterWare (http://www.ess.co.at/WATERWARE/) is a management
information system based on a range of linked simulation models that utilize
data from an embedded GIS, monitoring data including real-time data
acquisition, and an expert system. Accessible in a local area network from a
central server, and alternatively through the Internet for remote clients
(http://22.214.171.124/KELANTAN/) , the system uses a graphical interface to
provide interactive decision support information for water resources planners
and policy makers.
Water resources are at the heart of sustainable development in many regions
of the world. Water of sufficient quantity and quality is an essential resource
for agriculture, industry, and tourism, but also for everyday life in cities and
villages. A growing population and a growing economy not only lead to
increasing demand for water, they also cause increasing pollution that may
threaten the very water resources this growth depends on and thus threaten
the sustainability of development (Brookfield and Byron, 1993).
Water resources are distributed in time and space, and their availability may
vary greatly from time to time and place to place. This variability causes
problems: not enough or too much, drought or flood, and not of the right
quality, i.e., polluted: these are the main issues to be addressed.
SPATIAL PROBLEMS AND SPATIAL SOLUTIONS
The basic unit in water resources management is the river basin or hydrographic
catchment, and the network of draining channels, the river network that collects and
conveys surface water. River reaches, dams and reservoirs, diversion and pumping
stations, water works and secondary distribution networks are all spatially distributed
elements of this system. Underneath, we find the unsaturated and saturated zones of
groundwater aquifers, usually contributing considerable quantities of high quality
water with quite different, much slower storage and flow characteristics.
The elements of water resources management are distributed in space. Their
location, surrounding, and spatial relationships are critical for the resulting flow
characteristics and the quality, of the water resources and thus their availability for
different types of use. River basin management has obvious spatial dimensions,
since it is focused on a spatial unit, the hydrological catchment, in the first place.
Consequently, geographic information systems are one of the tools that can be used
for their analysis. This makes the use of GIS, and its integration with traditional water
resources models, and obvious strategy for the development of river basin
management systems (Maidment 1996, Fedra and Jamieson, 1996).
While the GIS is used to capture, analyse, and display spatial data, the models
provide the tools for complex and dynamic analysis. Input for spatially distributes
models, as well as their output, can be treated as map overlays and topical maps
(Fedra,1994) . The familiar format of maps supports the understanding of model
results, but provides also a convenient interface to spatially referenced data. And
expert systems, simulation and optimisation models add the possibility for complex,
and dynamic analysis to the GIS.
One major challenge in building effective river basin information systems is the
integration of dynamic models with the capabilities of GIS. The GIS can provide a
common framework of reference for the various tools and models addressing a
range of problems in river basin management, supply distributed data to the models,
and assist in the visualisation of spatial model results in the form of topical maps. In a
multi-media framework, it can also provide a common interface to the various
functions of an integrated river basin information and decision support system. This
interface has to translate the data and model functionality available into information
that can directly support decision making processes (Fedra, 1995).
FUNCTIONS AND TOOLS
WaterWare organises the data describing a river basin in terms of spatial objects:
they include elements such as monitoring stations and their associated time series of
measurements, sub-catchments and irrigation districts, the river network with it nodes
and connecting reaches, as well as the various simulations models and their
scenarios (Fedra and Jamieson, 1996a,b, Jamieson and Fedra 1996a,b). With all
objects geo-referenced and the models spatially distributed, the embedded GIS is a
The embedded GIS
The map layers used in WaterWare either provide background for spatial
reference and orientation, or direct data input for the simulation models.
Examples for the latter are the digital elevation model (DEM), land use maps,
and the river network.
The embedded GIS offers tools for layer selection and stacking, zooming,
color editing, a four window mode for map comparison, 3D display of the DEM
with any map draped over the elevation data, and read-back functions for
locations, distances, or areas.
FIGURE 1,2: GIS examples, four windows and 3D DEM display
Monitoring time series.
Historical data of rainfall, river flow, and air temperature, as well as water
quality are stored for the various monitoring stations. Continuous ongoing
measurements from selected stations are transferrd by GSM phones and
incorporated into the data base in real-time to provide an accurate and up to
date picture of the situation (http://jpsscada.moa.my/kelantanw.htm).
These hydrographic and hydrometeorological observation data are not only
analysed in their own right, they also form the input for the various simulation
FIGURE 3,4,5,6: Time-series analysis (flow), histogram, spatial homogeneity, spatial interpolation
Analysis of droughts
A major problem for water resources management are droughts: prolonged
periods of below-average rainfall that lead to low soil moistures, lowering of
the groundwater table, and, most importantly, low flow in the river. This, in
turn, leads to a combination of increased water demand for irrigation and a
low availability of irrigation water: below a certain low-flow level, pumping
water out of the river in fact becomes impossible, the pumps fall dry. Based
on a model by Jamaluddin et al.,(2000), WaterWare links the time series of
rainfall observations to a drought analysis module.
Sub-catchment and runoff modelling
The water resources model needs river flow at all of its start nodes,
representing inputs. These can be well fields, where groundwater enters the
surface water budget, or sub-catchments. For the latter, a rainfall-runoff model
provides data for ungaged catchments, but also the possibility for scenario
analysis of land-use changes or long-term climate change.
Data such as
catchment boundaries, elevations and slopes, land use, as well as rainfall
inputs are automatically taken from the GIS and time series data base,
FIGURE 7: Rainfall-Runoff Model results
Irrigation water demand
Irrigated agriculture, and rice paddies in particular, are the dominant
consumer of water, by far exceeding industrial and domestic demand. The
water demand in a given year depends on the naturally available water
through rainfall, but also the areas and crop varieties to be irrigated, irrigation
technology, the conveyance systems (e.g., lined versus unlined irrigation
canals), and operational control. A specific simulation model is used to predict
the water demand for any of the irrigation districts in the basin.
FIGURE 8,9: Irrigation Water Demand Model: irrigation district object and simulation model
Water resources allocation
The central model in the WaterWare system is a dynamic, water resources model
that computes a daily water budget for all nodes in the river network. The model
computes water budgets in terms of demand and supply, routing the water from the
start nodes (sub-catchments) to the demand nodes (irrigation districts and cities) and
ultimately the sea. Different allocation strategies and policies can thus be tested for
the effectiveness and efficiency.
By adding a simple estimation routine for the net
economic benefit for different types of water use, an overall economic optimisation of
the water allocation is possible.
FIGURE 10: Water Resources Management model results
River water quality
The flow in the individual reaches of the river network is a major determinant
for water quality: dilution is a major factor in pollution. The dynamic water
quality model describes the balance of organic load, measured as BOD
(biological oxygen demand) and dissolved oxygen, as well as any arbitrary
pollutant, conservative or undergoing first-order decay. Examples would be
agrochemicals such as fertilizers and pesticides, or the salts leached out from
irrigated agricultural soils. Sources of pollution are major settlements and their
waster treatment plants, as well as any major industrial or agricultural water
users that return used process or irrigation water to the system. The model
treats both points sources of pollution, as well as lateral inflow from diffuse
Groundwater flow and quality
Similar to the contamination of surface water, groundwater pollution can result
from the large-scale application of fertilizers and agrochemicals. Waste
management in the form of badly managed land fills is an other potential
source of groundwater pollution in the humid tropics. The groundwater model
describes the first, shallow aquifer that is directly exposed to non-point source
The major driving forces include the spatially distributed recharge
from rainfall depending on land use, infiltration or exfiltration from and to the
river, and the pumping of groundwater in shallow wells, that constitute the
majority of small, domestic wells. Spatially varying characteristics of the
aquifer and landuse are directly taken from the GIS. Excessive levels of
nitrates that can pose a long-term health hazard are the major problem.
FIGURE 11: Ground Water Model results
Environmental Impact assessment
A water resources management system is subject to structural changes such
as new reservoirs, or policy changes resulting in a modified water allocation
pattern. Any such project or policy change will have a range of environmental
impacts, positive or negative. For the screening level assessment of such
projects, and new reservoirs in particular, WaterWare offers a rule-based
expert system for environmental impact assessment (Fedra et al., 1991). A
checklist of potential problems is used together with a set of rules for the
evaluation, with the data coming from the GIS, the object data base, and
model results. The inference engine uses a combination of forward and
backward chaining (Fedra and Winkelbauer, 2002), to provide a classification
of all potential problems relevant for a given project and environment.
Beyond the implementation of the system on a PC server under Linux,
accessible from the console and any computer in the local area network, parts
of WaterWare are also accessible through the Internet. All major modules
export results as HTML files with their associated graphics into the directory
tree of a web server (http://126.96.36.199/KELANTAN/) running under
supports distributed, remote clients also on low-bandwidth connections, and
thus increases the potential group of users considerably.
WaterWare is an object oriented information and decision support system for
river basin management. The basic data framework combines a hybrid GIS as
the overall structure with classes of objects, including river basin elements,
models and model scenarios, and tasks or decision problems.
River basin elements are spatially referenced, and represent, for example,
sub-catchments, reservoirs, treatment plants, river reaches, etc. From the GIS
perspective, they are polygons, lines, points, or regular cell grids. Their state,
in a context defined by other objects in the system, is determined by a set of
methods, which are models or sets of rules for an embedded expert system.
Tasks are specific, problem oriented views of river basin objects or
combinations of objects. They present their state, usually over time, given a
number of decision variables or scenario assumptions, to the user to support
planning or management decisions.
The various objects are linked explicitly, eg., a reservoir might be linked to the
sub-catchment that provides its inflow, an observation station that monitors
the hydro-meteorological data, and an irrigation district it supplies water to.
Models such as a rainfall-runoff model or an irrigation water demand
estimation model are used to update the state of these respective objects,
and thus provide inputs (time series of demand or supply) to a water
resources model. The water resources model, in turn, provides input to a
water quality model, that again operates in the context of other objects such
as discharge nodes (treatment plants, industries, municipalities), or extraction
and monitoring points.
Models are embedded, as methods, with the respective objects. Rules are
used to configure the scenarios and estimate parameters. The models'
operation can either be transparent, when a task requires an update on an
object, or explicit, when the task is defined in terms of model scenario
The GIS, with the underlying spatial data such as land use, geology, and
topography, also provides the display functions; spatial model output is
dynamically mapped onto the map background as animated topical map
coverages. Textual, numerical, and pictorial attributes of an object, and meta
data providing background information to the user, are accessible through a
multi-media hypertext system, that objects use to present themselves to the
user. GIS, data base, and model interface are thus fully integrated, and
present a unified graphical and symbolic representation of a river basin to the
user. This interface supports an easy to learn, exploratory and experimental
access to a large and complex information and decision support system. The
multi-media nature of the system's interface also makes its extension into a
networked client/server version for access through the World Wide Web
straightforward, which increases the group of potential users, and eventually,
the planning and management decision they make.
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