ESRI Romania Bucharest, Romania

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National Institute of Hydrology and Water
Management
HYDROLOGICAL REGIONALISATION OF MULTIANNUAL MEAN
DISCHARGE USING GIS - TIMIS-BEGA RIVER BASIN
APPLICATION -
Bogdan CHEVERESAN, Simona RADU, V. Al. STANESCU
ESRI Romania Bucharest, Romania National
Institute of Hydrology and Water Management
Bucharest, Romania
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National Institute of Hydrology and Water
Management
The regionalisation technique is used to
transfer the hydrologic point information,
determined by direct computation to points in
which these data are missing. This paper
presents a method for calculating multiannual
mean discharge value, based on geo-referenced
raster format digital elevation model. We used
an ArcInfo GRID as raster format with one square
kilometer cell, obtained by exporting TIN digital
elevation models.
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Institutul National de Hidrologie si Gospodarire
a Apelor

• Hydrological regionalisation of the mean runoff

• Knowledge of the phenomena selecting the
  factors which have the greatest influence on the
  spatial distribution of the hydrological
  synthetic characteristics.
• Direct causative factors
• meteorological precipitation being the most
  important
• physico-geographical
• Analyzing the degree of influence which these
  factors have on the spatial distribution for the
  studied hydrological element.

One way is to make a regression analysis and
to keep those factors which have significant
coefficients in the resulting linear regression
equation. (Stanescu si Oancea, 1994)
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Institutul National de Hidrologie si Gospodarire
a Apelor

• Hydrological regionalization of the mean runoff

• As a result of the analysis we can say that
  altitude has probably the most important role in
  determining the water resources potential
• The steps of the relief reflected by the
  mean elevation integrate
• the variation of the meteorological factors
  (precipitation and evapotranspiration)
• global effects of the relief characteristics
  (basin slope, river slope,)
• The punctual capacity the
  potential of each square
• kilometre form the basin to produce a certain
  runoff of a given intensity

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Institutul National de Hidrologie si Gospodarire
a Apelor

• Hydrological regionalization of the mean runoff

The mean runoff is characterized by mean
monthly values and multi annual values, as well
as the runoff variation during that year and from
year to year.
Based on mean multi annual discharge data
we can calculate the specific mean multi annual
discharges, using the equation below
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National Institute of Hydrology and Water
Management
Timis-Bega River Basin Application - RIVER-LIFE
PROJECT -
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National Institute of Hydrology and Water
Management
In correlation with mean altitude of
Timis-Bega basin a five distinct zones resulted
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National Institute of Hydrology and Water
Management
The zones which are homogeneous have been
assessed by a method of clusterisation obtained
by the relationship between the annual variation
of discharge and the mean specific discharge.
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National Institute of Hydrology and Water
Management

• Digital elevation model

Using elevation information extracted from
topographic maps (elevation contours and spots )
a digital elevation model was generated in the
TIN (Triangulated Irregular Network) format for
every sub-basin.
3D Analyst extension Create TIN from Features
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National Institute of Hydrology and Water
Management
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National Institute of Hydrology and Water
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• Elevation GRID

A TIN for every sub-basin will be exported into
an integer elevation ArcInfo GRID (we can open
and see the attribute table only for integer
GRIDs ). There are two ways to convert a TIN
into an integer GRID - using ArcToolbox
application - in ArcMap application
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National Institute of Hydrology and Water
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• Grid attribute table

Every ArcInfo GRID attribute table will be
exported, and a new file with .dbf extension will
result.
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National Institute of Hydrology and Water
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• Exported attribute table

Exported attribute table can be opened either in
Microsoft Excel or directly added in ArcMap Table
of Contents. In both cases a new column of
multi annual mean discharge will be added and the
values will be calculated by a sub-basin
formula. It is indicate to work in ArcMap and
use the attribute table options to insert new
columns and to calculate their values.
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National Institute of Hydrology and Water
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• Join the tables

Using Join/Release function we join every
ArcInfo GRID attribute table with exported table
based on a common column Object ID or Value
(best suitable)
Multiannual mean discharge column
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National Institute of Hydrology and Water
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Classified symbology of multiannual mean
discharge
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Institutul National de Hidrologie si Gospodarire
a Apelor

• Conclusions

• The procedures of the hydrological
  regionalisation are inscribed in the
  international initiative (PUB) of International
  Association of Hydrological Sciences as one of
  the most important ways of Prediction in Ungauged
  Basins.

• The application of GIS in this domain is
  based on the Digital Elevation Model and the
  morphological characteristics of the catchments.

• The determination of the relationships
  between the hydrological elements and
  morphological characteristics of the basin as
  well as of the homogeneous zones, result in
  determining the equation valid for each pixel
  after which will be to determine the digitised
  map of mean specific discharge.

• If good accuracy is obtained, the errors will
  not exceed 10.

• This method can be applied at sub-basin level
  in order to determine other hydrological
  parameters.

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National Institute of Hydrology and Water
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Thank you !