LOW FLOW INDEX MAP OF NORWAY INTERACTION USING GIS-SOFTWARE AND - - PowerPoint PPT Presentation

LOW FLOW INDEX MAP OF NORWAY

INTERACTION USING GIS-SOFTWARE AND ANALYSIS Astrid Voksø, NVE

Nils Kristian Orthe, Hege Hisdal, Kolbjørn Engeland Olav Kavli, Geodata AS

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Low flow index map for Norway

■

Background

■ Calculate the common low flow , Qclf,

• Required information in

Decision-making concerning small hydro power plants Water supply a.s.o

■ Low flow index is different discharges indicating how low

discharge can be at a certain point Normal discharge Low discharge

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Inland catchments

Average runoff Common low flow Q95 summer

Runoff (m3/s) Coastal areas

Discharge-curve varies in the country

Runoff (m3/s)

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Low flow index map for Norway

■ Finding regression equations for homogenous regions in

Norway at ungauged sites

■ Establish a relationship between the common low flow and

some catchment characteristics

■ Engeland et al. 2006

■ GIS analyses defined for all the parameters using national

datasets prepared or developed at NVE

■ User interaction through a web-application towards a GIS

server

■ Engeland et al 2008

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Two main issues and a user interface

■

From a random point on all rivers in Norway, generate a watershed with high accuracy catchment boundaries

■ The method for creating watersheds are standard in

ArcGIS, but the result is depend on dataset used

■

Calculate all input parameters to the regression model automatically using ArcGIS with Spatial Analyst as extension

■ Develop dataset and analyses to be automated for all of

the parameters

■

User interface

■ The system should work on web using ArcGIS server

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Calculate watershed from a point

■

Require a flow accumulation grid derived from a digital elevation model with high resolution and quality

■ DTEM 25, adapt to hydrology

 Hydrological digital elevation model

■ Topo2raster input parameters

• Elevation points from DTEM25
• Lake with elevation
• River network – correct direction on lines

■ Create flow direction grid and flow accumulation grid

• River network burned 30 meter into Hydro DTEM in advance

■

Process is time-consuming because

■ River network correctness is crucial ■ Quality control is essential

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Comparing Flow accumulation grid

From DTEM25 Without river network From DTEM25 With river network REGINE waterdivide

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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National datasets

■ Required datasets developed at NVE

■ REGINE – watershed archive – 20.000 units ■ Lake database – all lakes > 2500 m² identified ■ River network –

• Centre line of rivers and lakes connected to rivers in
• nodes. Lines have direction towards outlet in sea

■ Runoff map – GRID pixel size 1 x1 km² , each cell

value is mean runoff from 1961-90 i mm. year

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Combine existing and generated watersheds

■ Automatic generating watershed for large areas

■ Takes time (up to 35 minutes) ■ Application runs in timeout

■ Combine generated catchment and existing

■ Select the sub catchment where the user has placed

the point, inside this extent find the watershed - REGINE – hierarchic catchment system. Identification can give both area of higher level and upstream areas.

■ Extent for the higher level used for automatic

generation

■ Upstream is used for generating upstream polygon

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Feature to Line Select shape_length > 2000 Feature to Polygon

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Demo

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http://gis.nve.no/ge/Viewer.aspx?site=Lavvann

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Velg punkt = Choose your point along the river network

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Genererer nedbørfelt = Catchment for chosen point is calculated

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Rediger nedbørfelt = Edit the calculated catchment

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Nedbørfelt Redigering = Edit the calculated catchment

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Generer feltparametre = Generate field parameters

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Generer feltparametre = Field parameters result:

• Vassdragsnummer: Catchment ID
• Climate region
• Area
• Mean runoff
• Min/max elevation of catchment
• Percentage of lake/glacier/forest/cultivated

land/bog/area above tree line

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Generer feltparametre = Field parameters result:

• Urban areas
• Effective lake percentage
• Several temperature parameters
• Length of catchment
• Length of river
• River gradient

Norwegian Water Resources and Energy Directorate

Generer feltparametre = Field parameters result:

• Several temperature parameters
• Length of catchment
• Length of river
• River gradient
• Elevation gradient
• County/municipality
• Catchment name

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Generer indekser= Generate low flow indexes Result is marked with red square

• Ordinary low flow index
• 5 percentile (annual/summer/winter)
• Average runoff (1961-90)
• BFI: Base Flow Index

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Eksporter til Shape= Export to shape file Last ned Shape = Download shape file

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Eksporter til Pdf= Export to pdf format Last ned pdf= Download pdf

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Calculate effective lake percentage

■ Area of the derived watershed ■ Lake area and catchment area for all lakes in the

derived watershed

■ Lake catchment area

• cell with highest value from the flow accumulation grid

inside the lake

■ Lake area

• Lakedatabase – unique ident and area for each lake

■ Store result in a table for each lake

■

Effpro = ∑(lake Area * Lake Catchment area)/(watershedArea)²

1363 * 625 / 1000000 = 0.85

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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River length - and gradient

River in REGINE REGINE-number - 024.15Z Rest rivers – random number Create route Calibrate route measure 0 at top Length route measure at end

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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River gradients

■

Cell value from DTEM is the chosen points elevation

■

Top of each river are identified with route name and elevation is calculated from the DTEM ST = (712.2 – 419 ) / 3.8 = 77

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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River - and catchment length

■

River length = distance to top of river from your point

■ measure at the chosen point

■

Catchment length = distance from chosen point to most remote point on the watershed divide

■ Change watershed divide from line to points and

measure the distance from all points to the chosen

• point. Use the point with largest distance (Near)

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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User interface

■ Web-application

■

Map - and application tools

■ ArcSDE ■ ArcGIS Server

■ Parameters from GIS are captured using web-services ■ Regression models are defined in a windows application

Norwegian Water Resources and Energy Directorate

• 2. jun. 2013

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Conclusion

■

The results of the GIS analyses are very good

■ Require a number of national datasets ■ Creating flowdirection and flowaccumulaton with high accuracy

enable us to generate watersheds to points and lakes

• Require quality check of river network

■ River network transform to routes with zero measure at top

This was crucial but took time

■

The calculated low flow indices +- 20 % uncertainty

■ Must be used with caution

■

Results have multipurpose range of use and has been a very popular tool both internal and external

Norwegian Water Resources and Energy Directorate

Where are the data stored

■ 2 feature classes in

ArcSDE

■ Point feature class ■ Catchment feature

class

• With all parameters

as attributes

• 2. jun. 2013

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Norwegian Water Resources and Energy Directorate

Low flow index web application - Number of daily analysis

Norwegian Water Resources and Energy Directorate

NVE’s Low Flow Index Tool

Thank you

Norwegian Water Resources and Energy Directorate

Standard layout of result as pdf file

Author and section

Norwegian Water Resources and Energy Directorate

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