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

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

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LOW FLOW INDEX MAP OF NORWAY INTERACTION USING GIS-SOFTWARE AND ANALYSIS Astrid Voks, NVE Nils Kristian Orthe, Hege Hisdal, Kolbjrn Engeland Olav Kavli, Geodata AS Low flow index map for Norway Background Calculate the common low

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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

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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

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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)

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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

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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

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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

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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

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Norwegian Water Resources and Energy Directorate

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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

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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

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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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Norwegian Water Resources and Energy Directorate

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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Norwegian Water Resources and Energy Directorate

Genererer nedbørfelt = Catchment for chosen point is calculated

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Norwegian Water Resources and Energy Directorate

Rediger nedbørfelt = Edit the calculated catchment

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Norwegian Water Resources and Energy Directorate

Nedbørfelt Redigering = Edit the calculated catchment

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Norwegian Water Resources and Energy Directorate

Generer feltparametre = Generate field parameters

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Norwegian Water Resources and Energy Directorate

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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Norwegian Water Resources and Energy Directorate

Generer feltparametre = Field parameters result:

  • Urban areas
  • Effective lake percentage
  • Several temperature parameters
  • Length of catchment
  • Length of river
  • River gradient
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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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Norwegian Water Resources and Energy Directorate

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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Norwegian Water Resources and Energy Directorate

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

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Norwegian Water Resources and Energy Directorate

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

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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

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Norwegian Water Resources and Energy Directorate

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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

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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

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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)
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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

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Norwegian Water Resources and Energy Directorate

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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

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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

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NVE’s Low Flow Index Tool

Thank you

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Standard layout of result as pdf file

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Author and section

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