Spatial tools lecture3

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Spatial tools lecture3

  1. 1. Spatial Tools in Water Resource ManagementSusan Steele-Dunne3. Watersheds and ArcGIS
  2. 2. Acknowledgements• ESRI: (http://webhelp.esri.com/arcgisdesktop/9.2)• HydroSHEDS• Prof. Nick van de Giesen 2
  3. 3. Learning objectivesBy the end of this lecture, you will be able to:1) Explain what a watershed is2) Explain how graph theory can be used to determine the watershed3) Use ArcGIS to calculate the watershed from a digital elevation model. 3
  4. 4. Lecture 3: Watersheds and ArcGIS• What is a watershed?• Introduction to Graph Theory• Determining watershed boundaries in ArcGIS• HydroSHEDS 4
  5. 5. What is a watershed? The area from which water drains to a common outlet. A watershed is also known as a drainage basin, basin, catchment, or contributing area. 5http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Understanding_drainage_systems
  6. 6. What is a watershed? A stream network is made up of nodes and links Nodes Pour point = outlet 6http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Understanding_drainage_systems
  7. 7. What is a watershed? A stream network is made up of nodes and links Stream channel = “link” 7http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Understanding_drainage_systems
  8. 8. Introduction to Graph Theory NodesGraph theory = study of graphsGraph = collection of nodes (aka vertices) Edge and edges (links). Undirected graphGraphs are used to model pairwise relationsbetween objects Directed graph aka network 8
  9. 9. Introduction to Graph theoryAdjacency MatrixWhich nodes are adjacent to which other nodes 1 2 •n x n matrix 3 •If node i drains into node j, set A(i,j)=1. 4 5 •Otherwise, set to zero 6 9
  10. 10. Drainage patternsAdjacency MatrixWhich nodes are adjacent to which other nodes: 1 2 0 0 1 0 0 0 0 0 1 0 0  0 3  4 0 0 0 0 1 0 5 A =   0 0 0 0 1 0 0 0 0 0 0 1 6   0  0 0 0 0 0  10
  11. 11. Drainage patternsAdjacency MatrixWhich nodes are adjacent to which other nodes: 1 2 0 0 1 0 0 0 0 0 1 0 0  0 3  4 0 0 0 0 1 0 5 A =   0 0 0 0 1 0 0 0 0 0 0 1 6   0  0 0 0 0 0  11
  12. 12. Drainage patternsAdjacency Matrix2Which nodes are connected by two steps: 1 2 0 0 0 0 1 0 0 0 0 0 1  0 3  4 0 0 0 0 0 1 5 A 2 =   0 0 0 0 0 1 0 0 0 0 0 0 6   0  0 0 0 0 0  12
  13. 13. Drainage patternsAdjacency Matrix2Which nodes are connected by two steps: 1 2 0 0 0 0 1 0 0 0 0 0 1  0 3  4 0 0 0 0 0 1 5 A 2 =   0 0 0 0 0 1 0 0 0 0 0 0 6   0  0 0 0 0 0  13
  14. 14. Drainage patternsAdjacency Matrix3Which nodes are connected by three steps: 1 2 0 0 0 0 0 1 0 0 0 0 0  1 3  4 0 0 0 0 0 0 5 A =  3  0 0 0 0 0 0 0 0 0 0 0 0 6   0  0 0 0 0 0  14
  15. 15. Drainage patterns“Water availability matrix”: Columns show Σ = A + A 2 + A 3 “upstream” nodes! 0 0 1 0 1 1 1 2 0 0 1 0 1 1   3 0 0 0 0 1 1 Σ =   4 0 0 0 0 1 1 5 0 0 0 0 0 1   0  0 0 0 0 0  6Which nodes are upstream from node 3? Nodes 1 and 2 15
  16. 16. Drainage patterns Rows show “Water availability matrix”: “downstream” Σ = A + A2 + A3 nodes! 0 0 1 0 1 1 1 2 0 0 1 0 1 1   3 0 0 0 0 1 1 Σ =   4 0 0 0 0 1 1 5 0 0 0 0 0 1   0  0 0 0 0 0  6Which nodes are downstream from node 2? … Nodes 3, 5 and 6. 16
  17. 17. Drainage patterns “Watershed matrix”: Σ + I = A + A2 + A 3 + I 2 1 1 0 1 0 1 1 0 1 1 0 1 1  3 0 0 1 0 1 1 4 Σ + I =   0 0 0 1 1 1 5 0 0 0 0 1 1   0 0 0 0 0 1 6  We want to include the “zero-th” step, i.e. that a node drains itself => We get the real watershed matrix! 17
  18. 18. Drainage patterns “Watershed matrix”: Σ + I = A + A 2 + A 3 + I 1 2 1 0 1 0 1 1 0 1 1 0 1 1   3 0 0 1 0 1 1 Σ + I =   4 0 0 0 1 1 1 5 0 0 0 0 1 1   0  0 0 0 0 1  6 1 1 3 1 5 6Summing the columns gives the “drainage area” or watershed size for18each pixel
  19. 19. Drainage patternsAdjacency/Watershed Matrix Used inInteresting property: GIS software! I + A + A2 + A3 = ( I − A) −1 GTOPO30 for the Volta Watershed of the Basin and environs Akosombo dam. 19
  20. 20. Drainage patternsAdjacency/Watershed MatrixInteresting property: I + A + A2 + A3 = ( I − A) −1 All the information needed to Adjacency Matrix describe watershed i.e. “local information” 20
  21. 21. Drainage patterns Σ + I = A + A2 + A3 + IFlow accumulation 1 0 1 0 1 1So far, we assumed all pixels 0  1 1 0 1 1 generated same amount of input. 0 0 1 0 1 1 Σ+I =  In practice run-off from pixels is 0 0 0 1 1 1variable 0 0 0 0 1 1   0  0 0 0 0 1  Q = [3.2 2.3 0 0 0 0]Build a row vector Q containingthe run-off produced at eachnode: e.g node 1 generates 3.2 units of water, node 2 generates 2.3 units 21
  22. 22. Drainage patternsFlow accumulation 1 2Build a row vector Q containingthe run-off produced at each 3node: 4Q = [3.2 2.3 0 0 0 0] 5Q * (Σ + I ) = [3.2 2.3 5.5 0 5.5 5.5] 6This gives the total flow accumulated in each node 22
  23. 23. Water use along river network This case will be a bit more complicated. 1 Let’s start by filling in the regular 2 adjacency matrix …. 0 1 0 0 0 0 4 0 0 1  1 0 0 3  0 0 0 0 1 1 W =  0 0 0 0 1 0 6 5 0 0 0 0 0 0   0  0 0 0 0 0  23
  24. 24. Water use along river network This case will be a bit more complicated. 1 Let’s start by filling in the regular 2 adjacency matrix …. 0 1 0 0 0 0 4 0 0 1  1 0 0 3  0 0 0 0 1 1 W =  0 0 0 0 1 0 6 5 0 0 0 0 0 0   0  0 0 0 0 0  24
  25. 25. Water use along river network But how can all the water go from node 2 1 to both nodes 3 and 4? 100% … It doesn’t! 2 70% 30% What happens to our adjacency matrix? 0 1 0 0 0 0 4 3 0 0 0.3 0.7 0 0 20%   0 0 0 0.2 0.8 0 100% 80% W =  0 0 0 0 0 1 6 5 0 0 0 0 0 0   0 0 0 0 0 0 25
  26. 26. Water use along river network But how can all the water go from node 2 1 to both nodes 3 and 4? 100% … It doesn’t! 2 70% 30% What happens to our adjacency matrix? 0 1 0 0 0 0 4 3 0 0 0.3 0.7 0 0 20%   0 0 0 0.2 0.8 0 100% 80% W =  0 0 0 0 0 1 6 5 0 0 0 0 0 0   0 0 0 0 0 0 26
  27. 27. Water use along river network 1 Put W into Matlab/excel and calculate W2: 100% e.g. Where does the water from node 2 2 get to in two steps? 70% 30% 0 0 0.3 0.7 0 0  4 3 0 20%  0 0 0.06 0.24 0.7   0 0 0 0 0 0.2 100% 80% W = 2  0 0 0 0 0 0  6 0 0 0 0 0 0  5   0 0 0 0 0 0  27
  28. 28. Water use along river network 1 Put W into Matlab/excel and calculate W2: 100% e.g. Where does the water from node 2 2 get to in two steps? 70% 30% 0 0 0.3 0.7 0 0  4 3 0 20%  0 0 0.06 0.24 0.7   (6%) 0 0 0 0 0 0.2 100% 80% W = 2 (70%) (24%) 0 0 0 0 0 0  6 0 0 0 0 0 0  5   0 0 0 0 0 0  28
  29. 29. Water use along river network 1 Put W into Matlab/excel and calculate W3: 100% e.g. Where does the water from node 1 2 get to in three steps? 70% 30%  0 0 0 0.06 0.24 0.7  4 3 0 0 0 20%  0 0 0.06   6% 0 0 0100% 0 0 0  80% W = 3  70% 24%  0 0 0 0 0 0  6 0 0 0 0 0 0  5   0 0 0 0 0 0 After 3 steps, 94% of the water from (1) has made it to an outlet, but 6%is just getting to node 4! 29
  30. 30. Water use along river network 1 One last time step, let’s calculate W4: 100% e.g. Where does the water from node 1 2 get to in four steps? 70% 30% 0 0 0 0 0 0.06  4 0 0 0 0 0 0  20% 3   0 0 0 0 0 0 100% W = 4  80% 0 0 0 0 0 0  0 0 0 0 0 0  6   5 0 0 0 0 0 0  30
  31. 31. Water use along river network 1 One last time step, let’s calculate W4: 100% e.g. Where does the water from node 1 2 get to in four steps? 70% 30% 0 0 0 0 0 0.06  4 0 0 0 0 0 0  20% 3   0 0 0 0 0 0 100% W = 4  80% 0 0 0 0 0 0  0 0 0 0 0 0  6   5 0 0 0 0 0 0  31
  32. 32. Water use along river network 1 Let’s calculate the water availability 100% matrix, , for this case: 2 Ω = W +W 2 +W 3 +W 4 70% 30% 0 1.0 0.3 0.76 0.24 0.76 4 0 0 0.3 0.76 0.24 0.76 20% 3   0 0 0 0.2 0.8 0.2 100% 80% Ω=  0 0 0 0 0 1.0  6 5 0 0 0 0 0 0    0 0  0 0 0 0   32
  33. 33. Water use along river network 1 Let’s calculate the water availability 100% matrix, , for this case: 2 Ω = W +W 2 +W 3 +W 4 70% 30% 0 1.0 0.3 0.76 0.24 0.76 4 0 0 0.3 0.76 0.24 0.76 20% 3   0 0 0 0.2 0.8 0.2 100% 80% Ω=  0 0 0 0 0 1.0  6 5 0 0 0 0 0 0    0 0  0 0 0 0   33
  34. 34. Water use along river network 1 Let’s calculate the water availability 100% matrix, , for this case: 2 Ω = W +W 2 +W 3 +W 4 70% 30% 0 1.0 0.3 0.76 0.24 0.76 4 0 0 0.3 0.76 0.24 0.76 20% 3   0 0 0 0.2 0.8 0.2 100% 80% Ω=  0 0 0 0 0 1.0  6 5 0 0 0 0 0 0    0 0  0 0 0 0   34
  35. 35. Water use along river network 1 Let’s calculate the water availability 100% matrix, , for this case: 2 Ω = W +W 2 +W 3 +W 4 70% 30% 0 1.0 0.3 0.76 0.24 0.76 4 0 0 0.3 0.76 0.24 0.76 20% 3   0 0 0 0.2 0.8 0.2 100% 80% Ω=  0 0 0 0 0 1.0  6 5 0 0 0 0 0 0    0 0  0 0 0 0   35
  36. 36. Water use along river network 1 Let’s calculate the water availability 100% matrix, , for this case: 2 Ω = W +W 2 +W 3 +W 4 70% 30% 0 1.0 0.3 0.76 0.24 0.76 4 0 0 0.3 0.76 0.24 0.76 20% 3   0 0 0 0.2 0.8 0.2 100% 80% Ω=  0 0 0 0 0 1.0  6 5 0 0 0 0 0 0    0 0  0 0 0 0   36
  37. 37. Water use along river network 1 Suppose we inject 200 units of water at 100% node 1. How much will we see at each node? 2 70% 30% 4 3 20%100% 80% 6 5 37
  38. 38. Water use along river network 1 Suppose we inject 200 units of water at 100% node 1. How much will we see at each node? 2 70% 30% Calculate P* where P=[200 0 0 0 0 0] 4 3 20%100% 80% 6 5 38
  39. 39. Water use along river network 1 Suppose we inject 200 units of water at 100% node 1. How much will we see at each node? 2 70% 30% Calculate Q=P* where P=[200 0 0 0 0 0] 4 3 20% Q=[0 200 60 152 48 152]100% 80% 6 5 39
  40. 40. Water use along river network 1 How do you account for water being 100% used at a node? 2 70% 30% 4 3 20%100% 80% 6 5 40
  41. 41. Water use along river network 1 How do you account for water being 100% used at a node? 2 Suppose we inject 200 units at node 70% 30% 1, but use 100 units at node 2: 4 3 P=? 20%100% 80% 6 5 41
  42. 42. Water use along river network 1 How do you account for water being 100% used at a node? 2 Suppose we inject 200 units at node 70% 30% 1, but use 100 units at node 2: 4 3 P=[200 -100 0 0 0 0] 20%100% 80% 6 5 42
  43. 43. Water use along river network 200 1 P=[200 -100 0 0 0 0] 100% 100 Q=P* 2 70% 30% 4 Q=[0 200 30 76 24 76] 20% 3100% 80% 6 5 43
  44. 44. Water use along river network 200 1 P=[200 -200 0 0 0 0] 100% 200 Q=P* 2 70% 30% 4 Q=?? 20% 3100% 80% 6 5 44
  45. 45. Water use along river network 200 1 P=[200 -200 0 0 0 0] 100% 200 Q=P* 2 70% 30% 4 Q=[0 200 0 0 0 0] 20% 3100% 80% 6 5 45
  46. 46. Water use along river network 1 What if you demand too much 100% water?? 2 70% 30% P=[200 -300 0 0 0 0] 4 Q=P* 20% 3100% 80% Q=? 6 5 46
  47. 47. Water use along river network 1 What if you demand too much 100% water?? 2 70% 30% P=[200 -300 0 0 0 0] 4 Q=P* 20% 3100% 80% Q=[0 200 -30 -76 -24 -76] 6 5 47
  48. 48. Watershed delineation in ArcGISWhat is a watershed?The area from which water drains to a common outlet.AKA drainage basin, basin, catchment, or contributing area. 48
  49. 49. Watershed delineation in ArcGIS Depressionless DEM Flow Feature Direction Pour Points Stream to Feature Stream Flow Raster (1/0) Accumulation Pour Stream Points Order Watershed 49Blue=> Hydrology ToolsetBlack=> Standard ArcGIS
  50. 50. Watershed delineation in ArcGISDigital Elevation ModelRaster data describing surface of earth. Accuracy depends on: Resolution Data type Observation method 50
  51. 51. HydroSHEDSHydrological data and maps based on ShuttleElevation Derivatives at multiple Scales)http://hydrosheds.cr.usgs.gov/ 51
  52. 52. HydroSHEDS:Shuttle Radar Topography Mission (http://www2.jpl.nasa.gov/srtm/index.html) 52
  53. 53. Watershed delineation in ArcGISIdentifying and filling Sinks Sinks most likely to be imperfections in DEM Remove before flow direction calculations!! Coarser DEM => More sinks!Peaks are more often natural, and cause fewer problems 53
  54. 54. Watershed delineation in ArcGIS Depressionless DEM Flow Feature Direction Pour Points Stream to Feature Stream Flow Raster (1/0) Accumulation Pour Stream Points Order Watershed 54Blue=> Hydrology ToolsetBlack=> Standard ArcGIS
  55. 55. Watershed delineation in ArcGISFlow DirectionWhere does the water flow from each cell? 55
  56. 56. Watershed delineation in ArcGISFlow DirectionWhere does the water flow from each cell? 56
  57. 57. Watershed delineation in ArcGIS Depressionless DEM Flow Feature Direction Pour Points Stream to Feature Stream Flow Raster (1/0) Accumulation Pour Stream Points Order Watershed 57Blue=> Hydrology ToolsetBlack=> Standard ArcGIS
  58. 58. Watershed delineation in ArcGISFlow accumulation 58
  59. 59. Watershed delineation in ArcGISFlow accumulation 59
  60. 60. Watershed delineation in ArcGISPour points:1) Create in a feature class2) Convert to raster=> Ensure you are in ahigh flowaccumulation gridcell!! 60
  61. 61. Watershed delineation in ArcGIS WatershedFlow accumulation Watershed Watershed tool rasterPour point raster 61
  62. 62. Watershed delineation in ArcGIS Depressionless DEM Flow Feature Direction Pour Points Stream to Feature Stream Flow Raster (1/NoData) Accumulation Pour Stream Points Order Watershed 62Blue=> Hydrology ToolsetBlack=> Standard ArcGIS
  63. 63. Watershed delineation in ArcGISStream to feature 63
  64. 64. Watershed delineation in ArcGIS Stream Ordering Classify the reach within the larger river system Strahler stream ordering method 64http://www.fgmorph.com/fg_4_8.php
  65. 65. Watershed delineation in ArcGIS“DEM” Sinks: “FilledDEM” “FlowDir” Flow Fill Fill Direction “FlowAcc” Pour points Watersheds Watershed 65
  66. 66. Case Studies Dr. Markus Hrachowitz, UD, Hydrology Rolf Hut, PhD student, Water Resources Management 66
  67. 67. Assignment 3:In this assignment, youwill use ArcGIS todelineate the watershed ofthe Red and White Voltabasin and to study thestream network. 67
  68. 68. Watershed delineation in ArcGIS Depressionless DEM Flow Feature Direction Pour Points Stream to Feature Stream Flow Raster (1/0) Accumulation Pour Stream Points Order Watershed 68Blue=> Hydrology ToolsetBlack=> Standard ArcGIS
  69. 69. Sources imagesIf a website or source is not added to a picture, then the image is taken from the ArcGIS softwareor from www.esri.com. 69

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