Application procedure for watershed delineation with lakes
To delineate watershed with lakes, following dataset are needed and an example of input dataset for a small watershed can be downloaded here:
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DEM [mandatory]: A hydrologically consistent DEM is preferred here. For example, global hydrologically consistent DEM dataset HydroSHEDS and MERIT. DEM dataset prefer to be in ".tif" format and can be in any resolution and spatial coordinate system. The extent of the DEM can be either larger than the extent of the target watershed or the same as the extent of the target watershed. Correspond to "merit_dem_big.tif" or "merit_dem_big.tif" in the example dataset.
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Lake polygons [optional]: The lake polygon should be in ESRI shp format. Follow attributes needs to be include in the lake polygon shpfile: 1) Hylak_id, the unique Id of each lake within the lake polygon shpfile; 2) Lake_type, type of the lake should be integer; 3) Vol_total, the volume of the lake in km3; 4) Depth_avg, the average depth of the lake in m; 5) Lake_area, the area of the lake in km2. The Lake polygons can be obtained from HydroLAKE database and all required attribute are included. To use lake polygon from other source, required attributes need to be added into the attribute table. Correspond to "HyLake.shp" in the example dataset.*
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Observation point file [optional]: This is a point files indicate the location of the streamflow observation gauges. Following attribute needs to be included in this files: 1) STATION_NU, the name of the observation guage; 2) Obs_ID, the observation guage ID, which is a unique number assigned to each gauge; 3) DA_obs, Observed drainage area in km2; and 4) SRC_obs, the source of the observation gauges, 'CA' for gauges in Canada and 'US' for observation gauge in United States. Correspond to "obsfinal.shp" in the example dataset.
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Stream shpfile for Bankfull width, depth and discharge [optional]: This is a line shpfile indicate river segments. The Bankfull width, depth and discharge for each river segment is stored in the attribute of this line shpfile. 1) WIDTH, is the Bankfull width in m; 2) DEPTH, is the Bankfull depth in m; 3) Q_Mean, is the annual mean discharge in m3/s. Correspond to "narivs_new_b5.shp" in the example dataset.
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Landuse raster [optional]: This is a landuse raster which will be used to estimate the floodplain roughness coefficient. Preferred to be the same resolution and the same coordinate system as DEM. Correspond to "landuse.tif" in the example dataset.
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Landuse roughness table [optional]: This is a table describing the floodplain roughness coefficient correspond to a given landuse type. The table should have two columns: RasterV and MannV. RasterV is the landuse value in the landuse raster for each land use type and the MannV is the roughness coefficient value for each landuse type. Correspond to "Landuse.csv" in the example dataset.
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Streamflow database [optional]: The toolbox can automatically download streamflow observation data from USGS website for US gauges or automatically read streamflow data from a HYDAT database for Canadian gauges. The 'Hydat.sqlite3' is needed if Canadian streamflow observation is needed.
The toolbox can be initialized and imported by:
############################ Import toolbox
from ToolboxClass import LRRT
import os
############################ Define Inputs
### Define where the example dataset are located
Example_Folder = 'xxx/xxx/example_folder/'
### Define where output should be saved
Output_Folder = 'xxx/xxx/output/'
### Define a project name
ProjectName = 'Project Name'
###Define path to input files
Path_DEM = os.path.join(example_folder, 'merit_dem_big.tif')
Path_Lake_ply = os.path.join(example_folder, 'HyLake.shp')
Path_obs_pt = os.path.join(example_folder, 'obsfinal.shp')
Path_bkf_wd = os.path.join(example_folder, 'narivs_new_b5.shp')
Path_Landuse = os.path.join(example_folder, 'landuse.tif')
Path_Roughness_landuse = os.path.join(example_folder, 'Landuse.csv')
Path_CA_HYDAT = os.path.join(example_folder, 'Hydat.sqlite3')
############################ Initialize toolbox
RTtool=LRRT(dem_in = Path_DEM,WidDep = Path_bkf_wd,Lakefile = Path_Lake_ply,Landuse = Path_Landuse,Landuseinfo = Path_Roughness_landuse, obspoint = Path_obs_pt,OutputFolder = Output_Folder,ProjectNM = ProjectName)
After import and initialize the toolbox, the first step is to define the processing extent. The processing extent is a region within which the toolbox will processing data and generate lake river routing networks. The processing extent can be defined in two different ways: 1) using the extent of the input dem as the processing extent (Figure 1); and 2) provide a outlet coordinate, then the toolbox will generate the drainage area controlled by this coordinate and using this as the processing extent (Figure 2).
############################Define the processing extent
#################
Option 1: use input DEM as the processing extent
#################
### Define processing extent
RTtool.Generatmaskregion()
############################Define the processing extent
#################
Option 2: Provide a big dem and outlet coordinate of region of interest
#################
### Define outlet coordinate
OutletPointxy = [-92.387,49.09]
### Define processing extent
RTtool.Generatmaskregion(OutletPoint = OutletPointxy)
The extent of input datasets needed by the Toolbox is normally global or continental. In the preprocessing step the toolbox will: 1) automatically crop all input datasets with the processing extent defined in previous step; 2) Resample raster inputs to match the extent and the resolution of DEM dataset; and 3) Transfer cropped vector inputs into raster datasets with the same extent and the resolution of the DEM dataset.
############################Preprocessing inputs data
RTtool.Generateinputdata()
In this step, the toolbox will generate predefined river system and catchments without considering lakes. A user specified flow accumulation thresthold is needed. The larger flow accumulation you provided, the coarser catchments and river system will be generated.
############################Generating river network and catchments without considering lakes
### Define flow accumulation thresthold
accthres = 500
### Generating river segments and catchments without considering
RTtool.WatershedDiscretizationToolset(accthresold = accthres)
In this step, first, lakes within the drainage area will be divided into two categories: 1) lakes that are connected by the predefined river network in previous step and 2) lakes that are not connected by the predefined river network (Figure 4A). Then the toolbox will selected connected lakes and none connected lakes using user provided lake area thresholds for connected lake and none connected lake, respectively. Only lakes with lake area larger than these thresholds will be processed and added into the routing network. Catchments generated in this step is showed in Figure 4B. In this routing structure showed in Figure 4B, all lake's inlets and outlets are presented as catchment outlet. Each none connected lakes is represented by a catchment with none connected lake, while some connected lakes that cover multiple predefined river reaches are represented by more than one catchments. Further steps will merge catchments covered by the same connected lakes, the final routing structure is showed in Figure 4C.
############################Add lakes into the routing network-Part1
### define lake area thresthold for connected lakes
Thresthold_Lake_Area_Connect = 0
### define lake area thresthold for connected lakes
Thresthold_Lake_Area_none_Connect = 0
#### Add lakes
RTtool.AutomatedWatershedsandLakesFilterToolset(Thre_Lake_Area_Connect = 0,Thre_Lake_Area_nonConnect = 0.1)
Routing related parameters for each catchments showed in Figure 4B will be calculated in this step, which can be found in Table 1. To calculate catchment area, river length, and slope etc, user need to specify a projected coordinate system. The toolbox will calculate length and area related parameters under this coordinate system.
| Name | Description | Unit |
|---|---|---|
| SubId | Subbasin ID | - |
| DowSubId | Downstream subbasin ID | - |
| BasArea | Area of the catchment | m2 |
| BasSlope | Averaged slope of the catchment | m m-1 |
| BasAspect | Averaged aspect of the catchment | degree |
| RivLength | The length of the river within catchment | m |
| RivSlope | The river slope | m m-1 |
| BkfWidth | The bankfull width of the catchment | m |
| BkfDepth | The bankfull depth of the catchment | m |
| Q_Mean | The annual averaged discharge | m3/s |
| IsLake | -9999 catchment is not a lake catchment; 1 catchment with a connected lake; 2 catchment with a none connected lake | - |
| HyLakeId | The lake ID | - |
| LakeVol | The lake volume | km3 |
| LakeDepth | The lake depth | m |
| LakeArea | The lake area | km2 |
| Laketype | The lake type | - |
| MeanElev | The mean elevation of the catchment | m |
| FloodP_n | The flood plain manning’s coefficient | - |
| Ch_n | The channel manning’s coefficient | - |
| DA | The drainage area of this catchment | m |
| Strahler | The Strahler order of each river reach | - |
| Seg_ID | The unique ID of each river reach | - |
| Seg_order | The unique ID of each river segment in each river reach | - |
| Max_DEM | the maximum elevation along the river segment | m |
| Min_DEM | the minimum elevation along the river segment | m |
| IsObs | > 0, means the catchment is has a streamflow observation gauge | - |
| DA_Obs | Observed streamflow gauge drainage area | km2 |
| DA_error | Percentage of drainage area error for a given gauge | % |
| Obs_NM | The observation gauge name | - |
| SRC_obs | Source of the streamflow observation guages. CA: Canada WSC gauge; US, USGS gauges | - |
| INSIDE_X | The longitude of the center of the catchment | degree |
| INSIDE_Y | The latitude of the center of the catchment | degree |
############################Calculate Routing parameters
### Define projection
user_projection = 'EPSG:3573'
### Calculate Routing parameters
RTtool.RoutingNetworkTopologyUpdateToolset_riv(projection = user_projection)
In this step, catchments in Figure 4B covered by the same connected lake will be merged into one catchment (Figure 4C). All routing related parameters will be updated.
############################Generate final catchments
RTtool.Define_Final_Catchment()
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