Working with Hydrosheds

Investigate how and where water flows

Step 1: Download the 30sec SHAPE: Drainage Basins (Beta) for Asia

step 2: Download the administrative boundaries for Indonesia.

Step 3: Use the clip function in ArcMap or QGIS to clip the watersheds within the country.

Step 4: Make a subset of all watersheds larger than 50 Sqm2 and save it as a layer.

Step 5: save the new layer as a KML.

Step 6: Upload the kml as a fusion table.

Follow these instructions to upload and display the fusion table.

Step 7: Display the fusion table in the GEE with the code below:

var ft = ee.FeatureCollection("ft:1iSZG5gJnLKJ4VYLfnBXGO9IoFWuVPMVd79j7q8rf")

Map.addLayer(ft)

Step 8: Use the inspector to select a watershed.

Step 9: Use the code below to select an watershed

// select polygon based on BASIN_ID
var myPolygon = ft.filter(ee.Filter.eq("BASIN_ID",254632));

// add single watershed
Map.addLayer(myPolygon,null,"my watershed");

Step 10: Use the code below to calculate the bounds

// get bounds of polygon
var bounds = ee.Feature(myPolygon.first()).bounds().geometry();

// add single watershed
Map.addLayer(bounds,null,"Bounds");

Step 11: Use the code below to calculate a buffer

// buffer bounds
var buffer = bounds.buffer(50000);

// add buffer
Map.addLayer(buffer,null,"Bounds with buffer");

Step 12: Import the
WWF HydroSHEDS Hydrologically Conditioned DEM, 3 arc-second.

Step 12: Import the
WWF HydroSHEDS Hydrologically Conditioned DEM, 3 arc-second.

var DEM = ee.Image("WWF/HydroSHEDS/15CONDEM");

// create the vizualization parameters
var viz = {min:0.0, max:1000, palette:"1400f7,00f4e8,f4f000,f40000,960424"};

// show DEM
Map.addLayer(DEM,viz,"DEM");

Step 13: Set the nodata values to -9999 instead of 0

// replace the mask by -9999
var mask = dem.mask()
var demMap = ee.Image(-9999).where(mask,dem)

Step 14:Export the data to the Google Driver

//Export the image, specifying scale and region.
Export.image.toDrive({
   image: demMap,
   description: 'DEMKapuas',
     scale: 1000,
    region: buffer
 });