An interactive hydrological atlas of 1,144 reservoirs and barriers across South and Southeast Asia. Explore watershed boundaries and downstream river networks.
1,144
Reservoirs
1,144
Watersheds
1,144
Downstream Paths
10
Countries
New here? See the How to Use page for a quick tour of every feature.
How to Use
A quick tour of the main interactions. Everything happens around the map and the left sidebar.
Step 1
Choose what to show
ReservoirsBarriers
Use the two checkboxes at the top of the sidebar to toggle Reservoirs (blue circles) and Barriers (red diamonds) on the map. The count next to each label shows how many features are loaded.
Step 2
Find a site by ID
Type any part of a numeric ID into the Search field. Matching results appear below the box — click one to fly to that location and load its data. You can also click a marker directly on the map.
Step 3
Explore watershed & downstream
WatershedDownstream
When you select a feature, its watershed boundary (green) and downstream river path (orange) are drawn on the map. Toggle either layer with the switches in the sidebar.
Step 4
Read the info card
Below the toggles, the info card shows latitude, longitude, country, basin, and areal impact for the selected feature. Click ✕ Clear to deselect and remove the watershed/downstream layers.
Step 5
View the time series
Selected features include monthly time series. Pick a metric — Surface Runoff, Sub-Surface Runoff, or Precipitation — from the dropdown. Runoff is shown as a line; precipitation as vertical bars. Hover for the date and value.
Step 6
Expand the chart
Click ⛶ Expand on the time series card to open a large, fullscreen view with more date ticks and a richer tooltip. Close with the ✕ button, the Esc key, or by clicking outside the box.
Step 7
Switch basemap & opacity
The ≡ Layers button at the bottom-right of the map opens a panel where you can pick a basemap (Dark, Light, Satellite, Topo, Street, Terrain) and adjust the opacity of the watershed and downstream overlays.
Step 8
Resize the sidebar
Drag to resize
Drag the vertical grip on the right edge of the sidebar to make it wider or narrower. Double-click it to reset to the default width. On small screens the sidebar becomes an overlay drawer.
Step 9
Collapse the sidebar
Click the small ‹ tab on the right edge of the sidebar to collapse it for a full-screen map view. Click › to bring it back.
Step 10
Light & dark theme
Use the sun / moon button in the top-right of the navigation bar to switch between dark and light themes. The map basemap stays the same, but every panel and chart adapts to your choice.
Tips
Marker tooltips on hover show the ID and coordinates without selecting the feature.
Changing the metric in either the small or large time series view syncs both.
Selected features stay highlighted on the map (slightly larger and brighter) so you can still see context while the layers load.
Time series chart type changes per metric: line for runoff, bars for precipitation.
Switching theme also auto-suggests a matching basemap the first time (Dark ↔ Light) — you can override it at any time from the Layers panel.
Dataset Details
Reservoir locations from GRanD v1.3 supplemented with the GBMIM dataset covering Ganges–Brahmaputra–Meghna–Irrawaddy–Mekong systems. Watershed delineations use HydroSHEDS DEM at 15 arc-second resolution.