An interactive hydrological atlas of 765 reservoirs across South and Southeast Asia. Explore watershed boundaries, downstream river networks, runoff timeseries, and storage data.
765
Reservoirs
765
Watersheds
765
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
Find a reservoir by ID
Type any part of a numeric ID into the Search field. Matching results appear below — click one to fly to that location and load its data. You can also click any blue marker directly on the map.
Step 2
Explore watershed & downstream
WatershedDownstream
When you select a reservoir, its watershed boundary (green) and downstream river path (orange) are drawn on the map. Toggle either layer with the switches in the sidebar.
Step 3
Read the info card
Below the toggles, the info card shows latitude, longitude, country, basin, and areal impact for the selected reservoir. Click ✕ Clear to deselect and remove the watershed/downstream layers.
Step 4
View runoff time series
Pick a metric — Surface Runoff, Sub-Surface Runoff, or Precipitation — from the dropdown. Runoff is shown as a line chart; precipitation as vertical bars. Hover for the date and value.
Step 5
View storage time series
Storage
Reservoirs with GWW storage data show a separate Storage card (violet border). Select a column from the dropdown to see monthly storage levels.
Step 6
Expand any chart
Click ⛶ Expand on either time series card to open a large fullscreen view with more date ticks and a rich tooltip. Close with ✕, the Esc key, or by clicking outside the box.
Step 7
Switch basemap & opacity
The ≡ Layers button at the bottom-right opens a panel to 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 to make the sidebar wider or narrower. Double-click it to reset to default width.
Step 9
Light & dark theme
Use the sun / moon button in the top-right of the navbar to switch themes. Every panel and chart adapts automatically.
Tips
Marker tooltips on hover show the ID and coordinates without selecting the feature.
Changing the metric in either the small or large chart view syncs both.
Time series chart type changes per metric: line for runoff/storage, bars for precipitation.
Switching theme also auto-suggests a matching basemap the first time — you can override it 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.