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Onehimachal · Data

One drop. Out of the mountains.

A drop of snow lands on a ridge in Spiti. Follow it down the Spiti and the Sutlej, past the dams at Karcham, Nathpa, Kol and Bhakra, to the edge of the plains. Drag the drop or press a place.

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Start
Height of the river here
4,840m
0 km along the line · 480 km to go
How much of the fall is done
0 of 4,502 m fallen (0%).
You are at
A ridge east of Kunzum La

Our drop starts here, at about 4,840 m on the height data.

Rain and snow that land on this slope run down into the Spiti valley, according to our line.

Heights: AWS Terrain Tiles (Mapzen). The start point is our choice.
How we made the line. We did not survey it. A computer let water run downhill over open height data (AWS Terrain Tiles, about 150 m squares) from a point just east of Kunzum La. It follows the Spiti, then the Sutlej, and passes within about 1 km of Kaza, Khab, the Karcham, Nathpa and Bhakra dams and Jhakri. Heights are the lowest the river has reached so far, so it only runs downhill. The distance is along our line and is about right, not exact.

Numbers and where they come from

PlaceWhat we saySource
The line and every heightAbout 480 km, from 4,840 m to 340 m. Traced by us.AWS Terrain Tiles (Mapzen; built from SRTM, GMTED2010 and others). Open data. Water run downhill by our code.
Kaza, 3,650 mTown height, for the Spiti valley.Wikipedia, Spiti.
Spiti valley rain, about 170 mm a yearA valley average, period not stated.Govt of India, UNESCO Tentative List no. 6055 (footnote); Kapadia (1999).
Dharamshala rain, 2,905.1 mm a year1951-2000 normal.IMD, Climate of Himachal Pradesh (2010), Table V(a).
Khab: the Spiti meets the Sutlej, about 2,550 mMeeting point.Wikipedia, Spiti and Khab.
Karcham Wangtoo: 1,091 MW, 88 m dam, 13 Sep 2011Older sources say 1,000 MW.JSW Energy, Karcham Wangtoo plant page.
Nathpa dam 62.5 m; tunnel 27.394 km; design head 426 mAlso 1,500 MW; first unit 18 May 2004.SJVN, Nathpa Jhakri page.
Kol Dam: 800 MW (4 x 200); 40 km lakeUnits commissioned March to June 2015.The Pioneer, 18 Oct 2016 (NTPC project); Wikipedia, Koldam Dam (dates).
Gobind Sagar: 9,621 million cubic metresGross storage by design. Other pages give 9,868 or 9,340; to confirm.Govt of India, Vikaspedia (Bhakra Dam); FAO.
Bhakra Dam: about 226 m high, 518 m long, 1963Power: 785 MW right bank + 594 MW left bank = 1,379 MW. Wikipedia says 1,325 MW.Govt of India, Vikaspedia (Bhakra Dam).
Sutlej enters India at Khab; leaves the hills near RoparCourse.Wikipedia, Sutlej.

What this page does not say

It does not compare governments, states or projects. It does not say who gains or loses from any dam. It shows one line down one river. Figures are as published on the dates shown and may have changed. Checked 16 Oct 2026.

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