Trek to Gaumukh
The real reason most foreigners come to Gangotri is for the trek to Gaumukh Glacier – the source of the Ganges River.
Don’t be daunted by the trek – the trail rises gradually and is completely solid. Four to six hours (14km) up the trail, at Bhojwasa (Bhojbasa; 3790m), there’s a GMVN Tourist Bungalow and other rudimentary tented dorm lodging; Gaumukh is 4km (1½ hours) past that. On clear days, the best time to visit the source is early to midafternoon, when it’s out of the shadows. There, the water flows out of Gangotri Glacier beneath the soaring west face of Bhagirathi Parvat (6856m), with the peak of Shivling (the 6543m ‘Indian Matterhorn’) towering to the south.
It is possible to do Gaumukh Glacier as a day trip from Gangotri, but you'll have to set out as early as you can (park office is open 6am to 6pm) and it'll be rushed. Your best bet is to take a pony (one-way/return ₹1350/2500), which can be hired in Gangotri. Ponies aren't permitted for the last leg from Bhojwasa to Gaumukh, so you'll have to walk that 8km-return trek. A porter is ₹800 to ₹1500 depending on the season, while a guide is ₹1500 to ₹2000.
More ambitious hikers with camping gear often continue to the gorgeous meadow at Tapovan, 6km beyond Gaumukh; tents can be hired from Real Adventure or Hotel Mandakini in Gangotri. As of late 2018 no permits were being issued for overnight stays in Tapovan due to an ongoing court case banning camping in the bugyal (meadows).
Before trekking to Gaumukh, you must first get a permit, since access is limited to 150 people per day. This can be obtained from the permit office above the bus stand at Gangotri, or from the District Magistrate Office in Uttarkashi. At both places, you'll need to bring a copy of your passport ID page and visa. The permit is valid for two days and costs ₹150/600 per Indian/foreigner (then ₹50/250 for each extra day); camping permits are ₹100 to ₹200, and a cooking permit is ₹200. You can also attempt to arrange a trekking permit online at www.swsuttarkashi.com/permission/gangotrinationalpark. Solo trekkers are required to bring along a guide (a permit won't be issued without one – however a porter will suffice, a cheaper alternative to a guide).
Before Bhojwasa there's only a tea shop along the trek, 9km into the journey at Chirwasa, so you'll need to bring along enough water.