Assan Barrage Bird Sanctuary located 40 kms towards west of Dehradun valley on Dehradun Panota Road. The activity for which it is famous is Bird Watching. The place is popularly known as Dhalipur Lake.

Assan Barrage Bird Sanctuary, a bird watchers paradise was created in the year 1967 when the construction of Assan dam at the combined stream of river Yamuna and Asan through Dhalipur power house.

The Assan lake attracts 53 types of water birds. 19 of these are migrants from Eurasia. In winter 90% of the waterbird consists of 11 migratory type which are Brahminy Duck, Pintail, Red Crested Pochard, Gadwall, Common Pochard, Mallard, Coot, Wigeon, Common Teal, Tufted Duck, and Shoveller.

The place Assan Reservoir is a small man-made artificial lake of ca. 4 sq.km area. The grographical location of the place is between latitude 30°24' – 30°28' N and longitude 77°40' – 77°44' E. The barrage over Yamuna river and Assan is 287.5 m long. The river bed is 389.4 m above sea level with minimum water level of 402.4 m and maximum water level of 403.3 m.

The Asan reservoir remains throughout the year and is fed from the river Asan and the discharge channel of Yamuna through Dhalipur powerhouse. Even though the water level is controlled, it often goes down, and swampy islands in the middle become visible, attracting a variety of marsh-loving birds like Egrets, Herons and Lapwings, etc.

The area here has the climate of typical North India monsoon climate with distinct summer and winter. In summer max temperature goes to 38°C and Minimum temperature goes to 14°C whereas in winter maximum temperature goes till 21°C and minimum drops down to 2°C. Average rainfall in here is 250 cm which comes during June to September.

Assan Barrage Bird Sanctuary The water vegetation of the reservoir consists of Eichhornia crassips, Potamogeton pectinatus, Typha elephantina, and Ceratophyllum demersum. The bushes surrounding include Xanthium strumarium, Eclipta prostrata, Ipomoea sp., Mimosa pudica, Achyranthus aspera, Polygonum glabrum, P. lanigerum, Aeschynomene sp., Ageratum conyzoides, phyllanthus sp., Monochoria hastata, Mosla dianthera, and Lantana camara. Agriculture fields surround the barrage on the south side. There are mixed forest if we go further south in Siwaliks comprising principally Shorea robusta, Anogeissus Latifolia, Lannea coromandelica, Dalbergia sissoo, and Bombax ceiba.

Normally one can see birds in this area are in the month of October, November, December, March-end or Early April and sometimes even in April end.

One can reach here by road which is the most preferred route for Himachal, Punjab, Haryana and Chandigarh which results to a lot of traffic on this road.