The Ukai Dam, constructed across the Tapti River, is the second largest reservoir in Gujarat after the Sardar Sarovar. It is also known as Vallabh Sagar. Constructed in 1972, the dam is meant for irrigation, power generation and flood control. Having a catchment area of about 62,225 km² and a water spread of about 52,000 hectares, its capacity is almost the same as that of the Bhakra Nangal Dam. The site is located 94 km from Surat.

Ukai dam
Ukai Dam
Official name	Ukai Water Resources Project
Country	India
Location	Tapi district
Coordinates	21°14′53.67″N 73°35′21.87″E / 21.2482417°N 73.5894083°E / 21.2482417; 73.5894083
Status	Operational
Construction began	1964
Opening date	1972
Construction cost	Rs 1389.6 Million
Dam and spillways
Impounds	Tapi River
Height	345ft
Height (foundation)	105.156 metres (340 ft)
Length	4,927 metres (16,000 ft)
Spillways	22, radial
Spillway type	Ogee
Spillway capacity	46,269 m3/s
Reservoir
Creates	Vallabhsagar
Total capacity	7,414 MCM OR 261.82 TMCft
Active capacity	6,730 MCM OR 237.67 TMCft
Catchment area	62,225 square kilometres (6.7×1011 sq ft)
Surface area	612 square kilometres (6.6×109 sq ft)
Power Station
Type	Conventional
Hydraulic head	57 metres (190 ft) to 34 metres (110 ft)
Installed capacity	300 MW
Website Ukai dam

The dam is an earth-cum-masonry dam. Its embankment wall is 4,927 m long. Its earth dam is 105.156 meters high, whereas the masonry dam is 68.68 meters high. The dam's left bank canal feeds water to an area of 1,522 km² and its right canal to 2,275 km².^[1]

Vajpur fort, built by the Gaekwad dynasty of Baroda, was submerged in the reservoir. It can be spotted when water level in the reservoir is low.^[2]