The Ukai Dam, constructed across the Tapti River, is the largest reservoir in Gujarat. 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 62,255 km2 and a water spread of about 52,000 hectares, its capacity is almost same as that of the Bhakra Nangal Dam. The site is located 94 km from Surat.
The storage capacity of Ukai dam is almost 46% of the total capacity of all the other existing dams in Gujarat if put together. Thus it can be concluded that the rest of the dams have as little as 0.1% average storage capacity. During the last 40 years, the actual irrigation potential is attained through all the major and medium water resources projects in the State, which comprises only 14 million hectares.
The dam is an earth-cum-masonry dam. Its embankment wall is 4,927 m long. Its earth dam is 80.77 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 provides water to 2,275 km2 of land.