Crimea’s harvest of grapes, rice, maize and soya will be ruined if it does not get more water soon, officials say.
Russia says the Crimea-Ukraine border is now officially a state border.
The Russian government plans to establish permanent checkpoints there, as well as new rules for entering or leaving Crimea, Ria Novosti news agency reports.
The North Crimea Canal delivers water to Crimea from the River Dnieper, in Ukraine’s southern Kherson region. The canal accounts for 80% of Crimea’s water.
The current water shortage is threatening 120,000 hectares (296,000 acres) of Crimea’s crops, which rely on irrigation, Russian Agriculture Minister Nikolai Fedorov said.
A ruined harvest across that area would mean losses of up to 5bn roubles (£83m; $140m), he told the Gazeta.ru news website.