A report published by the Scottish Environment Protection Agency (Sepa) has warned of dry conditions, and updated the warning for the Borders, which joins parts of the Lothians, Fife, Aberdeenshire and Tayside in reaching alert level.
Recent rainfall has not improved the water scarcity situation in these areas, where groundwater levels are falling. River flows also remain low for this time of year across the east of Scotland, Sepa said.
Businesses in these areas that extract water from the environment are now being asked to do so more efficiently.
In an earlier report, Sepa suggested businesses could protect water supplies “by planning ahead, reducing volumes and irrigating at night where possible”.
If dry periods continue, water users may be encouraged to reduce the volume of water they use or temporarily suspend water abstractions.
Due to climate change, SEPA said areas that have never experienced water scarcity before may face issues with their water resources. The organisation warned food and drink production, hydropower generation and other businesses reliant on a consistent water supply could be affected.
SEPA has advised members of the public, especially those with a private water supply, to be aware of the risk of water scarcity this summer.
Nathan Critchlow-Watton, head of water and planning at SEPA, said: “In March this year, SEPA warned that water scarcity conditions could deteriorate quickly if dry weather continues. We are seeing that happen now in the east of Scotland as warning levels increase and expand to more areas each week.
“We have been working with businesses to ensure they have a plan to deal with water scarcity that protects their operations and the environment. This should include carrying out checks to their equipment, considering upcoming water needs and following best practice such as irrigating at night.
“Water is a finite resource, even in Scotland, and pressures on the water environment will only get worse with climate change. By following our advice and working together, we can all play a part to reduce the impacts.”
The Scottish Government confirmed earlier this month that bottled water would be provided to households in the event of water shortages.