Norwich ― With one drinking water reservoir below 70% capacity, Norwich Public Utilities Tuesday issued a water supply warning and put in place water conservation measures, asking residential and commercial customers to cut water usage by 10% “until conditions improve.”

NPU spokesman Chris Riley said no specific measures are mandated for customers, but businesses and residents are asked to “be mindful” of all water usage and refrain from non-essential watering, take shorter showers and make sure washers are run with full loads.

As of Monday morning, NPU’s two reservoirs were at a combined 72.43% of their capacity. With little to no rain expected this week, NPU estimated these levels will more than likely be below 70% by the end of this week. According to weekly water level reports, NPU’s Deep River Reservoir at the Lebanon-Colchester border was at 69.15%, while its Stony Brook Reservoir in Montville was at 81.64% of capacity.

The Stony Brook Reservoir has been in limited use recently, as the treatment plant there is undergoing a major upgrade, Deep River Reservoir chief plant operator Jesse Burns said Tuesday. NPU hopes the upgrades will be approved by state Department of Public Health officials later this week, increasing water output from that reservoir.

NPU has approximately 228 days of water supply in its reservoirs for its 11,000 commercial and residential customers. At 100% capacity, NPU’s two reservoirs have nearly 1.8 billion gallons of water, enough for 321 days of supply.

The Deep River Reservoir has received 2.87 inches of precipitation in August and Stony Brook 4.53 inches.

Statewide August data has not yet been posted on the Connecticut Precipitation Report, New London County already was way behind in rainfall through July. In July alone, the county received just 0.98 inches of rain, just 26% of the normal amount of 3.72 inches. From May through July, rainfall is 4.51 inches less than normal.

“With the ongoing drought in the region and no significant rain in the immediate weather forecast, we are approaching a serious water supply situation,” NPU General Manager Chris LaRose said in a news release announcing the warning. “Therefore, we must strongly encourage our customers to be more aware of how they are using water.”

The U.S. Department of Agriculture on Aug. 16 declared New London County a natural disaster area because of the drought, and on Tuesday, the U.S. Small Business Administration’s Disaster Field Operations Center East announced the availability of low-cost loans for affected farms and businesses.

On Aug. 18, Gov. Ned Lamont raised the drought level for New London County to Stage 3, with the region experiencing less rain than other regions.

On Friday, the Connecticut Water Co., which has about 350,000 customers in 60 towns, asked for voluntary water conservation. East Lyme Water Department instituted mandatory conservation measures on Aug. 15.

As part of its water supply warning, NPU is contacting major water users to determine the potential for emergency water conservation and request that they reduce consumption. NPU also is evaluating emergency supply options, such as bringing the reserve Norwichtown well online, which can provide an extra 1 million gallons of water per day.

NPU is encouraging residential customers to reduce their day-to-day water use by taking a few steps that should not impact their lifestyle. Such steps include:

• Take shorter showers

• Only run dishwashers and washing machines with full loads

• Limit non-essential water use, such as watering lawns and gardens or washing cars

• Delaying the refilling of swimming pools

NPU spokesman Chris Riley said Tuesday the last time NPU issued a water supply warning was 2016. He said last week’s heavy rain was spotty and much of it did not reach the reservoirs.

“If people can be mindful, if people can take some small steps,” Riley said. It’s really important and can make a big difference, and we need our customers to respond.”

c.bessette@theday.com