State Water has advised of a 5000-megalitre outflow every 24 hours, down from 8000 in the lead-up to the Christmas and new year holiday period.

The dam is currently at 55 per cent capacity, but the corporation expects that by the end of the irrigation season it will have fallen to 40 per cent.

Extreme weather conditions are driving "record irrigation demand" for water from the state's major dams, operated by State Water.

Its water delivery rates this summer may turn out to be the highest in more than a decade.

The corporation's manager water delivery, Adrian Langdon, reports that more favourable conditions for the irrigation industry, the heatwave and environmental deliveries have boosted demand beyond that of the 2001/2002 season.

"Near-record demand for irrigation water was already being experienced this year, and with the current spell of hot weather, that demand has recently intensified," he said.

Burrendong Dam is playing its part in keeping crops alive and taps running in communities such as Dubbo.

"It is likely water delivery in the Macquarie Valley out of Burrendong Dam could exceed previous totals, driven by high irrigation demand and an increase in environmental releases," a State Water spokesman said.

"Up to the holiday period Burrendong had been releasing at a rate of 8000 megalitres per day, approximately 3000 of which was for the environment.

"Burrendong daily releases are currently at 5000 megalitres per day, the bulk of which is to service irrigators holding a legal entitlement to the water."

State Water is the rural bulk water delivery business in NSW.

It owns, maintains, manages and operates major infrastructure to deliver bulk water to about 6300 licensed water users along the state's 7000 kilometres of regulated rivers and environmental assets.

State Water reports of working at "full capacity" this summer.