Data shows CDHB wards in its various hospitals, including Christchurch, hit full capacity at the end of February and well before the current surge in cases, which are forecast to increase in the next few weeks.
But the DHB insisted it had additional capacity to call upon by reducing other services and redeploying staff.
Chief executive Peter Bramley said there had been over 2000 new cases in the region in the previous 24 hours, taking the number of active cases past 12,000. Only 18 inpatients are Covid-19 cases.
He said around 400 CDHB staff are impacted - including around 150 positive cases.
"We, from our modelling, believe we are about three weeks away from the peak," he said.
"The big challenge is supporting the health system as a whole.
"The challenge in the next three or so weeks is going to be particularly around staff absences."
Canterbury incident controller Tracey Maisey said the CDHB was in stage two of its planning where it was consolidating services in preparation for the peak.
"We've combined wards, particularly in our non-acute facilities, both (in) Ashburton and Burwood [hospitals], and proactively relocated some residents from our rural facilities to enable some staff to be redeployed."
Maisey said the DHB is considering moving to the next phase of its Omicron response but the decision has not yet been made.
"The next phase includes deferring non-urgent elective care, postponing non-urgent outpatient activity and increasing the utilisation of telehealth appointments."
In the Ashburton District, people who tested positive to Covid-19, and who needed hospital-level care, would be admitted to Ashburton Hospital. But if their care needs escalated, then they would be transferred to Christchurch Hospital.
Ashburton Hospital has already been under pressure due to staffing shortages.
Bramley said there were significant gaps in the health workforce for a variety of reasons which was putting the frontline teams under significant pressure.
He also confirmed that rural facilities in Waikari, Darfield, Ellesmere, and Oxford, that were temporarily closed, were guaranteed to reopen after the Covid-19 peak.
However, the long term future of those facilities would be up to Health New Zealand.
In March 2021, the government announced it would abolish all 20 District Health Boards and create a single health organisation, Health New Zealand, centralising New Zealand's healthcare system from July.
-Jonathan Leask
Local Democracy Reporter