The extended dry spell across New Zealand highlights the need for further storage projects based on alpine water systems, IrrigationNZ says.
Without substantial rain during much of winter and spring, many farmers are already experiencing soil moisture deficits and irrigation would be critical this season, IrrigationNZ chief executive Andrew Curtis said.
Water restrictions, imminent in many regions, could have a huge impact on production levels.
''The only way to guarantee water in our summer-dry foothill river systems is to invest in alpine water storage. We don't want another season like 2011-12 when billions of dollars was lost from the economy when drought struck the North Island and dry spells plagued the South Island.''
Lake levels in the Opuha Dam were hovering just above 50% of the lake's full level. Opuha Water Ltd chief executive Tony McCormick said that was a first for this time of year.
Restrictions were being imposed in an attempt to preserve storage and extend the time in which water could be supplied to maintain river flows and for irrigation, he said.
Environment Canterbury would issue a water shortage direction to restrict consented water takes when the lake fell to 50% full.
Weather patterns in South Canterbury in the spring were variable but the overall result was little rain, Mr McCormick said.
''The lack of snow in our lowlands catchment coming out of winter has been a significant factor in our low storage levels. This situation is unprecedented in the history of Opuha but has always been anticipated. We are describing it as a one-in-20-year event.''
River flows in the region's foothill rivers were also exceptionally low in spring, leading ECan to step up its monitoring - a move applauded by IrrigationNZ.
''Farmers need to know on a daily basis how their water supplies are faring so more regular river flow measurements help,'' Mr Curtis said.
''When there's no rain, irrigating farmers need to turn off systems when river flows hit minimum flows, so the more advance warning the better.
''In these one-off unprecedented years, farmers and other stakeholders more than ever need to be working together to balance the economic and environmental values of our water resources.''
IrrigationNZ supported a collaborative approach to address the practical implementation of water restrictions.
''Any response needs to account for different irrigation system designs and combine rostering and rationing approaches to achieve the required water restrictions.
''As Opuha's proactive response to the lake's current situation illustrates, irrigation schemes need to be trusted in the management of the water resource as they have a range of options available to them to most efficiently address declining water supplies,'' Mr Curtis said.