Environmental & Recreational Impacts of Irrigation John Hayes

Environmental flow regimes: - critical flow regime features for sustaining instream values Flow variability at a range of scales, Minimum flow - for:  water quality,  instream habitat,  amenity values.

Ecologically important components of flow regimes Example flow regime, Lower Waiau River, Tuatapere, Southland Low/min. flow = Habitat quantity High flows = Habitat quality Flood flows = Channel maintenance

Critical values The most flow sensitive and important instream value(s)  often salmon or trout (habitat) - trout and salmon have higher flow & water quality requirements than most native fishes  or angling  sometimes birds  sometimes boating (e.g. jet boating) Assumption that if flow needs of critical value are met then less flow sensitive values will be also be OK.

Those pesky trout and salmon Why should the instream needs of introduced fishes be allowed to constrain flow allocation to irrigation and hydropower generation?  they are the nation’s most important freshwater fisheries – economically (incl. to tourism) & socially (and contribute to recreational and cultural diversity)  they substitute for otherwise limited native freshwater fisheries  they belong to all New Zealanders and all have the opportunity to participate in the fisheries (c.f. recreational and subsistence marine fisheries). These values have been recognised in statute in the responsibility invested by Gov’t in Fish & Game and DOC for protection & management of these fisheries on behalf of public of NZ (Conservation & Fisheries Acts) - and hence too in environmental law (e.g. RMA)

Flow management mechanisms to provide for environmental flow requirements Annual or seasonal minimum flow for maintaining instream habitat A flow allocation limit, or flow sharing rule, for maintaining flow variability over a range of scales and avoiding prolonged flat-lining at the minimum flow  size and frequency of channel forming and flushing flows may be prescribed

Flow variability – why is it so important? Large floods  frequency - multiyear  for channel maintenance Medium floods (freshes)  frequency - months  flushing periphyton  flood recessions contribute to aquatic invertebrate production? Minor variation  frequency – weeks-months  maintenance of fine sediment and periphyton (refreshing channel margins)? ? needs research

Mid range flow variability – everyone wants a share of it: flushing and benthic production Wairau River

Mid range flow variability – everyone wants a share of it: salmon angling

Mid range flow variability – everyone wants a share of it: trout angling Optimal flow range Effect of 40 m 3 /s abstraction on trout angling opportunity

Mid range flow variability – everyone wants a share of it: jet boating Optimal flow range Effect of 40 m 3 /s abstraction on jet boating opportunity