Water Management Options For Drought
26 October 2013
Water Management Options For Drought
Hawke’s Bay Regional Council yesterday discussed its response to the significant nationwide drought last summer and future response options.
Some new solutions were used in last summer’s drought and, through the collaborative policy discussions in the TANK group, are being considered as ways to provide assurances in the future. The TANK group is the collaborative stakeholder group brought together by HBRC to look at future catchment management options for the Tutaekuri, Ahuriri, Ngarururo and Karamu catchments.
Following submissions to the Annual Plan in June, Council requested that a higher urgency be placed on the review of options for management of ground water and surface water consented takes, particularly in areas where low flow limits are imposed.
There are 1770 consented water takes from the Heretaunga aquifer and of these, 38 are in the ‘Twyford unconfined zone’ of the aquifer, where groundwater takes affect nearby surface water flows. These 38 takes are tied to a minimum flow in the Ngaruroro River of 2400 litres per second at Fernhill.
The flow limits have been developed through public input and scrutiny and are the river’s environmental bottom lines. There are still a number of consents in the Twyford area to be replaced, so the full impact of the current water management regime is still to be realised.
During the drought, HBRC staff took a number of specific actions to assist growers, particularly in the Twyford unconfined zone which is most affected by the current water management regime. HBRC worked with consent holders to use legally available options which did not affect the environmental bottom lines of nearby streams and rivers. Options used were global consents, voluntary staged reductions, temporary allocation transfers, and sustainable augmentation to improve flows.
HBRC is developing these options further in discussion with the TANK Group and developing a computer model to provide more guarantees around the science of water management.
HBRC also considered issuing water shortage directions under section 329 of the Resource Management Act. However, it was not used as it offered less flexibility for managing through the drought crisis and may have resulted in all takes being banned, rather than allowing some water movement where possible.
Councillors noted that, among other initiatives, HBRC staff are continuing to work on -
• supporting and resourcing the collaborative policy process for the Greater Heretaunga/Ahuriri Catchment area (TANK process).
• exploration for sources of ‘new’ water that may be found at depth and be unconnected to surface waters.
• collaborating with irrigators and stakeholders to develop a coupled surface-groundwater model. HBRC is well underway with the development of a computer model that will better show the interaction between surface water and groundwater. This will involve some members of the TANK group and groundwater technical advisors. By engaging community stakeholders in the science and model outputs, there should be a firm, agreed foundation on which HBRC and the community can to discuss development of water management policies.
• reviewing the options for assessing stream depletion following the Tukituki Plan Change (6) Board of Inquiry process.
• a technical review of minimum flows and allocations for soft bottomed systems such as the Raupare.
• a review of tree and crop water demand with Crop and Food Research staff.
• discussions with the Twyford Irrigators Group (TIG) to address historical consent application errors. This is a long standing issue whereby some irrigators sought water using incorrect take rates and volumes, and have subsequently been consented with lower amounts than they have historically taken.
• the option of sustainable augmentation of the Raupare Stream.
The Regional Council was also updated yesterday on the development of the water model using information from the 2012/13 season, issues around over allocation, the TANK process, and the information provided to growers to allow efficient water management.
- Options for water management in drought
Options to be used in a drought need to be legally available and not affect the environmental bottom lines of nearby streams and rivers.
• Both global consents and ‘soft stops’ are seen as sensible and pragmatic, however at the moment these cannot be legally imposed on individual consent holders and so must be voluntary. Global consents allow irrigators to work as a group and use real time data to adjust water use amongst the group, e.g., an irrigator using less water on a crop for a period enables another grower to use more. ‘Soft stops’ or staged reductions is where a group of irrigators coordinate themselves to voluntarily reduce their take as river flows drop, and has the potential to help avoid the low flow limit being reached. This system was used over the drought by the Ngaruroro Irrigation Society who gained several extra days of irrigation.
• Another option used was temporary allocation transfers within existing rules to augment takes. As with global consenting, this allows water to be moved within the same water management area. HBRC could assign water to a user group and allow them the flexibility to move it as needed.
• Sustainable augmentation using aquifer water or limited storage is another option that was used last summer on the Raupare. It could be developed for longer term consenting on smaller waterways. Storage is an option for larger waterways, such as the Ngaruroro and is being discussed by the TANK group. Irrigators have provided information to HBRC on their preferred options, and each option has points in its favour depending on the water source and the ability of irrigators to work as a group.