Klondyke Water Storage Facility overview Pond Design Pond

Klondyke Water Storage Facility overview

Pond Design • Pond is constructed from soils excavated from within the footprint. • Pond is lined with a imported synthetic liner. • Pond is fed directly from the Rangitata Diversion Race (RDR). • Pond delivers water to the MHIS and therefore frees up canal flow for two other existing schemes and other users. • Water can be spilled into the Rangitata River and the RDR if required to maintain the full supply level. • The discharge of water into the Rangitata River is via a natural gully that will be reengineered for this purpose.

Design Standards • Pond is classified as a High Potential Impact Dam as defined by the NZSOLD Dam Safety Guidelines (2015). • Because of classification the pond would be designed for 1 in 10, 000 annual exceedance probability earthquake and probable maximum flood. • Earthquake resistance is provided by nature of the foundation and embankment soils and slopes adopted. • Flood resistance is provided by being able to spill both to the Rangitata River and the RDR. • The design details will be furthered developed and peer reviewed in detail in order to obtain a Building Consent.

Canal Modifications • Additional 10 m 3/s will raise water level by approximately 0. 5 m • Parts of the canal will require the canal bank to be raised and in a small number of areas widened • Most of the work on canal can be undertaken independent of operation. • Three bridges will need to be replaced • Dam break Assessment - Three areas highlighted where canal constructed in fill. Canal is assessed as Low PIC. • Construction will be mostly be earthworks to raise the canal bank levels based on Design drawings. • Three new bridges will to be constructed (to replace three existing bridges)

Fish Screen • • • Rotary Cylinder Fish Screens Design to exclude native fishery and Salmon/Trout Rotary Cylinder Fish Screen Located upstream of existing Fish Screen Can be constructed offline from RDR Design to achieve all criteria in the NIWA Fish Screen Guidelines including: • Average Approach Velocity < 0. 12 m/s • Sweep Velocity > Approach. (Average 1 m/s for Sediment Management) • Fish Bypass designed to enable safe passage of fish back to river. • Fish screen – 2 mm wedgewire • Construction will be mostly in cut. • Main construction is excavation of new canal, fish screen structures (concrete) and fish bypass. • The offline construction means the construction can mostly be undertaken with no effects on existing users. Fish Screen Layout Schematic Fish Screen Location

White Water Course • Proposed to construct a Recreation wave at the outlet of the proposed Klondyke Storage Facility. • The WWC will provide recreational use when water is released to the Mayfield Hinds Irrigation Scheme (MHV). • The storage facilities, disposal areas, and erosion control measures already in place for the storage pond are available for the construction of the WWC. • Construction includes control gate and weir as well as carpark and toilet facilities.

Flow Management Regime Rangitata River • Water Conservation Order 2006 sets flow management regime for the Rangitata River • Abstraction of water from Rangitata River cannot exceed 33 m 3/s unless the naturally occurring flow at Klondyke exceeds 110 m 3/s. 33 m 3/s block • A total of 33 m 3/s can be abstracted from the ‘reliable block’ of water which is fully available when flows in the Rangitata River at Klondyke are at or above 66 m 3/s. • Full 33 m 3/s is currently allocated and RDRML has an allocation of 30. 7 m 3/s in this ‘reliable block’. • No (further) abstraction of water when flows are between 66 and 110 m 3/s. High flow allocation • When flows at Klondyke are above 110 m 3/s water may be abstracted on a pro-rata basis. • Currently 22. 6 m 3/s of this high flow water is allocated in the Rangitata River

Existing and proposed RDRML takes and diversions Existing • Take of up to 30. 7 m 3/s from the Rangitata River for irrigation, stockwater and hydro - generation. • Divert up to 3 m 3/s for the existing fish bypass between approximately 10 September and 15 March. Proposed • Take an additional 10 m 3/s from the Rangitata River in accordance with the Water Conservation Order when flows at Klondyke are above 142. 6 m 3/s. • Standard pro-rata restrictions when flows are between 132. 6 and 142. 6 m 3/s and no take below 132. 6 m 3/s. • Divert up to 5 m 3/s for fish bypass purposes (year round). Table: Proposed Fish Bypass Diversion Flows (m 3/s) Rangitata River at Klondyke Flows Proposed Fish Bypass Flow > 142. 6 5 > 132. 6 and < 142. 6 4 <132. 6 3

Ecological Refuge Native plantings and habitat for birds, invertebrates, lizards 1 ha of re-located/new stone piles as lizard habitat 3 ha of plantings of broadleaf/hardwood, open shrubland/grassland 2 ha of wetland