Joseph Thomas, Peter Thomson, John Grimston, Sally Marx
The Waimea Basin is located in the South Island of New Zealand. The area has an acute water shortage with recent studies showing the water resources to be over-allocated by 22% for a 1 in 10 year drought security. The current area irrigated is about 3,700 ha and there is additional productive land that could potentially be irrigated if more water were available. Water users have suffered severe restrictions on their water use over recent years through drought management measures imposed to meet critical environmental flow requirements and coastal salinity buffering. This has caused significant production cutbacks for irrigated crops resulting in regional economic loss, affected major urban water supplies resulting in water supply cut-backs affecting domestic and industrial users and also affecting the important environmental values of the Wairoa/Waimea Rivers and the coastal springs that are highly valued by the community and local iwi (Maori).
The principal objective of this project is to carry out a study into the feasibility of water storage in the upper parts of the catchment for enhancing water availability for both consumptive and environmental/community/ aesthetic benefits downstream. The outcome from this feasibility study will provide the community with the necessary information to make an informed decision on proceeding with potential storage options. The Waimea Water Augmentation Committee is overseeing this feasibility study. The study will be completed byJune 2007.
The Waimea Plains area is also quite unique as to the interest and values relating to the water resource as it has multi stakeholder interest. Being close to urban centres, the water resource not only caters for irrigation use but also public water supplies as well as recreational, community interest and cultural values.
This paper sets out the project’s aim, general methodology being followed, and summarises the progress to June 2005.
Peter Hill, Kristen Sih, Rory Nathan, Phillip Jordan
This paper presents a number of innovative hydrologic investigations undertaken for the recent detailed design of upgrades for Ross River Dam in North Queensland. A key issue for estimating extreme floods in the tropics is the estimation of flood events of long critical durations. The implication is that there is an increased focus on estimating the correct volume (not only the peakflow). This paper describes the regional analysis of flow volumes that was used to validate the estimated flood volumes.
Another issue of considerable importance is the assumed relationship between inflows and initial reservoir level. The analyses described in this paper showed that inflows are independent of reservoir levels for the more frequent events but for more extreme events they are correlated. This has important implication on how the initial reservoir level is incorporated in the hydrologic analysis. The final aspect covered by the paper is the derivation of seasonal flood frequency curves. This is particularly important given the highly seasonal nature of rainfalls in the tropics and the results are important for assessing risks during construction and scheduling the upgrade works
Sonny Connors, Shaun Nugent, Brett Taylor, Brian Walford
The Tarong coal-fired power station near Kingaroy in southern Queensland discharges ash to a storage facility of 42,000 ML capacity, impounded by a 48 m high-zoned earth and rockfill dam embankment. The embankment was constructed in 1980–81. In recent years, Tarong Energy Corporation (TEC) has investigated a number of options for a new storage facility as the remaining capacity of the existing ash dam storage diminishes. TEC determined that the existing facility should be upgraded to provide additional storage capacity for the short term. At the same time, there emerged a requirement to improve the long-term seismic resistance of the embankment. Enlarging the existing spillway cut provided the material for a 400,000 m3 weighting zone and, by reducing the design flood freeboard, extended the ash disposal capacity by several years without a need to raise the embankment. Challenges included significant foundation seepage and deteriorated riprap. The paper describes the issues, risks, adopted criteria, investigation undertaken, and implementation of the upgrading works. Innovative approaches to the provision of future storage capacity are outlined.
Robert Humphries, Caroline Minton, Andrew Baker and Mark Leathersich
There is a constant stream of criticism levelled at the perceived or actual adverse environmental
effects of large dams. These criticisms include prevention of fish migration, thermal and chemical and biological disturbance of downstream riverine habitats, silt trapping and drowning of terrestrial
habitats by flooding behind the dam wall. The beneficial effects of dams are rarely discussed, but
include aquatic habitat creation, catchment protection, flood mitigation, carbon sequestration and
protection of endangered species, amongst others.
Critics of large dams rarely present an analysis of the environmental costs and benefits of other water supply options, which include abstraction of shallow or deep groundwater, desalination of seawater, and reclamation of human or other wastewater.
In this paper we compare the environmental costs and benefits of water supply from large dams with
the common alternative options, and assess the relative sustainability of them all.
This paper sets out the principles, practices and issues relevant to the sharing of
costs for dam safety upgrades in southwest Western Australia and other locations.
? the general principles (noting that in practice multiple conditioning factors
? the practical outcomes for cost sharing in Australian jurisdictions;
? the beneficiaries of the dams, the water and the safety upgrades;
? legacy costs (including IPART’s framework and whether this can be directly
applied to the southwest);
? the Bulk Water Service Agreement;
? the question of price impacts and affordability based on surveys of farm
performance, water use and profitability; and
? the pricing impact of treating safety upgrades as if Harvey Water owned the
We examine the impact of applying economic allocation principles to this task and the
impact of other criteria such as dam safety obligations, hazards presented by a large dam,
community expectations for public safety, the broader public safety, welfare and state and
regional economic benefits reliant on dam safety, significant community costs subsidised by
irrigation customers, State Government ownership, and the effects on bulk water prices
should customers be required to fully fund the necessary dam safety upgrading.
Don Macfarlane; Nick Eldred; Sigi Keis
Project Aqua was planned to be a major hydropower development along the lower Waitaki Valley, New Zealand. Geotechnical investigations for the project were conducted in two main stages – from the late 1970’s to mid-1980’s, and again in the period from 2002 to 2004.
Community consultation was an important part of the 2002-2004 investigations, and was a key risk management issue for Meridian Energy. The proposed scope of the work included 512 drillholes and 734 test pits spread along the 60km project corridor. All proposed drillholes and test pits were subject to the Resource Management Act 1991 and needed Resource Consent applications, which required consultation with landowners, territorial authorities, and community and cultural groups including three Maori tribes.
A number of proposed investigations could not be undertaken because the landowner would not allow land access, but over 70% of the proposed work was completed with community support.