Anke Leroux

Hedging Supply Risks: An Optimal Water Portfolio

Although water supply diversification has been proposed as a solution to dwindling water reserves, the optimal mix of natural and manufactured sources of water remains largely unexplored. We develop a dynamic portfolio model of water supply that hedges against the supply risks from all potential water sources, by taking into account the size of water reserves, uncertainties of water flows as well as differences in supply costs. The optimal portfolio shares for an existing water supply system are derived and compared with the observed contributions to total water stock, revealing unexploited hedging opportunities between various naturally occurring water sources as well as a general over-reliance on manufactured water. The optimal solution implies that future supply augmentations should target natural sources of water ahead of manufactured water. It is estimated that the optimization of the water supply portfolio for a medium-sized city results in annual cost-savings of up to

The Optimal Time to Remove Quarantine Bans Under Uncertainty: The Case of Australian Bananas*

463 million.

Valuing environmental services provided by local stormwater management

Import restrictions on biological materials are used widely as protection against exotic invasive pests and pathogens. While a scientific risk assessment is needed to justify an import ban under the WTO SPS Agreement, economics plays little role in determining the choice of import regime. Using a real option framework, we model the uncertain and irreversible costs from lifting an import ban and derive decision rules about the optimal timing, when ex ante research and development yields positive but uncertain benefits. The insights gained are applied to Australias current import policy for bananas.

Optimal conservation, extinction debt, and the augmented quasi-option value

Decentralized stormwater management systems deliver a number of environmental services that go beyond the reduction of flood risk, which has been the focus of con-ventional stormwater systems. Not all of these services may be equally valued by the public, however. This paper estimates households’ willingness to pay (WTP) for im-provements in water security, stream health, amenity values, as well as the reduction in flood risk and urban heat island effect. We use data from nearly 1,000 personal interviews with residential homeowners in Melbourne and Sydney, Australia. Our re-sults suggest that the WTP for the highest levels of all environmental services is A

Advancing Water Trade: A Preliminary Investigation of Urban‐Irrigation Options Contracts in the Ovens Basin, Victoria, Australia

409 per household per year. WTP is mainly driven by the residents’ positive valuation for exemptions in water restrictions, improvements in local stream health, and decreased peak urban temperatures. We further conduct a benefit transfer analysis and find that the WTP is not significantly different between the study areas. Our findings provide additional support that decentralized stormwater management systems have large non-market benefits and that, under certain conditions, benefit values can be transferred to different locations.