Environmental triage decisions during a drought

Abstract

Abstract The Murray Darling Basin Current is currently in drought. There are low water levels in most dams, and increased uncertainty about future rainfall. As a result management of the ecosystems in the basin that depend on river flows involves some hard decisions about what assets to save and what assets to let go. This paper models this triage problem using a stochastic and dynamic programming approach. This model is used to identify how optimal management is affected by hysteretic and irreversible effects of drought on ecosystem assets and uncertainty about future climate. Key Words: Triage, irreversibility, climate change. 1 Introduction This paper looks at the problem of allocating environmental water among different ecosystems during a drought. The key feature of this problem is that failure to allocate adequate water to a particular ecosystem may result in irreversible or hysteretic changes in the nature of ecosystem such as the death of key populations of some species. This problem is applicable to a range of environmental flow decisions in the Murray-Darling Basin (MDB) and at several scales. For example the Murray-Darling Basin Commission’s living Murray program identified six “Icon sites” as the focus of its environmental water management strategy, and is currently exploring options for how to provide water to maintain the health of these sites. The aim of this paper is to develop an understanding of optimal management strategies of environmental water during drought. We calculate optimal water management decision rules for a simple model and compare optimal management to a decision rule that aims to keep as many ecosystems alive for as long as possible by always providing water to an ecosystem that would otherwise die. The analysis therefore focuses on the value of a strategy that deliberately does not provide water to