Multi-What (?!) Analysis
Abstract
Since 1988, states in the Murray Darling Basin have been obliged to enter their drainage and disposal projects’ salinity effects on a MDBC Salinity Register. Salinity effects are measured in the Murray River at Morgan, in South Australia. States must always have a nett Credit of salinity effects.
In the past the calculation of a project’s salt load changes has required only an understanding of relatively straightforward physical processes backed up by historic data. However, matters have become much more complicated. Recently there have been dramatic reductions in the flow and salt export of irrigation drains. Reductions may be due to low rainfall, low seasonal allocations, nett trade-out of water, and greater efficiency of water use on-farm. In future, the allocation of one-fifth of Sales Water to the environment under the terms of the Victorian White Paper will also be relevant.
Managers will need to have the ability to partition the reductions in salt load into those due to transient factors (e.g. low rainfall) and those due to State and irrigator initiatives (e.g. water trade). A statistical technique known as multi-variate analysis can be used for this. The paper reports on the successful use of the technique in two case studies, at Barr Creek and Tragowel Plains, both in the lower Loddon valley in North Central Victoria.
Authors
Keith Collett & Rebecca Lett