No abstract

Dryland salinity has been conceived of as a problem involving massive off‐site impacts and therefore requiring coordinated action to ensure that land managers reduce those off‐site impacts. In economic terms, salinity is seen as a problem of market failure due to externalities, including external costs from one farmer to another and from the farm sector to the non‐farm sector. In this article, we argue that, at least in Western Australia (WA), externalities are much less important as a cause of market failure than has been widely believed. If all externalities from salinity in WA were to be internalised, the impact on farm management would be small.

By 1994, an estimated 1.8 million hectares of cleared land in Western Australia was affected by secondary dryland salinity to some extent. The area affected is likely to double in the coming 20 years. The cause of this salinity is excessive recharge under traditional agriculture, leading to rising groundwater levels. Monitoring changes in groundwater levels is helpful in indicating the degree of threat to agricultural land and public assets. Many researchers have studied groundwater level rises and attempted to explain them statistically. We present an approach for statistically estimating trends in groundwater levels. The approach separates the effect of atypical rainfall events from the underlying time trend and the lag between rainfall and its impact on groundwater is explicitly represented. Rainfall is represented as an accumulation of deviations from average rainfall. Application of the approach is demonstrated using data from 49 bores in Jerramungup Shire, Western Australia. The approach provides high explanatory power, particularly for deeper bores.

By 1994, an estimated 1.8 million hectares of cleared land in Western Australia was affected by secondary dryland salinity to some extent. The area affected is likely to double in the next 20 years. The cause of this salinity is excessive recharge under traditional agriculture, leading to rising groundwater levels. To effectively reduce land and water salinity a deep-rooted perennial is needed to mimic the temporal and spatial distribution of leaf area that existed prior to clearing. Previous studies have shown lucerne lowers groundwater levels in areas with favourable conditions. We present data showing that lucerne lowered groundwater levels in 4 different landforms and under unfavourable conditions. All sites had very saline groundwater, high sodium chloride chemistry and high groundwater levels. This paper shows that the effectiveness of lucerne in salinity control measures depends on the attributes of the groundwater flow system. salinity, salinity management, monitoring, sustainability.