Using Ground Water Responses to Improve Understanding of Climate Variation Impacts and Salinity Risk

Abstract

Dryland salinity is a serious threat to the sustainable management of land and water in many parts of Victoria. However, the onset of dry climate conditions has reduced its priority as a natural resource management issue in recent years. Apart from the elevated need for water taking the spotlight, the dry conditions reduce the risk of salinity, temporarily at least. Questions are naturally posed about what impact that these conditions have on salinity incidence. Does salinity retreat to some or any extent? How significant is the recession or improvement, if any? Obviously, a number of other factors besides climate influence whether, and to what degree, a salt affected area alters. This paper concentrates on investigating the climate variation impacts on several ground water flow systems to gain some further insight into salinity risk in time and space, as well as management of this risk. Close observation of the landscape and analysis of the ground water level record improves knowledge about the ground water flow systems and their responsiveness to changes in climate and landscape management. A review of observation bore data has revealed considerable declines in ground water levels across northern Victoria since 1996. The dry climate conditions during this time are hypothesised to have been largely responsible for these declines despite a number of landscape factors. The declines have been accompanied by marked changes in the occurrence and spatial distribution of recharge. In upland salt-affected areas of north central Victoria, cleared crest and upper slope landscape positions, which have typically had a high potential recharge status, have recorded very little recharge since 1996. During the same time, many lower slope and discharge positions in these areas have continued to record some seasonal recharge in most years. This recharge is argued to be due more to local infiltration than aquifer throughflow and has significant implications for salinity management priorities.