What is salinity?
Salinity is the discharge of high levels of salt to the environment. Rain naturally contains small amounts of salt, which is harmless to the environment, but plants generally exclude this small amount of salt when they take up water with their roots. This leaves salt to accumulate in the soil, below the root zone of plants.
Periods of higher rainfall, or decreasing the amount of water plants are using by removing native vegetation for example, can mobilise this salt and allow it to pass into the groundwater, which in turn can allow it to flow into rivers and streams, or low lying areas of land.
Elevated levels of salt will stress plants and animals that have not adapted to it. In rivers and streams fish, invertebrates and plants will all be affected and some species may not be able to survive as salt levels increase. Elevated salt levels on land stresses and kills trees and also impacts upon crops and pasture.
Wimmera CMA is implementing the Wimmera Regional Salinity Action Plan to manage salinity. This involves a range of different approaches across the landscape ranging from:
Parts of the Wimmera River, particularly the Lower Wimmera, are very salty. Salt levels in waterways are determined by measuring Electrical Conductivity (EC). The higher the EC, the more saline the water. To give you an idea, drinking water should be less than 800 EC and seawater is approximately 58,000 EC.
Due to the relatively flat landscape, the watertable does not need to rise far to put Wimmera wetlands at risk from salinity. Many wetlands in the Douglas Depression are naturally saline, however there are now also many in the Edenhope area that have become more saline as a result of changed land management practices since European settlement.
The National Land and Water Resources Audit (the Audit) collates data and information on the status of Australia's natural resources. The Audit has found that about 22,000 ha, or 1% of the Wimmera, is visibly affected by salinity. This includes almost 6000 ha of severely impacted land. Another 56,000 ha of the region is expected to be at high risk of salinity due to groundwater levels being close to the surface.
A number of selected bores are monitored for changes in groundwater levels over time. You can click here to access this information, including a brief summary of the trend observed over time.