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Salt loads to streams and stream salinity One of the most important impacts of salinity is on water resources. The Murray-Darling Basin Commission Salinity Strategy involves end-of-valley targets for salt loads and salinity for all of the main river valleys. Predicting how large areal land use changes may impact on end-of-valley salinity and salt loads involves: 1. Estimating how the land use changes impact on catchment water yield 2. Estimating how land use impacts on groundwater recharge 3. Predicting the groundwater response to changed recharge 4. Relating groundwater discharge to 'quickflow' and 'slowflow' components of water flow from catchments. Salt coming off at high flow may not be as important as salt coming off at low flows. 5. Combining water yield and salt generated from each catchment with operational releases from dams etc. Generally, models such as IQQM or REALM are used for this. The Catchment Classification Project (D9004), together with Project D2013 "Integrated Assessment of the Effects of Landuse Changes on Water Yield and Salt Loads" are concerned with steps 1, 3 and 4. Impacts of afforestation on water yield There is currently strong interest in expanding forestry plantation areas (see for example AFFA 2020 vision). This is being driven by a combination of commercial opportunities, concerns on environmental degradation issues such as dryland salinity and also by potential for greenhouse credits. Such expansion needs to be cognisant of potential adverse impacts through reduced water flows. Such a reduction in higher rainfall areas is now well-substantiated and not only affects water resources, but could also impact on environmental flows during drought periods as well as dilution impacts on salinity. Targeting afforestation towards lower rainfall areas will have less impact on water yield and is more likely to benefit salinity-affected areas; but is less attractive from a commercial perspective. The Cooperative Research Centre for Catchment Hydrology (CRCCH) project, Predicting the effects of land use changes on catchment water yield and stream salinity is: 
Developing GIS tools to predict impacts of afforestation and other landuse on long-term average water yield.
Investigating the impacts of afforestation on inter-annual and seasonal variability of water yield. Such information is important for reservoir operation and environmental flows.
Linking with the groundwater flow systems approach developed elsewhere in the catchment Classification project to aid the development of tools for end-of-valley predictions.
Contact: Lu Zhang, CSIRO Land and Water |
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| design & production by Talkin' Technical Communications | last updated: April 2002 |