In regards to what is happening with AGL in the Gloucester or other projects whereby irrigation will be used in the distribution of waste water this is possibly one of the most important documents released ... Assessing the salinity impacts of coal seam gas water on landscapes and surface streams Final Report February 2013 Soil and regolith (unsaturated zone) properties While all companies are now required to undertake soil surveys as part of their irrigation development, the quality and scale of data and information used is still variable. The majority of CSG development is in areas where only regional scale data is publicly available, hence detailed surveys are essential. This is further discussed in Section 7.3.1. Better quality surveys and improved collation/correlation of the data will improve all stakeholders’ capacity to assess salinity risk. Associated with this is a need to dig deeper. Studying soil/regolith properties to only 1.5 m depth is no longer acceptable. Studies must be undertaken to depths below the “root zone” as this is where deep drainage ends up. Furthermore, the root zone for different crops must be more effectively defined. Critical attributes that need attention are porosity, starting soil water content, substrate permeability/conductivity and lateral flow processes. Rainfall salinity Rainfall salinity data is required for salt mass balance calculations. While the equations of Biggs (2006) provide a starting point for the region, they have limitations. The widespread presence of weather stations on CSG tenements for environmental monitoring purposes and their use to calculate daily water balances for irrigation provides a clear opportunity to substantially improve the input side of the salt balance equation for relatively low cost. Such data could also feed into the national rainfall salinity monitoring network. While this is not a critical data gap, it is one that could be improved with ease and relatively low investment. Catchment hydrology The development of irrigation areas changes catchment hydrology, just as clearing of the catchments has over the last 150 years. In many instances, companies are currently being conditioned to install gauging stations for various monitoring purposes. A more strategic approach to locating these stations and collation of the data, e.g. provision to BoM, is needed that takes into account the objectives for collecting the data and the way in which the data is collected and used. Such an approach across the industry is also likely to lead to cost savings and will provide broader long-term benefits by contributing to the assessment of cumulative risk in catchments. Critical thresholds The use of critical thresholds in regulatory frameworks remains an issue. While these provide a clear decision point for operators and regulators, experience indicates that there is a need for an improved approach. The best example of this is “an acceptable root zone salinity”. There are so many variables in the field that can affect this number that setting one based on “textbook values” can be a relatively meaningless exercise. Considerable research is needed to better define critical thresholds for agronomic and degradation purposes across the landscapes of the region. Process understanding Surface wash off, lateral flow and deep drainage are the main mechanisms for water (and therefore salt) transport in soils. An understanding of the fate of excess water (e.g. whether it become lateral flow or deep drainage) in soils plays a major role in determining salinity risk. Understanding deeper soil/regolith processes and properties is therefore essential to calculating salinity risk. Unfortunately, our knowledge of these factors is very poor. More detailed soil survey and research of lateral flow process is required.
Posted on: Sat, 15 Jun 2013 02:13:57 +0000
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