Hydrogeological Landscapes framework: a biophysical approach to landscape characterisation and salinity hazard assessment

Abstract

In Australia, salinity has the potential to affect up to 17million hectares of agricultural and pastoral land. For many degraded sites, biophysical hazards are often poorly understood and consequently poorly managed. Attempts to remediate areas affected by salinity have met with varying degrees of success. The New South Wales (NSW) Office of Environment and Heritage, NSW Department of Primary Industries, University of Canberra and Geoscience Australia have collaborated to develop a biophysical expert-based approach for the assessment and management of salinity within landscapes. The Hydrogeological Landscape (HGL) framework provides a structure for understanding how salinity manifests in the landscape, how differences in salinity are expressed across the landscape and how salinity may best be managed. The HGL framework merges the flow dynamics of the groundwater flow system with the landscape elements of the soil landscape or regolith landform approaches. This is the first approach to specifically address all three manifestations of salinity: land salinity, in-stream salt load and in-stream salt concentration. The HGL framework methodology recognises the interplay between surface and subsurface flow systems, as well as the capacity for water to interact with salt stores in the landscape, and identifies biophysical landscape characteristics (e.g. amount and type of vegetation cover, typical land use practice) that affect these interactions. The HGL framework is an expert system that integrates the spatial variability of landscape characteristics and salinity processes to produce a salinity hazard assessment for any given area.

Application of the Soil Security Concept to Two Contrasting Soil Landscape Systems—Implications for Soil Capability and Sustainable Land Management

“…On the direct drill treatment which was not tilled and still retained a cover of 80% lupin stubble, the soil loss was measured as 65 t/ha with an estimated soil depth loss of 5 mm. Altering catchment hydrology to reverse saline outbreaks slow [77,78] Nutrient decline can be rapidly recovered by fertilising programs and introduction of legumes into rotations.…”

“…Soil salinity can have a number of degradation effects: land salinity on-site, effects on water quality of water resources and effects on salt loads to river systems. Given the nature of the soils, geology and groundwater, the Cowra Trough Red Soils do not have a major salinity problem [40,41,77,78]. Mandagery Creek does have a significant salt load, but measurements suggest the major source of the salt contributing to the salt load comes from the tributaries to the north of the Cowra Trough Red Soils that are associated with soil landscapes on the Dulladerry Rhyolite and perhaps some of the granites to the north [77].…”

“…Recovery from salinity is required for a few saline outbreaks that do occur in some of the drainage lines in the Cowra Trough Red Soils. Revegetation on the saline site using salt-tolerant species plus revegetation in the catchments suppling groundwater to the saline sites is seen as the means to recover these sites [78]. Recovery from salinization is a slow process of changing the hydrology of hillslopes and catchments and can take a long time [78].…”