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4. Salinity Management

Salinity

Salinity – the accumulation of salt in the soil - is one of the major issues facing the NSW landscape. The problem affects both urban and rural landscapes, harming production in dryland farming and irrigation areas, damaging wetlands and rivers, lowering the quality of drinking water, and damaging infrastructure such as buildings and roads.

While salt occurs naturally in our landscape, human activities such as land clearing and inefficient water use can exacerbate the problem. It has taken many decades for the problem to emerge and will be with us for a long time to come. Solving it is a shared responsibility involving land managers, conservationists, Aboriginal communities, scientists, businesses and all levels of government.

The NSW Government has implemented a Salinity Strategy which is designed to slow down the increase in salinity by 2010, and lay the foundations for salinity management into the future. The Central West CMA will further build on this plan, actively tackling the problem with land managers and thorough research until 2016.

Our key areas of focus will be aimed at reducing the level of salt that enters water courses within the catchment. Reduced Salt Load and Electrical Conductivity levels in our in river systems will be the primary indicators of the success of our plan.  Activities undertaken to address this problem include;

• increasing areas of well-managed perennials that minimise water table recharge

• retaining and managing remnant vegetation in saline landscapes to control water table accessions and saline outbreaks

• developing effective interception plantings to control recharge for salinity management

• increasing water use efficiency on cropped landscapes

Our plan for achieving this is outlined below, with multiple catchment and management targets aimed at lowering salt levels and impacts on productivity for subsequent catchments and downstream water users.

 

Salt scald rehabilitation site, landholders learning about rehabilitation opportunities.

 

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Catchment and Management Target Overview till 2016:

The Salinity theme has 3 Catchment Targets and 9 Management Targets. The Management Targets are designed to attribute to the Catchment Targets and result in an improvement in the salinity issue over the longer term.

Catchment Target (CTSA1):

• By 2016, EC readings in the 50th and 80th percentiles respectively will be: Macquarie River @ Carinda, 500 EC and 800 EC; Bogan River @ Neurie Plains, 550 EC and 1450 EC; Castlereagh River @ Coonamble, 315 EC

Catchment Target (CTSA2):

• By 2016, salt loads in the 50th and 80th percentile respectively will be : Macquarie River @ Carinda, 35,000 tonnes/yr and 65,000 tonnes/yr ; Bogan River @ Neurie Plains, 30,000 tonnes/yr and 55,000 tonnes/yr ; Castlereagh River @ Coonamble, 18,000 tonnes/yr

Catchment Target (CTSA3):

• By 2016, optimum landuse practice implemented (minimising leakage) on 300,000ha (5%) of high risk salinity hazard landscapes.

 

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Management Target (MTSA1):

• By 2016, the EC and salt load levels for within valley sites in the Macquarie and Bogan Catchments will be: (refer to table in following detail section)

Management Target (MTSA2):

• By 2016, establish and manage large interception plantings on 30,000ha of suitable sites in identified key upland landscapes.

Management Target (MTSA3):

• By 2016, retain and improve 150,000ha of existing remnant vegetation within key saline landscapes.

Management Target (MTSA4):

• By 2016, establish and manage for salinity outcomes 2,000ha of large forestry plantings within key saline landscapes.

Management Target (MTSA5):

• By 2016, increase by 100,000ha the spatial area of perennials in identified recharge landscapes across the catchment for optimal water use.

Management Target (MTSA6):

• By 2016, 300,000ha of dryland cropping landscapes in the catchment will be undertaking farming systems that increase water use efficiency.

Management Target (MTSA7):

• By 2016, increase water use efficiency in irrigation farming systems on 35,000ha of irrigated lands.

Management Target (MTSA8):

• By 2016, involve all 17 local government councils in urban salinity management.

Management Target (MTSA9):

• By 2016, 5,000ha of known salinity discharge sites in priority hazard landscapes have improved perennial based management.

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Targets in Detail:

The salinity targets meet the following Natural Resources Commission's Statewide Targets as referenced in the Catchment Action Plan:

• Community Targets - 12, 13, 14;
• Water Targets - 5, 8;
• Biodiversity Targets - 2;
• Land Targets - 10, 11.

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Catchment Target (CTSA1):

• By 2016, EC readings in the 50th and 80th percentiles respectively will be: Macquarie River @ Carinda, 500 EC and 800 EC; Bogan River @ Neurie Plains, 550 EC and 1450 EC; Castlereagh River @ Coonamble, 315 EC The target is consistent with the targets suggested by the MDB Salinity Audit and NSW State Salinity Strategy.

• The salinity target figures for the catchment and within valley targets are based on modelled information. Further modelling is currently being undertaken for the catchment and the revised modelled figures will be incorporated when available.

• The current trend for instream salinity concentrations are predicted to increase markedly over the next ten years, with the greatest rises predicted within the Macquarie and Bogan River systems. The target aims to keep salinity concentrations below the thresholds for drinking water where possible and to not exceed the thresholds for aquatic ecosystems.

 

Clarification of terms:

50th / 80th PERCENTILE:

• The percentile value represents the proportion of time that a certain value (ie EC) will not be exceeded. For example, the 50th percentile for EC is the level that EC will be at or below 50% of the time. For the 80th it would mean that the specified value is only exceeded 20% of the time.

EC:

• A convenient method of measuring the salinity of water is by electrical conductivity (EC) measured in micro-siemens per centimetre (µS/cm). EC reflects the concentration of salt in the water.

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Catchment Target (CTSA2):

• By 2016, salt loads in the 50th and 80th percentile respectively will be : Macquarie River @ Carinda, 35,000 tonnes/yr and 65,000 tonnes/yr ; Bogan River @ Neurie Plains, 30,000 tonnes/yr and 55,000 tonnes/yr ; Castlereagh River @ Coonamble, 18,000 tonnes/yr The target is consistent with the targets suggested by the MDB Salinity Audit and NSW State Salinity Strategy.

• The salinity target figures for the catchment and within valley targets are based on modelled information. Further modelling is currently being undertaken for the catchment and the revised modelled figures will be incorporated when available. The target aims to slow the rate of landscape deterioration due to salinity, and in the long term, reverse the trend.

 

Clarification of Terms:

SALT LOAD:

• The amount of salt carried in a specific volume of water within a certain time period.

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Catchment Target (CTSA3):

• By 2016, optimum landuse practice implemented (minimising leakage) on 300,000ha (5%) of high risk salinity hazard landscapes. This target recognises that landuse is the main driver of effecting change to saline processes in the catchment. There is an element of risk that a river based, end of system target may be affected by climate over the 10 year period of the plan. With this in mind, the CAP includes this target that focuses on land based change.

• The management of salinity within the Macquarie, Castlereagh and Bogan catchments will be focused on applying the appropriate management recommendations to landscapes associated with specific groundwater flow systems (Department of Infrastructure Planning and Natural Resources, 2004). It is currently estimated by CMA expert team assessment that 5,888,000ha of the Central West Catchment area is at a high risk of salinity hazard.

• The target was set to address 5% of the high risk salinity landscape. This target was considered an achievable area, given costs and indicative budget over 10 years. It is acknowledged that ‘optimum landuse’ would vary according to the individual site and over the period of the plan as knowledge and best practice changes.

 

Clarification of Terms:

OPTIMUM LANDUSE:

• Land use practices that minimises leakage and are appropriate to the capability of the land.

LEAKAGE:

Water that is not utilised in the soil profile.

HIGH RISK SALINITY LANDSCAPES:

• Classification of salinity risk within the Central West catchment according to the hazard rating completed by Humphries (2000). The risk classification is based upon overlaying a number of components within the landscape, such as complexity of the geology, the potential of the underlying rocks to store salt, soil permeability, application of water for irrigation and other landuses.

• A high and very high risk classification would exhibit a high salt load in the landscape, a significant recharge potential and poorly suited landuse types.

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Management Target (MTSA1):

By 2016, the EC and salt load levels for within valley sites in the Macquarie and Bogan Catchments will be:

• This target follows on from the river based catchment targets. This targets sets out EC and salt load targets for various subcatchments within the Central West. This ensures that investment can be targeted in priority areas across the catchment.

• The target is consistent with the targets outlined by the MDB Salinity Audit and NSW State Salinity Strategy. Further modelling is currently being undertaken for the catchment and the revised modelled figures will be incorporated when available. A particular risk to the success of this catchment target is climatic conditions.

• A period of low flows in the river system will result in possible saline groundwater intrusions and a peak in the EC reading for that section of the river. This peak would be addressed in the long term monitoring of the EC readings in order to determine a long term trend. The monitoring of this target will rely on the existing collection of instream EC and flow data, as collected by Department of Natural Resources.

 

Table 1: Target Electrical Conductivity (EC) and Salt Load levels for the Macquarie and Bogan Catchments.

 

Clarification of Terms:

EC:

A convenient method of measuring the salinity of water is by electrical conductivity (EC) measured in microsiemens per centimetre (µS/cm). EC reflects the concentration of salt in the water.

SALT LOAD:

The amount of salt carried in a specific volume of water within a certain time period.

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Management Target (MTSA2):

• By 2016, establish and manage large interception plantings on 30,000ha of suitable sites in identified key upland landscapes. The intent of the target is to strategically place highly effective interception plantings of perennial vegetation that will significantly reduce the level of land salinisation in local groundwater flow systems. This technique would have the most dramatic effect in landscapes that exhibit suitable groundwater flow systems, as outlined in the groundwater flow systems report for Central West (Department of Infrastructure Planning and Natural Resources, 2004).

• The current estimate of area of suitable sites in the upland landscapes is estimated at 48,000ha, based on local expert knowledge. The target figure has been established based on this estimation, combined with budgetary indications over the life of the plan.

 

Clarification of Terms:

KEY UPLAND LANDSCAPES:

• These refer to landscapes that have a high hazard of becoming saline, or currently contribute large salt loads or concentrations.

INTERCEPTION PLANTINGS:

• Plantings of perennial vegetation that intercept sub-surface flow. These may be trees, shrubs or pastures.

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Management Target (MTSA3):

• By 2016, retain and improve 150,000ha of existing remnant vegetation within key saline landscapes. The intent of this target is to control clearing in high risk saline landscapes to prevent further degradation of land and water resources. This target was set to reflect the achievability of retaining existing remnant vegetation over the period of the plan.

• Landscapes that have a high hazard of becoming saline have been determined through salinity hazard mapping (Department of Land and Water Conservation, 2000) and the target figure reflects a manageable target based on recent community uptake rates of previous incentive funding.

 

Clarification of Terms:

SALINE LANDSCAPES

These refer to landscapes that have a high hazard of becoming saline, or currently contribute large salt loads or concentrations.

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Management Target (MTSA4):

• By 2016, establish and manage for salinity outcomes 2,000ha of large forestry plantings within key saline landscapes. Large areas of upland landscapes (ie upper part of the catchment) have a geological pattern that is prone to the development of salinity. These upland sites present an opportunity to control recharge. The intent of the target is to establish plantation forestry within this area within the term of the plan.

• This is expected to have a considerable benefit in the reduction of salt mobilisation in the area and therefore for the catchment. A risk to the success of this target is the rate of uptake by industry and private landholders for private forestry in the identified key saline areas. This will be monitored over time and the target figure adjusted appropriately.

Clarification of Terms:

FORESTRY PLANTINGS:

Range in size from 5 to > 500 ha in size. May be native or exotic species. KEY

SALINE LANDSCAPES:

Landscapes that have a high hazard of becoming saline, or currently contribute large salt loads or concentrations and respond to recharge management by dense plantations.

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Management Target (MTSA5):

• By 2016, increase by 100,000ha the spatial area of perennials in identified recharge landscapes across the catchment for optimal water use. The intent of this target is to reduce groundwater recharge by increasing the water used in the landscape, this includes the implementation of grazing and farming systems that optimise water-use and reduce recharge. Perennial species have been identified as a key element for controlling the capability of recharge in groundwater systems that are susceptible to subsequent saline discharge.

• This target has been set to reflect an achievable target for landholders over the life of the plan, based on costs and rate of uptake. Monitoring of this target will determine a trend for effectiveness and achievability of this target over time and will be modified if required at time of review.

 

Clarification of Terms:

RECHARGE LANDSCAPES:

• Areas of the landscape where recharge dominates the relationship between surface and groundwater. While geology, soil type, topography and climate have a bearing on the recharge potential of a landscape, land-use and vegetative cover can be the limiting factor in terms of recharge capability.

PERENNIALS:

• Type of vegetation that continues its growth for at least 3 years. These usually deep rooted species will intercept sub-surface flow. These may be trees, shrubs, forbs, native grasses or pastures. Management Target (MTSA6): By 2016, 300,000ha of dryland cropping landscapes in the catchment will be undertaking farming systems that increase water use efficiency. The intent of this target is to encourage landholders to incorporate farming systems that maximise water use within the soil profile by using methods such as minimum till or no till cropping methods.

 

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Management Target (MTSA7):

• By 2016, increase water use efficiency in irrigation farming systems on 35,000ha of irrigated lands. The intent is to prevent an increase in the areas of saline lands induced by irrigation inefficiency by encouraging adoption of best management irrigation practices. It is estimated that there is 56,000ha of irrigated land in the Central West catchment. The aim of the target is to reduce benchmarked accessions to the water table by 25%.

• The CMA expert panel process stated that water use efficiency programs on 70% of irrigated land will effect change. The expected outcome is to reduce the area of shallow watertables under irrigated areas, allowing production to continue and to reduce the associated levels of salinity in rivers, which are impacted via natural or man-made drainage systems.

 

Clarification of Terms:

WATER USE EFFICIENCY:

• Optimise the amount of water used by the crop and minimise the volume of water going to deep or shallow drainage and subsequently causing land salinisation.

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Management Target (MTSA8):

• By 2016, involve all 17 local government councils in urban salinity management. Urban salinity is a reality for many towns in the Central West catchment. The intent of this target is to have all 17 local councils in the Central West making a conscious effort to raise awareness of urban salinity, reduce the use of water and particularly reduce the inefficient use of water, by means of integrated water cycle management.

Clarification of Terms:

SALINITY MANAGEMENT:

• To have strategies in place that prevent the onset of salinity outbreak, or if salinity is present, to maintain and improve the extent of the condition. In terms of Local Government, this could include pricing, metering, leakage detection and communication/education programs or other strategies.

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Management Target (MTSA9):

• By 2016, 5,000ha of known salinity discharge sites in priority hazard landscapes have improved perennial based management. This target specifically targets discharge sites for rehabilitation with perennial species to prevent further degradation and increase productivity. This target will be primarily implemented through the incentives delivered by the Central West CMA to landholders. The majority of discharge sites in the catchment are well known to the Central West CMA, however there is a risk that incentives will identify further discharge sites. If this occurs, the situation will be addressed in the review of the targets and the target will be modified accordingly.

 

Clarification of Terms:

SALINITY DISCHARGE SITES:

• an area in the landscape where the watertable is close to, or reaches the surface of the ground. These areas bring salts to the surface which have a degrading effect on the soil structure and limit production of most traditional annual crops.

PRIORITY HAZARD LANDSCAPES:

• areas of the catchment that are identified as exhibiting a high possibility of salinity discharge. This is identified through features in the landscape such as geology, vegetation cover and known levels of the groundwater table.