Inquiry into rural drainage in Submission from the Mallee Catchment Management Authority

1. Introduction The Mallee Catchment Management Authority (CMA) welcomes the opportunity to respond to the Victorian Government’s Environment and Natural Resources Committee Inquiry into Rural Drainage in Victoria.

The Terms of Reference for this inquiry clearly state that the term “rural drainage” does not include irrigation drainage or regional urban and metropolitan drainage. However, in areas of irrigated horticulture in the Mallee , clear delineation does not exist between rural, irrigation and regional urban drainage.

As such, this submission will address issues posed by the decommissioned Mallee Channel System, which is a surface channel system established for transporting water that has also influenced drainage and storm water flow paths in the southern part of the Mallee CMA region. This system fits the inquiry’s definition of rural drainage. Where relevant, this submission will also provide information relating to rural drainage in the irrigated areas in an effort to illustrate the complexities of rural drainage in the Mallee region.

1.1 Organisational overview The Mallee CMA is a statutory authority, formed by the Victorian Government in 1997 under the Catchment and Land Protection Act (1994) and the Water Act (1989).

The Mallee CMA’s primary responsibility is to ensure that natural resources in the Victorian Mallee are managed in an integrated and ecologically sustainable way. The Mallee CMA is a statutory body responsible for the delivery of natural resource programs in this region in partnership with government agencies, local organisations and community groups.

The Mallee CMA’s responsibilities include the management of waterways, biodiversity, floodplains, salinity, pest plants and animals, and soil health. This is achieved through the development and maintenance of strong links to the community, underpinned by science-based programs and strategies.

1.2 Regional summary The Mallee CMA region covers 3.9 million hectares (Ha), which is about one-fifth of Victoria. It is the largest catchment area in the state and runs along the from to the South Australian border, through areas of high value irrigated horticulture and National Parks, and south through vast dryland cropping areas and public reserves to the Wimmera.

The region’s significant productive irrigated and dryland agriculture is interwoven amongst world-class environmental assets, including two of the six Icon Sites defined in The Living Murray Initiative: The Hattah Lakes Icon Site and the Victorian component of the Chowilla

Floodplain - Lindsay Wallpolla Islands Icon Site; along with part of a third, the Murray River channel icon site, which extends the entire length of the Mallee’s northern border. The floodplains and associated River Murray environs also support significant Red Gum and Black Box communities and a cultural landscape with heritage sites that date back thousands of years.

In the Mallee CMA region the Murray River directly supports more than 70,000Ha of diverse irrigation industries, comprising some 2,300 properties with an annual Bulk Water Entitlement of 500 gigalitres (GL). Permanent plantings of high value horticultural crops dominate the irrigated landscape.

2. Rural drainage in the Mallee CMA region This submission has been formulated to respond directly to the Terms of Reference in relation to the Mallee CMA region.

(i) The historical basis for the establishment and operation of former drainage schemes, including management arrangements.

Rural drainage in the southern Mallee The Mallee CMA’s boundary encompasses part of the decommissioned Wimmera Mallee Channel System. This complex earthen channel network was used to provide stock and domestic water to many Wimmera Mallee properties and towns until mid-2010, when it was replaced by the continuous supply provided by the Wimmera-Mallee Pipeline system.

Decommissioning of the Wimmera Mallee Channel System began in 2009, but the significant rain events of 2010/11 highlighted the important role the channel system had historically played in surface water drainage. Not only had this gravity-fed channel system supplied water, it had also provided an avenue for surface water to drain away from crops, roads and residences in low lying landscapes where surface water pooled and over-topped the channel banks. In many cases the channel was still in place but the road crossing asset had been decommissioned leaving the crossing as a blockage. This practice needs to ensure the works do not create issues for third parties.

Management of the Wimmera Mallee Pipeline and the redundant Wimmera Channel System is provided by Wimmera Mallee Water. The Mallee CMA supports this management arrangement through its strong working relationship with the water corporation.

Rural drainage in the irrigated areas of the Mallee Many of the irrigated area of the Mallee CMA region is serviced by an extensive sub-surface drainage system to remove excess water that seeps down through the Mallee’s sandy soil profile. Surface drainage as adopted in areas of heavy clay soils, is not a common feature of production areas in the Mallee landscape.

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This sub-surface network was established in the 1930s in an attempt to avoid shallow water tables forming, water logging and irreversible salinisation of permanent irrigation plantings such as grapevines and citrus.

During the “Salt Action-Joint Action” movement of the 1990s a number of community driven drainage disposal schemes were constructed in the Mallee irrigation areas including Nangiloc- Colignan, immediately surrounding Lamberts Swamp, Psyche Bend Lagoon and - Boundary Bend, to improve drainage disposal and reduce the salinity impacts associated with irrigating Mallee soils.

Increased urbanisation of rural areas has resulted in these drainage systems becoming predominantly used for stormwater drainage. In addition to this, a community expectation has developed that these sub-surface systems should also be capable of mobilising stormwater from low-lying areas.

Management of sub-surface drainage systems in the Mallee irrigation region including drainage diversion schemes is provided by Lower Murray Water and in the urban areas by Rural City Council. The Mallee CMA supports these management arrangements through its strong working relationship with the water corporation and local council.

(ii) The status of rural drainage across the Mallee CMA region, including effectiveness, regulation, ownership, responsibility and maintenance on both public and private land.

Rural drainage in the southern Mallee As noted previously, the Wimmera Channel System has almost been decommissioned and replaced by the Wimmera Mallee Pipeline system. The status of the channel system is redundant; Grampians Wimmera Mallee Water is in the final stages of its decommissioning process, which affects infrastructure on both public and private land.

Rural drainage in the irrigated areas of the Mallee Rural sub-surface drainage in the irrigated areas of the Mallee has undergone significant change in recent years. Improved on-farm water efficiencies have led to significantly less water entering the sub-surface drainage systems, while increased urbanisation of rural areas has resulted in these drainage systems becoming predominantly used for stormwater drainage without stormwater capacity.

For example: • Nichols Point, near Mildura, was developed in the early 1900s as an irrigation district and planted with wine and table . In recent times, the wine and table plantings have been subdivided to make way for widespread housing development. As a result, the sub-surface drainage now predominantly carries stormwater as opposed to irrigation run-off. • Lake Hawthorn is located approximately six kilometres west of Mildura. It is a naturally occurring low point in the landscape that has been utilised as an irrigation drainage basin. Similar to Nichols Point, improvements to irrigation practices has led to 3

decreased irrigation drainage into the lake, while increased housing development has resulted in greater volumes of stormwater draining to Lake Hawthorn. • The are a series of connected lakes 15 kilometres south-west of Mildura. Historically these lakes were used as drainage disposal basins for freshwater outfall from irrigation channels and saline drainage water from the surrounding irrigation district. However, these lakes also have significant environmental values as they are home to a population of Murray Hardyhead, which are a threatened native fish species in Victoria. The cessation of channel outfall and reduced drainage water flowing into the lakes has required the delivery of environmental water to keep this fish population alive.

(iii) The benefits of rural drainage for both productive land and environment, together with community expectations for rural drainage programs.

Rural drainage in the southern Mallee The opportunity, for these man-made channels to be maintained where required, with minimal maintenance, will provide mobilisation of the large storm water events but also bolster catchment supplies to low lying natural water storage areas (wetlands and lakes). These wetlands and local lakes are typically surrounded by Black Box Eucalypts, which highlight their naturalness in the landscape. The focus is to allow storm water to reach these low lying areas to ensure the wetland will remain functional for longer and ensure productive land water recedes at a natural rate with no artificial blockages.

Rural drainage in the irrigated areas of the Mallee The direct benefit of rural sub-surface drainage in irrigation areas is primarily related to protecting the productivity of horticultural areas by: - Preventing the formation of perched water tables which cause water logging and salt accumulation in the root zone of the crop; - Leaching of salt introduced to the soil in irrigation water depending on river salinity and amount of water applied to the crop.

There are also benefits of rural sub-surface drainage in the preservation of both public and private infrastructure such as roads, buildings, fencing, trellising etc by preventing water- logging and subsequent salinisation of soil surfaces.

Environmental benefits are similar to those associated with irrigation as the root-zone of native trees are protected from rising saline groundwaters. Additionally, many of the drainage diversion schemes constructed in the 1990s had a direct salinity benefit under the Federal Murray Darling Basin Agreement, Basin Salinity Management Strategy in reducing the intrusion of saline groundwater into the Murray River by decreasing groundwater pressures associated with the disposal of irrigation drainage water.

Community expectation for rural sub-surface systems are that they should be capable of removing stormwater from low-lying areas even though they have been historically designed to

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meet irrigation drainage requirements. The unprecedented rain events of February 2011, the drainage systems where overwhelmed in many parts of the rural irrigation areas.

(iv) The impacts of rural drainage, including on other landholders and the environment, including waterways, wetlands, flora, fauna and water quality.

Rural drainage in the southern Mallee The redundant channel infrastructure of the Wimmera Channel System was regarded by many residents in the southern Mallee to have had a significant impact on the movement of surface water during the 2011 flood. Channels and associated infrastructure (e.g. culverts) that had been backfilled as part of the decommissioning process were regarded by many to have contributed to the flooding of crops, residences and access roads. This was an issue noted by the Committee’s 2012 “Inquiry into flood mitigation infrastructure in Victoria”.

Rural drainage in the irrigated areas of the Mallee The sub-surface drains in irrigation interconnect into regional drainage pipes that dispose drainage water in near-by disposal basins, wetlands and in some cases direct to the River Murray channel. There are some examples of re-use of irrigation drainage water albeit limited. These flows and salinity levels are monitored at representative sites across the irrigated Mallee.

The examples cited in the response to point two (ii) under the Terms of Reference illustrate the multiple uses of drainage systems within the Mallee’s horticulture zones and highlight the complexities now arising around drainage responsibilities, maintenance and future use. Each example emphasises the importance of the role of local government, water corporations and catchment management authorities and productive working relationships in addressing issues relating to drainage.

(v) Options for improved rural drainage management across Victoria, including regulation, installation and funding arrangements, operation, responsibility and maintenance on both public and private land.

Rural drainage in the southern Mallee The Mallee CMA is committed to supporting the lead agency, Grampians Wimmera Mallee Water, to determine ongoing ownership and associated responsibilities for redundant channel infrastructure in the Wimmera and the Mallee. One way the Mallee CMA may be able to offer support is by providing geographical information systems (GIS) analysis of the landscape and how surface water be affected by the decommissioned channel system, using Light Detection and Ranging (LiDAR) spatial elevation data. However, it must be noted that existing LiDAR for the area in question is not detailed enough to provide the level of comprehensive information required. Mallee CMA would be able to utilise other projects that undertake property plans with each landholder through the EMAP program. A combination of the EMAP program with the Grampians Wimmera Mallee Water authority rural drainage project would give good access to all landholders and all landholders good access to the latest in technology.

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A brief examination of the 2010-11 floods in the southern Mallee and Wimmera highlights the deficiencies of existing LiDAR. At this time, the Mallee CMA worked with emergency services, water authorities and agencies to provide flood intelligence on two areas within the former Wimmera Channel System region – the Tyrrell and Lalbert Creeks, Dunmunkle North and Yarriambiack Creek. The Mallee CMA had access to the Department of Sustainability and Environment’s state-wide, 10 metre Digital Elevation Model (DEM), which was the most detailed data set available. Data at one metre resolution existed for Yarriambiack, Tyrrell and Lalbert Creeks; however, this was only available in very narrow strips of the creek lines and offered little value to analysis of the wider landscape.

The resolution and accuracy of DEM data is of particular importance in the Mallee region as the flat nature of the landscape means low quality LiDAR can assume the topography is flatter than it is in reality. This can result in unhelpful distortions when attempting to analyse how floodwaters may behave.

As the data available for the southern Mallee was only accurate to within 10 metres, Mallee CMA staff were forced to draw on whatever relevant supporting data was available in order to produce information useful for predicting how flood waters may behave or be influenced by the decommissioned channel system. This is not ideal and it is important that planning for future management of rural drainage considers major improvements to spatial information in this region.

Increasing the resolution and vertical accuracy of LiDAR available for the area within the decommissioned Wimmera Channel System would assist in providing information that could be utilised by Grampians Wimmera Mallee Water and stakeholders to analyse how actions such as backfilling disused channels and destroying water management infrastructure (e.g. culverts etc) may impact on the movement of surface water across the landscape. This will be vital information that should be considered when determining how to further manage the decommissioning process and determine ongoing ownership and associated responsibilities for this infrastructure.

The Mallee CMA is well placed to support Grampians Wimmera Mallee Water and stakeholders to work through the rural drainage issues associated with the decommissioned Wimmera Channel System. The Authority has a sound understanding of the landscape, which is backed up by strong technical skills in GIS. In addition to this, the Mallee CMA has also had the opportunity to establish mutually beneficial working relationships with agencies and communities in the region through the Wimmera Mallee Pipeline Wetlands Connection program. This program was coordinated by the Mallee CMA and involved Grampians Wimmera Mallee Water, North Central CMA, Wimmera CMA, and numerous local stakeholders. This program encouraged local residents to nominate wetlands on public or private land for reconnection to the pipeline. The Mallee CMA remains committed to enhancing these important regional partnership arrangements and to working with the local community.

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Rural drainage in the irrigated areas of the Mallee Through the regional Land and Water Management Plan, a proactive approach has been adopted to modern irrigation practices that maximise the efficiency of irrigation water by using pressurised systems to better target specific crop watering requirements and match soil water holding capabilities. This approach has reduced the required capacity for rural sub-surface drainage systems to cope with irrigation water as is reflected in the reduced irrigation drainage flows and lowered groundwater levels. This has reduced the effect on neighbouring landholders and the environment.

In addition, the modern irrigation approach creates strips of dry soil (i.e. between drip lines) increasing the ability for soils to absorb rainfall and buffer the effects of high rainfall events.

The complexities surrounding sub-surface irrigation in this region are expected to continue to grow along with the increasing urbanisation of rural areas. As development expands into former irrigation areas, the sub-surface drainage system will increasingly become a stormwater system, which will bring with it environmental, financial and other concerns about appropriate management and responsibilities for maintaining these drains and the resulting output of stormwater.

By raising these complexities, the Mallee CMA does not purport to have the answer but, instead, seeks to alert the Committee to this emerging issue.

(vi) The Committee’s report on the Inquiry into Flood Mitigation Infrastructure in Victoria.

Rural drainage in the southern Mallee The Environment and Natural Resources Committee’s 2012 “Inquiry into flood mitigation infrastructure in Victoria” noted “t he effects of decommissioned irrigation channels on flooding were of concern to some stakeholders in western Victoria. Irrigation channels in the west were found to have limited impact on flood levels. However, ownership and associated responsibilities for infrastructure needs to be clarified in some areas” (ENRC, 2012).

Recommendation 4.16 of the aforementioned inquiry nominates Grampians Wimmera Mallee Water as the agency responsible for working with the Victorian Government and stakeholders to determine ongoing ownership and associated responsibilities for redundant channel infrastructure in the Wimmera and the Mallee. As a stakeholder in this region, the Mallee CMA supports this recommendation and is committed to working with the water corporation in order to provide more clarity regarding ownership and associated responsibilities related to the disused channel infrastructure within the Mallee CMA’s region of responsibility. Please refer to point five (v) in the Terms of Reference for further discussion on the need for improving the spatial data relevant to the Wimmera Mallee.

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3. Summary of key points I. Rural drainage – as defined by this inquiry -- occurs mainly in the southern Mallee part of the Mallee CMA region and relates to the decommissioned Wimmera Channel System. II. LiDAR of at least one metre DEM or less is required to provide accurate modelling of the affect of the decommissioned channel infrastructure on surface water movement. III. Mallee CMA will support Grampians Wimmera Mallee Water, the community and stakeholders to determine ongoing ownership and associated responsibilities for redundant channel infrastructure in the Mallee and Wimmera. IV. Within irrigated horticulture areas in the Mallee CMA region, clear delineation does not exist between rural, irrigation and regional urban drainage. As such, complexities are now arising around issues of drainage responsibilities, maintenance and future use in particular capacity expectation.

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