Gravity Irrigation - Surface Drainage

Gravity Irrigation - Surface Drainage

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We’re committed to listening to you and we understand drain maintenance is a key issue.


Surface drainage is the network of surface drains and drainage courses that enable irrigated farms to be drained of excess water and rainfall runoff when required.

Good surface drainage is an essential part of any surface irrigation scheme. Within the Goulburn Murray Irrigation District (GMID), GMW owns and operates networks of surface drains; and manages declared drainage courses, to ensure your land receives adequate drainage.

Farm productivity is impacted and crop losses occur when excess water, through water logging and inundation, isunable to drain from irrigated land effectively.  Poor surface drainage also leads to costly environmental issues (e.g. salinity) and impacts to local council road assets.

We undertake a range of activities to keep drains maintained, however spraying and controlling weeds is a keymaintenance issue across our drains and channel network. We currently spraydrains twice a year to ensure they are not choked by weeds.

There are generally few complaints from you (our customers) about our drainage network except:

  • after rainfall events when you would like water to be removed more quickly than the design capacity of a drain allows
  • about level of ongoing maintenance relative to the drainage rating applied to your property.

GMW relies on our customers to report any issues in its drainage network.

The current service standard ‘Availability of Surface Drainage’ means GMW makes surface drainage available by efficiently operating and maintaining a surface drainage system.

We’re committed to listening to you and we understand drain maintenance is a key issue. So, we’re seeking information from you about ways we can improve this.

Why is this topic being considered?

GMW’s provision of drainage in Irrigation Districts is required under the Water Act 1989.

It is a standard service and makes up a small component (about 10%) of a typical irrigation customer account.

However, it is important that the operation and maintenance of our drainage network takes into account key changes, such as the way farms are irrigated, patternsof water use and climate. This ensures we are providing an efficient service that represents good value-for-money to you.

What are the decisions to be made?

· Should GMW’s surface drainage service change (e.g. how or when maintenance occurs)?

· How our customers use their land is changing, and so is the environment –so do GMW’s surface drainage service standards need to change with it?

· Do we need to provide more information about surface drainage to our customers?

· Do you know how to report a drainage maintenance issue to GMW?

How does this matter affect customers?

Surface drainage is a key element of irrigation and supports you in producing healthy crops and products.

The surface drainage system is a system of passive assets and its availability is particularly important during rainfall events.

Historically, key functions of the surface drainage system in irrigation areas have been to:

· Receive excess farm irrigation water;

· Receive GMW channel outfalls;

· Receive farm irrigation induced runoff from minor rainfall events; and

· Alleviate impacts of major rainfall events.

Greatly improved on-farm irrigation management, water use efficiency and automation of our channel system means there is less of the first three functions occurring. The key service you receive from the surface drainage system in irrigation areas is now to provide relief after major rainfall events on irrigated land. These larger rain events are now more random, frequently occur in summer and are often localised.  

What is not negotiable in this topic?

GMW is required to manage constructed surface drains and declared drainage courses within its Irrigation Districts to ensure we provide an efficient and effective drainage service that fulfils a key function under the Water Act 1989.

What is negotiable in this topic?

· How GMW’s network of surface drainage assets are maintained and operated, given changing conditions

· What work GMW does to operate and maintain the drains

What are the known, viable options?

· Developing a risk-based approach to surface drainage maintenance and operations, that considers new thinking based on changing conditions

· Reviewing how surface drainage issues are identified and managed by GMW.

If other options are identified, can they be considered?

Yes – GMW is committed to working with customers to meet their needs for surface drainage.