Water Available for Irrigation
As outlined in Water Sharing Plans and A History of Water Reform, all water within the Gwydir Valley is managed through the implementation of Water Sharing Plans. With all water managed within Water Sharing Plans, the total volume of water available for diversion by water users, annually and over the long-term has been established for the Valley.
The key surface water sources utilised for regular irrigation production are the Regulated River and Unregulated systems, with the Regulated River water source providing the more regular and larger volume of water availability. Both systems provide stock and domestic and town water supplies. The current Regulated Water Sharing Plan limit is 392,000 ML per year, and combined unregulated limit is 67,000 ML (as calculated from available entitlement).
The limit for the Regulated River has been reduced to 283,000 ML via water purchases for the environment to enable the setting of the Sustainable Diversion Limit for the Basin Plan. This is to be implement on 1 July 2019. Effectively those in the Gwydir already meet the SDL, which equates to approximately 19% of long-term average annual river flows are available for irrigation use.
Historical assessment of Water Sharing Plan rules, climate, water usage and behaviours via hydrological models reveal the long-term reliability of each entitlement type. The Gwydir Valley's surface water resources are considered a low water reliability catchment compared with others in NSW, although water reliability is comparable to other northern NSW systems.
The long-term reliability of entitlements types are:
- High security, town water supplies and stock and domestic: 100%
- General security: 36%
- Supplementary: 55%
- Unregulated: 55% (estimated similar to supplementary)
The key groundwater water sources utilised for regular irrigation production is the Lower Gwydir aquifer, although irrigation in other areas is limited, with the majority of water from these sources used for town water supply, recreation or stock and domestic purposes.
The current Water Sharing Plan allows for an extraction limit of 32,000 ML per year, which equates to 85% of the long-term sustainable yield of the Lower Gwydir aquifer.
A historical assessment of Water Sharing Plan rules, climate, water usage and behaviours via three-dimensional hydrological models reveals the long-term reliability of each entitlement type, with all entitlement types having 100% reliability.
A summary of licences within each of the major plan areas is provided below. Key aspects of each plan are also outlined within the comments section.