Introduction
Water property rights in the Murray Darling Basin (MDB) involve a system of “entitlements” (perpetual rights to a share of water from a particular source/location) that receive annual water “allocations” (volumes of water available for use within the current year). These entitlements and allocations are “unbundled” in the sense that each is separately tradeable. The trade of annual water allocations between the water entitlement holders is known as Temporary Trade (MDBA, 2022). The water trade has become an effective water management tool for the entitlement holders to manage their water resources and reduce risk (MDBA, 2024).
The Trade Manager (TM) functionality in Source replaces a plugin built by the MDBA. The purpose of Trade Manager in core Source is to improve and standardise the functionality of defining how trade happens in Source. The incorporation into the core source provides additional features and recorder options. The trade manager incorporates the conceptualisation of economic demand and supply concepts into how trades occur between water users.
The TM functionality allows policy makers and modellers (MDBA, 2024) to:
Understand and predict the impacts of water trade and associated changing patterns of usage on conveyance losses and delivery risks.
Continuous improvement of water user’s behavioural assumptions and
Strengthen the capability to forecast and incorporate trends in crop mixes and climate-change scenarios.
Trade Manager concept
The total available water balance calculated in the Resource Assessment is passed to the water users, and the expected use is calculated based on the antecedent use (sum of previous 10 days use) or by user defined values (for example, time series, constant value or functions). Subsequently, total tradeable water is calculated for each water user, group and system based on available water and the value of water.. The tradeable water represents the portion of the total available water balance permitted for trade based on the regulation of the relevant jurisdiction or the defined limitations.
At each timestep, water availability and deficit are derived for each water user and trade group participating in trade. Water is traded from a user having surplus water to that having a deficit. However, trade can also happen even when there is no surplus water if there is a deficit for a water user with a higher value of water. The higher the value of water for a water user, the higher the priority it gets in trade. The water traded out from a group is equally traded by its water users, whereas water within a group is traded based on the proportion of surplus water held by its water users. This is evident in the example model given in the last section of this user guide.
A group of water users can be combined to form a water group. This could be based on the geographical proximity of those water users or on jurisdictions. These trade groups are bound by trade rules which can be set by the user. For example, there are rules pertaining to group water trade participation, and the maximum water that could be traded in and out from a group.
Trade Manager functionality in Source
The objective of the Trade Manager (TM) is to implement and enhance the water trade functionality available in the Plugin, thereby making water trade modelling available to all users. The Trade Manager (TM) functionality can be viewed and selected from the Edit menu in the toolbar, as shown in Figure 1.
When the TM is selected, a separate window with various options appears (Figure 1). From that window, TM options can be enabled by ticking the ‘Enabled’ check box. Also, users can indicate the start of water year in the Trade Manager.
As in other functionalities in Source, there are certain parameters associated with TM and they are:
Group definitions – a group of water users
Which water user is in which group
Whether a water is trading
The method by which an expected use is determined for each water user
The value or importance of expected use for each water user
Whether a group is trading
The annual trade in and trade out limits for each group
All the above parameters are incorporated into the TM using two main options which are ‘Trade Groups’ and ‘Trade Rules’.
Trade Groups
Trade Groups represent a collection of water users that can be defined by the user to reflect geographic or administrative regions. Within each group, water users are allowed to trade freely.
New groups can be added to the trade groups by right clicking on the ‘Trade Groups’ (Figure 2) and the newly created group name can be renamed as well.
In Figure 2, there are three groups added to the Trade Manager named TG1, TG2 and TG3. When a particular group is selected (TG1 in this case), the following screen is displayed as in Figure 3.
