Irrigator operates on a daily basis generating demands and extracting water to meet these demands via the water user and supply nodes. Irrigator maintains a daily water balance for each cropping area during its planting season to calculate the daily soil water deficit and an irrigation requirement. The irrigation requirements are used by the Water User to generate orders and opportunistic requests and to subsequently place orders and requests and to extract water from a water source.The model can be applied in both regulated and unregulated systems.
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This describes a number of parameters that can be set at an irrigation district level. The maximum irrigated area represents the maximum area that can be irrigated within a district. This is used to calculate the fallow area at each time-step, which impacts on the rainfall runoff from the fallow area. The total irrigated area can exceed the maximum irrigated area if incorrectly configured, causing a warning message to be recorded runtime. Soil moisture capacity is specified at the district level and this is assumed constant for all crops in the district. Soil moisture capacity is nominally the difference between the soils field capacity and permanent wilting point. If you have configured the irrigation season and end dates, orders and requests will only be generated within the irrigation season.
Figure 1. Irrigator demand model
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Climate Configuration
There are four parameters that can be defined for climatic data:
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Figure 2. Irrigator demand model (Climatic parameters)
Fallow Crop
Areas that are not being cropped are referred to as fallow. Every irrigator demand model has, by default, one fallow area. Fallow area occurs between cropping seasons or during the irrigation season if the maximum developed area is not planted. The fallow cropping area does not order or receive irrigation water. However, a soil water balance of the fallow crop is maintained, and impacts on rainfall runoff from the fallow area and the initial souild moisture assigned to new crops area. The depth of rootzone for fallow represents the depth of soil from which evaporation can occur.
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This is used to define parameters specifically related to the crop to be planted. To add a new crop, right click Irrigator and choose Add Crop Type. Consult the Source Scientific Reference Guide for greater detail regarding parameters for the following sections.
Figure 3. Irrigator demand model (General
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and Soil
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Configurations)
Soil Configuration
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Figure 4. Irrigator demand model (Planting Decision Trigger)
Soil Depletion
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Figure 5 - Irrigation demand model (Crop Economics)
Runoff
The supply escape efficiency defines the amount of applied irrigation water that becomes runoff. A value of 0 results in no irrigation runoff, 10% indicates that 10% of the applied irrigation water becomes runoff. You must also specify a return efficiency, which means that the proportion of runoff that is returned to the water user can be stored in the farm storage or returned to the river. By default, both are set to 0, and do not need to be configured.
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