IQQM crop demand model 2
The IQQM CropMod2 replicates the water requirements for a cropped area. This is a process-based model which allows you simulate a farmer’s decision on the area to plant in each season and evapotranspiration of the different crop types, and generates a demand based on the maintenance of a target soil moisture level. You can also simulate rice irrigation by specifying ponding behaviour and return flows.
Configuring generic crop settings
Before configuring an IQQM CropMod2 Demand model on a Water User node, you must specify crop factors for the entire scenario using . Crop factors defined in this way are accessible for each water user node.
The method for defining crop factors is based on FAO 56 which divides the growth period of every crop into four developmental stages based generally on water requirements. These stages are:
- Initial (or establishment) stage - occurs between planting and when there is approximately 10% ground cover. Water requirements are quite low and constant;
- Crop development (or vegetative) stage -sees a rapid increase in the amount of water required by the crop until there is generally about 70% to 80% ground cover and maximum rooting depth is achieved;
- Mid-season (or flowering) stage - requires the maximum amount of water in the life of the crop; and
- Late (or yield and/or ripening) stage - there is an approximate halving of water requirement as the crop ripens, reaches maturity and is harvested.
The Crop Parameters window is at Figure 50 and the parameters required for each crop type are described in Table 18.
Configure Crop Parameters
Crop Factor Editor
Planted Area tab
This tab (Feature Editor 35) broadly defines the area to be used and the proportions between the primary and secondary crops.
Water User node (IQQM CropMod2, Planted Area)
Soil tab
This tab (Feature Editor 36) defines soil inputs. There are individual stores for each crop type. Each store changes from a single layer during irrigation, to two layers during non irrigation (fallow area). An irrigated crop area becomes fallow after the irrigation period.
Water User node (IQQM CropMod2, Soil)
Climate tab
This tab defines four parameters (Table 21) for climatic data.
You can specify four parameters for rainfall data in the Rain data tab (Feature Editor 40 & Table 22).
Water User node (IQQM CropMod2, Climate, Evaporation)
Water User node (IQQM CropMod2, Climate, Avg. Evap)
Water User node (IQQM CropMod2, Climate, Rainfall)
Water User node (IQQM CropMod2, Climate, Rain data)
Water User node (IQQM CropMod2, Risk)
Risk tab
Risk represents historical practices of farmers in selecting area to be planted by considering available water resource and antecedent catchment wetness. In Source, when the area has a primary and secondary crop , the Risk tab allows for an optional application of risk factors for each of the two crops. If the Use Risk Functions For Area checkbox is not selected, the maximum area will be planted.
In the Inflow section, a time series of flow is used to assess catchment wetness conditions using the Tributary Inflow Index (TII). This is estimated as the ratio of the past six months of flows to the long term median flow for the same six month period.
Farmers’ Risk Functions
Efficiency tab
Source allows for 2 discharge paths from a water user node. One path conceptually retains water on the farm for reuse, whereas the other discharges into the river or other nominated return node The former returns water to either an OFS, or the river system. The latter includes the Escape System and Tile Drainage which discharges to the river system.
Water User node (IQQM CropMod2, Efficiency)
Return flow tab
This defines rainfall runoff and Tile Drainage parameters. Return drainage water is surplus drainage water from irrigation or from rainfall runoff that is redirected into the on farm storage, or be a system loss if there is no on farm storage. Alternatively is to direct the water to the river system at an inflow node/confluence node. Tile Drainage combines with the Escape drainage system and returns to the river system.
Water User node (IQQM CropMod2, Return flow)
Crop mix tab
This tab defines the proportions and timings of different crops planted in the defined area.
Water User node (IQQM CropMod2, Crop mix)
Crop Model - Crop parameters
Parameter | Type | Description |
|---|---|---|
Crop Name | text | Reference name for crop |
Repeats | integer | The growth pattern and duration is repeated by the specified number. For example a growth season of 5 months when repeated by a factor of 3 will have a growth period of 15 months. |
Ponded |
| When ticked the crop mix in the water user node for this crop type requires input for targets for minimum and maximum pond level. Levels are used as targets to irrigate and drain area as occurs for rice. |
Crop coefficients | Coefficients that define the straight lines connecting the four growth stages for the crop water requirements | |
Initial | Coefficient at start of the initial phase | |
Development | Coefficient at end of the initial phase and start of development phase | |
Mid-Season | Coefficient at end of the development phase and start of Mid-Season phase | |
Late-season | Coefficient at end of the Mid-Season phase and start of Late-Season phase | |
Maturity | Coefficient at end of the Late-Season phase | |
Number of growing days | days | Number of days within each stage of crop growth. |
Losses | Crop factor editor window (Figure 51) |
Crop Model - Planting Area parameters
Parameter | Units | Description |
|---|---|---|
Maximum irrigable area | ha | maximum area that can be planted |
Proportion of Area Developed | % | Proportion of area that is actively farmed. Maximum Area available for cropping in a particular scenario is the Maximum Irrigable Area by the Proportion of Area Developed. |
Maximum area for primary crop | ha | Primary crop is the crop grown during the summer months, which is defined in the Crop Mix (‘Summer’). The maximum area of primary crop(s) is the maximum area to be used in a simulation for all crops nominated as "summer". This area cannot exceed the Maximum Irrigable Area multiplied by the Proportion of Area Developed |
Maximum area for secondary crop | ha | Secondary crop is the crop grown during the winter months, which is defined in the Crop Mix (‘Winter’). The maximum area of secondary crop(s) is the maximum area to be used in a simulation for all crops nominated as "winter". This area cannot exceed the Maximum Irrigable Area multiplied by the Proportion of Area Developed |
Crop Model - Soil parameters
Parameter | Units | Description |
|---|---|---|
Maximum available soil moisture | mm | Depth of soil moisture available to the crop. The node will apply water to replenish the soil moisture store when evapotranspiration depletes to half this value. At the beginning of a simulation, the store is set to full. |
Upper soil moisture depth of Fallow | mm | Depth of the upper soil moisture store for fallow field. The lower soil store depth is equal to the Maximum Available Soil Moisture less Upper soil moisture depth. Upper soil moisture store cannot be greater than the depth of the Maximum Available Soil Moisture. The upper store is depleted by evaporation. The lower store is depleted by seepage rate. Water can move from the upper store to the lower store at the Infiltration Rate. At the beginning of a simulation both the upper and lower stores start half full. |
Infiltration rate from upper Fallow to lower Fallow | mm/d | The rate of water movement from the upper soil moisture store to the lower moisture store. |
Seepage | mm/d | Maximum rate that water drains from the Lower soil moisture store when area is not irrigated (fallow). Soil moisture will be depleted by the product of this rate, and the ratio of actual soil moisture to maximum soil moisture. |
Fallow factor | % | Crop factor for fallow ground. One value is used throughout the year. Percentage value refers to daily evaporation. |
Crop Model - Climate parameters
Tab | Units | Description |
|---|---|---|
Evaporation | mm | The model uses pan evaporation with crop factors to calculate evapotranspiration volumes. Pan evaporation may be input as monthly averages or daily data and entered as either a time series or referenced to another Source scenario. See Feature Editor 37. |
Average Evaporation | mm | The Average Evaporation pattern tab can be used instead of the Evaporation tab. This allows for a daily average value. |
Rainfall | mm | The model uses rainfall data to replenish soil moisture. Excess runoff can be drained to tail-water drain for reuse. Rainfall may be input as monthly averages or daily data entered as either a time series or referenced to another Source scenario. See Feature Editor 39. |
Crop Model - Climate parameters (Rain data)
Parameter | Units | Description |
|---|---|---|
Rainfall interception loss | mm | The depth of rainfall intercepted by the vegetative cover of the crop. Effective rainfall onto crops is the actual rainfall less this interception loss. |
Fallow interception loss (optional) | mm | The depth of rainfall intercepted in fallow area. Zero loss is assumed if this is not specified. |
Expected usable rainfall in primary growing season | mm | Depth of usable rainfall available for use by a crop during the primary growing season. Usable rainfall is actual rainfall less allowance for runoff and interception losses. This value is used when calculating the area to be planted at the decision date. |
Expected usable rainfall in secondary growing season | mm | Depth of usable rainfall available for use by a crop during the secondary growing season. Usable rainfall is actual rainfall less allowance for runoff and interception losses. This value is used when calculating the area to be planted at the decision date. |