Irrigation is a function of land use. The coefficients show the amount of irrigation water applied to the specific land use (Applied Water Rate), and specify the sources of irrigation water as a percentage of the total water available from each source. Following is the appearance of the Irrigation tab of the Catchment Coefficients dialog:
Following is a description of the parameters associated with Irrigation. Refer to the main Catchment Coefficients page for information on other categories of coefficients. To save the changes made when closing this dialog, click OK. To ignore changes, click Cancel.
Irrigation is applied to individual land uses with water diverted from a river or reservoir or pumped from groundwater. To apply irrigation, select the applicable land use to which the water is applied and click on Add. Choose a file which contains data for a diversion used to irrigate the selected land use in the catchment. Then enter the percentage of water in the selected diversion which is applied to the selected land use in the catchment. Take care to ensure that no more than 100% of a diversion is allocated to all the irrigated land uses in all the catchments it supplies. To remove an irrigation source, click on its row in the spreadsheet and hit Ctrl+Del.
A Prescribed Ponding Depth File can be selected to simulate management of a specified depth of water on the surface of a land use, such as a diked wetland or a rice field. By default, the flow and depth of surface runoff are calculated simultaneously using Manning’s equation. If this option is selected, an observed data file with a time series of depth is used to specify the target depth of ponded water. The flow is then calculated based on the depth.