The possibility of GIS for easily creating and changing scenarios allows the consideration of multiple alternatives of irrigation scheduling, including the adoption of crop specific irrigation management options.Scenarios may include different irrigation scheduling options inside the same project area applied to selected fields, crops, or sub-areas corresponding to irrigation sectors. This allows tailoring irrigation management according to identified specific requirements .The irrigation scheduling alternatives are evaluated from the relative yield loss produced when crop evapotranspiration is below its potential level. Examples of those successful applications are presented by for surface irrigation in the Mediterranean region.Irrigation scheduling is the farmers decision process relative to “when” to irrigate and “how much” water to apply at each irrigation event. It requires knowledge of crop water requirements and yield responses to water,the constraints specific to the irrigation method and respective on farm delivery systems, the limitations of the water supply system relative to the delivery schedules applied, and the financial and economic implications of the irrigation practice.
Irrigation scheduling models are particularly useful to support individual farmers and irrigation advisory services . reported about an irrigation model embedded within the GIS. The data were correlated to digital data sets on soils, agro-climate, land use, hydroponic grow table and irrigation practice to produce tabular and mapping outputs of irrigation need and demand at national, regional, and catchment levels.The GIS-based modeling approach is also currently being used to administer irrigation needs for irrigated crops. Map and tabular output from the GIS model can provide licensing staff with the information necessary to establish reasonable abstraction amounts to compare against requested volumes on both existing and new license applications for spray irrigation.The main value of models results from their capabilities to simulate alternative irrigation schedules relative to different levels of allowed crop water stress and to various constraints in water availability .The main limitation of simulation models is that some model computations are performed at the crop field scale for specific soil, crop, and climate conditions, which characterize that crop field and the respective cropping and irrigation practices.
When the computation procedure is applied at the region scale it becomes heavy and slows due to the need to consider a large number of combinations of field and crop characteristics to be aggregated at sector or project scales .Proper irrigation scheduling can reduce irrigation demand and increase productivity. A large number of tools are available to support field irrigation scheduling, from in-field and remote sensors to simulation models. Irrigation scheduling models are particularly useful to support individual farmers and irrigation advisory services. outlined applications of GIS-based modeling. For financial analyses, GIS is used to quantify and map the total financial benefits of irrigation and the financial impacts of partial or total bans on abstraction for irrigation.Irrigation water requirements are determined by mapping the spatial distribution of water requirements based on soil and crop distributions. GIS-based modeling approaches are used to establish irrigation scheduling based on water-balance modeling.GIS databases for irrigation include coverage for crops, irrigation methods, and soils. These data are coupled with agro-climatic data to provide information on growing-season and water-use requirements.As previously stated that the economic benefits of having such a system are: reducing monitoring costs, improving the speed of decision making by supporting the decision-makers with real time information, ability to access by everyone and everywhere over the Internet, reducing time and minimizing effort to reach data, high speed, security and high rate of error handling with new Internet technologies, having centralized database that provides a single source of common information which provide standardization and faster retrieval and selective modification of information, and finally, the ability to produce reports based on user specified parameters.
GIS tools and integrated models find extensive application for scheduling of water applications for an irrigation system. The GISAREG model is representative of a GIS-based modeling package directed to improving irrigation scheduling. The model uses the Arc View software and Avenue scripting language to integrate the spatial and attribute databases with legacy irrigation-scheduling models. The model can be applied for different water-management scenarios and produces crop irrigation maps and time-dependent irrigation depths at selected aggregation levels, including the farm scale. GISAREG simulates alternative irrigation schedules relative to different levels of allowed crop water stress as well as various constraints in water availability.