Studies of projected water demand and supply in Jordan have shown that the water deficit is increasing with time. Demands upon finite quantity of good quality water are ever increasing. With agriculture constituting about 70% of the overall demand, it became necessary to create a tool for the projection and management of irrigation demand in the country given available water quantity and quality.

The model is one single component of a constellation of digital tools developed in order to enable the Ministry of Water and Irrigation to carry out nation wide water balances based on the most recent data and various development scenarios. The irrigation model consists of several modules for the pre-processing of climatic data, calculation of Et_o, crops net irrigation requirements, and the estimation of present and future irrigation demand for the whole country or a selected planning/development region. The model is GIS-based and is linked to a Relational Database Management System under ORACLE thus allowing for the updating of data and visual presentation of the results.

The input parameters for the irrigation model include:

Reference Year Irrigation Areas

Reference Year Distribution of Irrigation Methods

Reference Year Conveyance Efficiency

Projected Increase or Decrease in Irrigated Areas in Relation to the Reference Year.

Projected Distribution of Irrigation Methods

Projected gains in conveyance and application efficiency

Water Salinity Class

Based on the above parameters, irrigation demand for different planning horizons is calculated and can be used as one demand component in the national water balance as a basis for water sector planning and decision making. Various scenarios reflecting different water strategies can be examined with variations in the input parameters.

Irrigation demand projections can then be reviewed in the light of the National water balance results, and hence allowing for easy modification of water sector strategies, including changes in irrigation areas and/or cropping pattern, improved irrigation technologies and rehabilitation of existing conveyance systems. Furthermore, the GIS-based application of the model allows the examination of the irrigation demand situation with regards to water allocation for any spatial unit or development region.

The model can be adapted to specific situations of different countries since the users can be familiarized with the internal procedures of the system. Permanent enhancement of the digital model is also possible as new algorithms can be integrated into the tool.