WaterWare Release Notes
    Release Level 5.0
    Release Date 2005 06
    Revision Level 1.0

Irrigation Water Demand Model

IWD is a dynamic (daily) model to estimate supplementary irrigation water demand for irrigation districts.

The model handles multiple crops from an integrated crop data base. Climate (daily temperature and precipitation), soil characteristics, irrigation technology and crops and cropping patterns are the main inputs defining a scenario.

The model generates time series of irrigation water demand, that can be exported for use in the Water Resources Model.

The irrigation model can handle several, crops in parallel. A limit of five is recommended for better interpretation of the results, but not enforced in the model.

Crops can be selected from the embedded crop data base. They are defined in terms of the area they occupy, planting date, and growing period until harvest time.

Each crop used in a scenario inherits its generic properties like physiological water demand etc., but the user can overwrite them to better represent local conditions.
Additional crops can be selected from the embedded crop data base.

This offers a selector showing crop names, planting dates, and the average crop water demand in mm (assuming optimal growing conditions) over a growing cycle or year for perennial plants like fruit trees.

Selecting a plant from the listing will show its data base entry.
The crop data base contains a basic listing of common crops subject to irrigation.

Crops are shown with their common and scientific name, as well as a short description of the data record indicating, for example, the source of information and any bibliographic references or links. Author, creation and modification dates complete the meta data.

The core of the description if multi-media material, shown in an embedded browser window, basic descriptive data like the CROPWAT Kc factor, average physiological water demand, planting date, and growing period.

A separate window shows the temporal variation of the basic data:

  • physiological water demand in mm;
  • soil moisture tolerance, expressed as a fraction of field capacity (saturation).
  • shading factor;
  • CROPWAT Kc factor;

The model results are presented as a tabular summary of the water budget:
  • Inputs composed of rainfall and supplementary irrigation;
  • Plant water consumption and transpiration;
  • Evaporation from the soil system;
  • Application and Percolation losses;
  • Storage change (soil moisture).

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