1.   Purpose and objectives

     Basin irrigation is the most widespread method of surface irrigation. Global-wise, the overall efficiency in level basin irrigation is rather poor. Basins can certainly be made bigger and can be irrigated more efficiently than is presently the case. The direct benefits of using the program for design and evaluation purposes will be considerable water savings. The indirect benefits will be that less water is being lost to the underlying aquifer resulting in less salinization hazards for both the shallow groundwater and the top soil.

2.   Description

     The program BASCAD simulates the flow of irrigation water over the land surface and concurrent infiltration. This surface flow is based on the Saint-Venant equations (zero-inertia approach). The equations are solved in the program by the Newton-Raphson iterative method.

     The program offers the possibility to guide the user in the design and evaluation of level basins. To this end, the program presents four so- called main calculation modes. Modes 1, 2, and 3 are to be used in typical design matters, i.e. how to achieve a certain minimum infiltrated depth and how to realize a certain minimum application efficiency. Modes 1 and 2 can be used to obtain first estimates on either the basin dimensions or flow rate. Mode 3 can then be used to refine these results; it can also be used directly by more experienced users. Mode 4 can be used to analyze an existing situation, i.e. to determine the actual irrigation performance in terms of minimum infiltrated depth, under-irrigation and/or over- irrigation.

3.   Input

     The program is fully interactive and user-friendly with pull-down menus and help screens to guide the user through the data entry. In all modes, data are required on the infiltration characteristics of the soil, flow resistance of the land surface, and depth of water to be applied to the soil. Depending on the calculation mode, data are also required on the available flow rate, basin dimensions, or both.

4.   Output

     The results of the simulations are advance time, cut-off time, recession time, and actual irrigation performance in terms of minimum infiltrated depth, under-irrigation, over-irrigation, application and 
storage efficiency. The results of the calculations can be either directly printed or stored in files to be processed in commercially available spreadsheet or word processing programs. Graphics are included showing advance time, infiltrated depth, and over-/under-irrigation along the length of the basin.

5.   Operational requirements and restrictions

     Minimum requirements are a personal computer with 80286 micro- processor, 640 kB RAM, 20 MB hard disc, EGA graphics, MS-DOS operating system; co-processor is recommended.

     The flow over the land surface is evenly distributed over the width of the basin (1D horizontally); the flow resistance and infiltration characteristics are assumed to be homogeneous within the basin.

6.   Form of presentation

     The program is available on diskette and supported by a manual, giving more background information on basin irrigation, the input and output parameters involved, program features, error messages, guidelines and sample problems.

7.   Operational experience

     More than 500 copies of the program have been distributed all over the world. The program has been used successfully both in national and international training courses on irrigation.

8.   Originator and technical support

     International Institute for Land Reclamation and Improvement ILRI
     P.O. Box 45, 6700 AA  Wageningen, The Netherlands
     Tel:  (31 317) 490144
     Fax:  (31 317) 417187

9.   Availability

     Through the HOMS National Reference Centre for The Netherlands or directly from ILRI.

10.  Conditions on use

     The program and manual are for sale. Discounts are available for educational purposes.