1.   Purpose and objectives

     The expansion of large scale irrigation systems in the world has caused wide spread waterlogging and salinity, which threatens the sustainability of irrigated agriculture. Installation of vertical or 
horizontal drainage systems can provide watertable control and at the same time provide the discharge capacity required for salinity control. SALTMOD was designed as a tool to predict developments of depth to watertable and soil salinity under different drainage and irrigation scenarios. SALTMOD 
can also be used in research as a monitoring tool to follow watertable and salinity developments in time. It is easy to handle and is also used by field workers.

2.   Description

     SALTMOD uses equations of seasonal water and salt balances and is not  based on traditional equations to describe flow of water and transport of  salt through aquifers and soils. As a result the predictions are seasonal estimates. This gives SALTMOD the character of an expert system, which can make long term predictions of depth to water table and soil salinity for a defined area. In flat land a typical area covered by SALTMOD is in the order of 10,000 ha. In undulating land the area is smaller. 
SALTMOD is built on four reservoirs, i.e. a surface reservoir, a soil reservoir or root zone, a transition zone and a deep reservoir or aquifer. SALTMOD calculates water and salt balances for each reservoir and the transfer of water and salt between the reservoirs.

3.   Input

     The input requirements are less and more readily available than those of models using the traditional equations describing flow and transport of salt through aquifers and soils. Input data is the components of seasonal water balances related to surface hydrology such as rainfall, runoff, evaporation, irrigation and drain water reuse and related to aquifer hydrology such as upward seepage, natural drainage and water pumped from wells. Initial values of depth to water table and salinities of irrigation water and soil should be given as well as some soil and aquifer characteristics. SALTMOD works with menus to assist the user with input data.

4.   Output

     Output data is remaining components of the water balance such as downward percolation, upward capillary rise, gravity drainage and resulting depth to watertable and soil salinity.

5.   Operational requirements and restrictions

     Minimum requirement for application of SALTMOD is a 360 kB RAM PC.

6.   Form of presentation

     The program is available on diskette with a draft user manual. ILRI is working on a new version of this manual which will be issued in the ILRI publication series.

7.   Operational experience

     SALTMOD has been developed, tested and adjusted over the past ten years. It has been successfully used in Portugal, Egypt and India. Application in Pakistan and China is in progress.

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 of use

     Current versions of program and manual are available from ILRI at no cost on condition that (1) the user acknowledges ILRI in any publication of work conducted with SALTMOD and (2) the users shares its experiences with ILRI.