FLOOD-CONTROL, DRAINAGE AND IRRIGATION PROJECTS IN BANGLADESH AND THEIR IMPACT ON SOILS - AN EMPIRICAL-STUDY

The combination of a rising population and increased food demand has p laced tremendous pressure on the land resources of Bangladesh. These p ressures are exacerbated by the annual wet-season floods which frequen tly devastate much of the agricultural land. Successive governments ha ve therefore sought international aid to assist in the development of flood control measures. Of particular importance are 14 major schemes which aim to provide protection from 20-25 year return floods by the c onstruction of earth-embanked enclosures. There is no doubt that these schemes have been very successful in protecting valuable agricultural areas from floods and hence increasing agricultural production. There is, however, growing evidence from a range of sources for long-term d eterioration in soil fertility within the project areas. The study rep orted here is the first to systematically examine the changes taking p lace in soil properties following the establishment of a flood control , drainage and irrigation project. Comparison of two soil series, samp led from within and without the project area, demonstrate that within six years of project establishment, significant adverse changes have o ccurred in several soil properties; these include increasing acidity a nd a decline in available nutrients. The changes are attributable to a combination of poor management strategies and the absence of the annu al flood input of silt. As Bangladesh cannot afford any decline in agr icultural output, it is vital to establish whether adverse changes rec orded here are occurring in other projects. This can be achieved by th e establishment of a nationwide programme of soil fertility monitoring . (C) 1998 John Wiley & Sons, Ltd.