Exercises and Solutions in Biostatistical Theory

Salinity affects 10 to 16% of all irrigated lands while the annual rate of land loss due to waterlogging and salinity is about 0.5 million hectares per year. In this dissertation, the role of subsurface drainage to reduce these problems in irrigated agriculture in arid and semi-arid regions has been analysed and challenges for improving subsurface drainage practices have been formulated. _x005F_x000D__x005F_x000D_Although the installed subsurface drainage systems are in general technically sound and cost-effective, drainage development lags behind irrigation development and consequently a substantial part of the irrigated areas suffers from waterlogging and salinity. This is mainly because the subsurface drainage systems are designed and implemented by government, with the users, the small farmers, having little responsibility and having little input. In the adopted top-down approach the location-specific conditions and farmers preferences are hardly taken into consideration. Furthermore, the emphasis has been on the technical aspects (the physical infrastructure), while the organizational aspects (institutional infrastructure) have been largely neglected._x005F_x000D__x005F_x000D_To reverse the negative trend in salt build-up and waterlogging in irrigated lands in semi-arid and arid regions, a number of challenges for enhancing the role of subsurface drainage have been formulated: (i) balancing top-down against bottom-up, (ii) from standardization to flexibility and (iii) focus on capacity development.