Performance of Biodrainage Systems in Arid and Semiarid Areas with Salt Accumulation in Soils

摘要

Biodrainage is the use of vegetation to manage water fluxes through evapotranspiration. It is an alternative technique that has recently attracted interest in drainage and environmental management. Sometimes "drainage" has become a "dirty word" and its implementation has been restricted. Biodrainage is one of the alternative options. The absence of effluent makes the system attractive. However, biodrainage systems must be sustainable in the long-term. Biodrainage theory does not go back too far. Therelationship between soil, climate, irrigation management and salinity is not yet well defined. In this research the SAHYSMOD mathematical model was used with two different approaches. 1) Evapotranspiration rate of plantation strips does not change because of increased salinity with the passage of time (S. Akram et al., 2009); and 2) Evapotranspiration rate decreases due to salt accumulation in the soil. While the first approach showed that in most cases the system can perform for about 15 to 20 years,the second approach showed that the life time of the system may not exceed 10 years. In the second system water table draws down during the first 3 to 4 years; however, it rises afterwards due to lower evapotranspiration rate caused by salt accumulationin the soil of plantation strips. This, however, shows that the system may not be considered sustainable in arid and semi arid areas especially where the irrigation water js saline. The result agrees with Heuperman et al. (2002) who says that it is doubtful that biodrainage can maintain soil salinity to an extent that crops could be grown economically. The result, however, does not agree with Kapoorand Denecke (2001) who indicates that biodrainage could be used in various regions ranging from humid to semi arid areas, except when the ground water EC is greater than 12 dS m-1. Hybrid system that combines bio-drainage and conventional drainage technology and/or salt removal and extra land for tree plantation may lengthen the life of the system.