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Design of Sustainable W ater Management Systems 211

If the soil drainage is poor, drainage systems have to be installed to
remove the water leaching below the root zone.

6.7.3 Dealing with Water Quality Issues
When the drainage water outflow is diverted to an outlet, it has to
meet the water quality standards. Depending on the quality of the
drainage water, excess water may need to be applied to dilute the salt
concentration below the permissible limit. Sometimes, the water
needs to be treated in a desalination facility before it can be disposed
into an outlet. However, this may be too costly to be economically
viable.
Engineered wetlands can be used to hold the drainage return
flows. Halophytic plants that can grow in saline environments can be
planted in these wetlands to help remove the salts. Halophytic plants
have the capability to uptake salts and accumulate the salts within
the plant biomass. Periodic harvesting of the biomass can remove the
salt load from engineered wetlands. Biosystems engineers learn about
plant physiology to understand this process and design better wet-
lands.

6.8 Summary
Biosystems engineers are knowledgeable about the physical and
chemical properties of soil as well as plant–soil–water relations, and
plant physiology. They understand how to optimize the conditions
to maximize plant production while sustaining the environment.
Their training in fluid mechanics and material sciences will help them
design efficient irrigation and drainage systems. In addition, new
and innovative instrumentation is used to assess the need for irriga-
tion and drainage and protect the quality of the drainage water.
Biosystems engineers play a major role in expanding food and fiber
production through irrigated agriculture, reclaiming salinity-affected
land, and protecting water quality in rivers and lakes.

References
ASAE (American Society of Agricultural Engineers). 1990. Management of Farm
Irrigation Systems, eds. G. J. Hoffman, T. A. Howel, and K .H. Solomon. St.
Joseph, MI: American Society of Agricultural Engineers. 1038 pp.
FAO (Food and Agriculture Organization). 1998. Crop Evapotranspiration, eds. R. G.
Allen, L. S. Perara, D. Raes, and M. Smith. Irrigation and Drainage Paper No.
56. , Rome, Italy. 300 pp.
Fouss, J. L. and Fausey, N. R. 2007. Research and development of laser-beam auto-
matic grade-control system on high-speed subsurface drainage equipment.
Transactions of the ASABE 50(5):1663–1667.
Hillel, D. 1998. Environmental Soil Physics, San Diego, CA:Academic Press.
Hillel, D. 2000. Salinity Management for Sustainable Irrigation: Integrating Science,
Environment, and Economics, Washington, DC: The World Bank Group. 104 pp.