Drainage of Agricultural Lands - Practices of Irrigation and On-farm Water Management - page 328

9.6.1 Factors Affecting Spacing and Depth of Subsurface Drain ........ 356
9.6.2 Data Requirement for Subsurface Drainage Design ........... 357
9.6.3 Layout of Subsurface Drainage .................... 357
9.6.4 Principles, Steps, and Considerations in Subsurface Drainage Design ... 358
9.6.5 Controlled Drainage System and Interceptor Drain ........... 361
9.6.6 Sample Workout Problems ...................... 362
9.7 Envelope Materials ............................. 365
9.7.1 Need of Using Envelop Material Around Subsurface Drain ....... 365
9.7.2 Need of Proper Designing of Envelop Material ............. 365
9.7.3 Materials for Envelope ........................ 365
9.7.4 Design of Drain Envelope ...................... 366
9.7.5 Use of Particle Size Distribution Curve in Designing Envelop Material .. 367
9.7.6 Drain Excavation and Envelope Placement ............... 368
9.8 Models in Drainage Design and Management ................. 368
9.8.1 DRAINMOD ............................ 368
9.8.2 CSUID Model ........................... 369
9.8.3 EnDrain .............................. 369
9.9 Drainage Discharge Management: Disposal and Treatment ........... 369
9.9.1 Disposal Options .......................... 369
9.9.2 Treatment of Drainage Water ..................... 370
9.10 Economic Considerations in Drainage Selection
and Installation .............................. 371
9.11 Performance Evaluation of Subsurface Drainage ................ 371
9.11.1 Importance of Evaluation ...................... 371
9.11.2 Evaluation System ......................... 372
9.12 Challenges and Needs in Drainage Design
and Management .............................. 373
Relevant Journals ................................ 373
FAO/World Bank Papers ............................. 374
Questions .................................... 374
References ................................... 376
For the maximum growth of plants, it is essential to provide a root environment that
is suitable for it. Water logging has an effect on the uptake of nutrients by plants.
Drainage provides favorable condition for root growth, enhance organic matter
decomposition, reduce salinity level above the drain, and maintain productivity of
the land. For successful drainage design, the complex interaction of water, soil and
crop in relation to quality of water must be well understood beforehand. The knowl-
edge of drain material (drainage conveyance conduit) and placement technique of
the drain (including selection of envelop material and its design with respect to soil
bedding) are also of great importance. Judgment of alternate design options, and,
monitoring and evaluation of the system after installation are demanded for success-
ful outcome from the drainage projects. Disposal and treatment issues of drainage
effluent are of concerns now-a-days. This chapter discusses all of the above points.