Reduction of Deep Percolation and Drain Water

Principle considerations in examining water‐management options for the control of toxic trace elements in agricultural drainage waters are addressed, including a number of improvements in off‐farm water delivery systems, as well as efficiency of on‐farm irrigation systems and water reuse. Potentials exist to improve off‐farm water‐delivery systems through reductions in seepage losses with canal linings, operational spills through systems irrigation scheduling, and interception of water losses and reuse. Potentials also exist in improving on‐farm water management through improved irrigation application systems, on‐farm irrigation scheduling, and other cultural products such as changes in cropping patterns. These on‐farm management options will affect net farm income due to increased costs of equipment and structures, increased labor requirements, and changes in crop revenue. But not all of these will have a negative economic input. For instance, efficient irrigation systems not only value drainage but tend to increase crop yield or decrease crop production inputs. Installation of structural system improvements and use of system scheduling of water delivery may result in decrease in operation and maintenance costs. Institutional and legal constraints, particularly water‐right ownership, may constrain efforts to minimize drain‐water production and toxic‐element problems. The long‐term economic viability of irrigated agriculture will require careful consideration of both off‐farm and on‐farm management options.