Rice Irrigation Systems for Tailwater Management (5/7)
J.E. Hill, S.C. Scardaci, S.R. Roberts, J. Tiedeman, J.F. Williams
Gravity Recapture Irrigation System
Gravity tailwater recapture systems utilize drop pipes and gravity flow to bypass drains thereby keeping drain water and pesticide residues out of public waterways. This system can be installed on single farms with multiple adjacent fields or among cooperating neighboring farms. Although these systems are relatively low in cost they are highly effective.
| Figure 7. Schematic diagram of gravity recapture system. |
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 In the gravity recapture system, water flows by gravity, eliminating the tailwater pumps and sump. Bypass drain pipes in upstream fields are installed in the bottommost basin for maximum effectiveness (fig. 7). The pipe can enter the downstream field at any point, although entry into the upper portion of the field allows the greatest flexibility. This system is particularly cost-effective for fields with significant elevation differences, where static and return systems are apt to be more expensive.
The cost associated with this system is the installation of drop pipes across drainage courses. A gravity system can be installed on multiple adjacent fields with a small tailwater recovery system to recirculate water in the last field.
Table 4 presents the advantages and disadvantages of a gravity recapture irrigation system.
| Table 4. Gravity recapture systems for rice production in California |
| Advantages: |
 Tailwater and pesticide residues can be contained on farm(s) |
| Provides management flexibility during water-holding periods |
| Low cost |
| Disadvantages: |
 When many basins are interconnected, the large water surface area may make quick and precise water management difficult |
| Lacks independent control of each basin |
| Requires coordination of water among many fields and may require neighbors to synchronize management |
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Comments to jayoung@ucdavis.edu