ColoradoComments13

• Basin: Colorado
• Title: Comments 13
• Date: 11/3/2003
• SWSI - Doc Type: Comments

Comments to SWSI, November 3, 2003J by John Wiener

29

2. ditch to gated pipe
3. pipe to gated pipe
4. pipe to surge valve
5. furrow to sprinkler
6 ~ furrow to drip
7. furrow to subsurface drip
8. sprinkler to better sprjnkJer (e.g. low pressure or drag hose)
9.. sprinkler to drip
10. sprinkler to subsurface drip
11. better sprinkler to drip
12~ better sprinkrer to subsurface drip
13. drip to subsurface drip

Structural changes to land:

14. terracing, contouring
15. leveJin 9
16. aJtered tiUage or conservation tiUage.

Information management
17. 'rrigation scheduling to meet needs by soH moisture
18. deficit irrigation (strategic deficits; timing shortages)
19. fertilizer timing

Crop changes
20. change crops J cr,op m ix, or rotation

Although the permutations of these factors would be intractable, farming does not apply all of
them, and the scope of practical inquiry is considerably smaUer.

What to do? An approach to the problem of estimating irrigation efficiency and
return flow obligations:

A. To the extent possible, a first step would be to narrow the range of crops and thus agronomic
faotors which may be relevant. Perhaps only a few need be considered, such as fodder cornt
table or sweet corn, alfalfa, a hay crop, a small grain (oats?), and a representative vegetable.

B. Secondt the set of 20 changes noted could be narrowed as well, using expert opinion and
experience to select the most likely or most common changes for a given basin or agricultural
reg ion.

c. Third, the 5oi' and sub-soil properties cQurd be consjderedt and representative types could be
identified if there is sufficient representativeness in a given region. The Arkansas Val fey t for
example, has underlying georogic and geomorphic uniformity, but ditches have different areas of
soil types and soil processes which may be important variables (e~g4 the different salinity
conditions mapped by Gates at al., as well as different soils).

D. The integration of the first three steps would be identification of the range of cases which can
be reasonably expected to cover a usefuJ portion of current water use and potentia' transfers.
Although daunting in prospect, the extent of Jocal knowredge from agricultural extension and
USDA and other experts, as wen as the private sector, will quickly provide much of this.

E. Taking the selected set of representative cases~ the final question may be asked: can the
re'evant irrigation and return flow conditions be adequately estimatedJ given the current state of
knowledge?