ArkansasComments11

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

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

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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 sprinkler (e.g. low pressure or drag hose)
9. sprinkler to drip
10. sprinkler to subsurface drip
11. better sprinkler to drip
12. better sprinkler to subsurface drip
13. drip to subsurface drip

Structural changes to land:
14. terracing, contouring
15. leveling
16. altered tillage or conservation tillage.

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

Crop changes
20. change crops, crop mix, 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 smaller.

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
factors which may be relevant. Perhaps only a few need be considered, such as fodder corn,
table or sweet corn, alfalfa, a hay crop, a small grain (oats?), and a representative vegetable.

B. Second, 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
region.

C. Third, the soil and sub-soil properties could be considered, and representative types could be
identified if there is sufficient representativeness in a given region. The Arkansas Valley, for
example, has underlying geologic and geomorphic uniformity, but ditches have different areas of
soil types and soil processes which may be important variables (e.g. the different salinity
conditions mapped by Gates et aI., 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 useful portion of current water use and potential transfers.
Although daunting in prospect, the extent of local knowledge from agricultural extension and
USDA and other experts, as well 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
relevant irrigation and return flow conditions be adequately estimated, given the current state of
knowledge?