7020

• UCREFRP Catalog Number: 7020
• Author: Oamek, G. and S. R. Johnson.
• Title: Economic and Environmental Impacts of a Large Scale Water Transfer in the Colorado River Basin.
• USFW Year: n.d.
• USFW - Doc Type: \
• Copyright Material: YES

PROCEDURES
Activities were developed to transfer water to the Lower Basin when it becomes more
profitable than its value to irrigation. By parameterizing water's selling (or leasing)
price in the PQP models and summing the water transferred at each price across PA's, a
normative supply curve for Upper Basin irrigation water can be derived. This supply
curve can then be used to observe how much water might be forthcoming from the
basin as a whole at given water prices.
The volume of water transferred in this anaivsis is assumed to be 300,000 acre feet, the
mid-range of the Galloway Proposal. The above supply relationship determines where
in the basin this amount could be most economically obtained and its marginal value
was to irrigation.
Drought years will surely drive up water's marginal value to agriculture. Annual
variation in deliveries were observed from the CRSS model over its 30 year period of
record and the corresponding change in water value resulting from it can be derived
from the supply curves.
Adjusting the CRSS model to reflect the transfer proposal involves allowing an
additional 400,000 acre feet in excess of existing compacts to pass through Glen Canyon
and Hoover Dams annually to reach the intake of the Colorado River Aqueduct at Lake
Havasu. Upper Basin demand and return flow figures are adjusted, based on the results
of the previous exercise, to capture the decreased salt loading and increasing flows at
certain locations on the river system. Resulting changes in salinity and hydropower
production resulting from this were then observed over the period of record and
valuated with estimates from other previous studies.
RESULTS OF THE ANALYSIS
Parameterizing the selling price of water resulted in two normative supply curves
depending on how land conversion was handled. Assuming that after the water is sold
the formerly irrigated land can revert to dryland production yielded a lower marginal
value of water than a no conversion situation (Figures 2 and 3). With conversion
possiblities, about 1.8 million acre feet of Upper Basin irrigation water have a marginal
value of S40 per acre foot or less. Without conversion, the same volume has a value
topping out at $70 per acre foot. Both situations illustrate the low value of irrigation
water here and are generally consistent with previous studies by Gisser (11) and Howe
(12)•
At a transfer level of 400,000 acre feet, with conversion possibilities, a marginal value of
$5.05 was derived from Figure 3. Similarly, but without conversion, a value of 59.40
resulted It is difficult to definitively state whether conversion to dryland production is
feasible or not. In some areas of the Upper Basin it would be possible, but in other
areas possibly not due to extreme aridity. For brevity, the remainder of the analysis will
present only the results for the case with conversion.
Table 1 illustrates changes resulting from the transfer of water use, cropping patterns,
production, and other itemized variables from their base levels. Of note in Table 1 is
the slight increase in land use in PA 82 resulting from previously idle lands being
brought into dryland production. More important, however, is the observation that a 22
percent reduction in total consumptive of irrigation water results in a much less than
proportional decrease in the recorded variables.