3.2.3. IE Policy

Canal lining and precision irrigation are strategies implemented here to represent IE policy. The scenario analysis is conducted with the cost of infrastructure development deducted from agricultural income. The deduction of cost counts as the impact of investment on agriculture or non-agriculture, which does not impact the cost of capital development. This means that agricultural income in the paper, in effect, represents a "net income" that reflects the impact of technological investment costs.

Canal lining aims to improve conveyance efficiency. Conveyance efficiency increases through investment in irrigation infrastructure that reduces canal seepage and increases water delivery to the fields relative to water released from the reservoir upstream. Improvement of conveyance efficiency necessitates irrigation infrastructure and involves deduction from profit. Canal lining cost varies depending on lining material, canal cross-section design, and installation approaches. Based on the Bureau of Reclamation's historical record, the canal lining cost ranges from 14.9 to 37 dollars per square yard [33]. The canal lining cost ranges from up to 2000 dollars per acre-foot of water saved [34]. Multiplying the unit cost of canal lining and surface water divisions yields the total cost. More of surface water withdrawals will be delivered to the field with canal lining, and less water will be "lost" as canal seepage. In the model, as conveyance efficiency increases, the total cost for canal lining will be deducted from agriculture income. The regional canal lining project is a long-term process, so canal lining takes ten years to plan and ten more years to implement. The service life of the canal lining is deemed to be forty years [34]. The canal lining process continues until the total irrigation supply reaches the largest yearly water supply of surface water. The variables involved in the policy test are listed in Table 2.


**Table 2.** Variables setting for IE policy.

Precision irrigation aims to improve field irrigation efficiency. Irrigation systems could be altered to improve field efficiency (e.g., through drip and sprinkler irrigation). High IE irrigation systems typically maintain the same productivity with less water applied or increase productivity with the same water application rate due to more water delivered to the fields being available to crops [35,36]. Field irrigation efficiency refers to irrigation technology and practices that attempt to apply only the water necessary to replenish the amount of water lost through ET and reduce percolation past the root zone. Costs associated with irrigation conservation have been cited for having varied installation costs per acre and operation costs [37]. As summarized in a report of drip irrigation experiments, the cost for design, materials, and installation of a drip irrigation system for the case of a farm in Rincon, New Mexico, which was a 26-acre farm, was 52,000 dollars [38]. The variables involved in the policy test are listed in Table 2.
