**Appendix A**

### *Appendix A.1 Irrigation Efficiency Equations*

We define the regional irrigation efficiency as a product of two components: conveyance efficiency (IEc) and field irrigation efficiency (IEf). Conveyance efficiency is defined as

$$\text{IE}\_{\text{c}} = \frac{SD - CD}{SD} \tag{A1}$$

where *SD* is surface water diversion and *CD* is the amount of water that is lost through conveyance. Field irrigation efficiency is defined as follows:

$$\text{IE}\_{\text{f}} = \frac{ET - P\_{\text{ag}}}{SD - CD + GWD} \tag{A2}$$

where *ET* is evapotranspiration; *Pag* is effective precipitation during the growing season; *GWD* is groundwater diversion. Thus, the following may be deduced:

$$\text{IE} = \frac{ET}{SD + GWD} \tag{A3}$$

where IE is total irrigation efficiency.

### *Appendix A.2 Behavior over Time Diagrams of System Dynamics Model Outputs*

The figures below show basic behavior-over-time diagrams of the model's outputs results with complete methodology and full descriptions in the Supplementary Materials, pp. 81–82. Black lines represent the results simulated by the model applied in this paper. These results are plotted against the Dynamic Statewide Water Budget data (blue dots) and observations (red dots).

**Figure A1.** Behavior reproduction results (water variables).

**Figure A2.** Behavior reproduction results (socioeconomic variables).

### *Appendix A.3 Result over Time Diagrams of Simulations*

The figures below show simulation results-over-time of base runs and scenario tests of variables chosen in this paper. Simulation results show varied trends as climate inputs and model's dynamics correspondingly.

**Figure A3.** Simulation results for selected variables with three climate projections.
