Take Home Message

Adoption of policies that address water efficiency and land use make a difference. This is particularly true regarding agricultural water use.

Key Findings

  • Water demand varies widely by sector and by management scenario. Because of it's extensive area in the basin, natural shrubland is estimated to be the largest "consumer" of water in the basin, followed by agriculture.
  • It is also clear from these results that for "agriculture boom" scenarios, management matters; there are quite marked differences between less managed and more managed scenarios. In the less managed scenarios, agricultural water demand is projected to increase by roughly 50%, while under the more managed scenario, agricultural water demand stays roughly constant, despite increasing temperatures and a robust agricultural sector. In the "tourist boom" scenarios, agricultural water use either stays flat (less managed) or decreases (more managed).

Background

Water demand in the basin is reported for each section - Agriculture, Forests, Natural Shrubland, and Municipal Uses. 
  • Agricultural water demand focuses on the water used to support crop production, including irrigation. Agricultural water use is determined based on evapotranspiration of the crops, which is determined based on crop type, weather, soil type, and soil moisture status. A description of the methodology used to estimate crop water demand here.
  • Forest and natural shrubland water demand is based on estimates of evapotranspiration, estimated in a similar manner to that of crops.

The Data

The following chart depicts the results of two management scenarios: 1) the status quo cropping systems and conveyance/irrigation efficiency under future climate (avg. of all three climate scenarios); and 2) a future where there is an increase in use of lower water demanding crops and increase in conveyance efficiency from 60% to 70%. As expected water demand increases under warmer climate in the status quo scenario, where as demand is generally maintained or decreased under the alternative scenarios despite warmer temperatures

. Municiapl Water Use Summary

 
Results, expressed as percent of total water demand, are presented in the table to right, for current conditions (ca. 2010) and with ranges under the different scenarios for 2070. Demand per unit area was determined for the Ag Boom scenarios; other scenarios have similar results.
Land Cover Type Percent of Total Demand Demand/Unit Area (gal/acre)
2010 2070 2010 2070
Natural Shrub 49 47-54 0.012 0.013
Agriculture 26 20-31 0.020 0.023
Forest 25 22-26 0.014 0.016
Municipal < 1 < 1 183 113
 

The following chart depicts projected agricultural water use through 2070, using results from two scenarios reflecting 1) more and 2) less management of water water use, reflecing agricultural land use and irrigation system investments focused on improvements in conveyance and application efficiency. Each series on the plot represents the range associated with the three climate scenarios used in this effort.

 

The following chart shows estimated water demand by sector for the various scenarios. It is helpful to "filter" the information presented on the chart to get a better understand of the effect of different management scenarios of the distribution of water demand.

 

Annual Water Demand by Sector 2010-2070

The following chart depicts there results of two management scenarios: 1) the status quo cropping systems and conveyance/irrigation efficiency under future climate (avg. of all three climate scenarios); and 2) a future where there is an increase in use of lower water demanding crops and increase in conveyance efficiency from 60% to 70%. As expected water demand increases under warmer climate in the status quo scenario, where as demand is generally maintained or decreased under the alternative scenarios despite warmer temperatures. Each series on the plot represents the range associated with the three climate scenarios used in this effort.

 

 

Agricultural Water scarcity, expressed as the percentage of irrigated crop water demand that was not satisfied, is depicted in the charts below for the four major agricultural areas in the basin. Each series on the plot represents the range associated with the three climate scenarios used in this effort.

Annual Irrigation Water Scarcity Index (% of Crop Water Demand that is not satisfied), 5-year Moving Average)
Camas PrairieTriangle
RichfieldNorth Shoshone