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Snake River and its tributaries. Total groundwater storage in the upper 500 feet of the aquifer is
estimated at about 200 to 300 million acre-feet (Cosgrove et al., 1999). In most parts of the
ESPA, rainfall is insufficient to support commercial levels of agriculture without irrigation.
We define 667 representative farms in 16 counties, with the irrigated and non-irrigated
land acreage specified for each farm. These representative farms are determined based on their
soil characteristics, location, and sources of water used. The soil maps of each farm in each
county are obtained to determine yields of various crops depending on the soil characteristics
(NRCS, 2005). The information on crop-specific variable costs such as inputs, planting and
harvesting were obtained from the University of Idaho Crop Budgets (2003). The input costs
include seed, fertilizers, labor, pesticides, and other production inputs. Using the crop yields,
production costs and output prices, we generate crop-specific crop budgets for each
representative farm.
The irrigation water used in agriculture in the ESPA comes from both the groundwater
and surface water sources. The use of surface water in irrigation is the main source of the
recharge in the aquifer. The empirical model considers the sources of water available in each
county. Our model also distinguishes between irrigated and non-irrigated crop productions in the
ESPA. In some parts of the ESPA, there is currently a small amount of non-irrigated crops
acreage. The empirical model will allow farmers to switch to non-irrigated crops in response to
the various public policy proposals in these areas. The major crops grown in the region include
potatoes, wheat, barley, alfalfa, sugar beets, corn grain, corn silage, and dry edible beans. We
define over 72 different crop rotations, with rotations ranging from 2 to 7 years. These rotations
incorporate agronomic constraints and include many commonly used rotation practices in the
ESPA. Some of the examples of these rotation practices are two-year grains followed by one-
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