Snowpack, Surface Water Supply, and the Effect of Climate on Agriculture in the Western U.S.
Abstract
A changing climate affects irrigated and non-irrigated agriculture differently, yet most efforts to estimate the effect have focused on non-irrigated monoculture crops grown east of the 100° meridian, where rainfall and temperature are the pathways through which climate affects the value of agricultural production. But the paths through which climate affects surface water irrigated agriculture are more complex. Smaller snowpacks melting earlier in the season affect water availability, potentially severely constraining water supply. At the same time, on irrigated farms in the Western U.S. farmers have substantially more flexibility in terms of crop choice and other responses to new climate conditions.
We confront the question of irrigated agriculture directly, using irrigated cash rents to estimate the effect of changes in climate. Rents are a better outcome than profits or land values because they are less volatile than profits while still reflecting future profit expectations. Moreover, cash rents are reported separately for irrigated and non-irrigated farms, allowing an explicit focus on climate effects on irrigated farms. We use an interdisciplinary approach to account for water supply in which we estimate the historical relationship between watershed snowpack and county water use per acre to predict water availability under different CMIP5 climate projection scenarios. For irrigated agriculture, one acre-foot of surface-water use per acre leads to a 6.3 factor increase in cash rents. Surface water use has no effect on non-irrigated rents, as expected. An additional growing degree day during the growing season increases rents by 0.14 percent, while an additional heating degree day decreases rents by 0.27 percent. Given that under RCP 8.5 projections snowpack is estimated to decline by 48 to 95 percent by the end of the twenty-first century (Gergel et al. 2017), irrigated cash rents are estimated to decrease by 5.4 to 10.6 percent. Infrastructure management for better water storage, and institutional change for better water marketing, would be key to addressing these potential negative economic effects of climate change.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B11R2212P
- Keywords:
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- 1807 Climate impacts;
- HYDROLOGY;
- 1884 Water supply;
- HYDROLOGY;
- 6319 Institutions;
- POLICY SCIENCES;
- 6344 System operation and management;
- POLICY SCIENCES