Perennial crop dynamics may affect long-run groundwater levels

Authors: FRANKLIN, BRADLEY - The Nature Conservancy; SCHWABE, KURT - University Of California; Levers, Lucia

Submitted to: Land
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2021
Publication Date: 9/15/2021
Citation: Franklin, B., Schwabe, K., Levers, L.R. 2021. Perennial crop dynamics may affect long-run groundwater levels. Land. 10(9): 971. https://doi.org/10.3390/land10090971.
DOI: https://doi.org/10.3390/land10090971

Interpretive Summary: Over-drafted groundwater systems worldwide are increasingly becoming the norm. A common drought mitigation strategy is to fallow land. However, in certain areas, such as California’s Central Valley, land fallowing’s opportunity cost may be increasing as high-value perennial crops become more and more common. Increases in the costs of fallowing may put additional pressure on another common “go-to” drought mitigation strategy – groundwater pumping. There has been little modelling of the potential effect of increased perennial crop production on groundwater use and the implications for public policy. We develop a dynamic, integrated model of agricultural production in the Central Valley and find that perennial crops may lead to slower aquifer draw-down, highlighting the importance of accounting for the dynamic nature of perennial crops in understanding the co-evolution of agricultural and groundwater systems under climate change.

Technical Abstract: During California’s severe drought from 2011 to 2017, a significant shift in irrigated area from annual to perennial crops occurred. Due to the time requirements associated with bringing perennial crops to maturity, more perennial acreage likely increases the opportunity costs of fallowing, a common drought mitigation strategy. Increases in the costs of fallowing may put additional pressure on another common “go-to” drought mitigation strategy—groundwater pumping. Yet, overdrafted groundwater systems worldwide are increasingly becoming the norm. In response to depleting aquifers, as evidenced in California, sustainable groundwater management policies are being implemented. There has been little modeling of the potential effect of increased perennial crop production on groundwater use and the implications for public policy. A dynamic, integrated deterministic model of agricultural production in Kern County, CA, is developed here with both groundwater and perennial area by vintage treated as stock variables. Model scenarios investigate the impacts of surface water reductions and perennial prices on land and groundwater use. The results generally indicate that perennial production may lead to slower aquifer draw-down compared with deterministic models lacking perennial crop dynamics, highlighting the importance of accounting for the dynamic nature of perennial crops in understanding the co-evolution of agricultural and groundwater systems under climate change.