Assessing the impacts of climate change on agricultural production in the Columbia River basin: incorporating water management

Abstract:

Changes in global population, food consumption and climate lead to a food security challenge for the future. Water resources, agricultural productivity and the relationships between them will to a large extent dictate how we address this challenge. Although food security is a global issue, impacts of climate change on water resources and agricultural productivity, as well as viability of adaptation strategies, are location specific; e.g., it is important to consider the regional regulatory environment.

Our work focuses on the Columbia River basin (CRB) of the Pacific Northwest US. The water resources of the CRB are heavily managed to meet competing demands. There also exists a legal system for individuals/groups to obtain rights to use the publicly owned water resources, and the possibility of curtailing (i.e., restricting) some of these water rights in times of shortage. It is important to include an approximation of this water resource regulation and water rights curtailment process in modeling water availability and impacts of water shortages on agricultural production. The overarching objective of this work is to apply an integrated hydrologic-crop-water management modeling framework over the CRB to characterize the impacts of climate change on irrigation water demands, irrigation water availability, water shortages, and associated impacts in the 2030s.

Results indicate that climate change has both positive and negative effects on agricultural production in the CRB and this varies by region and crop type. Certain watersheds that are already water stressed are projected to experience increasing stress in the future. Although, climate change results in increased water shortages and water rights curtailment in the region, this does not necessarily translate into an increased negative effect on yields; some crops are projected to increase in yield despite curtailment. This could be attributed to higher water use efficiency under elevated CO₂ levels as well crops moving through growth stages earlier in the season with wetter and warmer spring conditions. Incorporating regulations into integrated modeling framework results in a more realistic assessment of climate change impacts.