Design and operation of agricultural water distribution systems as hard and soft climate change adaptation strategy

The accelerating impacts of climate change pose significant threats to the agriculture sectors. On one hand, the rising summer temperature caused by climate change increases the agricultural water demand due to a higher rate of soil water evaporation and higher crop water demands. On the other hand, a decrease in precipitation amounts and timing threatens the availability of water for rainfed and irrigated agriculture. As such, the current patterns in water usage from existing water resources may soon be insufficient particularly during the warm seasons. Hard adaptation strategies involving infrastructure development and expansion, such as agricultural water systems for water transfers and surface water storage, have the potential to safeguard national and international food security. This study presents a conceptual model to simultaneous design, operation, and layout of an agricultural water distribution systems using robust optimization to deal with the uncertainties in the climate-change impacted agriculture water demand models while considering the impacts on crop yields. An integrated assessment model (IAM), involving climate change projections, a hydrologic model, and a crop production model, is used to determine the water demand at each crop field node. The water demands determined by the IAM can have significant uncertainties due to inherent uncertainties that exist in sub-models and input data. These water demand uncertainties are represented by deterministic variability in robust optimization. Meanwhile, continuous water supplies can incentivize the farmers to adapt to a new and higher yield crop rotation. Therefore, water demand at each node is also correlated to the potential yields, which is bounded above by the water rights assigned to each node. We will demonstrate the use and effectiveness of this approach in the agriculture communities of Umatilla River Basin, Oregon, USA, where water rights, environmental laws, Columbia River Treaty, and overused groundwater aquifers constrain water use and distribution for irrigated agriculture.