Water is a central issue of adaptation to climate change in agriculture. Agricultural production depends critically on how climatic variables such as precipitation and temperatures vary across regions and over time. The effects of climate change on agriculture occur through crop water requirements, availability and quality of water, and other factors, which are affected by both long-term gradual change and extreme events, and across a range of scales from local to regional to continental. Moreover, climate is not only changing but is becoming non-stationary, meaning that expectations can no longer be based only on past observations.