Technical Abstract: Irrigation, in the process of storing, diverting, transporting, applying, consuming, and returning water, impacts the environment. These impacts are both positive and negative. The largest positive impact is the production of food and fiber for human use. Sixty percent of the crop value in the U.S., and about 40% of global food production is produced with irrigation. We could not feed the current or projected world population without irrigation. Negative impacts include restricting fish migrations with dams, depleting and changing river flows, depleting groundwater aquifers, and degrading the quality of river water and groundwater with salts and agricultural chemicals from leaching and sediments and nutrients in runoff water. It is critical to understand the impacts and design and manage the irrigation process to minimize the negative impacts.