Willamette’s Water Resources: 70 Years of Urbanization

Oregon State recently released a study examining the impact of urbanization on water use in the Willamette Valley. Interestingly enough, the study – which was conducted by economists seeking to evaluate changes in land and water use over the next 70 years – found that population growth in Oregon has less of an effect on water use than you might think. 

The study focused on the cities of Woodburn, Salem-Keizer, and Eugene-Springfield due in part to their surrounding farmlands. Woodburn and Salem-Keizer utilize irrigation, and a combination of irrigation and rain, while Eugene-Springfield relies much less on irrigation.

As the Willamette’s population continues to increase, more and more rural land will succumb to housing. However, the study concluded that population growth or not, water consumption will be affected little if at all.

As stated in the study, “Despite population growth of approximately 85 percent and a doubling of income, water withdrawals in two urban areas increase by at most 12 percent and in another area, decrease slightly.”

How is this possible? As it turns out, the water laws followed by many western states basically allow for farmers to utilize water for irrigation so long as they are actually farming. Makes sense, but when said farm is sold and becomes a neighborhood, the new owners must acquire new water rights. These new rights allow for much less water consumption.

In short, farms use a lot more water than the equally sized neighborhoods replacing them, so that’s good. However, farms make food while neighborhoods consume food, so, losing them is kinda bad. Only time will tell how we balance these land uses, but studies like this will help us make the best decisions possible.

How Does Urbanization Affect Water Withdrawals? Insights from an Econometric-Based Landscape Simulation was published in the journal Land Economics in August.

By Anthony Vitale