How does our society conserve water resources and still enjoy an abundant food supply? The Pajaro Valley, in the Monterey Bay area of California, is ideally suited for agriculture. There one can see acres and acres of fruit trees, vegetable, berries, and flowers. In fact, the Pajaro Valley and the nearby Salinas Valley produce nearly half of the 2 billion pounds of strawberries grown in the United States yearly. The water source for the valley is a confined underground aquifer that is slowly being depleted. Estimates for the overdraft vary, but the amount of water being used each year is between 125% and 150% of the sustainable yield. The overdraft creates a problem of salt water intrusion along the coast, making many coastal wells unusable, and lowers the water table over the entire valley.

How can mathematics help solve this problem? In January of 2011, AIM held a Sustainability Problems workshop, http://aimath.org/pastworkshops/sustainability.html with the goal of bringing together mathematicians and industry representatives to work on a variety of sustainability problems, including renewable energy, air quality, water management, and other environmental issues. One of the industrial participants was Driscoll’s, whose associated growers are the largest supplier of fresh berries in North America. Three Driscoll’s employees teamed up with nine applied mathematicians to evaluate how various water and land management techniques could be utilized by landowners and growers to work towards balancing aquifer levels. During the week of the workshop and with followup activity in an AIM SQuaRE program, the team has made significant progress in the creation of a virtual farm model to study alternative crop management strategies and their affect on water usage and profit. The model uses an optimization framework (with over 200 constraints) to maximize a profit while meeting a water budget constraint. Dan Balbas, Vice President for Operations for Reiter Affliated Companies, (a Driscoll associated grower) said, “the results of the optimization program validated much of what the growers thought before and gave validation and new information to our crop growing strategies.” The team also investigated a surface water analysis to understand feasible ways to capture rainfall for re-infiltration (or recharging) into the aquifer.

Driscoll’s has also spearheaded a community effort in to help solve the overdraft problem. Pajaro Valley community members are working in smaller groups on a number of additional strategies, including the determination and promotion of best practices for irrigation and the identification of the most promising areas in the valley for aquifer recharge projects.