With California's Wildlife Conservation Board funding, Pepperwood is implementing a streamflow enhancement project. We are testing the hypothesis that forest thinning can increase water yield by employing a paired watershed approach. This approach involves comparing the amount of water in the air, soil, and streams between a treated watershed and an untreated one. This study, which explores the relationship between forest management and watershed responses, is the first of its kind in our region.

The work at Pepperwood and at a partner site in the Northern Sierras address critical data gaps by providing some of the first empirical measurements of the land's "exhalation"—the fluxes of gases, including water vapor and carbon dioxide, in Northern California. We are combining these measurements with data on soil moisture and stream water levels to determine whether our forest thinning prescription, which involves removing all trees less than ten inches in trunk diameter at breast height within a designated area, increases the amount of water available to the ecosystem.

There are four eddy covariance flux towers, each 71 feet tall and weighing 200 pounds. There are two towers located at Pepperwood and two at our partner site in Tahoe National Forest. At each location, the towers are placed in separate watersheds, one managed, while the other serves as a control. Each tower is equipped with an ultrasonic anemometer and an infrared gas analyzer to measure the flow of carbon dioxide and water vapor in and out of our watershed systems. Additional instruments allow us to capture real-time measurements of stream flow, soil moisture, and even leaf wetness, ensuring an accurate assessment of the water balance at each location.