Pierson-Upper is a private dam located in Oregon, specifically in the Tualatin River watershed. Built in 1965, it serves primarily for irrigation purposes, with a capacity of 18 acre-feet and a normal storage level of 16.5 acre-feet. The dam stands at a height of 31 feet and spans 120 feet in length, providing water for individual residences in the area.

Managed by the Oregon Water Resources Department, Pierson-Upper is classified as a low hazard potential structure, with a needle outlet gate for water release. While it has not been rated for its condition, the dam undergoes inspections every six years to ensure its safety and integrity. The surrounding area has a drainage area of 0.82 square miles, with a maximum discharge capacity of 205 cubic feet per second.

Despite being a relatively small dam, Pierson-Upper plays a crucial role in providing water for agricultural purposes in the region. Its location in the scenic landscape of Washington County, Oregon, highlights the importance of sustainable water resource management in the face of changing climate conditions.