1880s. A gauge at RM 161 (RK 259) in Harrisburg recorded an average flow of over the 65 years between 1945 and 2009. Flow is regulated by eight dams on upstream tributaries, and withdrawals for irrigation also affect water levels. The maximum flow recorded since 1945 was on December 29, 1945. The minimum flow was on October 30, 1944. The Harrisburg gauge measures the flow from an area of about , about 30 percent of the Willamette watershed. During the 115 years of 1894 plus 1896–2009, the average discharge recorded by a gauge at the Ellsworth Street Bridge in Albany, Oregon, at RM 119.31 (RK 192.01), was . Nine upstream dams on tributaries regulate the flow, which is also affected by diversions for irrigation, municipal water supplies, and electricity generation. The maximum discharge during the period of record, including fragmentary data from 1878–88, was on January 14, 1881, and the minimum discharge was on September 1 and 2, 1940. This was from a drainage basin of , or about 43 percent of the watershed. Extremes outside the period of record include a discharge of on December 4, 1861, and on February 4, 1890. A gauge at RM 84.16 (RK 135.44), near the Center Street Bridge in downtown Salem recorded an average discharge of over the 93 years between 1910–16 and 1924–2009. Flow is regulated by 12 reservoirs on upstream tributaries and is also affected by diversions for irrigation. The maximum flow recorded at this station was on January 8, 1923. The minimum flow was on August 27, 1940. The Salem gauge measures the flow from an area of about , which is about 63 percent of the Willamette watershed. Extremes outside the period of record include a maximum discharge of on December 4, 1861, based on flood marks and other data. The average discharge at a gauge near the Morrison Bridge in Portland was between 1972 and 2009. Located at RM 12.8 (RK 20.6), the gauge measures the flow from an area of , roughly 97 percent of the Willamette basin. During these years, the flow was regulated by many dams on upstream tributaries, and was affected by withdrawals for irrigation and by tidal fluctuations. The maximum flow recorded at this station was on February 9, 1996, during the Willamette Valley Flood of 1996, and the minimum was on July 10, 1978. Extremes outside the period of record include flood