A Chemical Survey of Remote Lakes of the Alagnak and Naknek River Systems, Southwest Alaska, U.S.A.

An analysis of the chemistry of 12 remote lakes of the Naknek and Alagnak drainages demonstrated significant differences in surface water alkalinity, due in part to high concentrations of naturally-occurring sulfate in the Alagnak drainage. The average surface water alkalinity for lakes in the Alagnak drainage (109 μeq L−1) is much less than that for the Naknek drainage (425 μeq L−1), and below that for lakes from South Central Alaska, indicating a potential sensitivity of the lakes in the Alagnak river system to acid depostion. The upper Alagnak drainage contains Iron Springs Lake, a naturally acidic lake (pH 3.65) with a surface area of 70 ha. The acidity of this lake may be due to oxidation of surficial iron sulfide deposits, which would also explain the relatively high sulfate concentrations (120-1516 μeq L−1) in the Alagnak drainage.