Abstract Searles Valley, a closed basin in southeast California(U.S.A.), now contains a dry salt flat 100 km2 in the area known as Searles Lake (Figure 1). Its subsurfacesaline layers and interstitial brines have been thesource of approximately $4 billion of assorted industrialchemicals. During about 75% of the late Plioceneand Pleistocene periods, however, the valley containeda perennial body of water. This lake level was as much as 200 m above its present surface during the late Pleistocene; the depths of the earlier lakes are poorly constrained. Climatic fluctuations during the entire period caused major fluctuations in lake level, and during the late Pleistocene at least, they resultedin overflow from its southeast corner during wetperiods, and in shrinkage or desiccation during dryperiods.Searles Valley is near the middle of a succession offive closed basins, four of which filled and overflowedat times during the past to make a chain of asmany as five lakes. These were fed primarily by the south-flowing Owens River that drained the highelevation,east-facing slopes of the Sierra Nevada.Upstream from Searles Lake were Owens Lake (terminus of the Owens River, 695 km2 surface area when full), and China Lake (which coalesced with Searles Lake when that lake was nearly filled, forminga single body of water having an area of nearly1000 km-). At times, Owens Lake received overflowfrom Mono Lake (690 kru-, "Lake Russell") in anadjoining now-closed valley to the north. Downstream from Searles Lake were Panamint Lake (710km/, "Lake Gale") and Death Valley Lake (1600 km","Lake Manly"). During the wettest periods, the