干旱区生态环境知识资源中心

This study addressed the lake evolution of the Juyanze paleolake with the goal of calculating precipitation and evaporation during 34-26 cal kyr BP, which will aid evaluation of the reliability of using lake level changes to assess past changes in climate. Fourteen paleoshorelines were recognized at the Juyanze paleolake, and C-14 dating results showed that the highest 8 formed during 34-26 cal kyr BP. A unified Juyanze paleolake with an area of 7601 km(2) reached 932 m above sea level (a.s.l.) at 34 cal kyr BP. The paleolake then decreased to an area of 6104 km2 and an elevation of 930 m a.s.l. at 32 cal kyr BP, and to 5589 km(2) and 926 m a.s.l. at 26 cal kyr BP. Using water and energy balance equations, catchment paleo-precipitation and paleo-runoff were calculated for 3 previous periods. The results revealed that the catchment of the Heihe River required approximately 177 +/- 29 mm yr(-1) of precipitation to sustain the maximum lake area, which is a 32% increase compared with the modern value. Runoff from rivers to the lake was 61.9 x 10(8) m(3) at 34 cal kyr BP, with a calculation error of +/- 22.3 x 10(8) to 29.7 x 10(8) m(3). The humid climate and high lake levels of Juyanze paleolake that occurred during 34-26 cal kyr BP might have resulted from an enhanced monsoon. Moreover, low levels of evaporation may also have affected moisture changes.