An assessment of the mean annual precipitation needed to sustain Lake Sambhar in Rajasthan,India,during mid-Holocene time

Abstract

An application of a simple hydrological model to likely climatic conditions of Lake Sambhar provides tighter bounds on the range of increased precipitation seen during the early- to mid-Holocene than those inferred from paleoclimatic proxies. To examine past lake levels, we developed a simple lake model, based on hydrological principles of a watershed balance between precipitation, evaporation, and runoff from the watershed to calculate daily depth and volume. Calculations reveal that early- to mid-Holocene rainfall was most likely in a range of 40–65% greater than present levels, resulting in lake depths of ~6–8 m. This estimate incorporates all major sources of uncertainty into the lake model, but it is likely that the value of mid-Holocene precipitation lies in the lower part of the 40–65% range. Additionally, a 40–65% greater precipitation could have led to greater interannual variability in lake levels, which may account for the lack of clear shorelines. We find, however, that it is unlikely that Lake Sambhar filled to its maximum depth of 21 m above the present-day lakebed during this period due both to the much greater precipitation than today required to maintain a lake of such depth (greater than double present-day precipitation) and to the lack of current evidence (no shorelines and little vegetation). We also find that differences between mid-Holocene and present-day winter insolation alone have virtually no effect on average annual lake depths.