Climate change effect on water temperature and evaporation in Lake Qarun

Abstract

ABSTRACT Climate change can have significant effects on the water and heat budgets of lakes and reservoirs. This study examined the effect of climate change on Lake Qarun through analyzing the temporal variation in lake surface temperature and evaporation from the lake. The analysis was based on the remote-sensing dataset MOD11A1 and the ERA5 climate reanalysis dataset. Daily surface temperatures for 1-km MOD11A1 pixels were filtered to remove outliers, averaged to obtain mean lake temperature, and then aggregated to compute the monthly average lake temperature. Lake evaporation was estimated by applying an un-mixing algorithm to ERA5 evaporation fluxes for mixed land-lake pixels and land-only pixels. The resulting monthly evaporation from the lake was corrected using a regression model based on evaporation estimates available in the literature for Lake Qarun. The regression model performance was confirmed through the Nash–Sutcliffe efficiency coefficient, correlation coefficient, and root mean square error. Over the period 1980 to 2019, findings show that annual evaporation ranged between 140 and 190 cm/year. Maximum average monthly evaporation for the study period is 21 cm in July while the minimum is 6.7 cm in February from 1980 to 2019. For the average lake surface temperature, it varied between ~31.9 and 33.9°C over the period 2000 to 2019. For the same time period, average maximum and minimum monthly temperatures were 44°C in August and 20.1°C in January. It is concluded that the average increase in evaporation and lake surface temperature is 37 mm/decade and 0.4°C/decade, respectively. The increase in both lake surface temperature and evaporation is likely due to climate change effects. However, using datasets with a larger temporal record for lake surface temperature, further studies can be applied for confirmation. Also, further confirmation can be obtained by applying the same analysis to other lakes in Egypt.