Temperature analysis for lake Yojoa, Honduras

Abstract

Lake Yojoa is the largest freshwater lake in Honduras, located in the central west region of the country (1405' N, 88° W). The lake has a surface area of 82 km2, a maximum depth of 26 m. and an average depth of 16 m. The locals believe that the anthropogenic activities around the lake for the past 25 years have impacted the water quality of the lake. Temperature analysis of the lake helps to understand the seasonal changes in the thermal structure of the lake, and it also indicates the seasonal changes in the water quality of the lake. The lake is marginally stratified most of the year, with a maximum difference of 4°C between the water surface and the lake bottom. The temporal changes in the thermal structure of the lake are studied using the lake stability analysis and a temperature model CE-THERM. The two analyses confirm that the lake overturns once a year. However, they differ on the onset of the overturn event and the seasonal changes in the stratification depth. The stability analysis indicates an overturn in November and for some years less stable lake conditions in June. The CE-THERM model was run for year 2005 and it indicates a possible overturn in June, and the lake remaining mixed until December.

(cont.) Further analysis using additional data is recommended to improve the temperature model predictions. Higher wind speeds, and lower air temperature were observed during the October and November time period, their combined effect appears to be mixing the lake. The inflow water is about 3 °C colder than the lake surface for most of the year, and it tends to sink in the bottom of the lake water column. Poor quality of inflow water settling in the bottom of the lake during a sudden overturn event can cause negative consequences on the dissolved oxygen of the lake, and thus the aquatic processes depending on it. Further studies are recommended to study the transport of the inflowing waters and their circulation in the lake water column, especially during the periods of low stability. Additionally, the thermal analysis can be extended to analyze other water quality constituents, and ultimately leading to the study of eutrophication.