Investigating the Sources of Fresh Water Production Affecting the Hydrological Balance of Lakes Enriquillo and Azuei (Hispaniola)—Modeling and Observations

The Enriquillo and Sumatra are saltwater lakes located in a rift valley that is a former marine strait created around 1 million years ago when the water level fell and the strait was filled in by river sediments. The lakes, part of the Enriquillo closed water basin in the southwestern region of the island of La Hispaniola, have been experiencing dramatic changes in total lake-surface area coverage during the period 1980-2012. The size of Lake Enriquillo presents a lake surface area of approximately 276 km2 in 1984, gradually decreasing to 172 km2 in 1996. The surface area of the lake reaches its lowest point in the satellite observation record in 2004, at 165 km2. Then the recent growth of the lake begins reaching its 1984 size by 2006, on December 2009 the lake size is 333 km2, 17% larger than in 1984 and almost double than in 2004. Based on surface area measurement for June and July 2013, Lake Enriquillo has a surface area of ~358 km2. Sumatra sizes at both ends of the record are 116 km2 in 1984 and 134 km2 in 2011, an overall 15.8% increase in 27 years. Determining the causes of lake surface area changes is of extreme importance due to its environmental, social, and economic impacts. The goal of this study is to quantify the changing water balance in these lakes and their catchment area using satellite and ground observations and a regional atmospheric-hydrologic modeling approach. Data analyses of environmental variables in the region reflect a hydrological unbalance of the lakes due to changing regional hydro-climatic conditions. Historical data show precipitation, land surface temperature and humidity, and sea surface temperature (SST), increasing over region during the past decades. Salinity levels have also been decreasing by more than 30% from previously reported baseline levels. We hypothesized that the increases in SSTs may be leading to increases in regional moisture content which leads to decreases in evaporation capacity from the lakes, and simultaneously to increases in fresh water production in the neighboring sierras. A network of rain and fog gauges along these high sierras reflects the capacity of the tropical cloud montane forest to produce fresh water throughout the year, independently of the season. Results from the high-resolution mesoscale modeling system, validated against the newly deployed network of monitoring stations, clearly reflect increases in the amount of liquid water content in the vertical column as function of changing regional climate conditions, and how the lakes water volume and surface area respond to these atmospheric inputs.