Laguna de Apoyo (Nicaragua) Hydrogeological Study and management proposals

Abstract

The blind drainage lake of Apoyo, located within a caldera in the Nicaraguan Volcanic Chain, suffers from several environmental and socioeconomic problems among which stands out a continued decline in its water level, estimated at more than 15 meters from 1950, and a natural pollution of arsenic. Difference between average annual Precipitation (1420 mm/year) and Evaporation (2017 mm/year) over lake surface is the main factor that determines the evolution of its water levels, which also depends on outlets-inlets underground water balance. Piezometry and hydrochemistry data corroborates the existence of an underground inflow area located South-West and an underground outflow area located North-East, both in regard to the Las Sierras regional aquifer which has its base level in Nicaragua Lake, East of Apoyo Lake. Hydrogeological budget indicates an annual water shortage of 6 hm³/año, showing the Apoyo Lake water imbalance.Works have been shared and followed by municipality and government technicians and watershed management proposals were presented to the population and authorities to solve environmental and health difficulties, such as the Apoyo Lake high arsenic levels and the affection to wells located near shore and over the underground water outlet area.