A gap analysis of water quality data in a gold mining region of Nicaragua




Chambers, Katherine

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Communities in the vicinity of the Mico River, located in Chontales, Nicaragua, suffer from periodic dry season water shortages. The Mico River is impacted by artisanal and industrial mining, cattle ranching, effluent from local dairies and tanneries, and poor waste management practices in the watershed. Available water quality data consists of short term assessment studies and monitoring data for a mine operating in the headwaters, but to date this information has not been collated and interpreted as a whole. Communities in the vicinity of the Mico River have expressed an interest in having this data reviewed to verify information they have received from government and industry with regards to impacts from the La Libertad Mine. A gap analysis of existing water quality data in the headwaters of the Mico River is presented, with interpretation of current data and identification of further data needs. Recommendations are provided for future water quality monitoring in the region. The study area was defined as the Mico River watershed upstream of the town of Santo Tomas. A total of 14 studies were identified with information about the Mico River in this area. Individual study reliability was assessed, and study data were compiled to assess conditions in comparison to water quality guidelines and any spatial or temporal trends. Both water chemistry and bioassessment studies were assessed. The major gaps in existing information are: insufficient baseline/ reference information, insufficient information on impacts from contaminants other than metals, insufficient coverage of streams not directly impacted by the La Libertad Mine, poor quality and reliability of data, and poor coordination/ continuity between studies done to date. Cyanide concentrations were found to be below drinking water criteria at the majority of sample locations. Metals concentrations were elevated throughout the study area but it cannot be determined if this is due to natural background levels or anthropogenic sources. Water quality conditions with regards to other parameters (e.g., dissolved oxygen, temperature, pesticides and bacteria) and bioassessment data cannot be assessed due insufficient data quality and quantity. Existing monitoring in the region should be expanded to include reference locations. It is recommended that a benthic invertebrate bioassessment program designed for tropical mountain streams be implemented to supplement existing monitoring and identify areas where stream function is impaired, as bioassessment is cheaper and requires less equipment and logistical coordination than water chemistry monitoring programs. Whatever future work is done, care must be taken that study design and implementation is of a higher quality than that done to date, so that results are comparable and reliable. Coordination and cooperation between bodies involved in monitoring is essential for efficient use of scarce resources.



mining, water quality, Nicaragua, Central America, gap analysis, artisanal mining, gold, benthic invertebrate, bioassessment, freshwater