Preliminary assessment and classification of the water quality of the Tarcoles and Reventazan river basin Part III: Quality of bodies receiving water according to the Dutch System of Evaluation

Two of the most important basins of the country are those from Tarcoles River and ReventazOn River, where almost 70% of the population lives and discharges domestic wastewaters without any treatment coming from the cities of San Jose, Heredia, Alajuela and Cartago. Besides, the contamination of surface waters will affect later the underground waters, because of the relationship between them. One of the objectives of the project was to classify the quality of waters using the Holland Classification System, based on potential water use. Sampling was done in the four control zones of Tarcoles River and ReventazOn River Basins during the six month period study. In order to determine the quality of water, dissolved oxygen, ammonium nitrogen and biochemical oxygen demand were analized. The Holland Classification Model resulted to be a useful tool. But even better was the contamination classification of water by each individual parameter to find the cause of this resulting contamination. High levels of contamination in rivers were associated with high density populations nearby the rivers studied. An adecuate wastewater discharge management would be helpful for the recovery of the rivers.