Water quality trends in a changing landscape in Puerto Rico

Background/Question/Methods Puerto Rico is a tropical Caribbean island with drastic socioeconomic and land use changes over the 20^th Century.  Since 1950, the industrialization of Puerto Rico caused the abandonment of agricultural lands and the natural reforestation of watersheds.  The natural reforestation of the Island has improved water quality conditions in some rivers watersheds, like Río Fajardo, that have remained forested. However, this trend has not been documented in other watersheds.  With this project, we explore water quality trends in watersheds across the Island that has experienced land use change.  We have evaluated up to 30 years of water quality data collected quarterly by the USGS in five watersheds spread over Puerto Rico.  We have conducted trend analysis on the following parameters: temperature (° C), discharge (cfs), dissolved oxygen (mg / L), total nitrogen (mg / L), total phosphorus (mg / L), fecal coliform (Col. / 100 mL), total suspended sediment   (mg / L) and total dissolved solids (mg / L).  Land use change has been assessed by comparing land cover data for 1977 and 2000.  In addition, demographic changes and public investments in wastewater collection and treatment have been evaluated in each watershed to study the effects of human activities on the water quality in these basins. 

Results/Conclusions

We can see that the changes have been observing on parameters that tells us that they are well connected with the use of the land, not to mention other factors like social-economics, where over the years we have seen an improvement in water quality by the reforestation of agricultural areas. Agricultural areas have made a great impact on water quality. We can conclude that the stations that have been studied have been affected over the years but we have also seen them have been recovering. This improvement was observed as a watershed this reforested completely or in its entirety large, where the parameters are conducive to the improvement of water quality.