Managing Global Resources for a Secure Future

2017 Annual Meeting | Oct. 22-25 | Tampa, FL

107562 Water Quality of Streams Draining Mixed-Used Agricultural Basins in Southwestern Puerto Rico.

Poster Number 1315

See more from this Division: SSSA Division: Soils and Environmental Quality
See more from this Session: Soils and Environmental Quality General Poster

Tuesday, October 24, 2017
Tampa Convention Center, East Exhibit Hall

David Sotomayor1, Gustavo Martinez2, Juan Cruz-Motta3, Paloma Rodriguez2, Luis Pérez-Alegría4 and Dave Bachoon5, (1)PO Box 9030, University of Puerto Rico at Mayaguez, Mayaguez, PR
(2)Agro-environmental Sciences Department, University of Puerto Rico, Mayaguez, Mayagüez, PR, Puerto Rico
(3)Marine Sciences Department, University of Puerto Rico, Mayaguez, Mayagüez, PR, Puerto Rico
(4)Agricultural and Biosystems Engineering, University of Puerto Rico, Mayaguez, Mayagüez, PR, Puerto Rico
(5)Georgia College and State University, Milledgeville, GA
Poster Presentation
  • Poster_fecal-water-quality-Lajas-Valley_2.pdf (1.8 MB)
  • Abstract:
    The Eastern Lajas Valley Watershed in southwestern Puerto Rico is an important agricultural area. A combination of citizen science volunteers and professionals was used for land-use/land-cover analysis and partial physical, chemical and biological characterization of stream waters and at the drainage outlet of five pre-defined basins (Mondongo, La Plata, Bárbara, Maginas, Cristales). Unmanaged shrubland/forest-land was the most dominant land use class followed by agriculture and urban land use with 61, 30 and 9% of total land area of 14,668 ha; the population was estimated at 33,936. Mondongo basin had the greatest land-area under agriculture, urban footprint and population, numerous passive and active discharge conduits, plus had a waste-water treatment plant (WWTP) that discharged secondary/tertiary treated effluents for an estimated annual total P and total N load of 1,471 kg P and 6,034 kg N, respectively. In contrast, Cristales basins had the lowest land-area under agriculture, population, and urban footprint. The PR water quality standard and/or suggested levels of enrichment were exceeded in 30%, 43%, and 61% of the sampling stations, for total N, dissolved NO3-N and total P concentrations, respectively. Overall, stream total N was positively correlated to the proportion of basin area in urban land (UD) (r= 0.49), while negatively correlated to grazed pastures (GP) (r= -0.42), row crops (RC) (r= -0.29) and pond (P) (r= -0.31). The best fit geographically weighted regression models showed positive relationships of total N with the proportion of UD and population. Stream total P was negatively correlated to unmanaged forest/shrubland (UF) (r= -0.40) while positively correlated to UD (r= 0.40), and hay and silage (HS) (r= 0.33). The main sources contributing to stream N and P concentrations are the Lajas WWTP and northern urban areas of the watershed and to a lesser extent agricultural areas consisting primarily of row crops and grazed pastures.

    See more from this Division: SSSA Division: Soils and Environmental Quality
    See more from this Session: Soils and Environmental Quality General Poster