Runoff and soil loss estimation using N-SPECT in the rio grande de anasco watershed, puerto rico

Abstract

Over the last decades, the Rio Grande de Añasco watershed in the western part of Puerto Rico (PR) has been experiencing changes in land use due to conversion of agricultural lands into suburban use. The conversion contributed to sediment movements and pollutant loads to rivers and other water bodies. Agricultural practices contributed to nutrients to rivers via surface runoff and erosion. According to the US Environmental Protection Agency (EPA), concentrations of sediments from the uplands of the watershed are the main non-point sources of runoff entering the Mayagüez Bay, PR. The Non-point Source Pollution and Erosion Comparison Tool (N-SPECT) was used to study the relationships between land cover, soil characteristics, topography, and precipitation to assess spatial patterns of surface water runoff, non-point source pollution, and erosion. This paper uses N-SPECT to calculate runoff and erosion in the Rio Grande de Añasco watershed. Results show the most permeable soils are located in the northwest side of the Rio Grande de Añasco; while the highest probability of soil loss is in areas located in the west side of the watershed. The event-based runoff depth patterns coincide with the precipitation spatial patterns where the south part of the watershed, which lies in the Maricao Municipality, is expected to have major runoff events.