Sources and Transport of Phosphorus to Rivers in California and Adjacent States, U.S., as Determined by SPARROW Modeling

Abstract

The SPARROW (SPAtially Referenced Regression on Watershed attributes) model was used to simulate annual phosphorus loads and concentrations in unmonitored stream reaches in California, U.S., and portions of Nevada and Oregon. The model was calibrated using de-trended streamflow and phosphorus concentration data at 80 locations. The model explained 91% of the variability in loads and 51% of the variability in yields for a base year of 2002. Point sources, geological background, and cultivated land were significant sources. Variables used to explain delivery of phosphorus from land to water were precipitation and soil clay content. Aquatic loss of phosphorus was significant in streams of all sizes, with the greatest decay predicted in small-and intermediate-sized streams. Geological sources, including volcanic rocks and shales, were the principal control on concentrations and loads in many regions. Some localized formations such as the Monterey shale of southern California are important sources of phosphorus and may contribute to elevated stream concentrations. Many of the larger point source facilities were located in downstream areas, near the ocean, and do not affect inland streams except for a few locations. Large areas of cultivated land result in phosphorus load increases, but do not necessarily increase the loads above those of geological background in some cases because of local hydrology, which limits the potential of phosphorus transport from land to streams.(KEY TERMS: nutrients; phosphorus; geology; transport and fate; simulation; watersheds; SPARROW.) Domagalski, Joseph and Dina Saleh, 2015. Sources and Transport of Phosphorus to Rivers in California and Adjacent States, U.S., as Determined by SPARROW Modeling.

Toward Explaining Nitrogen and Phosphorus Trends in Chesapeake Bay Tributaries, 1992–2012

“…; García et al. ; Domagalski and Saleh ) and between 17 and 24 kg/ha for nitrogen (Van Breemen et al. ; Domagalski et al.…”

Riverine Nutrient Trends in the Sacramento and San Joaquin Basins, California: A Comparison to State and Regional Water Quality Policies

“…Results from the SPARROW model for total phosphorus indicate that 65% of the phosphorus load in the lower Sacramento River originates from cultivated land and 21% from point sources with the remainder from geological sources (Domagalski and Saleh 2015). For the San Joaquin River system, about 58% of the phosphorus load to the Delta originates from cultivated land, while 15% is from point sources, and the remainder is from geological sources (Domagalski and Saleh 2015).…”

Spatially referenced models of streamflow and nitrogen, phosphorus, and suspended-sediment loads in streams of the Pacific region of the United States

“…Nitrogen fixation due to the symbiotic association of red alder trees (Alnus rubra) with certain soil bacteria was represented by the basal area of that tree species in each E2NHDPlus2 catchment (Oregon State University, 2019). The only substantial source of natural phosphorus in the Pacific region is from the weathering of phosphorus-containing minerals and this source has been parameterized in previous SPARROW models in different ways-as runoff from land cover types with minimal human impact (Moore and others, 2004; Wise and Johnson, 2013), as a function of the natural phosphorus content of local soil and rock (Garcia and others, 2011;Domagalski, and Saleh, 2015), and as weathering of specific geologic units that were expected to be important contributors to instream phosphorus (Ator and others, 2011). Two different approaches were evaluated in the total phosphorus model to represent natural phosphorus from upland areas.…”

“…All these advantages of SPARROW provide a means of mapping water-quality conditions over large regions while retaining significant spatial detail, mapping the factors that affect in-stream conditions, and relating upstream environmental factors such as sources of model constituents to downstream conditions. SPARROW nutrient models have been developed previously for large regions of the conterminous U.S. as part of a larger effort conducted by the U.S. Geological Survey (USGS) National Water Quality Assessment (NAWQA) (Preston and others, 2011;Wise and Johnson, 2013;Domagalski and Saleh, 2015;Saleh and Domagalski, 2015). Those models were focused on nutrients, were based on a 2002 time frame and extended over six large regions covering all but the southwestern part of the conterminous U.S.…”