What question did this study set out to answer?

The aim is to develop accurate models for total nitrogen and phosphorus transport in Mississippi using historical data.

January 25, 2026Open Access

The Development of Long-Term Mean Annual Total Nitrogen and Total Phosphorus Load Models for Mississippi, U.S., Using RSPARROW

VRVictor L. RolandUnited States Army EGEmily GainUnited States Geological Survey MHMatthew B. HicksUnited States Geological Survey

Key Points

The aim is to develop accurate models for total nitrogen and phosphorus transport in Mississippi using historical data.
Utilized the RSPARROW framework for model development
Analyzed 15 years of observation data from 2005 to 2020
Incorporated multiple nutrient sources, land characteristics, and attenuation processes
Agricultural sources identified as major contributors to total nitrogen loads
Fertilizer usage dominates in northern Mississippi, while livestock manure is significant in the south
Urban land cover and geological materials are key influences on total phosphorus levels

Abstract

Water-quality degradation from nutrient pollution remains a major challenge for resource managers. Developing effective strategies requires tools to characterize nutrient sources and transport. This study used the RSPARROW framework to develop and assess new, smaller-scale models for Total Nitrogen (TN) and Total Phosphorus (TP) transport across Mississippi (MS). These state-level models were built using 15 years (2005–2020) of observation data and considered variables including multiple nutrient sources, land characteristics, and attenuation processes. The MS models demonstrated comparable accuracy to larger regional SPARROW models, validating the use of smaller-scale models for local management. Results showed agricultural sources are the major contributors to TN, dominated by fertilizer in northern MS and livestock manure in the south. Urban land cover also significantly influenced TN and was the second most significant source of TP, following geologic material (background P). Fertilizer and manure were also important TP sources. This study provides valuable, spatially explicit data on nutrient distribution in MS streams, supporting the state’s nutrient reduction planning. It concludes by highlighting the need for future model improvements via updated source data and mean annual flow estimates.

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