Application of the RSPARROW Modeling Tool to Estimate Total Nitrogen Sources to Streams and Evaluate Source Reduction Management Scenarios in the Grande River Basin, Brazil

Matthew P Miller,Marcelo L De Souza,Alexandre De Amorim Teixeira,Alison P Appling,Richard B Alexander,Lillian G Sanisaca

doi:10.3390/w12102911

Abstract

Large-domain hydrological models are increasingly needed to support water-resource assessment and management in large river basins. Here, we describe results for the first Brazilian application of the SPAtially Referenced Regression On Watershed attributes (SPARROW) model using a new open-source modeling and interactive decision support system tool (RSPARROW) to quantify the origin, flux, and fate of total nitrogen (TN) in two sub-basins of the Grande River Basin (GRB; 43,000 km2). Land under cultivation for sugar cane, urban land, and point source inputs from wastewater treatment plants was estimated to each contribute approximately 30% of the TN load at the outlet, with pasture land contributing about 10% of the load. Hypothetical assessments of wastewater treatment plant upgrades and the building of new facilities that could treat currently untreated urban runoff suggest that these management actions could potentially reduce loading at the outlet by as much as 20–25%. This study highlights the ability of SPARROW and the RSPARROW mapping tool to assist with the development and evaluation of management actions aimed at reducing nutrient pollution and eutrophication. The freely available RSPARROW modeling tool provides new opportunities to improve understanding of the sources, delivery, and transport of water-quality contaminants in watersheds throughout the world.

Highlights

Large-domain hydrological models are needed to support water-resource assessment and management in large river basins (e.g., [1]) and coastal and estuarine waters with large contributing drainages [2]
While the RL7, composite method (CMP), and INT model comparisons did help us identify and correct a few data errors, we found no reasons for concern about the selected Beale’s Ratio Estimator (BRE) or RL5 models
Given the importance of water resources in this region of Brazil, as indicated by the prioritization of actions aimed at improving water quality outlined by the Integrated Water Resources Plan for the Grande River Basin [35], there is a need for continued efforts to quantify human-natural systems to understand nutrient sources, delivery and transport

Summary

Introduction

Large-domain hydrological models are needed to support water-resource assessment and management in large river basins (e.g., [1]) and coastal and estuarine waters with large contributing drainages [2]. Such models must be able to quantify the effects of a diverse range of land uses on streamflow and water quality as well as the climatic and hydrological processes that control water and contaminant transport in surface waters across large spatial scales [1]. The higher precision results from the inclusion of a greater number of stream monitoring sites and larger quantities of data from watersheds with widely variable contaminant sources and hydrological and biogeochemical transport characteristics [7,9,11]

Methods

Results

Conclusion