Modeling Landscape Change Effects on Stream Temperature Using the Soil and Water Assessment Tool

Mamoon Mustafa,Darren Ficklin,Meghna Babbar-Sebens,Brad Barnhart

doi:10.3390/w10091143

Abstract

Stream temperature is one of the most important factors for regulating fish behavior and habitat. Therefore, models that seek to characterize stream temperatures, and predict their changes due to landscape and climatic changes, are extremely important. In this study, we extend a mechanistic stream temperature model within the Soil and Water Assessment Tool (SWAT) by explicitly incorporating radiative flux components to more realistically account for radiative heat exchange. The extended stream temperature model is particularly useful for simulating the impacts of landscape and land use change on stream temperatures using SWAT. The extended model is tested for the Marys River, a western tributary of the Willamette River in Oregon. The results are compared with observed stream temperatures, as well as previous model estimates (without radiative components), for different spatial locations within the Marys River watershed. The results show that the radiative stream temperature model is able to simulate increased stream temperatures in agricultural sub-basins compared with forested sub-basins, reflecting observed data. However, the effect is overestimated, and more noise is generated in the radiative model due to the inclusion of highly variable radiative forcing components. The model works at a daily time step, and further research should investigate modeling at hourly timesteps to further improve the temporal resolution of the model. In addition, other watersheds should be tested to improve and validate the model in different climates, landscapes, and land use regimes.

Highlights

Stream temperature is an important water quality parameter that affects physical and chemical processes in streams [1]
We focus on a semi-distributed mechanistic watershed model called the Soil and Water Assessment Tool (SWAT) [11], which has been extensively used to evaluate the effects of landscape and land use changes on different hydrologic components
The model’s responses to each rain event are very rapid, and the water loss rates are excessive, which results in zero flow for late summer periods

Summary

Introduction

Stream temperature is an important water quality parameter that affects physical and chemical processes in streams [1]. Higher stream temperatures in river systems represent a growing concern worldwide and can affect the habitat and life spans of fish [2,3]. According to Eaton and Scheller [4], some fish species will disappear from the water body, if stream temperature transcends an upper limit. Using historical data ranging from 30 to 100 years, Kaushal et al [5] reported that stream temperatures have been increasing throughout the United States at a rate of 0.009–0.077 ◦ C/year, with a significant increase in the western United States. Stream temperatures in the Pacific Northwest have reached historical records—at times, they have exceeded the lethal limit of 21.1 ◦ C for some aquatic species such as salmon. In the summer of 2015, the river temperature in the Columbia

Methods

Results

Conclusion