Abstract
It has become increasingly important to recognize historical water quality trends so that the future impacts of climate change may be better understood. Climate studies have suggested that inland stream temperatures and average streamflow will increase over the next century in New England, thereby putting aquatic species sustained by coldwater habitats at risk. In this study we evaluated two different approaches for modeling historical streamflow and stream temperature in a Rhode Island, USA, watershed with the Soil and Water Assessment Tool (SWAT), using (i) original SWAT and (ii) SWAT plus a hydroclimatological model component that considers both hydrological inputs and air temperature. Based on daily calibration results with six years of measured streamflow and four years of stream temperature data, we examined occurrences of stressful conditions for brook trout (Salvelinus fontinalis) using the hydroclimatological model. SWAT with the hydroclimatological component improved modestly during calibration (NSE of 0.93, R2 of 0.95) compared to the original SWAT (NSE of 0.83, R2 of 0.93). Between 1980–2009, the number of stressful events, a moment in time where high or low flows occur simultaneously with stream temperatures exceeding 21 °C, increased by 55% and average streamflow increased by 60%. This study supports using the hydroclimatological SWAT component and provides an example method for assessing stressful conditions in southern New England’s coldwater habitats.
Highlights
Stream temperatures in the New England region of the United States have been increasing steadily over the past 100 years [1]
Since the hydroclimatological model was shown to be more accurate, future research projects should consider using the new component in similar watersheds throughout the region for both historical and climate change assessments
This study found that the long-term historical stream temperature data recorded by the USGS gauge at Cork Brook were necessary for model calibration
Summary
Stream temperatures in the New England region of the United States have been increasing steadily over the past 100 years [1]. This study used the Soil and Water Assessment Tool (SWAT) [17] developed by United States. Water 2017, 9, 667 groups and government agencies [18,19] This fish typically spawns in the fall and lays eggs in redds (nests) deposited in gravel substrate. High stream temperatures cause physical stress including slowed metabolism and decreased growth rate, adverse effects on critical life-cycle stages such as spawning or migration triggers, and in extreme cases, mortality [7,21,22,23,24]. Studies have shown that optimal brook trout water temperatures remain below
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