Quantifying and modelling urban stream temperature: a central US watershed study

Abstract

Abstract:Hydrologic models that rely on site specific linear and non-linear regression water temperature (T w ) subroutines forced solely with observed air temperature (T a ) may not accurately estimate T w in mixed-use urbanizing watersheds where hydrogeological and land use complexity may confound common T w regime assumptions. A nested-scale experimental watershed study design was used to test T w model predictions in a representative mixed-use urbanizing watershed of the central USA. The linear regression T w model used in the Soil and Water Assessment Tool (SWAT), a non-linear regression T w model, and a processbased T w model that accounts for watershed hydrology were evaluated. The non-linear regression T w model tested at a daily time step performed significantly (P < 0.01) better than the linear T w model currently used in SWAT. Both regression T w models overestimated T w in lower temperature ranges (T w < 10.0°C) with percent bias (PBIAS) values ranging from À28.2% (non-linear T w model) to À66.1% (linear regression T w model) and underestimated T w in the higher temperature range (T w > 25.0°C) by 3.2%, and 7.2%, respectively. Conversely, the process-based T w model closely estimated T w in lower temperature ranges (PBIAS = 4.5%) and only slightly underestimated T w in the higher temperature range (PBIAS = 1.7%). Findings illustrate the benefit of integrating process-based T w models with hydrologic models to improve model transferability and T w predictive confidence in urban mixed-land use watersheds. The findings in this work are distinct geographically and in terms of mixed-land use complexity and are therefore of immediate value to land-use managers in similarly urbanizing watersheds globally.

An Assessment of Mean Areal Precipitation Methods on Simulated Stream Flow: A SWAT Model Performance Assessment

“…Hubbart et al [33] showed that the differences in precipitation between urban and rural sites were not significant at the 95% confidence level in the HCW. However, precipitation was shown to be slightly greater by 3.3% in the urban area of the watershed indicating a slight influence of urban land use on total annual precipitation in the rapidly urbanizing lower elevations of HCW [38].…”

“…The stage was measured at each Hinkson Creek gauging site using Sutron Accubar ® constant flow bubblers with an accuracy of 0.02% at 0-7.6 m to 0.05% at 7.6-15.4 m [35][36][37][38]. Precipitation and stage data were stored on Campbell Scientific CR-1000 data loggers.…”

Advancing Understanding of the Surface Water Quality Regime of Contemporary Mixed-Land-Use Watersheds: An Application of the Experimental Watershed Method

“…Lenat and Crawford [11] reported higher total dissolved solids and specific conductance in an urban stream, relative to a forested reference stream; and noted urban stream biological parameters indicated a stressed environment. Rhodes et al [12] showed positive correlations between streamwater nutrient concentrations (i.e., NO 3 − , SO 4 2− , and Cl − ) and anthropogenic land uses (e.g., agriculture, urban, road density) in the Mill River Watershed, Massachusetts. Li et al [13] noted water temperature and nutrient concentration were significantly (p < 0.05) related to vegetative coverage at the sub-watershed-scale in the Han River Basin, China.…”

“…Land use/land cover change (e.g., forest removal, agricultural conversion, urbanization) has repeatedly and conclusively been shown to alter rates of mass (e.g., sedimentation of waterways, increased nutrient loadings) and energy flux (e.g., urban heat island, water temperature regime change) [1][2][3][4]. Such alterations impact water quality (e.g., chemical composition, pathogen presence and persistence) and quantity regimes (e.g., low flows, peak flows, flooding) [5][6][7][8], and can ultimately result in ecosystem degradation.…”

“…The nested-scale experimental watershed study design has been demonstrated an effective approach for quantitatively characterizing hydrologic and water quality perturbations in mixed-land-use watersheds [4,[22][23][24]. Nested watershed study designs partition a series of sub-basins inside a larger watershed to study environmental variables.…”