Abstract
The effect of the projected 21st century climate change on water quality in Old Woman Creek (OWC) watershed was evaluated using the Soil and Water Assessment Tool (SWAT) and the precipitation and temperature projections from three best Global Climate Circulation Model (GCM)l ensemble downloaded from the Coupled Model Intercomparison Project Phase 5 (CMIP5). These three best GCMs (GFDL-ESM2M, MPI-ESM-MR, EC-EARTH) were identified as those closest to the multivariate ensemble average of twenty different GCM-driven SWAT simulations. Seasonal analysis was undertaken in historical (1985–2014), current to near future (2018–2045), mid-century (2046–2075), and late-century (2076–2100) climate windows. The hydrological model calibration was carried out using a multi-objective evolutionary algorithm and pareto optimization. Simulations were made for stream flow and nine water quality variables (sediment, organic nitrogen, organic phosphorus, mineral phosphorus, chlorophyll a, carbonaceous biochemical oxygen demand, dissolved oxygen, total nitrogen, and total phosphorus) of interest. The average of twenty different CMIP5-driven SWAT simulation results showed good correlation for all the 10 variables with the PRISM-driven SWAT simulation results in the historical climate window (1985–2014). For the historical period, the result shows an over-estimation of flow, sediment, and organic nitrogen from January to March in simulations with CMIP5 inputs, relative to simulations with PRISM input. For the other climate windows, the simulation results show a progressive increase in stream flow with peak flow month shifting from April to March. The expected seasonal changes in each water quality variable have implications for the OWC estuary and Lake Erie water quality.
Highlights
In Parameter-elevation Regressions on Independent Slopes Model (PRISM) data, the lowest (54.8 mm) and the highest (100.2 mm) precipitation were recorded in January and May, respectively, while in the Coupled Model Intercomparison Project Phase 5 (CMIP5) model, the lowest (62.9 mm) and highest (97.8 mm) simulated precipitation occurred in February and June, respectively
The increase in sediment and nutrients transport simulated across the climate windows would increase the siltation level and nutrients enrichment in the estuary. This result is similar to the findings reported by The State of Ohio Environmental Protection Agency (EPA)
The average of the 20 CMIP5 models for the historical period compared with the PRISM climate data show good agreement in precipitation and almost perfect agreement in temperature with CMIP5 exhibiting low variability across the models
Summary
The rise in the earth’s surface temperature due to climate change observed in the last century has been projected into the 21st century. This temperature increase will further moisten the atmosphere and influence the water cycle [1]. The projected effects of climate change and management practices on hydrological variables have been studied using several climate models and basin scale hydrological models [3,4]. Hydrological modeling based on general circulation models (GCMs) are used to simulate the future changes in streamflow under projected climate conditions [5,6]. Githui et al [7] used SWAT with Model for the Assessment of Greenhouse
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