Assessment of land use urbanization impacts on surface temperature and hydrology
Land use alteration and climate change are major contributors to the hydrological cycle within watersheds. They can influence the quantity and quality of water resources, the ecosystem and environmental sustainability. Urban areas have expanded in recent decades, accompanied by a noticeable increase in energy and water use. Such changes in land use have many implications for humans to meet the increasing share of the planet’s resources and water issues. Hence, distinguishing the effects of land use change from concurrent climate variability is a particular challenge for studies on operational management processes. In this work, some shortcomings related to climate variability and land use change have been addressed, as applied to land surface temperature (LST) and groundwater resources. Thus, the main goal of this study is to evaluate the impacts of land use change on surface temperature and the impact of urbanization and climate variation on hydrology. The research methodology included modeling approaches that were used to estimate the land surface temperature and the responses of hydrology to climate change and urbanization.
Land use maps derived from Landsat datasets were analyzed using several classification techniques to evaluate the intensity and pattern of urbanization and land surface temperature in the Greater Cairo Region (GCR), Egypt. Accuracy of Landsat derived land use data were relatively high and up to 96.5%. Findings indicated that the GCR land use alteration was dynamic and that vegetation loss was the main contributor to urban expansion in the GCR. Consequently, this led to increased LST and modified urban microclimate. The results showed that vegetation cover decreased by 7.73% within a 26-year timespan (1990-2016).
Land use alteration impacted not only land surface temperature, but also, combined with variation in climate, affected watershed hydrology, specifically streamflow and baseflow. Changes in streamflow and filtered baseflow in three watersheds: Little Eagle Creek (LEC), Upper West Branch DuPage River (UWBDR) and Walzem Creek watershed, from 1980 to 2017, caused by climate alteration and land use change were separated and accessed using the SWAT (Soil and Water Assessment Tool) model. Results showed that SWAT performed well in capturing the streamflow and baseflow in urban catchments. SWAT model calibration and validation was within acceptable levels for streamflow and baseflow. About 30%, 30% and 12% of the LEC, UWBDR and Walzem Creek watershed areas changed from agricultural to urban areas. Findings for the LEC watershed indicated that the variability in the baseflow and streamflow appeared to be heavily driven by the response to climate change in comparison to the variability due to altered land use. The contribution of both land use alteration and climate variability on the flow variation was higher in the UWBDR watershed. In Walzem Creek, the alteration in streamflow and baseflow appeared to be driven by the effect of climate variability more than that of urbanization.
Finally, the impacts of basin lithology and physical properties on baseflow were examined using multiple regression models. Results suggest that the baseflow index (BFI) can be predicted using the basin’s physical and geological characteristics. This included different land uses and climate variables with high accuracy and low relative errors. BFI was found to be highly driven by precipitation and fractional areas of different lithologies in the basins in various regions. These could be estimated with a high accuracy, as opposed to evapotranspiration that caused lower model accuracy.
Information gleaned from these outputs can help in understanding the dynamics of land use change and climate variation, in order to help policy-makers predict and plan for future expansion in developing countries and across the globe, in achieving long-term sustainability of soil and water resources and their impact on climate change. Increasing efforts to prevent further urbanization and vegetation loss should be regarded as a practical management strategy and are of vital significance to many communities. In addition, the regression models developed in this study can be easily exploited in other areas with poor hydrological data quality and ungauged sites in order to estimate the amount of groundwater discharge.