Author: Amirhossein Shadmehri Toosi
Shadmehri Toosi, Amirhossein, 2025 Impacts of land use/land cover and climate variability on the hydrological cycle with a specific focus on evapotranspiration, Flinders University, College of Science and Engineering
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Water systems and biophysical environments undergo multiple complex interactions at both spatial and temporal scales. Over recent years, our understanding of hydrological processes and the conceptual details have remarkably increased. Much of the knowledge on these subjects results from applying remote sensing techniques and in situ observational information, which has significantly augmented data availability and coincidently increased computing capabilities. However, modelling hydrological processes on a large scale presents challenges, particularly in the context of climate change and Land Use-Land Cover (LULC) changes. The efficacy of current hydrologic models under conditions of change remains uncertain. To effectively integrate land cover dynamics and deepen our understanding of their impacts, assessing how LULC is represented in existing models and identifying any shortcomings is essential. These models consist of various components, each tailored to simulate specific elements of water partitioning within the hydrological cycle. Moreover, it is necessary to evaluate whether the variability in current LULC data is substantial enough to justify its inclusion in modelling efforts and how this variability might influence other processes like Actual Evapotranspiration (AET). Therefore, this study deals with these important subjects in three phases. First, in a comprehensive review, we discuss the hydrological processes affected by LULC and how conceptual models capture physical hydrologic processes and conceptualise LULC. This review highlights the existing gaps in LULC modelling and identifies avenues for improvement. Emphasis is placed on selecting the best model based on expected outcomes and improving LULC data. Finally, it highlights the need for a standardised LULC classification system for uniform modelling and comparison.
In the second phase of the investigation, we conduct a detailed analysis of year-on-year land cover changes within the Murray Darling Basin (MDB), leveraging the most accurate and contemporary datasets available. This endeavour aims to explain the significance of these land cover dynamics, pinpointing spatial and temporal patterns and emerging trends within MDB, which holds paramount economic and ecological value in Australia. The results indicate significant increases in natural bare surfaces and decrease in water bodies, with shifts in agricultural land use driven by water recovery initiatives and infrastructure developments. The drivers of LULC changes are influenced by climate variability, natural disasters, and water management practices, demonstrating varied impacts across different regions within the basin.
Subsequently, the third phase analyses the CMRSET and MODIS AET datasets over MDB. The study examines the temporal patterns and differences in AET across various land cover types, along with the existence of notable AET variation among the major land cover categories within the MDB. The research aims to determine if AET, on a broad scale, is affected by variations in rainfall or changes in land cover. The study reveals a reasonable alignment between the datasets in overall AET patterns, but significant variations in magnitude were observed. Basin-scale water balance assessments indicate that MODIS considerably underestimates AET. Rainfall is identified as the primary driver of AET variability across different land covers in most catchments.
This thesis points out areas that need improvement and the challenges we face because of limited and not always accurate data. It contributes to improved decision-making, formulating effective policy options, and predicting the likely unforeseen impacts for sustainable land and water management. Furthermore, the study highlights the need for regional studies given diverse hydrological characteristics and the significant influence of regional climate, terrain, and land cover changes on the hydrological process.
Keywords: Hydrological modelling, land use, land cover, conceptualisation,land cover dynamics, land conversion, environmental management, Murray Darling Basin, land-use policy,CMRSET, MODIS, actual evapotranspiration (AET), land cover, ecohydrology
Subject: Environmental Studies thesis
Thesis type: Doctor of Philosophy
Completed: 2025
School: College of Science and Engineering
Supervisor: Okke Batlaane