Satellite-based monitoring of surface water dynamics

Abstract

PhD journey is truly a marathon event full of challenges. Alongside the challenges, there is also the joy of the journey itself and the many inspiring people encountered along the way. I would like to thank everyone who was involved in this journey. First and foremost, I would like to express my sincere thanks to my promoter, Prof. dr. Andrew K. Skidmore, who provided me the opportunity to undertake this PhD research at ITC and led me to the scientific world in the first place. It has been an honour to be his PhD student. He always encouraged me to keep learning new things and seeking answers to "why". He has taught me, both consciously and unconsciously, how to think critically and defend my views, and how to work smarter instead of harder. I am very grateful for his continuous guidance and support. This thesis would not have been possible without the support and guidance of my daily supervisor A/Prof. dr. Anton Vrieling. I am so lucky to have him as my supervisor for this PhD research. During all these years, he guided me with infinite patience and full support, providing useful discussions, constructive criticisms, enlightened ideas, and excellent English editing. He was always the first person helping me out whenever I got in the coming years (Prigent et al. 2012; Vörösmarty et al. 2000). Natural factors affecting water bodies include anomalous high-rainfall-driven flood events (Cian et al. 2018), drought events due to rainfall deficits (van Dijk et al. 2013), seasonal thawing and snowmelt in spring (Watts et al. 2012), and longer-term environmental changes (Lutz et al. 2014; Street and Grove 1976). Many human activities directly affect the availability of water resources. Examples are groundwater pumping, drainage of wetlands, irrigation schemes, and construction of new dams. Anthropogenic changes in land surfaces such as urbanization, agriculture and deforestation also lead to changes in surface water. These changes strongly affect ecosystem functioning, which further results in shifting species distributions and composition (Koning 2005; Robledano et al. 2010), especially for species that are sensitive to hydroperiod variability (Baldwin et al. 2006; Roshier et al. 2002). It may also affect other ecosystem functions including ground water recharge and nutrient cycling (Leibowitz 2003). Globally, the biodiversity of water-related ecosystems continues to decline at an alarming rate (Collen et al. 2014). In addition to these direct threats, the changes of surface water further influence climate change (Degu

Detecting land surface water changes in the Upper Mzingwane sub-catchment using remotely sensed data

“…Water volume changes typically have severe effects (Balist et al 2022). For example, a rapid surface water rise may cause floods, while a rapid decline may lead to droughts (Li 2020). Therefore, it is critical to accurately identify surface water, quantify its volume, and monitor its dynamics over time.…”

“…In situ gauge measurements have traditionally been the primary data source for assessing hydrological dynamics. Gauge stations collect data on water level, discharge, and streamflow but not on the spatial dynamics of surface water extent (Li 2020). In most cases, gauge stations are located on major rivers and lakes, but their distribution varies across the world, and their numbers have been decreasing in both developed and developing countries (Shiklomanov et al 2002).…”

“…Because of the limited spatial coverage and unavailability of in situ observations, assessing changes in water resources is difficult. Remote sensing technology and high-resolution satellite data have made precise surface water mapping and detection possible, particularly in areas where ground data is scarce (Huang et al 2018;Li 2020). Moreover, remote sensing can effectively monitor surface water dynamics.…”