Submarine groundwater discharge (SGD) has been observed for thousands of years. However, its significance in coastal environments only gained considerable attention in the late nineteenth century. Since then, numerous reports have highlighted its role within the marine ecosystem and the factors that influence it. Most research, however, has been conducted in well-studied, easily accessible regions of the Northern Hemisphere, leaving the Southern Hemisphere and remote areas less examined. This comprehensive review of over 170 papers compiles and summarizes key advancements in SGD assessment techniques, evaluates their strengths and limitations, discusses uncertainties linked to individual methods, and explores the most effective ways to combine approaches to minimize measurement errors. It also presents the global distribution of studies on SGD estimations. The recommendations for method integration consider the driving forces behind SGD from terrestrial and marine sources, application scales, the ability to distinguish between terrestrial and recirculated SGD, and economic feasibility. The review examines commonly used SGD estimation techniques, their recent developments, and current global trends. It compares and summarizes prevalent approaches and their uncertainties, providing guidance on effectively combining methods to produce accurate estimates, identifying geographical gaps through updated global assessments, and outlining future directions to enhance SGD estimation.
Haile A. Shishaye (Tue,) studied this question.