Inland water level and its dynamics are key components in the global water cycle and land surface hydrology, significantly influencing climate variability and water resource management. Satellite observations, in particular altimetry missions, provide inland water level time series for nearly three decades. Space-based remote sensing is regarded as a cost-effective technique that provides measurements of global coverage and homogeneous accuracy in contrast to in-situ sensors. The advent of Open-Loop Tracking Command (OLTC), and Synthetic Aperture Radar (SAR) mode strengthened the use of altimetry missions for inland water level monitoring. However, it is still very challenging to obtain accurate measurements of water level over narrow rivers and small lakes. This scoping systematic literature review summarizes and disseminates the research findings, highlights major results, and presents the limitations regarding inland water level monitoring from satellite observations between 2018 and 2022. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline and through a double screening process, 48 scientific publications were selected meeting the eligibility criteria. To summarize the achievements of the previous 5 years, we present fundamental statistical results of the publications, such as the annual number of publications, scientific journals, keywords, and study regions per continent and type of inland water body. Also, publications associated with specific satellite missions were analyzed. The findings show that Sentinel-3 is the dominant satellite mission, while the ICESat-2 laser altimetry mission has exhibited a high growth trend. Furthermore, publications including radar altimetry missions were charted based on the retracking algorithms, presenting the novel and improved methods of the last five years. Moreover, this review confirms that there is a lack of research on the collaboration of altimetry data with machine learning techniques.

Inland water bodies, wetlands and their dynamics have a key role in a variety of scientific, economic, and social applications. They are significant in identifying climate change, water resource management, agricultural productivity, and the modeling of land–atmosphere exchange. Changes in the extent and position of water bodies are crucial to the ecosystems. Mapping water bodies at a global scale is a challenging task due to the global variety of terrains and water surface. However, the sensitivity of spaceborne Global Navigation Satellite System Reflectometry (GNSS-R) to different land surface properties offers the potential to detect and monitor inland water bodies. The extensive dataset available in the Cyclone Global Navigation Satellite System (CYGNSS), launched in December 2016, is used in our investigation. Although the main mission of CYGNSS was to measure the ocean wind speed in hurricanes and tropical cyclones, we show its capability of detecting and mapping inland water bodies. Both bistatic radar cross section (BRCS) and signal-to-noise ratio (SNR) can be used to detect, identify, and map the changes in the position and extent of inland waterbodies. We exploit the potential of unsupervised machine learning algorithms, more specifically the clustering methods, K-Means, Agglomerative, and Density-based Spatial Clustering of Applications with Noise (DBSCAN), for the detection of inland waterbodies. The results are evaluated based on the Copernicus land cover classification gridded maps, at 300 m spatial resolution. The outcomes demonstrate that CYGNSS data can identify and monitor inland waterbodies and their tributaries at high temporal resolution. K-Means has the highest Accuracy (93.5%) compared to the DBSCAN (90.3%) and Agglomerative (91.6%) methods. However, the DBSCAN method has the highest Recall (83.1%) as compared to Agglomerative (82.7%) and K-Means (79.2%). The current study offers valuable insights and analysis for further investigations in the field of GNSS-R and machine learning.

In this paper, a developed low-cost system is described, which aims to facilitate 3D documentation fast and reliably by acquiring the necessary data in outdoor environment for the 3D documentation of façades especially in the case of very narrow streets. In particular, it provides a viable solution for buildings up to 8-10m high and streets as narrow as 2m or even less. In cases like that, it is practically impossible or highly time-consuming to acquire images in a conventional way. This practice would lead to a huge number of images and long processing times. The developed system was tested in the narrow streets of a medieval village on the Greek island of Chios. There, in order to by-pass the problem of short taking distances, it was thought to use high definition action cameras together with a 360˚ camera, which are usually provided with very wide-angle lenses and are capable of acquiring images, of high definition, are rather cheap and, most importantly, extremely light. Results suggest that the system can perform fast 3D data acquisition adequate for deliverables of high quality.

Nature-based solutions (NBS) employ natural processes to mitigate climatic risks and evolving environmental challenges, offering sustainable, cost-effective alternatives to traditional grey infrastructure. Traditional stone weirs are considered multifunctional and environmental friendly structures contributing to sustain ecosystems and protect communities from water-related hazards. This type of NBS has shown potential to mitigate flood impacts through controlled water flow and sedimentation retention by reducing both water velocity and erosion during peak flows, with main objective to enhance community resilience to climate change. During CARDIMED project a network of 120 traditional stone weirs will be developed and applied in Sifnos island (Greece) strategically placed across two main streams aimed at mitigating flood risks, recharge aquifers, enhancing biodiversity, and supporting small-scale agricultural water use, tailored to the unique arid ecosystems of the Greek islands.This study aims to monitor the efficiency of stone weir NBS in order to quantify climate adaptation benefits, particularly in relation to stormwater regulation, with application area Sifnos island (Aegean sea, Greece). The analysis utilises an integrated monitoring approach which couples remote sensing observations with in-situ data collected through monitoring stations, off-the-shelf sensors, and crowdsourcing participatory campaigns. Earth Observation techniques based on Sentinel-2 are employed to derive relevant vegetation and water indices (i.e. NDVI, NDWI), enabling to assess of vegetation health, soil water availability, and land surface dynamics. These are expected to be complemented by high-resolution datasets from Copernicus Contributing Missions, such as WorldView and Pleiades imagery, to enhance spatial and temporal resolution at locations of interest. EO techniques are validated by in-situ data derived from monitoring systems installed at strategic locations which provide localized, real-time measurements of hydrological, meteorological, and ecological parameters under different climatic conditions. The proposed methodology has the potential to provide key information about the quantified impacts from the application of stone weirs but also an understanding about their scalability as sustainable solutions for enhancing climate resilience at regional scale.Acknowledgement:This research has been funded by European Union’s Horizon Europe research and innovation programme under CARDIMED project (Grant Agreement No. 101112731) (Climate Adaptation and Resilience Demonstrated in the MEDiterranean region).

Nature-based solutions (NBS) harness natural processes to address climate-related risks and evolving environmental challenges, providing sustainable and cost-effective alternatives to conventional grey infrastructure. Traditional stone weirs represent multifunctional and environmentally friendly structures that contribute to ecosystem sustainability while enhancing protection against water-related hazards. This type of NBS has demonstrated significant potential in regulating surface runoff by controlling water flow and retaining sediments, thereby reducing flow velocity and erosion during high-discharge events. Through these mechanisms, stone weirs support the enhancement of community resilience under changing climatic conditions. Within the framework of the CARDIMED project, a network of 120 traditional stone weirs was being developed and implemented on Sifnos Island (Greece). These structures are strategically distributed along two main stream networks with the objectives of improving water regulation, supporting aquifer recharge, enhancing biodiversity, and facilitating small-scale agricultural water use. The design and deployment of the weirs are tailored to the specific hydrological and ecological characteristics of the arid island environments of the eastern Mediterranean.This study presents an integrated assessment of the effectiveness of stone weir nature-based solutions (NBS) in quantifying climate adaptation benefits, with a particular focus on stormwater regulation, using Sifnos Island (Aegean Sea, Greece) as a case study. The analysis adopts a multi-source monitoring framework that combines Earth observation data with in situ measurements collected through fixed monitoring stations, low-cost sensor deployments, and participatory crowdsourcing campaigns. Remote sensing techniques based on Sentinel-2 imagery are employed to derive key vegetation and water-related indices, including the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI), allowing the evaluation of vegetation condition, soil moisture availability, and land surface dynamics. To enhance spatial and temporal detail, PlanetScope imagery is integrated through the Copernicus Contributing Missions (CCM) programme, providing observations at 3 m spatial resolution. The near-daily revisit frequency of PlanetScope enables the monitoring of short-term dynamics and the computation of indices during hydrologically critical periods. Earth observation products are validated using in situ data acquired from monitoring systems installed at strategically selected locations, delivering high-resolution measurements of hydrological, meteorological, and ecological variables under varying climatic conditions. Overall, the proposed methodology offers a robust framework for quantifying the impacts of stone weir implementation and supports the evaluation of their scalability as effective, sustainable solutions for enhancing climate resilience on the regional scale.Aknowledgments:PlanetScope © Planet (2025) provided under Copernicus by European Union and European Space Agency.This research has been funded by European Union’s Horizon Europe research and innovation programme under CARDIMED project (Grant Agreement No. 101112731) (Climate Adaptation and Resilience Demonstrated in the MEDiterranean region).