Arsenic found in agriculture water reservoirs represents a threat to water security and safe agricultural products in developing countries. Small farms do not implement traditional water treatments due to the high cost; hence, a nature-based solution is an alternative to tackling this challenge. This paper investigated the potential of artificial floating island with Vetiver (AFIV) for the geogenic arsenic removal present in the reservoir of the Ilinizas páramo in Ecuador. We constructed two AFIV systems using PVC pipes in a reservoir batch type with a 3.6 m³ treatment capacity. Arsenic and iron were analyzed in duplicated every 30 days at the affluent and effluent through 120 days. The average remediation of arsenic was recorded as 97% in water and 84% in sediment, while the average remediation of iron was 87% in sediment. The survival rate of macrophytes was 92%; they accumulated arsenic in its roots that acted as a barrier against the translocation. The research demonstrated that the use of AFIV has the potential to rehabilitate reservoirs contaminated with arsenic under adverse climatic conditions such as the páramo ecosystem.

The application of hydrologic and hydrodynamic models in flash flood hazard assessment is mainly limited by the availability of robust monitoring systems and long-term hydro-meteorological observations. Nevertheless, several studies have demonstrated that coupled modeling approaches based on event sampling (short-term observations) may cope with the lack of observed input data. This study evaluated the use of storm events and flood-survey reports to develop and validate a modeling framework for flash flood hazard assessment in data-scarce watersheds. Specifically, we coupled the hydrologic modeling system (HEC-HMS) and the Nays2Dflood hydrodynamic solver to simulate the system response to several storm events including one, equivalent in magnitude to a 500-year event, that flooded the City of Tena (Ecuador) on 2 September, 2017. Results from the coupled approach showed satisfactory model performance in simulating streamflow and water depths (0.40 ≤ Nash-Sutcliffe coefficient ≤ 0.95; −3.67% ≤ Percent Bias ≤ 23.4%) in six of the eight evaluated events, and a good agreement between simulated and surveyed flooded areas (Fit Index = 0.8) after the 500-year storm. The proposed methodology can be used by modelers and decision-makers for flood impact assessment in data-scarce watersheds and as a starting point for the establishment of flood forecasting systems to lessen the impacts of flood events at the local scale.

Accurate estimation of spatiotemporal precipitation dynamics is crucial for flash flood forecasting; however, it is still a challenge in Andean-Amazon sub-basins due to the lack of suitable rain gauge networks. This study proposes a framework to improve hourly precipitation estimates by integrating multiple satellite-based precipitation and soil-moisture products using random forest modeling and bias correction techniques. The proposed framework is also used to force the GR4H model in three Andean-Amazon sub-basins that suffer frequent flash flood events: upper Napo River Basin (NRB), Jatunyacu River Basin (JRB), and Tena River Basin (TRB). Overall, precipitation estimates derived from the framework (BC-RFP) showed a high ability to reproduce the intensity, distribution, and occurrence of hourly events. In fact, the BC-RFP model improved the detection ability between 43% and 88%, reducing the estimation error between 72% and 93%, compared to the original satellite-based precipitation products (i.e., IMERG-E/L, GSMAP, and PERSIANN). Likewise, simulations of flash flood events by coupling the GR4H model with BC-RFP presented satisfactory performances (KGE* between 0.56 and 0.94). The BC-RFP model not only contributes to the implementation of future flood forecast systems but also provides relevant insights to several water-related research fields and hence to integrated water resources management of the Andean-Amazon region.

Nature-based solutions (NbS) are gaining attention as viable strategies for restoring water-rich ecosystems such as the páramo. However, the lack of evidence on their effectiveness, coupled with a limited understanding of their political, economic, social, technological, environmental, and legal (PESTEL) context, hinders their widespread adoption. To address this gap, we propose a multi-method framework that (i) captures PESTEL factors influencing the implementation of passive ecological restoration in páramo ecosystems as a measure of NbS and (ii) assesses its associated environmental impacts. Our approach integrates a scoping review with remote sensing techniques, water quality assessment, and correlation analyses. Focusing on the Upper Pita and Upper Cutuchi River Basins-key water sources for Andean communities in Ecuador, we reveal that the deterioration of their páramo ecosystems in the 20th century was mainly due to camelid grazing and pine timber production. In response to these threats, bottom-up management efforts starting in 1999, guided by various PESTEL factors, promoted policies, regulations, social agreements, and financial support for achieving passive ecological restoration between 2010 and 2017 in the Upper Pita River Basin. As a result, the conservation of 73.4% of natural páramo with excellent water quality in 2022. By contrast, top-down management in the Upper Cutuchi River Basin was ineffective because national strategies failed to tackle the local environmental challenges posed by the PESTEL factors. Hence, only 31.6% of the natural páramo remained with poor water quality by 2022. Our study is the first to demonstrate that passive ecological restoration benefits these ecosystems, while its absence results in significant changes that require additional restoration strategies.

Water is the main way arsenic (As) can ge tinto the human body causing irreversible health damage such as poisoning, skin lesions and various types of cancer. One strategy for addressing pollution of arsenic in aquatic ecosystems is artificial floating islands (IFA) using Vetiver grass (Chrysopogon zizanioides). The objective of this study was to review 45 publications on the fundamentals of construction, implementation, description of decontamination mechanisms, characterization of macrophyte species and final disposal of plant material. Also, some mathematical models that can be applied to quantify removal rates and system efficiency were reviewed. Based on the literature reviewed, it is concluded that Vetiver grass is an effective alternative in removing As and its effect can be amplified by implementing an artificial floating bed. The importance of this relatively new ecotechnology requires further research in the field.