Precipitation plays a vital role in various fields, including hydroclimatic modeling, climate change studies, agricultural optimization, and water resources management. Precipitation data can be obtained through observational measurements using the rain gauge approach or as Gridded precipitation products (GPP) derived from satellites or atmospheric models. GPPs provide optimized global estimates of climate data without spatial or temporal gaps, making them a valuable solution for areas with sparse or nonexistent rain gauges. However, it is essential to assess their reliability and limitations across different time scales and regions before usage. This study aims to evaluate the accuracy of two specific GPP datasets, ERA5 and MERRA-2, in comparison with two observational datasets, focusing on the Tocantins-Araguaia watershed and Pará river estuary in Brazil. The results show that both GPPs, ERA5 and MERRA-2, captured the overall precipitation regime for the analyzed period. However, discrepancies emerged, particularly at the daily and annual scales, with better agreement observed at monthly and climatology scales when compared to observational datasets. ERA5 demonstrated a higher number of acceptable stations compared to MERRA-2. Although both reanalysis products showed good agreement in climatological analysis, a more detailed evaluation revealed shortcomings in simulating precipitation during the dry season. While GPPs offer consistent time series with higher temporal and spatial resolutions, the observational precipitation data is deemed the most suitable input for hydrological-hydrodynamic modeling in the Tocantins-Araguaia watershed. Its widespread coverage, numerous rain gauges, and accurate representation of reality make it an ideal choice for hydrological modeling in the region.

Peixoto, H.J.C.; Baia, L.P.; Pereira, D.R.; Rollnic, M., and Monteiro, S.M., 2018. Sedimentological Sectorization Model in an Amazonian Estuary. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 91–95. Coconut Creek (Florida), ISSN 0749-0208. The aim of this study is to check whether a macro tide-dominated Amazonian estuary might be separated in sectors according to recent sediment distribution, considering local hydrodynamics. The case study was conducted in the river Mojuim estuary (−0.72° and −48.00°), situated between the Pará River mouth and the Atlantic Ocean, northeastern Pará, Brazil. A total of 117 superficial sediment samples were collected using a Van Veen dredge in the lower estuary (16 km). Stations are equidistant and encompass margins and estuarine channel. We performed a sieving granulometric analysis and a calcination analysis of total organic matter and total calcium carbonate content (360° and 1000° C, respectively). Were used a multivariate statistical treatment to separate the estuary in sectors, with clustering analysis and principal component analysis (PCA). Recent sediment distribution of the river Mojuim estuary is characterized by fine, platykurtic, and poorly selected sediments (0.63–125 mm) with low organic matter content (5.8% ±0.30) and carbonate (2.4% ±0.04). The river Mojuim estuary is divided in three sedimentation subenvironments: 1) marine domain, located in the estuary mouth, with predominance of moderately selected sandy sediment, where reworking and sedimentary distribution are influenced by tidal currents; 2) river estuarine domain, with predominance of poorly selected muddy sediment, where sedimentation is influenced by river discharge; and 3) a transitional sector with sediments typical of both environments. The Mojuim estuary might be divided in sectors according to recent sedimentary distribution, However, it differs from classic model as it has: 1) a mixed mouth, where the East channel has marine characteristics (93%) and the West channel has transitional (20.7%) and freshwater characteristics; 2) widespread distribution of CaCO₃ throughout the estuary, with higher contents in the freshwater zone. Supplementary hydrochemical analyses are required to understand the processes that define these differences in the sedimentological sectorization of Amazon estuaries.

Recent studies have incorporated tidal elevation into hydrological models, yet they have not focused on simulating or evaluating tidal processes within these frameworks. Integrating tidal dynamics improves the representation of terrestrial–coastal interactions, including groundwater fluctuations, vegetation dynamics, and sediment transport. This study evaluates the capability of MOHID-Land, a physically based hydrological model, to simulate macro-tidal conditions in an Amazonian estuary. MOHID-Land enables tidal simulation by incorporating water-level time series as boundary conditions. A sensitivity analysis was conducted to (i) evaluate two global tidal models as boundary conditions; (ii) verify the impact of hydrological processes on water levels; and (iii) assess the effect of different bathymetries on water dynamics. The model effectively simulated tidal oscillations with good accuracy across eight tidal stations, although the inner stations required improved bathymetry. The Reference, Atmosphere, Porous Media and Vegetation (AtPmVg), and Finite Element Solution (FES) version 2014 (FES2014) simulations yielded similar water levels and goodness-of-fit metrics. While MOHID-Land is robust, and water level modeling is insensitive to meteorological, soil, or vegetation parameters, the model is highly sensitive to bathymetry. This study enhances the understanding of the applicability of hydrological models in terrestrial–coastal modeling.