Many fields have identified an increasing need to use global satellite precipitation products for hydrological applications, especially in ungauged basins. In this study, we conduct a comprehensive evaluation of three Satellite-based Precipitation Products (SPPs): Integrated Multi–satellitE Retrievals for GPM (IMERG) Final run V6, Soil Moisture to Rain (SM2RAIN)-Advanced SCATterometer (ASCAT) V1.5, and Multi-Source Weighted-Ensemble Precipitation (MSWEP) V2.2 for a subbasin of the Mekong River Basin (MRB). The study area of the Srepok River basin (SRB) represents the Central Highland sub-climatic zone in Vietnam under the impacts of newly built reservoirs during 2001–2018. In this study, our evaluation was performed using the Rainfall Assessment Framework (RAF) with two separated parts: (1) an intercomparison of rainfall characteristics between rain gauges and SPPs; and (2) a hydrological comparison of simulated streamflow driven by SPPs and rain gauges. Several key findings are: (1) IMERGF-V6 shows the highest performance compared to other SPP products, followed by SM2RAIN-ASCAT V1.5 and MSWEP V2.2 over assessments in the RAF framework; (2) MSWEP V2.2 shows discrepancies during the dry and wet seasons, exhibiting very low correlation compared to rain gauges when the precipitation intensity is greater than 15 mm/day; (3) SM2RAIN–ASCAT V1.5 is ranked as the second best SPP, after IMERGF-V6, and shows good streamflow simulation, but overestimates the wet seasonal rainfall and underestimates the dry seasonal rainfall, especially when the precipitation intensity is greater than 20 mm/day, suggesting the need for a recalibration and validation of its algorithm; (4) SM2RAIN-ASCAT had the lowest bias score during the dry season, indicating the product’s usefulness for trend analysis and drought detection; and (5) RAF shows good performance to evaluate the performance of SPPs under the impacts of reservoirs, indicating a good framework for use in other similar studies. The results of this study are the first to reveal the performance of MSWEP V2.2 and SM2RAIN-ASCAT V1.5. Additionally, this study proposes a new rainfall assessment framework for a Vietnam basin which could support future studies when selecting suitable products for input into hydrological model simulations in similar regions.

In the present day, the acceleration of urban surface heat impacts resulting from urbanization and industrialization is critical for citizens and municipal governments in developing-country cities. The previous key findings have indicated the association between urban surface heat and the following areas: forests, mixed agricultural land, built-up area, and water bodies. This study was motivated by a lack of knowledge regarding the variation of temperature, evaporation, and humidity in Central Vietnam’s major region. The non-parametric Mann–Kendall test, Sen’s slope estimator, and Landsat image analysis were employed to determine the trend and statistical significance of the variables across the 42-year study period for Da Nang city and Quang Nam province. Our results show that Da Nang city has a consistent trend with a high correlation between temperature, evaporation, and relative humidity, whereas Quang Nam province showed an inverse relationship between temperature and relative humidity since the beginning of the regional urbanization. The maximum, minimum, and mean temperatures have increased by at least 0.29 °C in Quang Nam province and 0.71 °C in Da Nang city since 2000. Between 1979 and 2021, the frequency of days with temperatures exceeding 35 °C has increased by two and seven days during the past decade at the meteorological stations in Da Nang and Tam Ky, respectively. The temperature in Da Nang city varied from 31.80 °C to 32.82 °C with high temperatures concentrated in urbanized regions with less coverage of small trees, plants, and water bodies. Thus, the results of this study will serve as a scientific basis for decision-makers and regional officials for land-use management and to increase community awareness of sustainable planning, particularly in Da Nang city and Quang Nam province in Central Vietnam.

Study region: The area of interest is the Upper Biebrza Valley, located in NE Poland. Study focus: We examined water exchange at the river-fen interface in a near-natural wetland system using the combined field research-modeling approach. The authors chose the Biebrza River as the research object: it is a specific case of fen marginal valley rivers, and it flows in the peat layer without direct connection to the mineral soil layer. Our case study introduces two new aspects not yet considered in the scientific literature: (1) the riparian aquifer is fen and (2) the river has no direct contact with the mineral layer. The following research questions were investigated: What is the role of the river in feeding and draining a fen? Which drainage paths are important for water exchange in a near-natural river-fen system? How important are the morphological settings for the river-fen relations? We applied a systematic hydrological research approach based on field measurements and observations of the river and surrounding fen hydrological characteristics, as well as on the modelling results. New hydrological insights for the region: We demonstrated that morphological settings have a significant influence on river-fen relations. We also demonstrated that due to the undeniable need to introduce increased protection and restoration of marginal fens, we may focus on river status in narrow valleys; however, in the wide valleys, the limitation of the drainage layer by decreasing the intensity of evapotranspiration is more promising. We propose to distinguish zones in the fen river valley to include them when proposing protection or conservation plans.

The objective of the present paper is to develop a methodology that could allow the representation of the analytical hyporheic flux equation model (AHF) in a numerical model done in MODFLOW. Therefore, the scope of the research is to show the viability of the methodology suggested in a real case (Biebrza river, Poland, Europe). Considering that the model requires extensive manipulation in the creation of the packages, a test phase through the seepage package of MODFLOW is carried out with the aim of representing the river package of MODFLOW. FloPy is the tool chosen to develop this implementation due to the versatility of manipulating the packages available in MODFLOW through coding. The obtained results showed a correct implementation of the AHF model using the example of the Biebrza River. The results obtained will enable a better understanding regarding the modelling of the interaction between the river and the aquifer, considering streams with specific geometries where the depth is dimensionally higher than the width.

The characteristics of peat’s are crucial for understanding natural processes and their suitable shaping through the management of water relations. This study focused on the results of one of the first hydraulic conductivity (k) laboratory tests of exemplary peat samples from the Biebrza Valley (a peatland of very high environmental importance) in relation to the stress state and hydraulic gradient. Further, the research was devoted to a specific test procedure of peat permeability as a key feature for landform development in wetlands. Detailed tests of dark brown/black samples were selected as the reference for the research investigations. Four long-term test series of water permeability were performed in a modified triaxial compression apparatus. In all selected hydraulic gradient variants (i = 5,10,25,40,55,85), the k values decreased from 6 × 10⁻⁸ m/s to 1.6 × 10⁻¹⁰ m/s with a stepwise increase in the effective confining pressures tested (10, 15, 30, 45, and 90 kPa). These results were related to the inherent soil features—a relatively high peat decomposition and external driver—confining pressure (radial stress) magnitude. Compared to the other Polish peat tests, the determined k values were at the lower end of their hydraulic conductivity range. The analysed organic soil is not a typical aquifer. Despite very high porosities (~88%) and a high organic matter content (81.1–89.4%) which is favourable for water accumulation, the characterized peat showed relatively low hydraulic conductivity values. Thus, this specific soil may differentiate the groundwater flow as it complicates strong contact with surface water.

Modelling of water flow in the hyporheic zone and calculations of water exchange between groundwater and surface waters are important issues in modern environmental research. The article presents the Analytical Hyporheic Flux approach (AHF) permitting calculation of the amount of water exchange in the hyporheic zone, including vertical water seepage through the streambed and horizontal seepage through river banks. The outcome of the model, namely water fluxes, is compared with the corresponding results from the numerical model SEEP2D and simple Darcy-type model. The errors of the AHF model, in a range of 11–16%, depend on the aspect ratio of water depth to river width, and the direction of the river–aquifer water exchange, i.e., drainage or infiltration. The AHF model errors are significantly lower compared to the often-used model based on vertical water seepage through the streambed described by Darcy’s law.