•Water impact effects on hydraulic properties of a loam soil were studied.•Beerkan experiments with six water pouring heights, H (0.03 to 2 m), were performed.•Higher H values induced a slowdown of ...the infiltration process.•No soil alterations were detected for 0.03 < H ≤ 0.25 m and H ≥ 1.5 m.•The experimental methodology seems promising to obtain hydrologically useful data.
Interpreting and simulating rainfall partition into infiltration and surface runoff has to consider that surface soil hydraulic properties, including saturated soil hydraulic conductivity (Ks) and sorptivity (S), could change even at very short temporal scales. Soil deterioration due to water impact can be tested in the field by the multi-height beerkan (MHB) method, that is, by pouring water on the infiltration surface from different heights. Soil hydraulic properties can be estimated coupling the MHB method with the steady version of the Beerkan Estimation of Soil Transfer parameters procedure (BEST-steady). The MHB method with six heights of water pouring (H) in the range 0.03–2 m was applied on a relatively dry loam soil to investigate height of water pouring effects on i) the established infiltration process, and ii) Ks, S, the scale parameter of the water retention curve (hg) and the characteristic microscopic pore radius (λm). Higher heights of water pouring generally induced a slowdown of the infiltration process, smaller S, Ks and λm values and higher |hg| values. The S, Ks, |hg| and λm vs. H relationships were statistically significant but the fitted relationships for S and Ks were stronger than those for |hg| and λm, indicating a different sensitivity of the considered parameters to the height of water pouring. Small or negligible soil deterioration was observed for both small (H ≤ 0.25 m) and large (H ≥ 1.5 m) heights. Between these two extremes, the soil deteriorated as H increased, suggesting that the external solicitations were high enough to overcome the resistance of the porous medium but not so high to determine a complete soil alteration. The tested methodology appears promising to determine the effects of water impact on the soil hydrodynamic behavior and it could be applied to perform a soil hydraulic characterization usable for modelling hydrological processes.
Key Points
Remote sensing validation of a hydrologic‐hydrodynamic model of the Amazon
Uncertainty of precipitation and river‐floodplain parameters cause model errors
Importance of floodplains and ...backwater effects on flood waves traveling
In this paper, a hydrologic/hydrodynamic modeling of the Amazon River basin is presented using the MGB‐IPH model with a validation using remotely sensed observations. Moreover, the sources of model errors by means of the validation and sensitivity tests are investigated, and the physical functioning of the Amazon basin is also explored. The MGB‐IPH is a physically based model resolving all land hydrological processes and here using a full 1‐D river hydrodynamic module with a simple floodplain storage model. River‐floodplain geometry parameters were extracted from the SRTM digital elevation model, and the model was forced using satellite‐derived rainfall from TRMM3B42. Model results agree with observed in situ daily river discharges and water levels and with three complementary satellite‐based products: (1) water levels derived from ENVISAT altimetry data; (2) a global data set of monthly inundation extent; and (3) monthly terrestrial water storage (TWS) anomalies derived from the Gravity Recovery and Climate Experimental mission. However, the model is sensitive to precipitation forcing and river‐floodplain parameters. Most of the errors occur in westerly regions, possibly due to the poor quality of TRMM 3B42 rainfall data set in these mountainous and/or poorly monitored areas. In addition, uncertainty in river‐floodplain geometry causes errors in simulated water levels and inundation extent, suggesting the need for improvement of parameter estimation methods. Finally, analyses of Amazon hydrological processes demonstrate that surface waters govern most of the Amazon TWS changes (56%), followed by soil water (27%) and ground water (8%). Moreover, floodplains play a major role in stream flow routing, although backwater effects are also important to delay and attenuate flood waves.
Multi-stage constructed wetlands (CWs) are widely used for water quality improvement, especially in the treatment of wastewater. Many studies focus on their treatment efficiency under steady loading, ...but fewer studies consider their sustainability under variable conditions. This study examines the multi-stage CWs in the Hong Kong Wetland Park for their long-term performance and sustainability in terms of water quality under seasonal changes, storm events, and shock loadings of pollutants. The results show that the multistage design performs well and is stable under these changing conditions. In such multistage CWs, the type of units and some changing conditions (e.g., inflow concentrations, seasonal changes of vegetation, and water levels) also affect the performance of the whole system. Compared to individual CW, a multi-stage CW system could recover more quickly on dissolved oxygen (DO), and ammonia nitrogen (NH4), but slowly on biochemical oxygen demand (BOD) and total phosphorus (TP). A pre-processing and buffering area is necessary to handle the shock loadings of BOD and TP in such a multistage CW system. Although water levels recover quickly in both, it is difficult to return to original water levels in multi-stage CWs compared to single ones. Besides, for sustainable operation, attention should be paid to the DO of the inlet, and aeration measures might be taken.
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•Multi-stage CW increases the difficulty of water level controls but improves the stability of treatment performance.•Multistage CWs are not better at treating BOD and TP than the single ones.•Aeration and enhanced sedimentation might be introduced for the gradual decreases of DO and increases of TSS.
Forest ecosystem has long been suggested as a vital component in the global mercury (Hg) biogeochemical cycling. However, there remains large uncertainties in understanding total Hg (THg) and ...methylmercury (MeHg) variations and their controlling factors during the whole hydrological processes in forest ecosystems. Here, we quantified Hg mass flow along hydrological processes of wet deposition, throughfall, stemflow, litter leachate, soil leachate, surface runoff, and stream, and litterfall Hg deposition, and air-forest floor elemental Hg (Hg0) exchange flux to set up a Hg mass balance in a subtropical forest of China. Results showed that THg concentration in stream was lower than that in wet deposition, while an opposite characteristic for MeHg concentration, and both THg and MeHg fluxes of stream were lower than those of wet deposition. Variations of THg and MeHg in throughfall and litter leachate had strong direct and indirect effects on controlling variations of THg and MeHg in surface runoff, soil leachate and stream, respectively. Especially, the net Hg methylation was suggested in the forest canopy and forest floor layers, and significant particulate bound Hg (PBM) filtration was observed in soil layers. The Hg mass balance showed that the litterfall Hg deposition was the main Hg input for forest floor Hg, and the elemental Hg vapor (Hg0) re-emission from forest floor was the dominant Hg output. Overall, we estimated the net THg input flux of 13.8 μg m−2 yr−1 and net MeHg input flux of 0.6 μg m−2 yr−1 within the forest ecosystem. Our results highlighted the important roles of forest canopy and forest floor to shape Hg in output flow, and the forest floor is a distinct sink of MeHg.
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•Forest canopy and forest floor shape mercury concentrations in runoff.•Both forest canopy and forest floor induce net Hg methylation.•Mineral soil is a distinct methylmercury sink.•Subtropical forest in south China plays a sink role of atmospheric mercury.
Abstract
Climate change is anticipated to have long-term effects on hydrological processes and patterns, leading to water stress in agroecological catchments. Climate change escalates water scarcity ...in the Usangu catchment, as evidenced by the drying up of rivers during the dry season. Therefore, this study was undertaken to assess climate change impacts on hydrology by utilizing the Soil Water Assessment Tool (SWAT) model and an ensemble mean of five Global Circulation Models (GCMs) under two shared socio-economic pathway (SSP) emission scenarios. Downscaling of GCMs was performed by the LARS-WG statistical downscaling tool. In comparison to the baseline period, short rain intervals are expected to occur between 2030 and 2060, with a mean annual precipitation increase of 7 and 17% in SSP 2–4.5 and SSP 5–8.5, respectively. Maximum and minimum temperatures are expected to rise by 0.6–2 °C. Corresponding to future temperature increases, evapotranspiration would increase to about 30% and decrease water yield and groundwater recharge by 7 and 26% in SSP 2–4.5 than in SSP 5–8.5. However, the effect of precipitation increase is shown by increased surface runoff and streamflow during wetter months. These findings provide watershed managers with crucial information for planning and managing the catchment in light of a changing climate.
The water level of Lake Qinghai, the largest lake on the Qinghai–Tibetan Plateau, has increased continuously, at an average speed of 0.21 m per year since 2005, causing a rapid expansion of the lake ...area. We investigated the hydrological processes of Lake Qinghai and the surrounding watershed that have influenced water level and lake area from 1956 to 2019. Relationships among water level, climate change and human activities were also assessed. Water level and lake area were positively correlated with precipitation and runoff into the lake, and negatively correlated with evaporation. Climate change factors including precipitation and runoff were the primary causes of lake level change, whereas human activities, including variation in a human footprint index, land use, and grassland irrigation, were secondary factors. A time series model forecasted that from 2020 to 2050 water levels will increase further by 2.45 m. Although this increase in water level may have some benefits, such as reduced local desertification, the expansion of lake area will continue to flood low beaches, pasture lands, near shore infrastructure and roads, and impact tourism locations. However, continued water level rise may also have negative ecological effects, such as reduce habitat of seasonal birds and reduced water quality due to erosion and sediment resuspension in shallow nearshore lake areas. Local stakeholders, government authorities, and scientists should give greater attention to anticipated changes in water level, and further ecological studies and infrastructure adaptation measures should be implemented.
•The climate change, human activities and hydrological processes in the Lake Qinghai Basin were studied.•The trend of the water level for the future 30 years were predicted.•Climate change dominated the water level variation in the Lake Qinghai.•The ecological and environmental effects by the rising water level were emphasized.
In the last years, the Mediterranean basin has been widely recognized as one of the most vulnerable areas in the world to climate change; because of its high concentration of urban and industrial ...settlements, it is one of the most impacted areas of the world in terms of water scarcity. The present paper aims at reviewing the main observed and predicted effects of climate change on hydrological processes directly related to water availability in the Mediterranean Basin, mainly focusing on the last ten years of research. While an in-depth discussion about possible future water scarcity problem in the Mediterranean area and the sources of uncertainty affecting future climate projections and impact assessments is presented in a companion paper (Noto et al., 2022), this study highlights how most of the more recent studies for the Mediterranean region are concordant and recognize a general increasing future trajectory in both the mean and extreme values of air temperatures. On the contrary, there is much less agreement about the intensity and directions of future projections for other variables, such as precipitation, evapotranspiration, and runoff, whose changes are less evident and variable in space.
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