Dynamics of iron and aluminum storages in a subtropical forest headwater stream

The forest headwater streams are important hubs for connecting terrestrial and aquatic ecosystems,with plant litter and sediments as the major carriers for material migrations;however,until now we knew little about the dynamics of trace elements such as iron(Fe)and aluminum(Al)in forest headwater streams.Here,we quantitatively identified the spatiotemporal dynamics of Fe and Al storages in plant litter and sediments and their influencing factors in a subtropical forest headwater stream,and assessed the potential pollution risk.The results showed that:(1)the mean concentrations of Fe and Al in plant litter(sediments)were 5.48 and 8.46(7.39 and 47.47)g·kg^(-1),and the mean storages of Fe and Al in plant litter(sediments)were 0.26 and 0.43(749.04 and 5030.90)g·m^(-2),respectively;(2)the storages of Fe and Al in plant litter and sediments significantly fluctuated from January to December,and showed a decreasing pattern from the source to mouth;and(3)storages of Fe and Al had no significant correlation with riparian forest type and the present of tributary and the Fe and Al storages in plant litter were mainly affected by water temperature and water alkalinity,and their storages in sediments were mainly affected by water temperature and frequency of rainfall;and(4)there were no anthropogenic pollution in Fe and Al in the forest headwater stream.Our study revealed the primary factors of concentrations and storages of Fe and Al in plant litter and sediments in a forest headwater stream,which will improve our understanding of the role of headwater streams in forest nutrient storage and cycling along with hydrological processes.

Effects of riparian land use on water quality and fish communities in the headwater stream of the Taizi River in China

Riparian land use remains one of the most significant impacts on stream ecosystems. This study focuses on the relationship between stream ecosystems and riparian land use in headwater regions. Four riparian land types including forest, grassland, farmland, and residential land were examined to reveal the correlation between stream water and fish communities in headwater streams of the Taizi River in north-eastern China. Four land types along riparian of 3 km in length were evaluated at 25, 50, 100, 200 and 500m widths, respectively. Generally, the results found a significant relationship between riparian land uses and stream water quality. Grassland was positively correlated with water quality parameters （con- ductivity and total dissolved solids） at scales from 100 to 500 m riparian width. Farmland and residential land was negatively correlated with water quality parameters at scales from 25 to 500 m and from 50 to 200 m riparian widths, respectively. Although the riparian forest is important for maintaining habitat diversity and fish communities, the results found that only fish communities were significantly correlated with the proportion of riparian farmland. Farmland had a positive correlation with individual fish abundance within a riparian corridor of 25 to 50 m, but a negative correlation with fish diversity metrics from 25 to 100m. This study indicates that effective riparian management can improve water quality and fish communities in headwater streams.

Effect of land cover on channel form adjustment of headwater streams in a lateritic belt of West Bengal(India)

Present work is exploring the influence of land cover on channel morphology in 34 headwater catchments of the lateritic belt of West Bengal.Non-parametric tests(Mann-Whitney U and Kruskal-Wallis)and multivariate analysis(Principal Component Analysis and Canonical Discriminant Function models)have successfully differentiated the performance of land cover on channel morphology adjustment among the three groups of headwater streams(forested,transitional,and agricultural)on the Kunur River Basin(KRB).Spatial Interpolation Techniques reveal that intense land-use change,particularly forest conversion to agricultural land,is significantly increasing channel widths(269%)and cross-section area(78%),whereas agricultural channels become shallower(40%)than would be predicted from forested streams.Catchments with the dominance of forest and agricultural land are classified as‘C′and‘B′types of streams respectively,as per Rosgen's Stream Classification Model.Finally,the work claimed that transitional stream group is the definitive area to exaggerate the river restoration plan to stabilize the anthropogenic deformation on channel morphology.

Augmenting freshwater availability in mountain headwater streams:Assessing the sustainability under baseline and future climate change scenarios

Mountain headwater streams are important freshwater sources,but they are mostly intermittent and highly susceptible to climate change.This paper examines the sustainability of augmented freshwater availability in mountain headwater streams for water supply under baseline and future climate change scenarios using an integrated modeling approach.The climate change data in the 2040s(2030e2059),under Representative Concentration Pathway 4.5 and 8.5 scenarios,were downscaled for the impact assessment.In the region,climate change raises the average precipitation by 5e7%and the temperature by 13e15%in the 2040s.SWATeMODFLOW model,integrating Soil and Water Assessment Tool(SWAT2012)and finite-difference Modular Groundwater Flow(MODFLOW)models in a single package,was used to assess the water balance.Results show that extracting a minimum of 16.2 m^(3)/day from the sand storage and 30 m^(3)/day from the aquifer was possible without affecting the groundwater table and water yield.The average annual catchment recharge was 6%of the precipitation under the baseline simulation.Climate change is projected to reduce the average water yield and groundwater recharge by 26%and 19%,respectively.However,the water supply-demand is significantly small compared to the exploitable rate of water in the area.This study was based on limited data,and therefore the findings need to be interpreted with caution,though the model output was validated using satellite products.Construction of a series of sand dams is suggested to maximize the benefit under the potential climate change and water supply-demand increase.

Influence of tributaries on downstream bed sediment grain sizes under flysch conditions

Tributaries are one of the most important factors contributing to variability in the downstream evolution of bed sediment grain size.The primary aim of this work is to evaluate the response of the bed sediment texture in the recipient channel induced by ten tributaries of the?ernáOstravice stream and find reach-scale and catchment-scale parameters that would be able to predict this response.The research was based on collecting information on the grain size distributions at sites adjacent to confluence zones.A significant change in sediment texture occurred in the vicinity of five confluences.Considering the other factors contributing to grain size variability(e.g.,local channel geometry,lithology,and lateral sediment sources),it was assumed that only four of them were associated with a sufficient bedload influx to alter the sediment calibre below the junction.Moreover,a significant morphological effect in the form of a large confluence bar was observed in one case.These tributaries had several common features:(i)they had a larger relative catchment area than that of nonsignificant tributaries;(ii)they were characterized by different bed grain sizes,with some exceptions;and(iii)they had a higher unit stream power close to the confluence in relation to that of the mainstream.These characteristics were represented by the proposed relative parameters,including the relative unit stream power and bed material texture,which allowed the best classification of significant and nonsignificant tributaries.In their simplified form,the parameters described the transport capacity and grain size distribution,which were generally considered to be primary factors responsible for a redefinition of the sediment texture in the recipient channel.However,it should be noted that these results are subject to some degree of uncertainty due to the relatively small sample size of only 10 tributaries.

Anthropogenic land use substantially increases riverine CO_(2) emissions

Carbon dioxide(CO_(2)) emissions from inland waters to the atmosphere are a pivotal component of the global carbon budget. Anthropogenic land use can influence riverine CO_(2) emissions, but empirical data exploring cause-effect relationships remain limited. Here, we investigated CO_(2) partial pressures(pCO_(2)) and degassing in a monsoonal river(Yue River)within the Han River draining to the Yangtze in China. Almost 90% of river samples were supersaturated in CO_(2) with a mean ± standard deviation of 1474 ± 1614 μatm, leading to emissions of 557-971 mmol/m^(2)/day from river water to the atmosphere. Annual CO_(2) emissions were 1.6-2.8 times greater than the longitudinal exports of riverine dissolved inorganic and organic carbon. pCO_(2) was positively correlated to anthropogenic land use(urban and farmland), and negatively correlated to forest cover. p CO_(2) also had significant and positive relationships with total dissolved nitrogen and total dissolved phosphorus. Stepwise multiple regression models were developed to predict p CO_(2) . Farmland and urban land released nutrients and organic matter to the river system, driving riverine p CO_(2) enrichment due to enhanced respiration in these heterotrophic rivers. Overall, we show the crucial role of land use driving riverine pCO_(2) , which should be considered in future large-scale estimates of CO_(2) emissions from streams. Land use change can thus modify the carbon balance of urban-river systems by enhancing river emissions, and reforestation helps carbon neutral in rivers.